Experimental and simulation studies on the performance of standing wave thermoacoustic prime mover for pulse tube refrigerator

The thermoacoustic prime mover (TAPM) has gained considerable attention as a pressure wave generator to drive pulse tube refrigerator (PTR) due to no moving parts, reasonable efficiency, use of environmental friendly working fluids etc. To drive PTCs, lower frequencies (f) with larger pressure amplitudes (ΔP) are essential, which are affected by geometric and operating parameters of TAPM as well as working fluids. For driving PTRs, a twin standing wave TAPM is built and studied by using different working fluids such as helium, argon, nitrogen and their binary mixtures. Simulation results of DeltaEc are compared with experimental data wherever possible. DeltaEc predicts slightly increased resonance frequencies, but gives larger ΔP and lower temperature difference ΔT across stack. High mass number working fluid leads to lower frequency with larger ΔP, but higher ΔT. Studies indicate that the binary gas mixture of right composition with lower ΔT can be arrived at to drive TAPM of given geometry.     

Experimental and theoretical studies of a two-stage pulse tube cryocooler operating down to 3 K

The development of a two-stage Pulse Tube Cryocooler (PTC) which produces a no-load temperature of ～3 K and delivers a refrigeration power of ～250 mW at 5 K is reported in this work. The system uses stainless steel meshes along with lead (Pb) granules and combinations of Pb, Er₃Ni and HoCu₂ in layered structures as the first and second stage regenerator materials respectively. With Helium as a working fluid, the pressure oscillations are generated using a 6 kW water-cooled Helium compressor along with an indigenous rotary valve. Different configurations of pulse tube systems have been experimentally studied, by both varying the dimensions of pulse tubes and regenerators as well as the second stage regenerator material composition. The pulse tube Cryocooler has been numerically analyzed by using both the isothermal model and the model based on solving the energy equations. The predicted refrigeration powers as well as the temperature profiles have been compared with the experimental results for specific pulse tube configurations.     

Automatic classification with concatenation of deep and handcrafted features of histological images for breast carcinoma diagnosis

Multimedia Tools and Applications - The second leading cause of death from cancer among women is breast cancer. In order to prevent avoidable deaths, early detection is extremely necessary....     

Growth performance, variability in yield traits and oil content of selected accessions of Jatropha curcas L. growing in a large scale plantation site

Jatropha curcas L. (JCL) is gaining global popularity as a potential feed stock of biodiesel and a candidate species for waste land reclamation. Although the oil yield of this species is better than any other non-edible oil yielding plants, the lack of agronomic practices defame this species for further exploitation. Furthermore, there is paucity of data on the growth performances and yield of JCL plantations. In this context, a systematic study on passport data and yield performance of JCL germplasms (including their indigenous collection number (IC No.), morphological characterization of seeds and seed oil content) growing in a large scale plantation site at Solar Energy Center, Gurgaon, India were carried out during 2007–2008. Ten elite accessions of JCL were screened from this site based on their growth performance and biomass characterization and were deposited at National Bureau of Plant Genetic Resources, New Delhi for registration. The oil content of the 10 registered accessions was ranged from 17% to 34%. Cluster analysis was performed to find out promising germplasms. Cluster analysis formed two prominent groups, each one with two sub-clusters. The promising accessions can be further explored for crop improvement programs. Furthermore, multi-locational trials are essential for optimizing the agropractices for maximum yield for a sustainable biodiesel production.     

Low‐Carbon Magnesia‐Carbon Refractory: Use of N220 Nanocarbon Black

Addition of nanocarbon black up to 3 wt% was done in MgO‐C refractories, containing fixed 3 and 5 wt% of graphite, to study the effect on various refractory properties. Uniform distribution of carbon particles even at 1 wt% of nanocarbon black with 3 and 5 wt% of graphite was found to improve the refractory properties. The coked strength, hot strength, corrosion resistance, and oxidation resistance were found to be improved for nanocarbon‐containing MgO‐C refractory compared with the conventional refractory due to in situ formation of Al₄C₃. Higher amount of nanocarbon black was found to deteriorate the refractory properties.     

