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[Display omitted] • S-shaped reinforced cores are designed by flattening hexagonal honeycomb cores. • S-shaped reinforced structures can effectively change the deformation mode of cores. • The peak load of S-shaped reinforced core can be 86.12% greater than plain core. • Theoretical prediction model of S-shaped reinforced honeycomb cores is proposed. • The design capabilities of cores are expanded because of S-shaped structure. Honeycomb structures serve as the core of sandwich structures in various industries, such as aerospace and rail transit. In this study, a novel design was introduced where hexagonal honeycomb cores were flattened in specific areas to form S-shaped reinforced cores. Compression tests were conducted on S-shaped reinforced honeycomb cores with different rotational structures – left-hand, right-hand, and mixed rotation. The deformation process of these cores was thoroughly investigated. Additionally, a theoretical prediction model was proposed to determine the Young's modulus and peak load of S-shaped reinforced honeycomb cores. The experimental data was compared with the theoretical model to validate its accuracy. Moreover, the study examined the effects of changing the relative density and cell wall angle of S-shaped reinforced honeycomb cores on the peak and specific peak loads. The results demonstrated that the use of S-shaped reinforced structures successfully altered the deformation mode of the honeycomb cores. In particular, the peak loads of S-LL and S-LR specimens were 29.14% and 86.12% higher than that of plain honeycomb, respectively. In summary, increasing the relative density of S-shaped reinforced honeycomb cores proved to enhance the peak load and specific peak load, thereby augmenting the design capabilities of these cores. [ABSTRACT FROM AUTHOR]

In the present study, honeycomb cores with periodic tight zones were proposed for carbon-fiber and aluminum-honeycomb sandwich panels by flattening hexagon-shaped cells of honeycomb walls. In-plane compression tests were performed for sandwich panels with three types of local-tight honeycomb cores to evaluate the effects of the local-tight configurations on mechanical properties and failure modes. Experimental results indicated that the mechanical properties of sandwich specimens were effectively increased by using the proposed local-tight honeycomb cores. In particular, the specific energy absorption of sandwich specimens with a local-orthogonal-tight core was increased by 400.46%. In addition, Digital Image Correlation (DIC) technique was employed to further investigate the compressive behaviors of the sandwich specimens with and without local-orthogonal-tight honeycomb cores. The experimental measurements and detailed DIC observations indicated that the local-orthogonal-tight honeycomb core sandwich structures, which provided improved load transferring paths and reduced mismatch between the high-stiffness face sheets and low-stiffness core, exhibited progressive crushing failure modes. [ABSTRACT FROM AUTHOR]

Grid structures have great potential for engineering application, inspired by the leaf texture, the rectangular grid is innovatively added to the honeycomb to form the grid-honeycomb hybrid core. The low-velocity impact response of the composite sandwich structure with grid–honeycomb hybrid core was investigated by experimental and numerical simulation. Low-velocity impact tests with 30 J energy were conducted of the sandwich panel to analyze the mechanical response and damage morphology at typical locations (intersection, rib, and center). The results show that the impact resistance at the intersection was the strongest, the peak load, damage threshold load, and initial stiffness at the intersection were 14.74%, 15.54%, and 16.06% higher, and the maximum displacement and residual displacement were 12.09% and 33.71% lower, respectively than those at the rib, and the center was the weakest. Compared with honeycomb sandwich panel, the impact resistance of unit mass at the intersection and rib was stronger and the internal damage was smaller. In addition, the parametric study of the structural parameters of sandwich panel was conducted. The grid thickness had a significant effect on the impact resistance, while the effects of honeycomb wall thickness and honeycomb unit cell diameter were smaller and had almost no effect on initial stiffness and energy absorption. Finally, the impact resistance efficiency analysis was performed to obtain the optimal design area of structural parameters to provide design guidance. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present work we demonstrated an ultrasensitive detection platform for specific DNA based on nonlinear hybridization chain reaction (HCR) by triggering chain-branching growth of DNA dendrimers. HCR was initiated by target DNA ( t DNA) and finally formed dendritic structure by self-assembly. The electrochemical signal was drastically enhanced by capturing multiple catalytic peroxidase with high-ordered growth. Electrochemical signals were obtained by measuring the reduction current of oxidized 3, 3′, 5, 5′-tetramethylbenzidine sulfate (TMB), which was generated by HRP in the presence of H 2 O 2 . This method exhibited ultrahigh sensitivity to t DNA with detection limit of 0.4 fM. Furthermore, the biosensor was also capable of discriminating single-nucleotide difference among concomitant DNA sequences. [ABSTRACT FROM AUTHOR]

