Flexible Barrier Research Articles

The effects of upstream flexible barrier on the debris flow entrainment and impact dynamics on a terminal barrier

The destructive nature of debris flows is mainly caused by flow bulking from entrainment of an erodible channel bed. To arrest these flows, multiple flexible barriers are commonly installed along the predicted flow path. Despite the importance of an erodible bed, its effects are generally ignored when designing barriers. In this study, three unique experiments were carried out in a 28 m long flume to investigate the impact of a debris flow on both single and dual flexible barriers installed in a channel with a 6 m long erodible soil bed. Initial debris volumes of 2.5 and 6 m3 were modelled. For the test setting adopted, a small upstream flexible barrier before the erodible bed separates the flow into several surges via overflow. The smaller surges reduce bed entrainment by 70% and impact force on the terminal barrier by 94% compared to the case without an upstream flexible barrier. However, debris overflowing the deformed flexible upstream barrier induces a centrifugal force that results in a dynamic pressure coefficient that is up to 2.2 times higher than those recommended in guidelines. This suggests that although compact upstream flexible barriers can be effective for controlling bed entrainment, they should be carefully designed to withstand higher impact forces.

Oblique water wave scattering by vertical elastic porous barriers

The mixed boundary value problem associated with scattering of obliquely incident water waves by a flexible porous barrier of different barrier configurations is considered here. The originally defined half-plane problem is converted into a quarter-plane problem. Then a novel connection is established between the solution potential of the converted problem and a resolvable potential in the quarter-plane. Further Galerkin approximation is used to obtain close bounds for the reflection and the transmission coefficients. Numerical results are presented for scattering quantities against various parameters in each of the problems under consideration.

Study of Second‐order Effects of Steel Posts Supporting Rockfall Flexible Barriers

AbstractFlexible barrier systems have been widely used to resist falling rocks to protect railways, highways and residential buildings. As one of the important components of the system, steel posts are the supporting structures to maintain the system integrality and should not fail before the failure of other components. Under the impact of falling rocks, the ring net panels undergo large deflection causing high compression forces on the steel posts. To more accurately capture the structural behaviour of the steel posts, the nonlinear effects due to the initial imperfection of steel posts are considered. The performance of an individual steel post extracted from a full‐scale test is studied and the result reveals that the post would suffer global buckling about the minor axis with initial imperfection considered. Hence, the second‐order effects of steel posts should be incorporated in the global analysis of the flexible barrier system under rockfall impacts.

LNG 화물창 2차 방벽의 기계적 성능에 아라미드 섬유가 미치는 영향에 대한 연구

Recently, although the size of the LNG Cargo Containment System (CCS) has been increasing, the secondary barrier is reported to remain unchanged, and the conventional Flexible Secondary Barrier (FSB) used in Mark-Ⅲ type has been pointed out to be vulnerable to failure owing to thermal and cyclic loads. In this respect, a tensile test was carried out to verify the reinforcing effect of FSB using aramid fiber on weft compared to the conventional FSB. In order to consider the LNG leakage situation, a series of tensile tests were conducted from ambient to cryogenic temperature, and mechanical properties were evaluated for each fiber direction on account of anisotropy. Tensile behavior and fracture analyses were performed to confirm the mechanical properties of each material according to temperature. Tensile test results proved that replacing the aramid fiber instead of E-glass fiber used on weft is effective in enhancing the mechanical properties.

Demonstration of an all‐in‐one solution for fire safe upholstery furniture: A benign backcoating for smoldering and flame‐resistant cover fabrics

SummaryThe development of fire prevention and mitigation technologies with a benign toxicological and environmental profile has become of particular interest in the USA due to the recent adoption of state regulations that severely restrict the use of flame retardants in certain products, like residential upholstered furniture (RUF). Herein, the effectiveness of a backcoating technology in RUF is demonstrated. The backcoating is a silicone‐based elastomer, filled with vinyl‐silane modified aluminum‐hydroxide that was applied to the back side of an upholstery fabric to generate a flexible and effective fire barrier. Chair mock‐ups were assembled using either an uncoated cotton fabric (UCF) or a backcoated cotton fabric (BCF) as cover fabric. The fire performance of the chair mock‐ups incorporating the UCF and BCF was compared in an open‐burning calorimeter after exposure to either a flaming ignition source or a smoldering ignition source. In the flaming ignition tests, the chair mock‐ups with BCF showed a reduction in the peak heat release rate and the total heat released by factors of about 6 and 45, respectively, as compared to the chair mock‐ups with UCF. In the smoldering ignition tests, the chair mock‐ups with UCF showed intense smoldering, which eventually transitioned to open flaming, whereas, the BCF chair mock‐ups showed no sign of foam or fabric smoldering. The backcoating also offered a durable fire protection solution, with an abrasion resistance of BCF roughly doubled compared to UCF. Ultimately, the backcoating provided an unusual combination of smoldering and flaming ignition resistance while complying with several recently enacted or pending U.S. state regulations.

