A complex eigenvector is a result of nonproportional damping present in a structural system. However, it is difficult to identify the accurate damping matrix considering the modal sparsity and ...coordinate sparsity. A nonproportional viscous damping parameter identification is formulated as an unconstrained optimization problem in the present study. The damping coefficient of each element is considered as the design variable for the optimization problem. The objective function is defined using the incomplete complex eigenvectors, which are generated because of the presence of external damping devices in the structure. This objective function is then minimized using standard particle swarm optimization to identify the damping coefficient of the damping matrix. The accuracy and efficiency of the particle swarm optimization are investigated by solving a few numerical problems with simulated measured data. The proposed method works well with the incomplete measured modal data. The current methodology performs satisfactorily with and without noisy data. A comparison study is performed with the existing gradient-based method, and the results show that the proposed method performs better than the existing gradient-based method for the present problem with and without noisy measurement data.
A methodology has been proposed to estimate non-proportional viscous damping matrix of beams from measured complex eigendata using finite element model updating technique. Representation of damping ...through a proportional damping matrix ignoring the complexity of eigenvectors may not be appropriate when external damping devices are employed. The current literature of determination of non-proportional damping matrix demands measurement of a large number of complex modes which is extremely difficult in practice. A gradient based finite element model updating algorithm implementing inverse eigensensitivity method has been presented through a series of numerically simulated cantilever beams. The method can accurately predict the non-proportional damping matrix even if the measured eigenvectors are polluted with random noise. The novelty of the current method is that it can sustain a high level of modal and coordinate sparsity in measurement. The method assumes prior determination or updating of the mass and stiffness matrices.
Recently, the use of sandwich composites in different fields of engineering such as aerospace, marine, automobile, pipelines, bridge structure, industrial work, has attracted significant attention. ...Sensitivity analysis of structures made of sandwich composites is necessary to design them properly and maintain their longevity. The present study analyzes stiffened sandwich composite bridge deck panels and focuses on its sensitivity analysis. The lack of control in the manufacturing of the sandwich composites may lead to non-uniform material properties, and thus variation in its behavior. The variation in the dynamic responses obtained through the free vibration analysis of the bridge deck panel models of stiffened composites due to is studied. The free vibration analysis is implemented using a finite element method. The analysis is carried out with the stiffeners located in different positions and alignments. The glass fiber-reinforced plastic (GFRP) and polyvinyl semi-rigid foam are considered in the face and core layer for modeling the deck panels, respectively. The sensitivity of the bridge deck panels is also observed with the presence of holes of different diameters in the core layer of the sandwich composite plate without stiffeners and with a transverse stiffener. It has been noticed that dynamic response, i.e. the eigenvalue, is sensitive concerning the in-plane parameters of the face layers compared to other parameters. Moreover, an increase in the size of the hole in the core layer results in a decrease in the dynamic response of the stiffened sandwich composite bridge deck panel. The knowledge of the sensitivity of the sandwich composites will be helpful to update the model and also to design the bridge deck for better performance and improved longevity.
The first atroposelective desymmetrization of prochiral N-aryl maleimides through its conversion to axially chiral phthalimides is developed by applying a de novo arene construction strategy. ...Catalyzed by bis(3,5-dimethylphenyl)prolinol TMS-ether, this reaction proceeds through oxidative 4 + 2-cycloaddition with α,β-unsaturated aldehydes to generate only a chiral C–N axis remote from the reaction sites with excellent enantioselectivity (up to 97.5:2.5 er).
Background
The physiological significance of a large family of heat-shock proteins (HSPs), comprised of the cytosolic HSP90A and the endoplasmic reticulum component of HSPB, is evident in prokaryotes ...and eukaryotes. The HSP90A is believed to play critical roles in diverse physiological functions of cell viability and chromosomal stability including stress management. Heightened abundance of
hsp90β
transcript was documented in
Channa striatus
, a freshwater fish, which is capable of surviving within an extremely hypoxic environment.
Methods and results
To better understand the mechanism of
hsp90β
gene expression, we investigated its genomic organization. Eleven exons were identified, including a long upstream intron with a remarkable similarity with human, but not with chicken counterpart. Dual-luciferase assays identified promoter activity in a 1366 bp 5′-flanking segment beyond the transcription initiation site. Examination detected a minimal promoter of 754 bp containing a TATA-box, CAAT-enhancer in addition to providing clues regarding other enhancer and repressor elements. The driving capability of this minimal promoter was further validated by its binding ability with TATA-box binding protein and the generation of GFP expressing transgenic zebrafish (F
2
). Further, deletion of an inverted HIF (hypoxia inducible factor) motif RCGTG (upstream of the TATA-box) dramatically reduced luciferase expression in a hypoxic environment (CoCl
2
treated cultivable cells) and was identified as a
cis
-acting HIF responsive element, necessary for the hypoxia-induced expression.
Conclusions
The results obtained herein provide an insight regarding how
hsp90β
gene expression is controlled by HIF responsive element in teleost both during hypoxia stress management and normal physiological functions, and suggested that the
hsp90β
gene promoter could be used as a potential candidate for generating ornamental and food-fish transgenics.
