Justification of the Asymptotic Expansion Method for Homogeneous Isotropic Beams by Comparison with De Saint-Venant’s Solutions

The formal asymptotic expansion method is an attractive mean to derive simplified models for problems exhibiting a small parameter, such as the elastic analysis of beam-like structures. Usually this method is rigorously justified using convergence theorems Yu and Hodges, 2004. In this paper it is illustrated how the Saint-Venant’s solution naturally arises from the lowest order terms of an asymptotic expansion of the elastic state for the case of homogeneous isotropic beams. It is also highlighted that the Saint-Venant solutions corresponding to pure traction, bending and torsion involve the solution of the first-order microscopic problems, while for the simple bending problem, the solution of the second-order microscopic problems is needed. The second-order problems provide therefore a way to characterize the transverse shear behavior and the cross-sectional warping of the beam.     

Thermomechanical Properties of Carbon Nanocomposites PEGDA Photopolymers

In this work, UV-curable resin poly (ethylene glycol) diacrylate (PEGDA) was reinforced with three different types of nanofillers: pristine graphene (G), multiwalled carbon nanotubes (MWNTs), and a hybrid of MWNTs and graphene 70/30 in mass ratio (Hyb). PEGDA was mixed homogenously with the nanofiller oligomer by shear mixing and then photopolymerized, affording thin, stable films. The thermomechanical properties of the afforded nanocomposites indicated the superior reinforcing ability of pristine graphene compared with MWNTs and an intermediate behavior of the hybrid.     

Discovery of 5-Methylthiazole-Thiazolidinone Conjugates as Potential Anti-Inflammatory Agents: Molecular Target Identification and In Silico Studies

A series of previously synthesized 5-benzyliden-2-(5-methylthiazole-2-ylimino)thiazoli- din-4-one were evaluated for their anti-inflammatory activity on the basis of PASS predictive outcomes. The predictive compounds were found to demonstrate moderate to good anti-inflammatory activity, and some of them displayed better activity than indomethacin used as the reference drug. Structure–activity relationships revealed that the activity of compounds depends not only on the nature of the substituent but also on its position in the benzene ring. The most active compounds were selected to investigate their possible mechanism of action. COX and LOX activity were determined and found that the title compounds were active only to COX-1 enzymes with an inhibitory effect superior to the reference drug naproxen. As for LOX inhibitory activity, the derivatives failed to show remarkable LOX inhibition. Therefore, COX-1 has been identified as the main molecular target for the anti-inflammatory activity of our compounds. The docking study against COX-1 active site revealed that the residue Arg 120 was found to be responsible for activity. In summary, the 5-thiazol-based thiazolidinone derivatives have been identified as a novel class of selective COX-1 inhibitors.     

A Generalized Information-Theoretic Framework for the Emergence of Hierarchical Abstractions in Resource-Limited Systems

In this paper, a generalized information-theoretic framework for the emergence of multi-resolution hierarchical tree abstractions is developed. By leveraging ideas from information-theoretic signal encoding with side information, this paper develops a tree search problem which considers the generation of multi-resolution tree abstractions when there are multiple sources of relevant and irrelevant, or possibly confidential, information. We rigorously formulate an information-theoretic driven tree abstraction problem and discuss its connections with information-theoretic privacy and resource-limited systems. The problem structure is investigated and a novel algorithm, called G-tree search, is proposed. The proposed algorithm is analyzed and a number of theoretical results are established, including the optimally of the G-tree search algorithm. To demonstrate the utility of the proposed framework, we apply our method to a real-world example and provide a discussion of the results from the viewpoint of designing hierarchical abstractions for autonomous systems.     

Microstructure-driven annihilation effects and dispersive excited state dynamics in solid-state films of a model sensitizer for photon energy up-conversion applications

Bimolecular processes involving exciton spin-state interactions gain attention for their deployment as wavelength-shifting tools. Particularly triplet–triplet annihilation induced photon energy up-conversion (TTA-UC) holds promise to enhance the performance of solar cell and photodetection technologies. Despite the progress noted, a correlation between the solid-state microstructure of photoactuating TTA-UC organic composites and their photophysical properties is missing. This lack of knowledge impedes the effective integration of functional TTA-UC interlayers as ancillary components in operating devices. We here investigate a solution-processed model green-to-blue TTA-UC binary composite. Solid-state films of a 9,10 diphenyl anthracene (DPA) blue-emitting activator blended with a (2,3,7,8,12,13,17,18-octaethyl-porphyrinato) Pt^II (PtOEP) green-absorbing sensitizer are prepared with a range of compositions and examined by a set of complementary characterization techniques. Grazing incidence X-ray diffractometry (GIXRD) measurements identify three PtOEP composition regions wherein the DPA:PtOEP composite microstructure varies due to changes in the packing motifs of the DPA and PtOEP phases. In Region 1 (≤2 wt%) DPA is semicrystalline and PtOEP is amorphous, in Region 2 (between 2 and 10 wt%) both DPA and PtOEP phases are amorphous, and in Region 3 (≥10 wt%) DPA remains amorphous and PtOEP is semicrystalline. GIXRD further reveals the metastable DPA-β polymorph species as the dominant DPA phase in Region 1. Composition dependent UV-vis and FT-IR measurements identify physical PtOEP dimers, irrespective of the structural order in the PtOEP phase. Time-gated photoluminescence (PL) spectroscopy and scanning electron microscopy imaging confirm the presence of PtOEP aggregates, even after dispersing DPA:PtOEP in amorphous poly(styrene). When arrested in Regions 1 and 2, DPA:PtOEP exhibits delayed PtOEP fluorescence at 580 nm that follows a power-law decay on the ns time scale. The origin of PtOEP delayed fluorescence is unraveled by temperature- and fluence-dependent PL experiments. Triplet PtOEP excitations undergo dispersive diffusion and enable TTA reactions that activate the first singlet-excited (S₁) PtOEP state. The effect is reproduced when PtOEP is mixed with a poly(fluorene-2-octyl) (PFO) derivative. Transient absorption measurements on PFO:PtOEP films find that selective PtOEP photoexcitation activates the S₁ of PFO within ∼100 fs through an up-converted ³(d, d^*) Pt^II-centered state.

