Wrapping Effect Research Articles

Synergistic modification by mercapto hyperbranched polysiloxane and functionalized graphene oxide on the surface of aramid fiber

With the purpose of improving the interfacial properties of aramid fibers reinforced rubber composites and enhancing the tensile strength of aramid fibers simultaneously, mercapto hyperbranched polysiloxane (HPSi) and functionalized graphene oxide (GO) were used to modify the surface of aramid fibers. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and other characterization methods were performed to confirm the process of synergistic modification. Judging from the results of mechanical property tests, it could be acquired that the tensile strength of modified aramid fiber was increased by 16.8%, which could be ascribed to the wrapping effect of GO sheets. The interfacial properties were assessed by the pull-out tests of composites, and the results showed that the maximum pull-out force after synergistic surface modification was increased by 99.3%, which could be mainly related to additive reaction between double bonds and mercapto groups and the promotion of surface energy. More critically, during pull-out test, aramid fiber bundles might bring a part of shear stress into the grafted GO sheets, namely, GO sheets could convert fracture energy into interfacial energy, which would improve interfacial properties dramatically.

A polynomial chaos expansion approach for nonlinear dynamic systems with interval uncertainty

This paper proposes a non-intrusive interval uncertainty analysis method for estimation of the dynamic response bounds of nonlinear systems with uncertain-but-bounded parameters using polynomial chaos expansion. The conventional interval arithmetic and Taylor series methods usually lead to large overestimation because of the intrinsic wrapping effect, especially for the multidimensional and non-monotonic problems. To overcome this drawback, a novel polynomial chaos inclusion function, based on the truncated polynomial chaos expansion, is proposed in the present work to evaluate interval functions. In this method, the Legendre polynomial in interval space is employed as the trial basis to expand the interval processes, and the polynomial coefficients are calculated through the collocation method. Two examples show that the polynomial chaos inclusion function is capable of determining tighter enclosures of the true solutions and effectively dealing with the wrapping effect. The response of nonlinear systems with respect to interval variables is approximated by the polynomial chaos inclusion function, through which the supremum and infimum of the dynamic responses over all time iteration steps can be easily estimated by an appropriate numerical solver. Four dynamics examples described by ordinary differential equations demonstrate the effectiveness, feasibility, and efficiency of the proposed interval uncertainty analysis method compared with other methods.

Example-dependent cost-sensitive credit cards fraud detection using SMOTE and Bayes minimum risk

This paper presents fraud detection problem as one of the most common problems in secure banking research field, due to its importance in reducing the losses of banks and e-transactions companies. Our work will include: applying the common classification algorithms such as logistic regression (LR), random forest (RF), alongside with modern classifiers with state-of-the-art results as XGBoost (XG) and CatBoost (CB), testing the effect of the unbalanced data through comparing their results with and without balancing, then focusing on the savings measure to test the effect of cost-sensitive wrapping of Bayes minimum risk (BMR), we will concentrate on using F1-score, AUC and Savings measures after using the traditional measures duo to their suitability to our problem. The results show that CB has the best savings (0.7158) alone, (0.971) when using SMOTE and (0.9762) with SMOTE and BMR, while XG has the best savings (0.757) when using BMR without SMOTE.

Properties of a double-layer EMW-absorbing structure containing a graded nano-sized absorbent combing extruded and sprayed 3D printing