Ladderane phospholipids, with their unusual ladder‐like arrangement of concatenated cyclobutane rings, represent an architecturally unique class of natural products. However, despite their ...fascinating structure and other necessary impetus, only a few synthetic studies of these molecules have been reported so far. We have now devised a concise total synthesis of 3‐ladderanol, a component of natural ladderane phospholipids, using an organocatalytic enantioselective desymmetrizing formal C(sp2)−H alkylation. Our synthetic strategy rests on the late‐stage introduction of chirality, thus allowing facile access to both enantiomers of 3‐ladderanol as well as an analogue. This is the first time a desymmetrization strategy is applied to the synthesis of 3‐ladderanol. The scope of this desymmetrizing C(sp2)−H alkylation of meso‐cyclobutane‐fused cyclohexenediones is also presented.
An enantioselective desymmetrization route to 3‐ladderanol has been devised that is centered around an organocatalytic enantioselective formal C(sp2)−H alkylation of tetracyclic meso‐cyclohexenedione. This strategy involving the late‐stage introduction of chirality offers flexibility and enabled the facile synthesis of both enantiomers of 3‐ladderanol as well as an analogue.
The use of cement in construction causes large amounts of CO2 emissions into the atmosphere. Moreover, the use of large amounts of natural coarse aggregate causes environmental damage, and the ...availability of such natural aggregate is also depleting. The present experimental study explores and optimizes the impact of various parameters on the fresh, mechanical, and durability properties of recycled waste concrete coarse aggregate (RWCA)-based geopolymer concrete (GPC) in combination with ground-granulated blast furnace slag (GGBFS) and fly ash (FA) using the Taguchi-Grey Relational Analysis Method (TGRAM). The coarse aggregates in GPC were fully replaced with RWCA produced by crushing waste concrete. The effects of FA inclusion (%), Na2SiO3/NaOH ratio (SS/SH), molarity of NaOH (SH), dosages of superplasticizer (%), and alkaline solution to binder (Al/Bi) ratio are investigated under ambient curing conditions. The obtained maximum compressive strength and split tensile strength along with minimum water absorption of GPC at 28 days were 67.90 MPa, 3.85 MPa and 2.92 % respectively. The microstructural studies of GPC having low, high, and optimal strength are carried out using XRD, FE-SEM, and EDAX analysis. These studies confirmed the presence of calcium-based hydration products such as CSH and N(C)ASH, which makes the matrix of optimized GPC more compact.
•This paper explores and optimizes the mix composition of GGBFS-FA based GPC using TGRAM.•FA inclusion had a dominant effect on flow value, mechanical strength, and water absorption of GPC.•Microstructure analysis shows the presence of N-(C)-S-H and C-S-H-based hydration products in GPC.•Confirmation test on optimized GPC confirmed competence of TGRAM.
Laboratory experiments were conducted to evaluate the ability of peracetic acid (PAA-containing 10% hydrogen peroxide by weight in equilibrium) to reduce subsequent chlorination disinfection ...by-product (DBP) formation (trihalomethanes, haloacetic acids, and adsorbable organic halides) in raw and post-filtered water collected from four Canadian utilities over a typical pH range. A 5 mg L
−1
PAA/H
2
O
2
(mixture) dose decreased DBP formation potential by up to 40%. It was also observed that H
2
O
2
is more effective than PAA for reducing DBPs on a per mg L
−1
basis, however, at a 10% (mass) fraction of H
2
O
2
in a PAA/H
2
O
2
mixture (typical of commercial products), the poorer reactivity of PAA is compensated for by its higher concentration and is the dominant factor leading to DBP minimization. PAA solution was more effective in reducing DBP formation potential at a higher pH (7.8-8.2) when compared to pH 6.
A 5 mg L
−1
PAA/H
2
O
2
(mixture) pre-oxidation decreased the DBP formation potential by up to 40%.
Bond shear strength is one of the governing characteristics that determines the failure in FRP composite structures and needs investigation. Multi-walled carbon nanotubes (CNTs) have recently gained ...popularity in various structural applications to enhance mechanical properties. The improvement in the bond shear strength of glass fibre-reinforced plastic (GFRP) splices by incorporating different percentages of MWCNTs in the adhesive is experimentally investigated in this study. Experimental results reveal that the optimum amount of MWCNTs results in approximately a 30% increase in bond shear strength. The bond shear strength may vary because of differential splice geometry, material properties, etc., even though the splices are prepared using the same materials and procedures. The current research further investigates the variability in the bond shear strength of lap splices statistically using Goodness-of-fit tests, namely Kolmogorov-Smirnov (K–S), Anderson-Darling (A-D), and Chi-Square (C–S). Appropriate statistical distributions for modelling the variability in the bond shear strength are obtained. The Gumbel Max and Gumbel Min distributions are recommended to model the variability in the bond shear strength of single-lap GFRP splices without MWCNTs and with 0.1% MWCNTs. Knowledge of the variability of the bond shear strength property will help the reliability-based structural analysis of FRP composite structures.
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•Bond shear strength governs the behaviour of GFRP lap splices.•MWCNTs in the lap splice adhesive for performance enhancement.•Significant variability in the performance of GFRP lap splices can be observed.•Goodness-of-Fit tests for modelling variability of bond shear strength.•Appropriate statistical distributions that describe experimental data.
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