In the present study, periodical grids were selected to reinforce soft honeycomb cores of sandwich structures. The grid reinforced honeycomb core can be considered as a combined core with multi-level lattice configuration. In-plane compression tests were carried out to investigate the mechanical properties of carbon fiber sandwich with combined core. Experimental results indicated that the combined core sandwich specimens provided increased stiffness, specific stiffness, energy absorption and critical load, which were higher than the sum of honeycomb core sandwich specimens and grid core sandwich specimens. In addition, a Finite Element Method (FEM) model was proposed to calculate the critical buckling load of the combined core sandwich structures. The effects of core heights, honeycomb-wall thickness and face-sheet thickness on the critical buckling loads of the combined core sandwich structures were examined. The aforementioned experimental and numerical results indicated that the present sandwich structure with grid reinforced honeycomb core could provide improved structural properties for engineering structures. [ABSTRACT FROM AUTHOR]

Carbon-fiber epoxy composites were bonded to four different types of aluminum substrates with different surface roughness and finish. The four aluminum substrates considered in this study have the following surface conditions: two solid aluminum substrates polished with two different grades of sandpapers, and two porous aluminum foams with two different as-received surface conditions, one with a patterned surface finish and one with rough pore structures. Moreover, the thin epoxy adhesive joints between the carbon-fiber face sheets and aluminum substrates were reinforced by adding short aramid fibers. During the fabrication process of the hybrid laminar, sparsely-distributed short aramid fibers were inserted between the fiber-metal interface to promote bridged fibers for tougher and stronger adhesive bonding, while at the same time to minimize any significant change in the thickness of the adhesive joint. Measurements of the critical energy release rate showed that the toughening effects of the low-density short aramid fibers were influenced by the metal-substrate surface roughness and finish. Further comparison indicated that the interfacial fracture toughness of aramid-fiber interleave adhesive joints increased via increase of surface roughness of metal substrates. The surface-roughness effect of metal substrate mainly depends on whether the free fiber ends of the short aramid fibers were pressed and embedded into the surface cavities of aluminum substrates according to scanning electron microscopy observations. The results indicated that the properties and performances of aramid-fiber interleaved adhesive joints between the carbon-fiber face sheets and aluminum substrates could be improved by surface treatments on the aluminum substrates to achieve appropriately surface roughness. [ABSTRACT FROM AUTHOR]

Due to their low vapor pressure, semi-volatile organic compounds (SVOCs) can absorb onto other compartments in indoor environments, including settled dust. Incidental ingestion of settled dust-bound SVOCs contributes to the majority of daily non-dietary exposure to some SVOCs by human beings. With this pathway in mind, an integrated kinetic model to estimate indoor SVOC was developed to better predict the mass-fraction of SVOC associated with settled dust, which is important to accurately assess the non-dietary ingestion exposure to SVOC. In this integrated kinetic model, the aerosol dynamics were considered, including particle penetration, deposition and resuspension. The newly developed model was evaluated by comparing the predicted mass-fraction of SVOC associated with the settled dust ( X dust ) and the measured X dust from previous studies. Sixty X dust values of thirty-eight different SVOCs measured in residences located in seven countries from four continents were involved in the model evaluation. The X dust value predicted by the integrated kinetic model correlated linearly with the measured X dust : y = 0.93x + 0.09 ( R 2 = 0.73), which indicates that the predicted X dust by the integrated kinetic model are in good match with the measured data. This model may be utilized to predict SVOC concentrations in different indoor compartments, including dust-bound SVOC. [ABSTRACT FROM AUTHOR]

Abstract: Critical local and global buckling loads of grid-stiffened carbon-fiber thin-shell structures, such as advanced grid-stiffened (AGS) conical shells relevant to aviation and aerospace applications, under uniform external transverse pressure were determined analytically using an equivalent stiffness model considering the influence of non-uniform grid distribution and the minimum potential energy principle. Experiments and finite-elements analysis have been carried out to assess the reliability of this analytical model. To maximize the buckling resistance for optimal design of the AGS conical shells, a hybrid genetic algorithm combining the genetic approach with a simulated annealing algorithm was developed, which considers the characteristics of multi-constraints and mixed discrete–continuous design variables. Comparisons between the benchmark results from the traditional genetic algorithm and simulated annealing algorithm confirmed the validity and efficiency of the hybrid genetic algorithms. Numerical examples show that the local-buckling constraint is a key factor for weight optimization of the AGS carbon-fiber conical. [Copyright &y& Elsevier]

Abstract: In this paper, we present the initial buckling and post-buckling responses of axial loaded advanced grid stiffened (AGS) composite cylindrical shells with reinforced rectangular or circular cutouts. The AGS cylindrical shells were reinforced by various local grid configurations near the cutout areas. The effects of different reinforcing grid configurations on critical loads were then examined and compared to those of different skin-reinforcing designs using Finite Element Analysis (FEA) simulations. A high-fidelity non-linear analysis procedure was proposed to predict the non-linear buckling response of the shell structures. The simulation results indicated that the grid reinforcements can reduce or eliminate the risk of local buckling response near the cutout areas and increase the critical load of the shell more effectively than the skin reinforcements. Furthermore, those results showed that an optimum grid reinforcement configuration exists, which significantly improved the initial buckling and post-buckling resistance of the cylindrical shells under axial loading. The above findings can potentially be useful to the analysis and optimum design of AGS composite cylindrical shells with cutouts. [Copyright &y& Elsevier]