A Review on Emerging Barrier Materials and Encapsulation Strategies for Flexible Perovskite and Organic Photovoltaics

AbstractPerovskite solar cells (PSCs) and organic photovoltaics (OPVs) have undergone rapid development within the last decade, exhibiting exciting properties such as high efficiency, flexibility, and the potential for large‐scale fabrication through roll‐to‐roll (R2R) processing. Despite this, operational stability is recognized to be an ongoing challenge as prolonged device lifetimes are scarcely observed. This instability can be narrowed down to both “intrinsic degradation” and “extrinsic degradation,” with exposure to moisture and oxygen having detrimental effects on device performance. A means of delaying the degradation of flexible PSC and OPV devices is through barrier encapsulation. Despite glass encapsulation exhibiting ideal barrier properties, the potential for flexible devices and high‐throughput R2R fabrication requires the development of flexible barrier materials and encapsulation strategies. These barriers must demonstrate outstanding moisture permeation resistance, high transparency, chemical and thermal stability, and must be able to withstand repeated mechanical deformation. Herein, the fundamental principles of PSC and OPV devices are initially discussed, highlighting the degradation mechanisms and current stability obstacles. A review of the latest flexible barrier materials and encapsulation strategies follows, introducing stability studies that have been undertaken on flexible PSCs and OPV, along with suggestions as to the direction that future research may take.

Weibull 통계분석을 이용한 MARK-III LNG CCS의 2차 방벽 FSB 파단강도 표준화 연구

In this study, the fracture strength of Flexible Secondary Barrier (FSB) composites was standardized by conducting a distribution analysis of the fracture probability, considering that the fracture strength of FSB composites such as glass fiber reinforced composites is relatively large. As the mechanical performance of FSB composites varies with the fiber direction, 20 replicate uniaxial tensile tests were performed for different temperatures ranging from the ambient to cryogenic conditions, considering the actual operating environment of liquefied natural gas. For the probability statistical analysis, the Weibull distribution analysis derived from the weakest link theory was used, considering the large variance in the fracture strength and brittle fracture behavior. The results of the Weibull distribution analysis were used to calculate the standard fracture strength of the FSB composites for different fiber directions. The findings can help ensure the reliability of the FSB mechanical properties in different fiber directions in the design of the secondary barrier and structural analyses.

Quantifying the transition of impact mechanisms of geophysical flows against flexible barrier

Flexible barriers have been increasingly used worldwide for mitigating natural hazards involving various geophysical flows. The analysis and design of flexible barriers need to distinguish two major impact mechanisms, runup and pile-up, which remain poorly understood due to complicated interactions between the impacting flow and the deformable barrier. In this study, a unified computational approach based on coupled computational fluid dynamics and discrete element method (CFD-DEM) is employed to examine the impact mechanisms of a wide spectrum of geophysical flows against a deformable and permeable flexible barrier. We consider geophysical flows including rock avalanche, debris avalanche, debris flow, debris flood and mud flow, and a flexible barrier consisting of a barrier net, cables and brakes. The signatures of runup and pile-up mechanisms are thoroughly analyzed, in terms of flow features and barrier responses. The effects of Froude numbers (Fr = 0.46–7.40), solid volume concentrations (0.1–1), and fluid rheologies (Newtonian and non-Newtonian fluids) on the impact mechanism transitions are systematically examined. Two nondimensional indices, the static-peak load ratio of the barrier and the momentum reduction ratio of the flow, are proposed for identifying the transition of impact mechanism from pile-up to runup. The transition is found to occur with either an increase in Fr or solid volume concentration of the flow. Increased viscosity of the fluid in a solid-fluid mixture may result in a transition occurring at a higher Fr. This study helps gain insights into the two impact mechanisms and their transitions and may provide a useful reference for the future design of flexible barriers in mitigating hazardous geophysical flows.

