On fatigue reliability under random loads

We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the material strength. For the material strength, the Weibull distribution is assumed, the parameters of which are estimated by a statistical analysis of the experimental tensile strength of steel specimens subjected to different periods of random loads. The statistical analysis shows that, with the application of random loads, the initial homogeneous distribution of strength changes to a two-component distribution, reflecting the two-stage fatigue damage. In the crack initiation stage, the strength increases initially and then decreases, while an abrupt decrease of strength is seen in the crack propagation stage. The consequences of this behaviour on the fatigue reliability are discussed.     

Biodiesel production using waste cooking oil: a waste to energy conversion strategy

In this study, biodiesel was produced using waste cooking oil that was discarded as a waste in the environment. The properties of the feedstock were determined using standard ASTM methods. The transesterification process was implemented to extract the biodiesel, and this process was optimized and standardized by selecting three different parameters: molar ratio (methanol:oil), catalyst concentration (KOH) and reaction temperature. The physicochemical properties of the biodiesel so produced were tested and analyzed using gas chromatography. Biodiesel and diesel were mixed in different volumetric ratios, and the exhaust emission characteristics of the blends were determined by testing the blends on a variable compression ratio engine. The study concluded that waste cooking oil has a great potential for waste to energy process. The highest yield of 93.8% was obtained by optimizing the process. Emission characteristics of CO for B50 blend showed a downward trend while NO _x emission was found to be greater for blending ratios above 10%. B10 showed the best results pertaining to lower NO _x and CO emissions.     

Dedicated finite elements for electrode thin films on quartz resonators

The accuracy of the finite element analysis for thickness shear quartz resonators is a function of the mesh resolution; the finer the mesh resolution, the more accurate the finite element solution. A certain minimum number of elements are required in each direction for the solution to converge. This places a high demand on memory for computation, and often the available memory is insufficient. Typically the thickness of the electrode films is very small compared with the thickness of the resonator itself; as a result, electrode elements have very poor aspect ratios, and this is detrimental to the accuracy of the result. In this paper, we propose special methods to model the electrodes at the crystal interface of an AT cut crystal. This reduces the overall problem size and eliminates electrode elements having poor aspect ratios. First, experimental data are presented to demonstrate the effects of electrode film boundary conditions on the frequency-temperature curves of an AT cut plate. Finite element analysis is performed on a mesh representing the resonator, and the results are compared for testing the accuracy of the analysis itself and thus validating the results of analysis. Approximations such as lumping and Guyan reduction are then used to model the electrode thin films at the electrode interface and their results are studied. In addition, a new approximation called merging is proposed to model electrodes at the electrode interface.     

Exergy efficiency improvement in hydrogen production process by recovery of chemical energy versus thermal energy

Exergy analysis is recently being employed as one of the preferred methods to improve the design performance of a system and to achieve overall sustainability. Exergy is mainly composed of physical or thermo-mechanical and chemical components and a single stream can possess one or more forms of exergy. Where there is exergy lost in unused chemical streams or wasted energy, the recovery of exergy would reduce losses and increase the second law efficiency of the process. In many chemical process plants such as hydrogen (H₂), ammonia, nitric acid, etc., there is a potential to recover waste or excess heat by process heat exchange or by generating utilities. For a process like steam–methane (CH₄) reforming (SMR), exergy efficiency can be improved by recovering the available excess heat partially or fully in the form of chemical energy or thermal energy. This paper presents the generalised system analysis to show that the recovery of exergy in the form of chemical energy is better than in thermal energy form due to fewer losses and higher efficiency. The concept is illustrated with the example of a simple combustion system with excess heat in which saving fuel proves to be more exergy efficient than generating utility. The approach is applied to an industrial case study of H₂-producing SMR plant with two modified cases of steam generation and recycling portion of unconverted CH₄ as feed. In the case study, heat exchanger network is treated as a separate process component and a simple methodology is proposed to calculate the exergy losses for the same. The results of the case study prove that the recovery of chemical energy is more efficient than that of thermal energy from an exergy perspective.     

Preparation of biomolecule gel matrices for electron microscopy

We report a new sample preparation method that allows the direct transmission electron microscopy evaluation of the architectural characteristics of biomolecules entrapped in gel matrices. We demonstrate that this sample preparation technique can be used for the identification and ultrastructural characterization of liposomes, collagen I and collagen III embedded in gel matrices, and has the potential to be useful for transmission electron microscopy (TEM) characterization of other biomolecule-gel matrix systems.     