Abstract: Polycyclic aromatic hydrocarbons (PAHs) of outdoor origin can enter indoor environment via infiltration or ventilation, and lead to human exposure. This study presents a kinetic partition model for the prediction of indoor PAH concentrations that are of outdoor origin. The model was verified with the previous published measurement conducted in a chamber. Indoor gas-phase, particle-phase and airborne concentrations (the sum of the gas- and particle-phases concentrations) of 16 species of PAHs listed by United States Environmental Protection Agency (EPA) as priority pollutants were calculated over a two-year period by the kinetic partition model. The predicted concentrations were compared with those calculated using a simple linear instantaneous model. Uncertainty in the differences between the predicted results by these two models caused by uncertain parameters was further conducted. For some PAHs, remarkable differences existed between the predicted indoor gas- and particle-phases concentrations of outdoor originated PAHs by the kinetic partition model and by the linear instantaneous model. The average relative differences of gas-phase PAHs ranged from 3.60 × 10−6 to 6.31 × 101 while those of particle-phase PAHs were between 5.47 × 10−2 and 9.15 × 10−1. However, there was no obvious average relative difference between the predicted airborne concentrations, which maximized to 6.52 × 10−2. The average relative differences for both the gas- and particle-phases PAHs were even larger when particle deposition rate was at its maximum. [Copyright &y& Elsevier]

Fibrosis is an inevitable stage in the development of chronic liver disease and has an irreplaceable role in characterizing the degree of progression of chronic liver disease. Histopathological diagnosis is the gold standard for the interpretation of fibrosis parameters. Conventional hematoxylin-eosin (H&E) staining can only reflect the gross structure of the tissue and the distribution of hepatocytes, while Masson trichrome can highlight specific types of collagen fiber structure, thus providing the necessary structural information for fibrosis scoring. However, the expensive costs of time, economy, and patient specimens as well as the non-uniform preparation and staining process make the conversion of existing H&E staining into virtual Masson trichrome staining a solution for fibrosis evaluation. Existing translation approaches fail to extract fiber features accurately enough, and the decoder of staining is unable to converge due to the inconsistent color of physical staining. In this work, we propose a prior-guided generative adversarial network, based on unpaired data for effective Masson trichrome stained image generation from the corresponding H&E stained image. Conducted on a small training set, our method takes full advantage of prior knowledge to set up better constraints on both the encoder and the decoder. Experiments indicate the superior performance of our method that surpasses the previous approaches. For various liver diseases, our results demonstrate a high correlation between the staging of real and virtual stains (ρ = 0. 82 ; 95% CI: 0.73-0.89). In addition, our finetuning strategy is able to standardize the staining color and release the memory and computational burden, which can be employed in clinical assessment. [ABSTRACT FROM AUTHOR]

Porous-core sandwich structures with CFRP face sheets have similar micro structures to biological tissues, for example, grass leaves. The sandwich structures are composed of two thin, stiff face sheets, which provide the primary in-plane structural stiffness, and a thick low-density porous core, which provides the functionalities and the majority of out-plane stiffness. However, the mechanical properties of these sandwich structures are often limited by local failures such as face-core debonding or core collapse. Inspired by the tree leaves with fractal distributed veins, which are larger and stiffer than grass leaves, in this paper, a topological optimization on the micro structures of core is conducted to achieve exceptional mechanical properties. By taking adhesive-area constraint, local-buckling constraint and embedding-volume constraint into consideration, a biomimetic hybrid core, which is similar to the fractal distribution of tree veins, is found to be an optimal core design for sandwich structures with CFRP face sheets. [ABSTRACT FROM AUTHOR]

• A modified surrogate model-based polynomial function is proposed in consideration of its uncertainty. • A bound approach is introduced to analyze the structural reliability of bogie frame under variable load cases. • The proposed approach is further applied to a practical bogie frame to demonstrate its efficiency and accuracy. Estimating failure probabilities of variable load cases during the design process remains a challenging task in structural reliability analysis of bogie frame. To address this issue, a bound approach by structural reliability analysis is investigated based on modified surrogate model-based polynomial function in this paper. The initial polynomial response surface (PRS) surrogate model of bogie frame under variable load cases is first developed with the results of finite element analysis (FEA) and experimental of design (DoE), and the fitting accuracy is checked based on the analysis of variance (ANOVA) method as well. A modified PRS surrogate model is then proposed to characterize the functional relationship between design parameters and responses. The performance function of bogie frame under variable load cases is next established based on the stress-intensity interference theory. And the subset simulation (SS) method is employed to calculate its failure probability. Finally, the unimodal and bimodal bounds is introduced into the structure reliability analysis of bogie frame to solve the reliability under variable load cases. In this study, the proposed approach is further applied to a practical engineering example to demonstrate its efficiency and accuracy. Simultaneously, the importance of considering the uncertainties of the surrogate model is also shown and discussed by comparing with the Monte Carlo simulation (MCS) results in this example. [ABSTRACT FROM AUTHOR]