Biodiesel production from jatropha oil (Jatropha curcas) with high free fatty acids: An optimized process

Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to optimize the three important reaction variables—methanol quantity (M), acid concentration (C) and reaction time (T) for reduction of free fatty acid (FFA) content of the oil to around 1% as compared to methanol quantity (M′) and reaction time (T′) and for carrying out transesterification of the pretreated oil. Using RSM, quadratic polynomial equations were obtained for predicting acid value and transesterification. Verification experiments confirmed the validity of both the predicted models. The optimum combination for reducing the FFA of Jatropha curcas oil from 14% to less than 1% was found to be 1.43% v/v H₂SO₄ acid catalyst, 0.28 v/v methanol-to-oil ratio and 88-min reaction time at a reaction temperature of 60 °C as compared to 0.16 v/v methanol-to-pretreated oil ratio and 24 min of reaction time at a reaction temperature of 60 °C for producing biodiesel. This process gave an average yield of biodiesel more than 99%. The fuel properties of jatropha biodiesel so obtained were found to be comparable to those of diesel and confirming to the American and European standards.     

Improved Repeatability of Pulsed Field Magnetometry Measurements Through Peltier Effect Temperature Control of Measurement Coils

Pulsed Field Magnetometers (PFMs) offer a method for high speed full loop characterisation of hard magnetic materials. As there is no dependency on iron to close a circuit, the repeatability of the technique is good. By utilising Peltier effect techniques to control the temperature of the measurement coil systems employed in a Pulsed Field Magnetometer, the level of repeatability of measurements can be significantly improved.     

Atmospheric Freeze Drying—Modeling and Simulation of a Tunnel Dryer

Drying is an important unit operation in processing of foods and other biotechnological products. Vacuum freeze drying is said to be the best drying technology regarding product quality of the end product, but the disadvantages are, among others, expensive operational costs and batch drying. Atmospheric freeze drying was introduced to lower the production costs of high-quality dried foods, and the need of simulation tools became important in estimations of the industrial drying processes.

A simplified mathematical model (AFDsim) is developed based on uniformly retreating ice front (URIF) considerations. The model is used to calculate theoretical drying curves of atmospheric freeze dried foods in a tunnel dryer. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensioning the drying process. The model can be used to simulate industrial atmospheric freeze drying of different foodstuff in a tunnel. The results from AFDsim modeling are in good accordance with the experimental results.     

An anisotropic theory of elasticity for continuum damage mechanics

This paper presents the development of an anisotropic elastic damage theory. This is achieved by deriving a modified damage effect tensor M(D) for the effective stress equations capable of including the effect of anisotropic material damage. The modified tensor removes the restriction of a priori knowledge of the directions of principal stresses imposed by a damage effect tensor developed earlier and can now be made for general practical engineering applications of failure analysis. Reduction of the proposed tensor to a scalar for isotropic damage is shown to be possible when it is expressed not only in the principal directions but also in any arbitrary coordinate system, a necessary condition to verify the validity of the proposed tensor. Uniaxial tension and pure torsion are chosen to illustrate the application of the theory as well as associated damage variables that may be experimentally determined using laboratory size specimens. The measured damage variables confirm the presence of anisotropic damage from an initially isotropic material specimen and the magnitude is more pronounced at higher stresses and strains.

---

Résumé On présente un développement d'une théorie sur l'endommagement élastique anisotrope en déduisant un tenseur modifié décrivant l'effet de l'endommagement pour un système d'équations de contraintes effectives susceptible d'inclure l'effet d'un endommagement dans un matériau anisotrope. Le tenseur modifié supprime la restriction de la connaissance a priori des directions des contraintes principales imposées par un tenseur d'effet d'endommagement développé précédemment; il peut à présent entrer dans les applications pratiques en construction de l'analyse des ruptures.On montre qu'il est possible de réduire le tenseur proposé à une valeur scalaire dans le cas d'un dommage isotrope, dès lors qu'il est exprimé non seulement suivant les directions principales, mais dans un système de coordonnées arbitraires, ce qui est une condition nécessaire pour en vérifier la validité.On choisit une traction multiaxiale et une torsion pure pour illustrer l'application de la théorie ainsi que des variables d'endommagement associées, susceptibles d'être déterminées expérimentalement à l'aide d'éprouvettes de laboratoire.Les variables d'endommagement mesurées confirment la présence d'un dommage anisotrope dans le cas d'une éprouvette d'un matériau initialement isotrope; son amplitude est plus prononcée à des contraintes ou des déformations plus importantes.

