The purpose of the present work is to study the mechanical behaviour of AA2219-T87 friction stir weld (FSW) joints at different temperatures (Room temperature (RT), 77 K and 20 K) and correlate them ...to the microstructures evolved during the joining process. For this purpose, standard full length tensile specimens as well as miniature tensile specimens extracted from different microstructural regions of the joint such as weld nugget zone (WNZ), thermo-mechanically affected zone (TMAZ) and heat-affected zone were used. Similarly, fracture toughness (FT) was evaluated by placing notches at the three microstructurally different regions. The tensile properties at 77 K and 20 K were higher compared to those at room temperature. Miniature tensile specimens extracted from WNZ and TMAZ regions showed similar strength properties; however lower hardness and ductility were observed in TMAZ. Failure of standard full length samples was always in TMAZ since it has lower hardness and ductility, as a result of strain hardening. The higher FT noticed in WNZ is attributed to the presence of very fine grains. The lower FT observed in the TMAZ is attributed to combined effect of the absence of strengthening precipitates and recrystallization. Comparison of the mechanical properties of AA2219-T87 FSW and TIG weld joints revealed superior tensile properties at room and cryogenic temperatures for FSW weld joints, thus making FSW, a better alternative for the fabrication of large sized earth storable and cryogenic propellant tanks of satellite launch vehicles.
In this paper, we present an approach for reconstruction of an impact load time history on structures by formulating the associated inverse analysis as a constraint optimization problem by minimizing ...the error between measured data and predicted data obtained from the forward analysis. The identification process is carried out by solving the formulated constraint optimization problem associated with the inverse analysis of impact load reconstruction. A newly developed hybrid adaptive differential search with dynamic interaction is employed for solving the complex constrained nonlinear multimodal optimization problem. The proposed variant of the differential search technique employs small multiple populations which perform the search independently and exchange the information with the dynamic neighbourhood. The adaptive features and local search ability features are built into the algorithm in order to improve the convergence characteristics of the technique. The constraint optimization formulations can considerably improve the robustness of the inverse problem associated with reconstruction of the impact load. Numerical simulation studies presented to demonstrate the effectiveness of the proposed approach indicate that it can precisely identify the spatial location of the impact load on the structure as well as the impact load time history even in the presence of measurement noise.
Active control devices can be implemented on seismically excited high rise buildings using appropriate active control theory, to reduce structural responses to a desired level. Certain locations of ...the structure are advantageous for placement of actuators in the sense that these locations effectively reduce the structural responses. Hence, optimal placement of actuators at discrete locations is an important problem that will have significant impact on control of civil structures like high rise buildings, bridges, etc. This optimal placement problem leads to a combinatorial optimisation and is difficult to solve.
This paper presents a multi-start meta-heuristic algorithm called multiple start guided neighbourhood search (MSGNS) algorithm, which makes use of the good features of guided local searches like simulated annealing (SA) and tabu search (TS). Four distinct design criteria which influence the active control design are considered in this paper to study the optimal actuator placement problem. The sensitivities of the four optimisation criteria with respect to different earthquake records are explored. Further, in this paper, we deviate from the usual practice of using shear building models (or simple lumped mass model) in active control research for finding optimal actuator locations. Instead, we use detailed finite element models and demonstrate through numerical examples their effectiveness in arriving at the optimal actuator locations. Finally, the superior performance of the proposed MSGNS algorithm over popular meta-heuristic algorithms like GA, SA and TS is demonstrated through numerical experiments.
