Flexible Barrier Research Articles

MPM modelling of debris flow entrainment and interaction with an upstream flexible barrier

Flexible barriers may be installed upstream in debris flow channels to reduce entrainment of bed material. Simulating both the entrainment and the impact on a barrier by the same numerical tool remains challenging. For this purpose, a three-dimensional one-phase material point method (MPM) software is used herein to back-calculate two large-scale flume experiments. These experiments were conducted to measure the entrainment of an erodible bed and the impact on a flexible barrier. To simulate the entrainment of the wet bed, a Mohr–Coulomb softening model is introduced. In the model, the apparent friction angle of the bed material decreases as a function of the distortional strain, effectively reproducing the pore pressure increase observed in the experiments. From the tests and the numerical simulations, we identify two main mechanisms leading to entrainment: (i) the direct rubbing and colliding effect of the flow on to the bed and (ii) a significant bed shear strength reduction. Concerning the first mechanism, existing models only consider the rubbing of the bed surface by a shear stress parallel to the slope. However, we observe that a ploughing-type erosion occurs due to normal stresses acting on the bed in the flow direction. The additional ploughing explains why beds which are mechanically stronger than the flow can also be partly entrained. Larger entrainment volumes are found when the bed material loses shear strength due to pore pressure buildup that eventually leads to a self-propelled entrainment where the bed no longer has frictional strength to carry its own weight.

Debris flow overflowing flexible barrier: physical process and drag load characteristics

Debris flow overflowing flexible barrier: physical process and drag load characteristics

Production of cellular polymers without solid outer skins by gas dissolution foaming: A long-sought step towards new applications

An innovative approach to reduce and eliminate the non-foamed solid skins of the cellular polymers fabricated by gas dissolution foaming is presented in this work. The incorporation of a flexible gas diffusion barrier on the polymer surfaces during the saturation and foaming processes provided significant reduction or even hindered the appearance of the non-foamed solid skins while enabling appropriate expansions in several polymers (PMMA, PS, PC, and PCL). Besides, this approach has allowed to achieve significant expansions by foaming polymer samples with thicknesses in the order of magnitude of the non-foamed solid skins, i.e., thin films (<100 µm). This paper discusses how the gas diffusion barrier allows reducing the solid skins, the mechanisms involved in the gas diffusion process, and the possibility of interconnecting the inner cellular structure with the external medium.

Study on Numerical Model and Dynamic Response of Ring Net in Flexible Rockfall Barriers

Developing reliable, sustainable and resilient infrastructure of high quality and improving the ability of countries to resist and adapt to climate-related disasters and natural disasters have been endorsed by the Inter-Agency Expert Group on Sustainable Development Goals (IAEG-SDGs) as key indicators for monitoring SDGs. Landslides pose a serious threat to vehicle traffic and infrastructure in mountain areas all over the world, so it is urgent and necessary to prevent and control them. However, the traditional rigid protective structure is not conducive to the long-term prevention and control of landslide disasters because of its poor impact resistance, high material consumption and difficult maintenance in the later period. Therefore, this study is aimed at the flexible rockfall barriers with good corrosion resistance, material saving and strong cushioning performance, and proposes a fine numerical model of a ring net. This model is used to simulate the existing experiments, and the simulation results are in good agreement with the experimental data. In addition, the numerical model is also used to study the influence of boundary conditions, rockfall gravity and rockfall impact angle on the energy consumption of the ring net. It is indicated that the fixed constraint of four corners increases the deformability, flexibility and energy dissipation ability of the ring net. Apart from that, the influence of gravity on the energy dissipation of the overall protective structure should not be neglected during the numerical simulation analysis when the diameter of rockfall is large enough. As the impact angle rises, the impact energy of the rockfall on the ring net will experience a gradual decline, and the ring at the lower support ropes will be broken. When the numerical model proposed in this study is used to simulate the dynamic response of flexible rockfall barriers, it can increase the accuracy of data and make the research results more credible. Meanwhile, flexible rockfall barriers are the most popular infrastructure for landslide prevention and control at present, which improves the ability of countries to resist natural disasters to some extent. Therefore, the research results provide technical support for the better development and application of flexible rockfall barriers in landslide disasters prevention and control, and also provide an important and optional reference for evaluating sustainable development goals (SDGs) globally and regionally according to specific application goals.