General equations for landslide-debris impact and their application to debris-flow flexible barrier

The runup height and impact load of landslide debris are the key parameters for design of debris hazard mitigation structures. However, the movement of obstacle (e.g., deformation of flexible barrier) still cannot be quantitatively considered in the existing analytical models. This study proposes general equations for landslide-debris impact under vertical jet and momentum jump modes. Especially, the influence of flow regime and obstacle movement (in the form of a modified Froude number), state of granular material, compressibility (density change), and flow resistance within the jump volume are explicitly considered in the momentum jump model. Through comparison between model prediction and experimental results, it is found that the vertical jet model prediction agrees well with the physical measurements. While the discrepancy between the momentum jump model and experimental results mainly comes from the inappropriate characterization of the unsteady flow properties (velocity and flow depth). Systematic parametric study demonstrates that the functionality of debris-flow flexible barrier primarily relies on the deflection of barrier, and the state of granular material also affects the impact load of dry granular flows.

Research Progress in the Preparation of Flexible Substrate Barrier Films

The development of flexible electronics towards for the direction of bend ability, lightweight, portability, long life against falling. The performance of the substrate in the flexible electronics plays a very important role in the development of electronics. In this article, three preparation technologies of thin films are introduced, including CVD, PVD and ALD. The paper also introduces the research progress on the preparation of substrate barrier films, and one main challenge that may face by the preparation of thin film materials. In order to satisfy the development of flexible electronics, improving the substrate’s performance constantly is needed. Finally, the development of preparing barrier films is prospected.

Impact of Flexible Work Arrangements, Self-Efficacy, and Barriers on Daily Physical Activity Among University Staff.

Little is known about the link between flexible work arrangements and health behaviors, such as physical activity. This study aimed to explore how self-efficacy and daily barriers to physical activity influence daily levels of physical activity on workdays when university staff members used a flexible work arrangement (flextime or telework). Full-time university staff employees (N = 61, mean age = 41; 89% female) participated in this daily diary study. Participants completed an initial survey followed by daily surveys over the course of one workweek, resulting in 281 diary days. The most frequently reported barriers to physical activity were as follows: lack of time, feeling tired, and not enough motivation. Multilevel models revealed that as the number of barriers increased, minutes of physical activity significantly decreased. Self-efficacy was not significantly related to daily physical activity. Participants reported fewer minutes of physical activity on flextime workdays compared to days when a flexible work arrangement was not used (ie,traditional workday). Daily use of a flexible work arrangement did not moderate the association between barriers and physical activity. This study illustrated the influence of daily barriers and flextime workdays on physical activity levels, which can inform workplace health programs for university staff.

Dynamic response of flexible rockfall barriers with different block shapes

Flexible rockfall barriers are commonly constructed on steep hillsides to mitigate rockfall. The evaluation of the dynamic response of proprietary flexible rockfall barriers is conventionally performed using full-scale field tests by dropping a block onto the barriers in accordance with the European test standard ETAG 027. The block typically has a spherical or polyhedral shape and cannot reproduce more complex rockfall scenarios encountered in the field. Little attention has been paid to the effects of the block shape on the impact force and structural response. This paper aims to quantitatively reveal the influence of the block shape on the dynamic response of flexible rockfall barriers. First, an ellipsoidal model is established to approximately simulate the block, and the sphericity is employed as the representative index of the block’s shape. A full-scale test on a typical flexible barrier system is carried out and then used to calibrate an advanced three-dimensional finite element model. Finally, the dynamic responses of flexible rockfall barriers are analyzed and discussed, focusing on the effects of the block’s shape. The numerical results show that the sphericity will obviously influence the maximum elongation of flexible barriers, the peak impact force, the peak force of the upslope anchor cable, the peak force of the lower main support cable, the axial peak force of the post, and the peak shear force at the post foundation. The assumption of spherical or polyhedral blocks in the test standard could lead to the defensive failure of flexible rockfall barriers in some impact scenarios.