Cinnamomum zeylanicum Blume is an important spice and aromatic crop having wide applications in flavoring, perfumery, beverages, and medicines. The steam-distilled volatile oil from cinnamon fruit ...stalks was analyzed with GC and GC-MS. It showed the presence of hydrocarbons (44.7%) and oxygenated compounds (52.6%). Twenty-seven compounds constituting ca. 95.98% of the volatile oil were characterized. (E)-Cinnamyl acetate (36.59%) and (E)-caryophyllene (22.36%) are found to be major compounds. The volatile oil was screened for its potential as an antioxidant by using in vitro models, such as the β-carotene-linoleate and phosphomolybdenum complex method. The volatile oil showed 55.94% and 66.9% antioxidant activity at 100 and 200 ppm concentration, respectively. Also, the volatile oil showed good antioxidant capacity, using the formation of the phosphomolybdenum complex. A comparison of the chemical composition of the volatile oil was made with that of buds, flowers, and fruits. This is the first report on the chemical composition of volatile oil of the fruit stalks of this species and its antioxidant activity.
The reaction of (p-cymene)RuCl22 and Cp*MCl22 (M = Rh/Ir) with chelating ligand 2-pyridyl cyanoxime {pyC(CN)NOH} leads to the formation of neutral oximato complexes having the general formula ...(arene)M{pyC(CN)NO}Cl {arene = p-cymene, M = Ru, (1); Cp*, M = Rh (2); Cp*, M = Ir (3)}. Whereas the reaction of 2-pyridyl phenyloxime {pyC(Ph)NOH} and 2-thiazolyl methyloxime {tzC(Me)NOH} with precursor compounds afforded the cationic oxime complexes bearing formula (arene)M{pyC(ph)NOH}Cl+ and (arene)M{tzC(Me)NOH}Cl+ {arene = p-cymene M = Ru, (4), (7); Cp*, M = Rh (5), (8); Cp*, M = Ir (6), (9)}. The cationic complexes were isolated as their hexafluorophosphate salts. All these complexes were fully characterized by analytical, spectroscopic and X-ray diffraction studies. The molecular structures of the complexes revealed typical piano stool geometry around the metal center within which the ligand acts as a NN′ donor chelating ligand. The Chemo-sensitivity activities of the complexes evaluated against HT-29 (human colorectal cancer), and MIAPaCa-2 (human pancreatic cancer) cell line showed that the iridium-based complexes are much more potent than the ruthenium and rhodium analogues. Theoretical studies were carried out to have a deeper understanding about the charge distribution pattern and the various electronic transitions occurring in the complexes.
Reaction of strongly electron withdrawing cyano substituted pyridyl oxime with metal precursor afforded the neutral oximato metal complexes due to the deprotonation of the oxime hydrogen whereas reaction of weakly electron donating substituted phenyl and methyl oximes yielded cationic oxime complexes. The iridium complexes were found to be more active against MIAPaCa-2 cancer cell line. Display omitted
•Neutral oximato and cationic oxime complexes of Ru, Rh and Ir are isolated with substituted pyridyl oximes.•DFT calculations demonstrate that the calculated values are in good agreement with the experimental data.•Iridium based oximato and oxime complexes exhibited better activity than ruthenium and rhodium complexes.
Calcium phosphate bioceramics and bioceramic composites Pattanayak, Deepak K.; Rao, B. T.; Mohan, T. R. Rama
Journal of sol-gel science and technology,
09/2011, Letnik:
59, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
This paper reviews selected aspects of research work carried out in bioceramics and bioceramic composites at the Ceramics Laboratory IIT, Bombay, India. The focus here is in understanding and ...developing calcium hydroxyapatite (HA) bioceramics and biocomposites, including calcium hydroxyapatite-titanium (HA-Ti) and calcium hydroxyapatite-polymethylmethacrylate (HA-PMMA). Research involving apatite-wollastonite (AW) bioglass ceramics and bioceramic composites of AW with titanium as well as with polymethylmethacrylate will be presented in a future article. HA powders were precipitated from solutions with varying Ca/P ratios and calcined at a range of temperatures to investigate their structural evolution. HA-Ti composites were prepared by powder metallurgical processes using HA powders calcined at 400 °C, followed by compaction at 600 MPa and subsequent sintering at 1,000–1,200 °C. HA-PMMA composites containing up to 40 wt% PMMA were prepared by hot pressing at 150 °C and 150 MPa pressure. The phases present in the various materials were identified by X-ray diffraction (XRD) and functional groups by FTIR, while the sample morphologies were investigated by SEM. The bioactivity of the composites was evaluated by soaking them in simulated body fluid (SBF) for 7 days, to evaluate their apatite-forming ability (a key indicator of bioactivity). The results obtained are interpreted to aid in the development of “design rules” for the use of such biocomposite materials in specific biomedical application.