     

Low-temperature CVD growth of carbon nanotubes for field emission application

For field emission application, carbon nanotube emitters were synthesized on catalyst-mixed thick-film electrode lower than 500 °C by chemical vapor deposition (CVD) method. Mixtures of Ni/tetraethyl silicate (TEOS) and conducting Ag powders were applied to fabricate the electrode by screen-printing processes. These processes are simple, low cost and easy to scale up for large sized panels. The field emission properties performed uniform emission image and high brightness (no less than 500 nits). The turn-on electric field was about 3.85 V/μm with an emission current destiny of 10 μA/cm², and the achieved current density was 1 mA/cm² driven by 5 V/μm.     

Crack growth in aluminium alloy sheet material under flight-simulation loading

Crack propagation tests were carried out on 2024-T3 sheet specimens to study the effects of omitting low-amplitude cycles from the gust-dominated TWIST load sequence (MiniTWIST) and the removal of small load ranges from the manoeuvre-dominated FALSTAFF load sequence (short FALSTAFF). In other tests high-amplitude loads of TWIST and MiniTWIST were truncated at different levels. The results are compared with data from similar test programmes, including crack initiation. Attention is paid to unstationary crack growth retardation and a transient retardation during initial crack growth started by an artificial crack.     

Fabrication methods for low-Pt-loading electrocatalysts in proton exchange membrane fuel cell systems

While the use of a high level of platinum (Pt) loading in proton exchange membrane fuel cells (PEMFCs) can amplify the trade off toward higher performance and longer lifespan for these PEMFCs, the development of PEMFC electrocatalysts with low-Pt-loadings and high-Pt-utilization is critical. Such development strongly depends on the electrode fabrication method and the loaded substrate. This study presents some of the latest research into promising methods of reducing the Pt loading while increasing the Pt utilization of the electrocatalysts used in PEMFCs.The application of the modified thin film method, despite its relatively higher Pt utilization, to micro-PEMFC applications has proven ineffective due to relatively higher Pt loadings.Although electrocatalysts fabricated by the electrodeposition method achieved the highest Pt utilization, the application of this method to large-scale manufacturing is doubtful due to concerns regarding its scalability.The advantage of the sputter method is its ability to deposit Pt directly onto various components of the membrane electrolyte assembly (MEA) with ultra-low-Pt-loadings. However, the low utilization and poor substrate adherence of the Pt remain challenges. Nevertheless, if these technical problems are overcome, this method appears to be the most promising technology for micro-systems and automotive application fields.Other methods, such as dual IBAD method, electro-spray technique and Pt sols methods, exhibited relatively lower Pt loadings and higher Pt utilization. However, these methods require further research to evaluate their capabilities and improve their reproducibility.Instead of the traditional carbon supports for electrocatalysts, nano-carbon supports such as nanotubes, powders, fibers and aerogels could be effectively used to reduce the Pt loadings.     

R curves for energy dissipative materials

This paper focuses on the theoretical simulation of fracture and stable crack growth of specimens with non-local damage. The first law of thermodynamics allows the identification or definition of appropriate crack-driving forces. The results are compared with recent ideas on defining tearing resistance for uncontained yield through the energy dissipation rate. A hypothesis regarding the conversion of mechanical into thermal energies within the non-local damage region is formulated to model the fracture behaviour of energy dissipative materials with rising crack resistance characteristics. The material's capacity to develop non-local damage is assumed to decrease with the actual damage level. This decrease relates linearly with the remaining resources of the material in dissipating energy. The hypothesis, which proposes a square root function for theoretical J-R curves, is verified by the regression analysis of experimental data regarding a European round-robin test of different steels.