The ever-increasing electromagnetic wave (EMW) energy and its reflections may impair human health and information security. An ordinary EMW-absorbing structure usually exhibits limited EMW-reflecting capacity given its ungraded structure in both the micro and macro scales. In this study, four nano-sized graded absorbents are explored by wrapping carbonyl-iron powder with nano-sized silicon dioxide. The micro-scale wrapping effects are assessed via a scanning electron microscopy experiment to identify the best sample, including a 5 wt% coupling agent and a 10 wt% dispersant in CIP ethanol. The 10 mm thick concrete matching layer containing the graded absorbent is built using spraying methodology, and the 15 mm thick absorption layer is fabricated using extruding methodology. The mercury intrusion porosimetry experiments show that the sprayed matching layer incurs maximum porosity at 19.8% while the 3D extruded layer ensures the minimum porosity at 11.13%, strengthening the laminar grading effect to improve the EMW impedance matching. The Naval Research Laboratory experiments corroborate that double-layer structures improve the EMW-reflecting capacity compared to their single-absorption-layer counterparts and that the double-layer element containing the best wrapping effect absorbent yields the best reflection loss value, with a minimum of −14.7 dB and a 9.72 GHz effective bandwidth. The EMW-reflecting mechanism for the novel graded double-layer structure containing the graded nano-sized absorbent is then summarized. Theoretical calculations using the transform line theory suggest that a 15 mm absorbing layer and a 15 mm impedance matching layer is specified as the most optimized configuration, with −10.47 dB in average reflection, −15.18 dB in maximum RL, and 9.56 GHz in effective bandwidth.

Strengthening and Rehabilitation of Concrete Prisms Using GFRP Sheets

The use of external strengthening by fiber reinforced polymer (FRP) technology has significantly increased in recent decades. This is because (FRP) has the properties that make it the most suitable option for strengthening and rehabilitation of damaged concrete structures instead of using traditional materials such as steel plates. In this paper, the behaviour of non-reinforced concrete beams externally wrapped with Glass Fiber Reinforced Polymer (GFRP) sheets has been examined. Fourteen unreinforced concrete prisms were cast with a rectangular section of (150 × 125 mm) and a length of (760mm), these specimens were divided into five group. First group was not externally wrapped with GFRP sheets (control specimens), and the remaining groups were GFRP wrapped with a variable number of GFRP layers (thickness of wrapping). In the first stage of study, the prisms have been tested and the effect of external wrapping and increasing the wrapping thickness on the behaviour of prisms was observed. In the second stage, the unwrapped concrete prisms that were tested and failed (control specimens) were rehabilitated by externally wrapping them with one layer of GFRP sheets. The results have shown that wrapping with GFRP sheets increased the capacity of the prisms and failure load had reached to (342.5%) for prisms wrapped with three layers when compared to the control specimens. It was also noticed that there was an increase in the toughness of the prisms by increasing the number of GFRP layers. The results have shown that there was a decrease in the failure load of the four layer wrapped prisms, and this was due to the early failure of the prisms due to the debonding of the GFRP sheets from the prism surface. The damaged specimens which were later rehabilitated have shown an increase in load carrying capacity compared to the control specimen.

On robust interval observer design for uncertain systems subject to both time-invariant and time-varying uncertainties

This paper proposes the design of an interval observer-based approach for linear dynamic systems affected by both time-invariant and time-varying uncertainties. First, different interval observer schemes are compared and analysed when dealing with the different types of uncertainties. Then, an integrated interval observer is proposed in order to overcome the drawbacks of using the set-based approach, i.e. the non-preservation of the parameter uncertainty time dependency and the wrapping effect. Furthermore, performance is considered in order to compute the observer gain by using an LMI technique. Finally, a numerical example and a real case study based on a two-tank system are employed for both illustrating and analysing the effectiveness of the proposed approach.

Prediction of Axial Compressive Strength for FRP-Confined Concrete Compression Members

In the current work, a new strength model was proposed for capturing the ultimate axial strength of fiber reinforced polymers (FRP)-confined concrete compression members. First, a preliminary evaluation of previous strength models for estimating the wrapping effect of FRPs-confined concrete specimens was performed a large database of 520 confined concrete specimens was constructed with the detailed information of various geometric and material parameters of confined concrete specimens. Then, a strength model was suggested using regression analysis in MATLAB. The validation of the proposed strength model was made in two different approaches. In the first approach, the validation of proposed models was done by performing an experimental work of 6 carbon fiber reinforced polymer (CFRP) confined concrete cylinders and in the second approach, the nonlinear finite element analysis (NLFEA) via a general-purpose program ABAQUS was performed. After validation, a detailed parametric numerical study was done using the newly suggested strength model. A close agreement could be found between tests, NLFEA and theoretical results.