Quantitative back analysis of in situ tests on guiding flexible barriers for rockfall protection based on 4D energy dissipation

Quantitative back analysis of in situ tests on guiding flexible barriers for rockfall protection based on 4D energy dissipation

Surface Treatment of Flexible Barrier Film for Improved Stability of Organic Photovoltaic Mini Modules

The lifetime and stability of organic photovoltaics (OPVs) are the key factors that influence the technology used to scale up and commercialize OPVs. High-performing and reliable devices are used to fabricate the devices of choice. Materials and methods that can be used to prevent the degradation of organic materials, enabling better OPV applications, are being increasingly researched in recent years. Herein, we present the surface modification process of a commercial, flexible barrier film based on polyethylene terephthalate (PET). A sol-gel deposition method was used to modify the surface. Two scalable coating techniques, spray- and bar-coating, were investigated as the processing methods. Treated films were optically, morphologically, and topologically characterized. The modification of the barrier film surface increased the surface hydrophobicity of the bar-coated and spray-coated treated films. This was validated by the contact angle measurements. OPV roll-to-roll (R2R) mini-modules with 4.2% power conversion efficiency were fabricated and encapsulated with the treated films. The lifetime and stability were assessed by conducting accelerated aging tests based on the ISOS-D-3 protocol. The spray-coating technique provided a more stable layer than the bar-coating technique, and the lifetime of the OPV modules encapsulated in spray-coated treated barrier films was increased. Surface modification has been demonstrated to be a promising approach for not only improving the barrier film properties (resulting in the improved lifetimes of the modules) but also reducing the extents of reflectance losses in the OPV modules post encapsulation.

A coupled SPH–DEM–FEM approach for modeling of debris flow impacts on flexible barriers

A coupled SPH–DEM–FEM approach for modeling of debris flow impacts on flexible barriers

Molecular and biochemical modifications of suspension-cultured tobacco cell walls after exposure to alternative gravity

The plant cell wall is a flexible physical barrier surrounding the cell which functions in growth and differentiation, signaling, and response to environmental stimuli including the Earth gravity force. In the present study, structural and molecular modifications of cell wall components of cultured tobacco (Nicotiana tabacum cv. Burley 21) cells under alternative gravity conditions induced by 7 days exposure to 2-D clinostat have been investigated. In comparison with the control group, clinorotation significantly increased biomass but reduced the total amounts of wall and the contents of cellulose, pectin, uronic acidic, and xyloglucan. Gene expression of H+-ATPase was not changed but of expansin A reduced in clinostat-treated cells. However, the gene expression and activity of xyloglucan endotransglycosylase/hydrolases (XTH; EC 2.4.1.207) and endo-(1,4)-β-D-glucanase (EGase; EC 3.2.1.4), the amount of arabinogalactan proteins (AGP), and the expression of wall-associated kinase (WAK) gene significantly increased by clinorotation. Altered gravity also reduced the activity of polyphenol oxidase and covalently bound peroxidase. The results suggest that altered gravity promoted orchestrated changes of wall-modifying genes and proteins which reduced its stiffness and enhanced cell expansion and division potential.

Mitigation of Hydroelastic Responses in a Very Large Floating Structure by a Connected Vertical Porous Flexible Barrier

The hydroelastic response of an elastic thin plate combined with a vertical porous flexible plate floating on a single- or a two-layer fluid is analyzed in the two-dimensional Cartesian coordinate system. The vertical and the horizontal plates are placed in an inverted-L shape and rigidly connected together. The problem is studied with the aid of the method of matched eigenfunction expansions within the framework of linear potential flow theory. The fluid is assumed to be inviscid and incompressible, and the motion is assumed to be irrotational. Time–harmonic incident waves of the traveling mode with a given angular frequency are considered. Then, the least-squares approximation method and the inner product are used to obtain the expansion coefficients of the velocity potentials. Graphical results show the interaction between the water waves and the structure. The effects of several physical parameters, including the length and the complex porous-effect parameter of the vertical plate, on the wave reflection and transmission are discussed. The results show that a vertical plate can effectively eliminate the hydroelastic response of the very large floating structure. The longer a vertical plate is, the more waves are reflected by the vertical plate. With the increase in the porous-effect parameter, the deflection of vertical plate decreases. Besides the effects of the flexural rigidity, the lateral stress, the mooring line angle, the fluid density ratio, and the position of interface on the wave reflection and transmission are discussed. Numerical results show the significant mitigation effect due to the presence of the additional vertical plate.

