A new methodology is presented for (a) detecting, (b) locating, and (c) quantifying the damage severity in a smart highrise building structure. The methodology consists of three steps: In step 1, the ...synchrosqueezed wavelet transform is used to eliminate the noise in the signals. In step 2, a nonlinear dynamics measure based on the chaos theory, fractality dimension (FD), is employed to detect features to be used for damage detection. In step 3, a new structural damage index, based on the estimated FD values, is proposed as a measure of the condition of the structure. Further, the damage location is obtained using the changes of the estimated FD values. Three different FD algorithms for computing the fractality of time series signals are investigated. They are Katz's FD, Higuchi's FD, and box dimension. The usefulness and effectiveness of the proposed methodology are validated using the sensed data obtained experimentally for the 1:20 scaled model of a 38-storey concrete building structure.
The progressive stacking of chalcogenide single layers gives rise to two- dimensional semiconducting materials with tunable properties that can be exploited for new field-effect transistors and ...photonic devices. Yet the properties of some members of the chalcogenide family remain unexplored. Indium selenide （InSe） is attractive for applications due to its direct bandgap in the near infrared, controllable p- and n-type doping and high chemical stability. Here, we reveal the lattice dynamics, optical and electronic properties of atomically thin InSe flakes prepared by micromechanical cleavage. Raman active modes stiffen or soften in the flakes depending on which electronic bonds are excited. A progressive blue-shift of the photoluminescence peaks is observed for decreasing flake thickness （as large as 0.2 eV for three single layers）. First-principles calculations predict an even larger increase in the bandgap, 0.40 eV, for three single layers, and as much as 1.1 eV for a single layer. These results are promising from the point of view of the versatility of this material for optoelectronic applications at the nanometer scale and compatible with Si and III-V technologies.
•A new methodology for modal parameter identification of large civil structures.•It uses MUSIC-EWT algorithm and Hilbert transform.•It is applied to a 123-story highrise building structure, Lotte ...World Tower.•It is effective for modal parameter identification of superhighrise structures.•It can deal with noisy signals.
A key issue in health monitoring of smart structures is the estimation of modal parameters such as natural frequencies and damping ratios from acquired dynamic signals. In this article, a new methodology is presented for calculating the natural frequencies (NF) and damping ratios (DR) of large civil infrastructure from acquired dynamic signals using a multiple signal classification (MUSIC) algorithm, the empirical wavelet transform (EWT), and the Hilbert transform. The effectiveness of the proposed method is validated by means of three examples: a benchmark 3D 4-story steel frame structure, a benchmark problem, subjected to dynamic loading, an 8-story steel frame subjected to white noise input on a shaking table, and a 123-story highrise building structure, Lotte World Tower (LWT), under construction in Seoul, South Korea. The results demonstrate that the new methodology is accurate for estimating the NF and DR of a superhighrise building structure using low-amplitude ambient vibrations data, a complex and challenging task since the measured vibrations signals are noisy and present non-stationary characteristics. The new methodology can deal with noisy signals without degrading its ability to estimate the NF and DR of different one-of-a kind civil structures thus is particularly suitable for health monitoring of large smart structures under dynamic loading.
An unusual spectrally reproducible near‐IR random lasing (RL) with no fluctuation of lasing peak wavelength is disclosed in polycrystalline films of formamidinium tin triiodide perovskite, which have ...been chemically stabilized against Sn2+ to Sn4+ oxidation. Remarkably, a quality Q‐factor as high as ≈104 with an amplified spontaneous emission (ASE) threshold as low as 2 µJ cm−2 (both at 20 K) are achieved. The observed spectral reproducibility is unprecedented for semiconductor thin film RL systems and cannot be explained by the strong spatial localization of lasing modes. Instead, it is suggested that the spectral stability is a result of such an unique property of Sn‐based perovskites as a large inhomogeneous broadening of the emitting centers, which is a consequence of an intrinsic structural inhomogeneity of the material. Due to this, lasing can occur simultaneously in modes that are spatially strongly overlapped, as long as the spectral separation between the modes is larger than the homogeneous linewidth of the emitting centers. The discovered mechanism of RL spectral stability in semiconductor materials, possessing inhomogeneous broadening, opens up prospects for their practical use as cheap sources of narrow laser lines.
Highly spectrally reproducible multimode random lasing is observed in thin polycrystalline films of tin iodide perovskite that cannot be explained by a strong mode localization. The observed spectral reproducibility can be due to the strong inhomogeneous broadening of photoluminescence spectra measured in tin‐based perovskites on the basis of a comparison with an analogous Pb‐based counterpart.
Surface engineering of nanomaterials is a promising tool towards the design of new materials for conversion of solar energy into chemical energy. In this work, we examine the influence of ligand ...exchange on the photocatalytic performance of solution-processed PbS films. We test different ligands such as oleylamine (OAm), 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The study demonstrates that PbS films capped with MPA and EDT exhibit 3.5-fold enhanced photocatalytic performance for the photodecomposition of methyl orange upon sunlight exposure. Both band energy alignment and charge carrier transport have a strong impact on the generation of reactive oxygen species (ROS), which play a key role in the photodecomposition process. Moreover, the stability and reusability of the photocatalysts are clearly improved after ligand exchange. We prove how both MPA and EDT provide much more stability to PbS QD films to operate very efficiently up to 8 cycles of photocatalysis. As observed in XPS, the oxidation of PbS is prevented after ligand exchange. We demonstrate how surface chemistry engineering of solution-processed QD films can open a new approach towards the design of highly efficient and stable visible-light-driven photocatalysts, which paves the way to low cost and large area fabrication of high-performance photocatalytic devices.
Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with ...tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density.
Abstract
Hybrid organometal halide perovskites (HP) present exceptional optoelectronic properties, but their poor long‐term stability is a major bottleneck for their commercialization. Herein, a ...solvent‐free approach to growing single‐crystal organic nanowires (ONW) is presented, along with nanoporous metal oxide scaffolds and HP, to form a core@multishell architecture. The synthesis is carried out under mild vacuum conditions employing thermal evaporation for the metal‐free phthalocyanine (H
2
Pc) nanowires, which are the core, plasma‐enhanced chemical vapor deposition (PECVD) for the TiO
2
shell, and co‐evaporation of lead iodide (PbI
2
) and methylammonium iodide (CH
3
NH
3
I/MAI) for the CH
3
NH
3
PbI
3
(MAPbI
3
/MAPI) perovskite shell. A detailed characterization of the nanostructures by electron microscopy, (S)‐TEM, and X‐ray diffraction, XRD, is presented, revealing a different crystallization of the HP depending on the template: while the growth on H
2
Pc nanowires induces the typical MAPI tetragonal structure, a low‐dimensional phase (LDP) is observed on the 1D‐TiO
2
nanotubes. Such a combination yields an unprecedentedly stable photoluminescence emission over 20 h and over 300 h after encapsulation in polymethyl methacrylate (PMMA) under different atmospheres including N
2
, air, and high moisture levels. Moreover, the unique 1D morphology of the system, together with the high refractive index, allows for a strong waveguiding effect along the HP nanowire length.
AbstractAlcohol-related liver disease (ALD) is a major cause of advanced chronic liver disease in Latin-America, although data on prevalence is limited. Public health policies aimed at reducing the ...alarming prevalence of alcohol use disorder in Latin-America should be implemented. ALD comprises a clinical-pathological spectrum that ranges from steatosis, steatohepatitis to advanced forms such as alcoholic hepatitis (AH), cirrhosis and hepatocellular carcinoma. Besides genetic factors, the amount of alcohol consumption is the most important risk factor for the development of ALD. Continuous consumption of more than 3 standard drinks per day in men and more than 2 drinks per day in women increases the risk of developing liver disease. The pathogenesis of ALD is only partially understood and recent translational studies have identified novel therapeutic targets. Early forms of ALD are often missed and most clinical attention is focused on AH, which is defined as an abrupt onset of jaundice and liver-related complications. In patients with potential confounding factors, a transjugular biopsy is recommended. The standard therapy for AH (i.e. prednisolone) has not evolved in the last decades yet promising new therapies (i.e. G-CSF, N-acetylcysteine) have been recently proposed. In both patients with early and severe ALD, prolonged abstinence is the most efficient therapeutic measure to decrease long-term morbidity and mortality. A multidisciplinary team including alcohol addiction specialists is recommended to manage patients with ALD. Liver transplantation should be considered in the management of patients with end-stage ALD that do not recover despite abstinence. In selected cases, increasing number of centers are proposing early transplantation for patients with severe AH not responding to medical therapy.
Sanchez-Aguilera and Quintanilla discuss sharp wave ripples in Alzheimer's disease (AD). AD is the most common cause of dementia. The disease is associated with the presence of plaques and ...neurofibrillary tangles in the brain which leads to synaptic and neuronal degeneration and progressive learning and memory impairment. Work of the last decades has produced a variety of diagnostic tools and treatment alternatives, yet the mechanisms underlying the disease are poorly understood, and interventions are still minimally effective, possibly in part because they are started after irreversible damage has been done.
ABSTRACT
Manuscript Type: Review
Research Question/Issue: The goal of this paper is to meta‐analyze the results of 35 studies that examine the effect on earnings management of firms' boards of ...directors and ownership structure. We examine whether differences in results are attributable to moderating effects related to the system of corporate governance, the measurement of the governance variable, or the particular specifications of discretionary accruals models.
Research Findings/Insights: The findings show that the variation in the results of previous studies on CEO duality and audit committee independence are caused by sampling error. In addition, the measurement of dependent variable, discretionary accruals, and the corporate governance system moderate the association between earnings management and some corporate governance variables.
Theoretical/Academic Implications: The measurement of variables, especially discretionary accruals, influences the findings found in previous studies. The findings emphasize the need to explicitly consider the legal and institutional setting when one analyzes the effect of mechanisms of corporate governance on discretionary accruals. Future research should include matrix correlations, and consider detailed measures of earnings management and more attributes of boards of directors in order to facilitate research using meta‐analysis.
Practitioner/Policy Implications: The results suggest that board independence, board size, and audit committee independence can improve investor confidence by constraining earnings management. Additional empirical evidence regarding refined measures of ownership and board, specifically board independence, would be very useful in gaining greater understanding of how the different approaches to these constructs influence earnings management.
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