Nanocomposite coatings obtained by electrophoretic co-deposition of poly(etheretherketone)/graphene oxide suspensions

Nanocomposite coatings were successfully prepared by electrophoretic deposition of poly(etheretherketone) (PEEK)/graphene oxide (GO) suspensions. The GO flakes developed a large-scale co-continuous morphology with the basal plane mainly aligned with the coating surface. However, the PEEK particles were also found to be wrapped by GO nanosheets when deposited on the stainless steel substrate. Both phenomena, the co-continuous morphology and the wrapping effect, were dependent on the initial GO content in the suspension and influenced the final morphological characteristics of the thermally treated coatings. The PEEK matrix developed a dendritic morphology during its cooling from the molten state because of transcrystallinity that was induced by the incorporation of GO. The preparation of suspensions involved tip ultrasonication (TS) to deagglomerate, disperse, and mill the PEEK particles. A detailed study of the microstructure revealed that TS tended not only to reduce PEEK particle size, but also to promote an elongated shape, favourable for the nanocomposite coatings.

Modeling muscle wrapping and mass flow using a mass-variable multibody formulation

Skeletal muscles usually wrap over multiple anatomical features, and their mass moves along the curved muscle paths during human locomotion. However, existing musculoskeletal models simply lump the mass of muscles to the nearby body segments without considering the effect of mass flow, which has been shown to induce non-negligible errors. A mass-variable multibody formulation is proposed here to simultaneously characterize muscle wrapping and mass flow effects. To achieve this goal, a novel cable element of the muscle–tendon unit, which integrates the mass flow feature with a typical Hill-type constitutive relationship, was developed based on an arbitrary Lagrangian–Eulerian description. In addition, sliding joints were used to constrain the elements to move over the underlying bone geometries. After validating the proposed modeling method using two benchmark samples, it was applied to build a large-scale lower limb musculoskeletal model, where knee joint moments were calculated and compared with isokinetic dynamometry measurements of 12 healthy males. The results of the comparison confirm that muscular mass distribution play an important role in the force transmission of muscle wrapping, and the proposed mass-variable formulation provides a better way of predicting and understanding the dynamics of musculoskeletal systems.

Verified Interval Enclosure Techniques for Robust Gain Scheduling Controllers

In real-life applications, dynamic systems are often subject to uncertainty due to model simplifications, measurement inaccuracy or approximation errors which can be mapped to specific parameters. Uncertainty in dynamic systems can come either in stochastic forms or as interval representations, when they are considered as bounded as it will be done in this paper. The main idea, here, is to find a joint approach for an interval-based gain scheduling controller while simultaneously reducing overestimation by enclosing state intervals with the least amount of conservativity. The robust and/ or optimal control design is realized using linear matrix inequalities (LMIs) to find an efficient solution and aims at a guaranteed stabilization of the system dynamics over a predefined time horizon. Since the resulting system is assumed to be asymptotically stable, a temporal reduction of the widths of intervals representing worst-case bounds of the system states at a specific point of time should occur. However, for commonly used approaches in the computation of interval enclosures those interval widths seemingly blow up due to the wrapping effect in many cases. To avoid this, we provide two interval enclosure techniques --- an exploitation of cooperativity and an exponential approach --- and discuss their applicability taking into account two real-life applications, a high-bay rack feeder and an inverse pendulum.