Effect of small-size space porous flexible PVC material on propane deflagration

The effect of porous flexible polyvinyl chloride (PVC) barriers on the kinetic properties of propane explosions is investigated based on fluid dynamics and combustion-related theory. Furthermore, using small-sized cylindrical pipes, separate experimental studies on propane deflagration are conducted with different types of flexible PVC barriers placed in the pipeline. The results show that when the conditions of the same nature as the obstacles appear at the outlet end of the pipeline and the blocking rate is low, the presence of porous flexible PVC barriers counteracts the effect of tail-end barriers on propane deflagration. In the tail-end opening experiment, the porous flexible PVC obstacle has a significant effect on the flame pattern passing through it but has a weaker effect on the flames before they pass through it. Furthermore, it only affects the degree of “fingertip” sharpening of finger-shaped flames; the fewer the number of holes in the obstacle, the higher the sharpness of the fingertip flame. The porous flexible PVC barriers can reduce the rate of flame propagation and creasing of propane deflagration. The porous flexible PVC barriers have a lifting effect on the overpressure of the blast and a delaying effect on the onset of peak overpressure; the larger the number of holes in the barrier, the stronger the delaying effect.

Vita COVIDa as a Biopolitical Modality of Life in a Pandemic

The pandemic of the COVID-19 coronavirus infection has formed a special biopolitical modality of life, that of vita COVIDa. Biopolitics, the tools of which the authorities turned to in a pandemic, re-assembled the social space, thus changing the flow of social time. In this accelerated mode, the path from isolation through quarantine to vaccination has been completed. Historically-proven tools to combat the pandemic have been consistently combined. What was new was the appeal to the arsenal of modern digital technologies which made it possible to create a unique flexible barrier environment and control the process of the immunization of the population. Vita COVIDa was a form of further restriction of active life (vita activa). During the pandemic, consumption increased as an aspect of the work managed by animal laborans; there is a lack of creative activity carried out by homo faber; and there is a collapse of public space, leading to a pseudo-political virtual polemic in which a person gets bogged down as a zoon politikon. In conditions when the contemplative life (vita contemplativa) is captured by the effect of stickiness in the interpassivity mode, vita COVIDa slides to routine work and hyper-consumption, increasingly assigning the priority role of animal laborans to a person. The special spaces of the stationary (“Red Zone” or “camp of life”) and mobile (QR code) camps, formed in the mode of an undeclared state of emergency, produce a “naked life” (vita nuda). The increasing tension creates prerequisites for the invasion of the friend/enemy political-identifier proper into social relations, situationally assigning the status of homo sacer to persons whose modus operandi is perceived as risky. Foucault understood racism is actualized in the biopolitical space of the pandemic. The contradictory trends of the pandemic should be considered within the framework of the Esposito immunization paradigm, in which the pandemic with its threats of social collapse should be considered as something that requires an immune response in the form of a coordinated response of the authorities and the population to the threats of social collapse. The intense confrontations between humanity and disease and between the authorities and the population in the field of imposed restrictions and responsible adoption of the proposed measures lead to the need to develop co-vida vita (co-life) as a way of living and overcoming vita COVIDa during the return to the “old” new normality.

ANALISIS BAHAYA, LINTASAN, DAN SISTEM PROTEKSI TERHADAP POTENSI LONGSORAN TIPE JATUHAN BATU PADA LERENG BANGUNAN PELIMPAH BENDUNGAN TUGU, JAWA TIMUR

The construction of the Tugu Dam spillway does not escape the problem of slope instability, especially the rock fall type landslide as a result of the rock slope cutting work at STA+80. The purpose of this study was to determine the characteristics of the rock discontinuity area and the solutions needed to address the potential hazards of rock fall on the slopes of spillway structure. In this study, a semi-quantitative method conducted based on the Rockfall Hazard Rating System (RHRS) which is carried out by identifying outcrops on rock slopes. Determination of the rock fall trajectory, was conducted by statistical methods on rock mass based on changes in velocity when rocks roll, slide, and bounce. Geologically, the research area belongs to the Mandalika Formation. Based on the RHRS weighting, the total score on the STA+80 slope is 399, which means that the slope needs to be repaired or given safely with a moderate level of urgency. The rock fall trajectory modeling at the measurement location X = 121,875 has a kinetic energy of 973.14 kJ andesite and 72.59 kJ of volcanic breccia, for high results of 0.43 meters of andesite reflection and 2.04 meters of volcanic breccia, and velocity results translational velocity obtained at 33.8 m/s andesite and 8.67 m/s volcanic breccia. The potential for rock fall requires a safety system with a type of retained flexible barriers with a height of 5 meters that can be applied to the toe of the slope.Keywords: rock fall, discontinuity, trajectory, protection system, Tugu Dam