In the present manuscript, the characterisation was done on liquid crystalline n-hexyloxycyanobiphenyl (6ocb) compound with dispersed citrate-capped gold nanoparticles (Au NPs) at different ...concentrations. It is observed that the birefringence enhances with increase in concentration of Au NPs. Also, strong Vander Waal's interaction takes place due to well capping between the Au NPs and 6ocb molecules. The refractive indices are determined by using modified spectrometer at different wavelengths. The orientational order parameter has been determined from various theoretical molecular internal field models namely, Kuczynski, Effective geometry, Haller's extrapolation and Vuks. The dispersive power ω is estimated for two consecutive wavelengths for the case of , n
e
and n
o
at different wavelengths found to be constant with temperature. The values of cross-over temperature, T
CO
determined from the temperature gradients of n
e
and n
o
. Further, the refractive indices measured are fitted with two and three coefficient Cauchy model. Three coefficient Cauchy model is favourable than two coefficient Cauchy model for high birefringence liquid crystals. The results obtained are compared and discussed. Further, the phase transitions can be easily identified by GMSD Image processing method with Matlab tool to reduce the costly equipment's usage in finding the heat flow with respect to temperature.
Power transformers represent one of the most abundant and expensive components in the electric power industry. Dissolved gas analysis (DGA) of transformer is the most widely accepted diagnostic tool ...across the globe to understand insulation incipient failures. Nevertheless, DGA fault gas interpretation is a remarkable challenge for transformer owners and utility engineers. Several computational techniques have been adopted for DGA fault classification along with offline methods. However, limited data availability, high ambiguity in DGA interpretation, suitability, and model accuracy are critical challenges in the DGA fault classification using computational techniques. In this work, highly diverse and large DGA data samples of in-service transformer fleets from five different utilities have been used to develop an efficient fault classification methodology. A total of 4580 DGA samples and IEC TC 10 database are used for training and testing, respectively, for various machine learning algorithms. Discussions on performance indicators and evaluation of several algorithms to verify the most suitable class algorithms are also the focus of this work. Furthermore, a best-performing model is identified based on various performance indicators. The hyperparameters of the best model are further tuned to achieve a most precise fault classification. It is inferred that non-parametric methods and non-linear SVM are best suitable for transformer DGA fault classification. Importantly, the rankings in the present study suggest that transformer DGA fault prediction is better with ensemble learning methods.
Cholesterol, in addition to providing rigidity to the fluid membrane, plays a critical role in receptor function, endocytosis, recycling, and signal transduction. In the present study, we examined ...the effect of membrane cholesterol on functional expression of tissue factor (TF), a cellular receptor for clotting factor VIIa. Depletion of cholesterol in human fibroblasts (WI-38) with methyl-β-cyclodextrin–reduced TF activity at the cell surface. Binding studies with radiolabeled VIIa and TF monoclonal antibody (mAB) revealed that reduced TF activity in cholesterol-depleted cells stems from the impairment of VIIa interaction with TF rather than the loss of TF receptors at the cell surface. Repletion of cholesterol-depleted cells with cholesterol restored TF function. Loss of caveolar structure on cholesterol removal is not responsible for reduced TF activity. Solubilization of cellular TF in different detergents indicated that a substantial portion of TF in fibroblasts is associated with noncaveolar lipid rafts. Cholesterol depletion studies showed that the TF association with these rafts is cholesterol dependent. Overall, the data presented herein suggest that membrane cholesterol functions as a positive regulator of TF function by maintaining TF receptors, probably in noncaveolar lipid rafts, in a high-affinity state for VIIa binding.
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