Interaction of spent FCC catalyst and asphalt binder: Rheological properties, emission of VOCs and immobilization of metals

Spent fluid catalytic cracking (FCC) catalyst and its reutilization in asphalt mortar was investigated. The interaction between spent FCC catalyst and Pen 60/80 asphalt binder has been evaluated by simultaneously discussing volatile organic compounds (VOCs) released from asphalt binder and mobility of selected metals elements existed in spent catalyst. Dynamic shear rheological test results showed that the high temperature performance of asphalt mortar was significantly improved by coarse spent FCC catalyst. Consequently, a higher rutting factor and lower fatigue factor can be obtained under similar filler to binder ratio. However, the low temperature performance reduced with an increase of spent catalyst compared with limestone powder asphalt mortar due to fluidity reduction of asphalt binder in pores of catalyst. Addition of spent FCC catalyst leaded to a reduction of VOCs released from asphalt binder in respect of relative content and categories, especially for polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, anthracene, phenanthrene and its derivatives. Spent FCC catalyst influences emission of VOCs in the manner of adsorption and assisted catalytic reaction by resident zeolite structure and rare earth elements. On the basis of better understanding about migration of metals from spent catalyst to asphalt matrix and to aqueous solutions, immobilization of vanadium, nickel, lanthanum and cerium was enhanced by possible chemical reactions asphalt binder as well as physical wrapping effect.

Strength Characteristics of Concrete Specimen Wrapped With Glass Fiber Reinforced Polymer

Glass Fiber Reinforced Polymer (GFRP) is one of a relatively new class of composite material. These materials are manufactured from a combination of fibers and resins. These composite materials have proven to be efficient and economical for the development of new structures and the repair of deteriorating structures in civil engineering. One of the important reasons for the use of GFRP composite materials is because of its superior mechanical properties. These mechanical properties includes impact resistance, strength, stiffness, flexibility and also its enhanced ability to carry loads. In construction industry, in order to meet the advanced infrastructure requirements, new innovative technologies and materials are being introduced. Also any new technology or material has its own limitations but to meet the new requirements, new technologies and materials have to be invented and put to use. With structures becoming old and increasing bar corrosion, old buildings have to be retrofitted with additional materials to increase their durability and life. For strengthening and retrofitting of concrete structures confinement with FRP has various applications. In this project concrete specimens are wrapped with glass fibre reinforced polymers to study the effect of confinement in the strength of specimens. For wrapping bi-directional and uni-directional glass fibre reinforced polymer mats are used. During the uni-directional glass fibre reinforced polymer wrapping, it is wrapped in both horizontal and vertical directions. The fiber used in this paper is bi-directional fibre. To find the effect of wrapping, specimens are wrapped in one rotation and two rotations.

Investigation on molecular and morphology changes of protein and starch in rice kernel during cooking

The composition and structure of starch are important indicators to evaluate the quality of rice, but the effect of protein on structural properties of rice has always been controversial. In the present study, the rheological properties and thermal properties were combined to investigate the effects of protein on mechanical and inner structure changes of rice kernel during cooking. The morphologic changes in overall form and inner structure of the kernel showed the limited and uneven gelatinization of starch, and reflected the good heating stability of protein. The comparison of molecular mobility in H2O/D2O reflected the special gelatinization behavior of starch and the hydrophobicity of protein during cooking. The similar proton distributions between starch, starch-protein mixture and rice flour indicated the weak interactions between starch and protein. The results of Fourier transform infrared spectra, thermogravimetric analysis and transmission electron microscope confirmed the wrapping effect of starch and surface interactions with protein.

Is high sensitivity always desirable for a grating-based differential phase contrast imaging system?