Study on the forming mechanism and corrosion resistance of doping graphene composite film on the 6061 Al alloy

Flexible barrier films preventing corrosion are important for many industries ranging from engineering to medical to electronic materials. It is necessary to improve the corrosion resistance of aluminum alloys. The aluminum alloy sample reacted with sodium hydroxide was immersed in a double -[3-(triethoxylated) silicon-propyl] tetrasulfide and graphene（BTESPT/rGO) and cured in an oven at 100 °C to prepare a BTESPT/rGO composite film and discuss its film forming mechanism. The results shown that the film was dense and hydrophobic, which helped to improve the barrier properties of the film to corrosive ions, and its corrosion resistance was significantly better than that of a single BTESPT film. The corrosion current density of the BTESPT/rGO composite film was three orders of magnitude lower than that of the aluminum alloy substrate. The 240 h salt spray experiment shown that the BTESPT/rGO composite film greatly improved the corrosion resistance of the aluminum alloy substrate.

SDBD Flexible Plasma Actuator with Ag-Ink Electrodes: Experimental Assessment

In the present work, a single dielectric barrier discharge (SDBD)-based actuator is developed and experimentally tested by means of various diagnostic techniques. Flexible dielectric barriers and conductive paint electrodes are used, making the design concept applicable to surfaces of different aerodynamic profiles. A technical drawing of the actuator is given in detail. The plasma is sustained by audio frequency sinusoidal high voltage, while it is probed electrically and optically. The consumed electric power is measured, and the optical emission spectrum is recorded in the ultraviolet–near infrared (UV–NIR) range. High-resolution spectroscopy provides molecular rotational distributions, which are treated appropriately to evaluate the gas temperature. The plasma-induced flow field is spatiotemporally surveyed with pitot-like tube and schlieren imaging. Briefly, the actuator consumes a mean power less than 10 W and shows a fair stability over one day, the average temperature of the gas above its surface is close to 400 K, and the fluid speed rises to 4.5 m s−1. A long, thin layer (less than 1.5 mm) of laminar flow is unveiled on the actuator surface. This thin layer is interfaced with an outspread turbulent flow field, which occupies a centimeter-scale area. Molecular nitrogen-positive ions appear to be part of the charged heavy species in the generated filamentary discharge, which can transfer energy and momentum to the surrounding air molecules.

Characteristic of flexible β-Ga2O3 Schottky barrier diode based on mechanical stripping process

The flexible transverse β-Ga2O3 Schottky barrier diode (SBD) was fabricated by transferring the stripped β-Ga2O3 single crystal film onto muscovite, and its electrical characteristic under flat and bending conditions were tested. It is found that the forward current of the device after bending increases in the small voltage range of 0–1 V and decreases in the large voltage range of 1–4.5 V as the curvature increases. This result is attributed to the two mechanisms that the barrier height decreases and the scattering increases with the increase of the curvature. The decrease in barrier height makes it easier for electrons to migrate from the cathode to the anode in small voltage range, while the current decreases in large voltage range due to scattering. It is further found that the maximum transconductance (gm) and subthreshold swing (SS) deteriorate with the increase of curvature and the corresponding voltage value of gm drifts to the right. In addition, the switch ratio of the device under flat conditions is 108, whereas in bending tests the switch ratio is 107 which is only reduced by one order of magnitude and it is essentially the same as the current level under flat conditions.

HBN Flake Embedded Al2O3 Thin Film for Flexible Moisture Barrier.

Due to the vulnerability of organic optoelectronic devices to moisture and oxygen, thin-film moisture barriers have played a critical role in improving the lifetime of the devices. Here, we propose a hexagonal boron nitride (hBN) embedded Al2O3 thin film as a flexible moisture barrier. After layer-by-layer (LBL) staking of polymer and hBN flake composite layer, Al2O3 was deposited on the nano-laminate template by spatial plasma atomic layer deposition (PEALD). Because the hBN flakes in Al2O3 thin film increase the diffusion path of moisture, the composite layer has a low water vapor transmission ratio (WVTR) value of 1.8 × 10−4 g/m2 day. Furthermore, as embedded hBN flakes restrict crack propagation, the composite film exhibits high mechanical stability in repeated 3 mm bending radius fatigue tests.