Effect of Ti Doping on Structural and Superconducting Property of YBa2Cu3O7−y High T c Superconductor

Dimensional fluctuations of superconducting order parameters in YBa₂(Cu_1?x Ti _x )₃O_7?y (x=0.01, 0.02, 0.04, 0.05) have been analyzed. SEM micrographs reveal the reduced grain size and the formation of TiO₂ nanowires covering over the grains of YBCO matrix. XRD graphs show the unchanged orthorhombic structure. With the increase of TiO₂%, it is found that the superconducting transition temperatures determined from standard four-probe method decrease gradually. Excess conductivity fluctuation analysis using the Aslamazov–Larkin model fitting reveals transition of two dominant regions (2D and 3D) above T _c . 2D to 3D crossover temperature, i.e., the Lawerence–Doniach temperature that demarcates dimensional nature of fluctuation inside the grains is influenced by Ti incorporation in YBCO matrix. The decrease in the Lawerence–Doniach temperature in the mean field region has been observed as a consequent dominance of 3D region with increase in Ti%.     

Comparative study of bio-ethanol production from mahula (Madhuca latifolia L.) flowers by Saccharomyces cerevisiae cells immobilized in agar agar and Ca-alginate matrices

Batch fermentation of mahula (Madhuca latifolia L., a tree commonly found in tropical rain forest) flowers was carried out using immobilized cells (in agar agar and calcium alginate) and free cells of Saccharomyces cerevisiae. The ethanol yields were 151.2, 154.5 and 149.1 g kg⁻¹ flowers using immobilized (in agar agar and calcium alginate) and free cells, respectively. Cell entrapment in calcium alginate was found to be marginally superior to those in agar agar (2.2% more) as well as over free cell (3.5% more) as regard to ethanol yield from mahula flowers is concerned. Further, the immobilized cells were physiologically active at least for three cycles [150.6, 148.5 and 146.5 g kg⁻¹ (agar agar) and 152.8, 151.5 and 149.5 g kg⁻¹ flowers (calcium alginate) for first, second and third cycle, respectively] of ethanol fermentation without apparently lowering the productivity. Mahula flowers, a renewable, non-food-grade cheap carbohydrate substrate from non-agricultural environment such as forest can serve as an alternative to food grade sugar/starchy crops such as maize, sugarcane for bio-ethanol production.     

Simulation of a two-slope pyramid made by SPIF using an adaptive remeshing method with solid-shell finite element

Single point incremental forming (SPIF) is an emerging application in sheet metal prototyping and small batch production, which enables dieless production of sheet metal parts. This research area has grown in the last years, both experimentally and numerically. However, numerical investigations into SPIF process need further improvement to predict the formed shape correctly and faster than current approaches. The current work aims the use of an adaptive remeshing technique, originally developed for shell and later extended to 3D “brick” elements, leading to a Reduced Enhanced Solid-Shell formulation. The CPU time reduction is a demanded request to perform the numerical simulations. A two-slope pyramid shape is used to carry out the numerical simulation and modelling. Its geometric difficulty on the numerical shape prediction and the through thickness stress behaviour are the main analysis targets in the present work. This work confirmed a significant CPU time reduction and an acceptable shape prediction accuracy using an adaptive remeshing method combined with the selected solid-shell element. The stress distribution in thickness direction revealed the occurrence of bending/unbending plus stretching and plastic deformation in regions far from the local deformation in the tool vicinity.     

Kinematic control of a redundant manipulator using an inverse-forward adaptive scheme with a KSOM based hint generator

This paper proposes an online inverse-forward adaptive scheme with a KSOM based hint generator for solving the inverse kinematic problem of a redundant manipulator. In this approach, a feed-forward network such as a radial basis function (RBF) network is used to learn the forward kinematic map of the redundant manipulator. This network is inverted using an inverse-forward adaptive scheme until the network inversion solution guides the manipulator end-effector to reach a given target position with a specified accuracy. The positioning accuracy, attainable by a conventional network inversion scheme, depends on the approximation error present in the forward model. But, an accurate forward map would require a very large size of training data as well as network architecture. The proposed inverse-forward adaptive scheme effectively approximates the forward map around the joint angle vector provided by a hint generator. Thus the inverse kinematic solution obtained using the network inversion approach can take the end-effector to the target position within any arbitrary accuracy.In order to satisfy the joint angle constraints, it is necessary to provide the network inversion algorithm with an initial hint for the joint angle vector. Since a redundant manipulator can reach a given target end-effector position through several joint angle vectors, it is desirable that the hint generator is capable of providing multiple hints. This problem has been addressed by using a Kohonen self organizing map based sub-clustering (KSOM-SC) network architecture. The redundancy resolution process involves selecting a suitable joint angle configuration based on different task related criteria.The simulations and experiments are carried out on a 7 DOF PowerCube? manipulator. It is shown that one can obtain a positioning accuracy of 1 mm without violating joint angle constraints even when the forward approximation error is as large as 4 cm. An obstacle avoidance problem has also been solved to demonstrate the redundancy resolution process with the proposed scheme.