In grating-based x-ray differential phase contrast (DPC) imaging, the measured signal amplitude of the phase shift induced by an image object is proportional to the so-called system sensitivity. Therefore, to achieve a better signal-to-noise (SNR) for improved imaging performance, it is generally believed that one should increase the system sensitivity by reducing the period of the analyzer grating or increasing the distance between the phase grating and analyzer grating. The purpose of this work is to theoretically and experimentally demonstrate that there is an optimal system sensitivity to attain the highest SNR for a given task provided that the standard phase-stepping acquisition and phase retrieval methods are used. When system sensitivity goes beyond this optimal value, SNR decreases and the imaging performance deteriorates. Due to the fundamental fact that the measured phase signal is a cyclic variable, the phase wrapping effect is inevitable in DPC imaging when the system sensitivity increases. The phase wrapping effect appears in both signal and noise measurements. The effect in the signal measurement is manifested in the so-called signal statistical bias and such effect often impacts the accuracy of the measurement. The phase wrapping effect also appears in the noise variance measurement and impacts the precision of the measurement. A thorough theoretical analysis was performed in this work to demonstrate the quantitative impacts of phase wrapping on both signal bias and noise variance and thus on the actual system SNR. The joint effect of phase wrapping in both the signal bias and noise variance yields an optimal system sensitivity to achieve the highest SNR. Both extensive numerical simulation studies and experimental studies were performed to validate the theoretical analysis. Both theoretical analysis and experimental studies show that the SNR of the DPC signal is not always proportional to the sensitivity due to the cyclic nature of the signal and the phase wrapping effect. For a given refraction angle and exposure level, there exists an optimal sensitivity factor that maximizes the SNR, beyond which, increasing the sensitivity will decrease the SNR. Increase of system sensitivity does not always improve x-ray DPC imaging performance provided that the standard phase-stepping acquisition and phase retrieval methods are used.

Utilizing Statistical Information for Interval Analysis: A Method for Analyzing the Interval Uncertainty of Line-of-Sight Measurement Error of Space-Borne Observation Platforms

Analyzing the space-borne observation platform's line-of-sight measurement error (SOPLME) is of great significance for the improvement of the space-borne optical tracking system. In this regard, we consider the space-borne observation platform (SOP) as a multi-body system and build both the target imaging model from the inertial space to the optical camera image plane and the line-of-sight measurement model. The relationship between the SOPLME and the satellite's orbit error, attitude error, platform angular vibration error, inner and outer frame rotation error, and position quantization error of target image point is deduced theoretically. However, since there are many error sources and the modeling process is highly nonlinear, the amplification of the output range caused by the “wrapping effect” may occur when using the interval calculation method to analyze the output range of the SOPLME. To solve this problem, we propose a novel method of interval analysis by using statistical information. This method combines the convenience of interval representation with the high accuracy of probability calculation, which can effectively avoid the overestimation problem caused by the inherent “wrapping effect” of the interval calculation method. Firstly, we describe the parameters of each error source with the interval constructed by upper and lower bounds. Secondly, the optimal Latin hypercube sampling (LHS) matrix of error source parameters is designed by the quasi-optimization method. Then we use the Gaussian mixture model (GMM) to approximate the distribution function of the SOPLME. Finally, the output range of the SOPLME is estimated by Taylor expansion. The simulation test verifies the reliability of the model and interval calculation method in this paper. The simulation example shows that the proposed method can get a more reliable error output interval with less sampling amount, which is suitable for analyzing the dynamic process of the output interval of the SOPLME.

Crashworthiness and optimization design of quadruple-cell Aluminum/CFRP hybrid tubes under transverse bending

This paper aims to investigate the bending collapse and crashworthiness of the quadruple-cell Al/CFRP (aluminum/carbon fiber reinforced plastic) hybrid tubes under quasi-static and dynamic loading. Three-point bending tests were first conducted for pure Al tubes and Al/CFRP hybrid tubes with different wrapping angles. Experimental results showed that the enhancement effect of CFRP wrapping on energy absorption efficiency of hybrid structures was affected by several factors. Numerical analyses were then carried out by ABAQUS/Explicit, and good agreements were achieved between the simulation and experimental results. The validated numerical model was further employed to investigate the effects of the partial wrapping, wrapping angle and ply thickness on the crashworthiness of Al/CFRP hybrid tubes. Results showed that the increase of wrapping angle and ply thickness could enhance the bending resistance and delay or avoid the fracture of CFRP in the bottom flange. The Al/CFRP tube with appropriate partial wrapping could achieve 7.9% higher specific energy absorption (SEA) than the entirely wrapped counterpart. In addition, the sequential response surface method (SRSM) was adopted to optimize the structural parameters and to further improve the crashworthiness of the hybrid tubes. The SEA of the Al/CFRP tube was increased by up to 30.3% by the RSM optimization.