Load testing and simulation of asymmetric cable-net used for flexible rockfall protection barriers

Flexible protection barriers are often located on the mountainsides in order to decrease the risk of rockfall. In the present study, different scales of experimental tests are considered, to gauge the behaviour and to estimate the bearing capacity of a new type of cable-nets used for these flexible barriers in case of quasi-static loads. A large experimental campaign addressing cables characterization, as well as the behaviour of the constitutive cells of the net, which particular shape, a water drop shape instead of the classical rings, induces asymmetric loading transfer. Finally, the net behaviour itself is characterized through appropriate tests. These tests highlighted the non-linear behaviour perceived at different scales and permitted to evaluate the bearing capacity of the various components. Numerical simulations using the finite element code Abaqus were also conducted for the different components, a group of constitutive cells with rigid or fuse clip or the whole net, to reproduce the behaviour observed experimentally.

A comparative assessment of ASM4 rockfall barrier modelling

One key element of flexible rockfall barriers is the net which intercepts the block trajectory. The ASM4 ring net is one of the widely spread net technology for medium to high energy impacts. The accurate modelling of its mechanical behaviour has thus been the aim of many research programs, most of which use the discrete elements method and tension members with material non-linearities. This paper proposes hence a comparison of the three main families of models: linear spring models, tensile ring models and flexural ring models. First, homogenisation techniques are used to characterise intrinsic properties at local scale. Then, the question of the experimental identification of these properties is addressed. Afterwards, the relevance of the identified behaviour is investigated through two case studies. The first one consists in a simple hyperbolic paraboloid structure which has a closed form solution involving large displacements. The second one is based on an experiment on a reduced scale barrier with centred impact and extend the comparison to various kind of data and loading cases. The conclusion presents the main results of the various comparisons, it gives insight on the features that each model can capture and provides some guidelines for designers at early stage design.

Recyclability and Redesign Challenges in Multilayer Flexible Food Packaging-A Review.

Multilayer flexible food packaging is under pressure to redesign for recyclability. Most multilayer films are not sorted and recycled with the currently available infrastructure, which is based on mechanical recycling in most countries. Up to now, multilayer flexible food packaging was highly customizable. Diverse polymers and non-polymeric layers allowed a long product shelf-life and an optimized material efficiency. The need for more recyclable solutions asks for a reduction in the choice of material. Prospectively, there is a strong tendency that multilayer flexible barrier packaging should be based on polyolefins and a few recyclable barrier layers, such as aluminium oxide (AlOx) and silicon oxide (SiOx). The use of ethylene vinyl alcohol (EVOH) and metallization could be more restricted in the future, as popular Design for Recycling Guidelines have recently reduced the maximum tolerable content of barrier materials in polyolefin packaging. The substitution of non-recyclable flexible barrier packaging is challenging because only a limited number of barriers are available. In the worst case, the restriction on material choice could result in a higher environmental burden through a shortened food shelf-life and increased packaging weights.

Surface wave propagation over small bottom undulations in the presence of a submerged flexible porous barrier

The problems of scattering of surface gravity waves over an undulated bottom in the presence of either a porous vertical elastic plate or a tensioned porous membrane are addressed. A simplified perturbation technique is employed to split the governing boundary value problem into a series of problems involving the zeroth and the first-order potential functions. The solution to the problem associated with zeroth-order potential is obtained by reducing it to a Fredholm integral equation with the help of Havelock’s theorems. An approximate solution of the integral equation is obtained by applying the multi-term Galerkin technique. Application of Green’s integral theorem leads to finding the first-order reflection and transmission coefficients in terms of integrals involving the shape function representing the bottom deformation and the solution of the zeroth-order problem. The accuracy of the present results is established by generating some previous results for the case of an elastic plate submerged in water with bottom deformation. From the graphical presentation of the results it is observed that at certain values of frequency related to the ripple wavenumber, the first-order reflection coefficient exhibits resonant nature, whereas the net reflection is affected by the flexibility characteristics as well as the porosity of the structure.