Dispersive diffusion and annihilation of excitations in the amorphous aggregate phase of a square-planar PtOEP sensitizer in the solid state result in the activation of delayed PtOEP fluorescence through an up-converted Pt^II-centered state.     

Stochastic synchronization of rotating parametric pendulums

In this paper synchronization of two pendulums mounted on a mutual elastic single degree-of-freedom base is examined. The response of the pendulums is considered when their base is externally excited by a random phase sinusoidal force, thus leading to stochastic parametric excitation of the pendulums. The target is for the pendulums to establish and preserve rotary response since this study is motivated by a recently proposed ocean wave energy extraction concept where the heaving motion of waves excites a pendulum’s hinge point. Since the wave bobbing motion is random the system’s excitation is modelled as a narrow-band stochastic process. Mounting two pendulums on the same elastic base creates a coupling between them through their interaction with the base, providing a path for energy exchange between them. The dynamic response of the pendulums is numerically investigated with respect to establishment of rotations as well as identification of synchronization with the pendulums characteristics spanning along non-identical parameters.     

Maximal solutions and universal bounds for some partial differential equations of evolution

Communicated by C. Dafermos     

Optimal and Heuristic Procedures for Row Layout Problems in Automated Manufacturing Systems

In many automated manufacturing environments, particularly flowlines and flexible manufacturing systems (FMSs), machines are arranged along a straight material handling track with a material handling device moving jobs from one machine to aother. These layouts are referred to as row machine layouts. In this paper we study the Row Layout Problem (RLP) under the design objective of minimizing the total backtracking distance of the material handling device, which is a NP-complete problem. We propose the use of a dynamic programming algorithm for its solution. Special cases of the problem, usually encountered in flexible manufacturing cells and which can be solved with polynomial procedures, are also discussed. For the equidistant case (i.e., successive candidate locations are in equal distances), we formulate the problem as an integer linear program. The use of standard mathematical programming codes can efficiently solve this formulation. Two effective heuristic procedures, which explore simple ideas based on local optimality conditions, are also presented. Extensive computational results demonstrate the effectiveness of such heuristics.     

Bounds on enhanced turbulent flame speeds for combustion with fractal velocity fields

Rigorous upper bounds are derived for large-scale turbulent flame speeds in a prototypical model problem. This model problem consists of a reaction-diffusion equation with KPP chemistry with random advection consisting of a turbulent unidirectional shear flow. When this velocity field is fractal with a Hurst exponentH with 0<H<1, the almost sure upper bounds suggest that there is an accelerating large-scale turbulent flame front with the enhanced anomalous propagation lawy=C _H t ^1+H for large renormalized times. In contrast, a similar rigorous almost sure upper bound for velocity fields with finite energy yields the turbulent flame propagation law within logarithmic corrections. Furthermore, rigorous theorems are developed here which show that upper bounds for turbulent flame speeds with fractal velocity fields are not self-averaging, i.e., bounds for the ensemble-averaged turbulent flame speed can be extremely pessimistic and misleading when compared with the bounds for every realization.     

Structural and magnetic evidence concerning spin crossover in formamidinate compounds with ru2 5+ cores

The magnetic and structural properties of two Ru2(DArF)4Cl compounds, where DArF is the anion of a diaryl formamidine, are presented here. The compounds with Ar = p-anisyl and m-anisyl both show temperature dependence of chiT (chi = molar magnetic susceptibility), but for different reasons. For the para compound, there is a Boltzmann distribution between a pi*3 ground state and a delta*pi*2 upper state, and this is confirmed by a temperature dependence of the Ru-Ru bond length: 2.4471(5) A at 23 K and 2.3968(5) A at 300 K. For the meta compound, a delta*pi*2 configuration persists over the range of 23-300 K as shown by an invariant Ru-Ru bond length, but the chiT drops with decreasing temperature owing to zero-field splitting of a 4B2u ground state.