Evaluation for RC Column Confined Partially with Externally FRP Wrapping Sheet Using Nonlinear FE Analysis

Little research has been carried out in validating, fiber reinforced polymer (FRP) concrete strengthened column and the effective using partial wrapping. Also the effect of several parameter on strengthen column using the partial wrapping sheet of desired width and thickness around column have not been found out. To this end, a nonlinear 3D finite element model has been developed in current study for CFRP strengthened reinforced concrete column to simulate the behavior accompanied by the effect of partial wrapping with emphasis on load capacity and failure mode. The finite element simulation of CFRP strengthened RC columns is performed using commercial finite element program ABAQUS. Modelling was conducted on reinforced concrete columns with dimensions of 160 x 250 x 960 mm. The finite element model incorporates the nonlinear material behavior of concrete, bilinear stress-strain curve of steel and linear elastic behavior of CFRP material. The concrete was modeled using a plastic damage model. The performance of the FE model was studied by simulating experimental columns from the literature. The load, and strain of CFRP obtained from the FE study were compared with the corresponding experimental results. The FEM results agreed well with the experiments. In addition, to enhance our understanding of the behavior of strengthened reinforced concrete column capacity using partial wrapping the effect of changing the spacing between the CFRP sheets and number of layers were examined. The increase number of layers and decrease spacing give a higher ultimate load capacity, and delay the failure.

The X Factor of opportunity structures: How grab and wrap effects of entertainment create inadvertent news audience in a high-choice media environment

In today’s high-choice media environments, newscasts increasingly compete for viewers against multiple entertainment options. This development has led to concerns over the demise of inadvertent news audiences, which is especially problematic for public service broadcasters who have an obligation to provide news to all segments of the population. However, this study demonstrates how entertainment shows can be used to create a favourable opportunity structure that generates substantial inadvertent news audiences. Using Danish TV meter data from 2008 to 2016, we show that scheduling the music talent show The X Factor before and after the newscast on the main public service channel increased news audiences dramatically. These ‘grab’ and ‘wrap’ effects of entertainment were particularly strong among young people and people with low news interest, and the effects became even stronger over time. Consequently, entertainment shows, indirectly, play a positive democratic role, by increasing the viewership of newscasts.

A novel method to increase the content of h-BN and the deposition efficiency of laser cladding Ni60/nano-Cu/h-BN coating by adding MoO3

In this work, the effect of MoO3 addition on the content of h-BN and the deposition efficiency in laser cladding nickel-based composite coating was investigated. The change of droplets, microstructure and evolution of deposition process were discussed. The results showed that the size of droplets increased enormously during laser cladding with MoO3 addition. Besides, due to the wrapping effect of MoO3 during laser irradiation, the content of h-BN and deposition efficiency of nickel-based composite coating raised from 3.9% to 8.4% and 43% to 83%, respectively. In the end, the outlook of this novel method is discussed.

Static and dynamic axial crushing of Al/CRFP hybrid tubes with single-cell and multi-cell sections

Adopting multi-cell sections and composite wrapping are two effective approaches to improve the crashworthiness performance of thin-walled tubes. The axial crushing of single-cell and multi-cell aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid tubes is investigated in this paper. Quasi-static and dynamic experimental tests are performed for CFRP, Al and Al/CFRP tubes with single-cell, double-cell or quadruple-cell sections. The influences of Al wall thickness and the number of composite layers and sectional cells on the crushing response and energy absorption characteristics of the tubes are analyzed. Results show that the increase of all these factors can improve the load bearing and energy absorption capability of the tubes. The enhancement effect of composite wrapping for the Al/CFRP hybrid tubes is determined by the relative strength/weakness on the energy absorption efficiency of Al and CFRP. The interaction effect between the Al and CFRP on energy absorption of various sections is also investigated and the results show that the interaction effect decreases with the increase of the number of the sectional cells, while it is enhanced by increasing the number of CFRP layers.