A novel weight based clustering algorithm for routing in MANET

Cluster based routing in Mobile AdHoc Networks are considered one of the convenient method of routing. Existence of Cluster Head (CH) in a group of nodes for data forwarding improves the performance of routing in terms of routing overhead and power consumption. However, due to the movement of CH and frequent change in cluster members, cluster reformation is required and increases cluster formation overhead. The stability of the cluster highly dependent of stability of the CH and hence during CH selection special care should be taken so that the cluster head survives for longer time. In this paper a method of cluster formation is proposed which will take into account two most vital factor node degree and bandwidth requirement for construction of the cluster and selection of the cluster head. Further, when two clusters come closer to each other they merge and form a single cluster. In such case out of two CHs one has to withdraw the role and other will take over. A new mechanism of merging two clusters is also proposed in the paper. We call this method as an Improved Cluster Maintenance Scheme and primarily focused on minimizing CH changing process in order to enhance the performance. The stated method makes cluster more stable, and minimizes packet loss. The proposed algorithm is simulated in ns-2 and compared with Least Cluster head Change (LCC) and CBRP. Our algorithm shows better behavior in terms of number of clusterhead changes or number of cluster member changes.     

A Cyanine-Bridged Somatostatin Hybrid Probe for Multimodal SSTR2 Imaging in Vitro and in Vivo: Synthesis and Evaluation

Multimodal imaging probes have attracted the interest of ongoing research, for example, for the surgical removal of tumors. Modular synthesis approaches allow the construction of hybrid probes consisting of a radiotracer, a fluorophore and a targeting unit. We present the synthesis of a new asymmetric bifunctional cyanine dye that can be used as a structural and functional linker for the construction of such hybrid probes. ⁶⁸Ga-DOTATATE, a well-characterized radiopeptide targeting the overexpressed somatostatin receptor subtype 2 (SSTR2) in neuroendocrine tumors, was labeled with our cyanine dye, thus providing additional information along with the data obtained from the radiotracer. We tested the SSTR2-targeting and imaging properties of the resulting probe ⁶⁸Ga-DOTA-ICC-TATE in vitro and in a tumor xenograft mouse model. Despite the close proximity between dye and pharmacophore, we observed a high binding affinity towards SSTR2 as well as elevated uptake in SSTR2-overexpressing tumors in the positron emission tomography (PET) scan and histological examination.     

Beyond classical theory: Predicting the free energy barrier of bubble nucleation in polymer foaming

Based on the Gibbs‐Tolman‐Koenig formalism, we considered the Tolman correction to the free energy barrier of bubble nucleation in polymer‐gas binary mixtures. For this class of systems, the correction may be estimated with a reasonable accuracy using experimentally accessible macroscopic thermodynamic quantities only. Although the Tolman correction is applicable only in the low supersaturation regime, a simple ansatz regarding the supersaturation dependence of the Tolman length can be made to extend the usefulness of this approach and to yield the free energy barrier that vanishes at the mean‐field spinodal as demanded by thermodynamic considerations. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3042–3053, 2013     

EIS studies on electro-electrodialysis cell for concentration of hydriodic acid

EIS studies were carried out on an electro-electrodialytic cell used for concentration of hydriodic acid using platinum electrodes and nafion117 membrane. Different impedance spectra were obtained where the concentration of iodine was varied while the concentration of HI was kept fixed at 55 wt%. Equivalent circuit model was used to simulate the experimental data and it was found that the impedance of the cell without membrane can be modeled using a single Warburg element along with ohmic resistance in series. This indicates presence of only diffusion transport resistance at the electrode and absence of any non-electroneutral layer. The impedance spectra for cell with membrane can be modeled using a Warburg element and a CPE with capacitive character along with ohmic resistance in series. This indicates formation of a non-electroneutral (heterogeneous transport) layer at the membrane in addition to a diffusion transport layer. It was found that the ohmic resistance increased with increase in the concentration of iodine while the impedances due Warburg and heterogeneous transport layer decreased with increase in iodine concentration.     

Influence of additives on dough rheology and quality of <Emphasis Type="Italic">Thepla</Emphasis>: an Indian unleavened flatbread

Thepla is Indian unleavened flatbread made from whole-wheat flour with added spices and vegetables. In the present study, effect of addition of various emulsifiers such as sodium stearoyl-2-lactylate (SSL), di acetyl tartaric acid ester of monoglyceride (DATEM) and glycerol mono-stearate (GMS) were studied. Further hydrocolloids (guar gum, carrageenan) and modified polysaccharides [hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose] were added at the concentration ranging from 0.25 to 1 % on the basis of whole wheat flour to prepared the doughs. These thepla doughs were analyzed for rheology and theplas were analyzed for tear force. Additives helped in improvement of dough and thepla quality. Guar gum increased dough stickiness and strength to the highest (31.12 and 1.76 g respectively). Also, guar gum decreased tear force value of thepla to 208.4 g. Tear force was found to be increasing with the duration of storage. Highest improvement in thepla dough and quality was obtained by the addition of guar gum at 0.75 % which retained the softest texture of thepla.