Poly(Vinyl Alcohol)-Hydrogel Microparticles with Soft Barrier Shell for the Encapsulation of Micrococcus luteus.

The encapsulation of bacteria in polymers results in hybrid materials that are essential for the long-term biological activity of bacteria and formulations in practical applications. Here, the problem of bacterial escape and the exchange of metabolism products from hydrogel microparticles within an aqueous environment are addressed. Bacteria are encapsulated in chemically cross-linked poly(vinyl alcohol) (PVA) hydrogel-microparticles followed by their encapsulation in a pH-responsive and soft antibacterial shell of poly(N,N-diethylamino ethyl methacrylate) (PDEAEMA). This polymer shell acts selectively with regards to the mass transport in and out of the microparticle core and is affected by environmental parameters, such as pH and antibacterial effect. The pH-responsive PDEAEMA shell forms an open porous structure that accelerates nutrient transfer into the PVA core containing living Micrococcus luteus (M. luteus). Results show that the antibacterial effect of PDEAEMA retards the escape of bacteria up to 35 days when the shell is open. Additionally, the permeation of a small molecule into the gel, for example, methylene blue dye through the core/open-shell structure, certifies a flexible barrier for mass transport, which is required in the long term for the biological activity of encapsulated M. luteus.

Transparent SiOxCyHz Barrier Film Prepared by PECVD with Upper and Lower Pair Electrode Rolls Structure

Flexible and transparent barrier film is demanded in the fields of organic solar thin-film cells, flexible organic light-emitting diodes, electronic paper and vacuum insulation boards. To prepare films with high water resistance, flexible SiOxCyHz films were prepared on PET using HMDSO as monomer and Oxygen (O2) as reaction gas. SiOxCyHz films were prepared by plasma enhanced chemical vapor deposition (PECVD) with upper and lower pair electrode rolls structure, with the width of electrode rolls up to 600 mm. The influences of oxygen content, film thickness, oxygen/monomer ratio, reaction vacuum degree on water vapor transmission rate (WVTR) were studied. This coating method of oxide high barrier film has great application potential in the development of barrier film industry.

Mathematical modelling and design of isolation diaphragms for pressure gauges

The paper discusses some questions of equilibrium, stability and shape optimization of circular membranes with arbitrary profile along the meridian. Such membranes can be used as a flexible barrier to isolate the media on one side of a diaphragm from media on the other side, whilst allowing the transmission of pressure with minimal loss. The main goal of the analysis is to propose techniques for designing such shape of corrugated membranes that satisfy the requirements of so call “slow growing linear or almost linear” behavior of the pressure-volume diagram. The applied Kirchhoff-Love theory for non-shallow shells was used as a base for deriving nonlinear as well as linearized boundary value problems of equilibrium. A genetic algorithm was used to evaluate and optimize the characteristics of corrugated membranes. The presented analysis of the membrane with the maximum linear stroke showed its efficiency and reliability. At the same time, special attention should be paid to the basic parametrization used in modelling, since the mathematically optimal solution is not always suitable from the point of view of membrane production technology.

A low power flexible dielectric barrier discharge disinfects surfaces and improves the action of hydrogen peroxide

There is an urgent need for disinfection and sterilization devices accessible to the public that can be fulfilled by innovative strategies for using cold atmospheric pressure plasmas. Here, we demonstrate a successful novel combination of a flexible printed circuit design of a dielectric barrier discharge (flex-DBD) with an environmentally safe chemical reagent for surface decontamination from bacterial contaminants. Flex-DBD operates in ambient air, atmospheric pressure, and room temperature without any additional gas flow at a power density not exceeding 0.5 W/cm2. The flex-DBD activation of a 3% hydrogen peroxide solution results in the reduction in the bacterial load of a surface contaminant of > 6log10 in 90 s, about 3log10 and 2log10 better than hydrogen peroxide alone or the flex-DBD alone, respectively, for the same treatment time. We propose that the synergy between plasma and hydrogen peroxide is based on the combined action of plasma-generated OH· radicals in the hydrogen peroxide solution and the reactive nitrogen species supplied by the plasma effluent. A scavenger method verified a significant increase in OH· concentration due to plasma treatment. Novel in-situ FTIR absorption spectra show the presence of O3, NO2, N2O, and other nitrogen species. Ozone dissolving in the H2O2 solution can effectively generate OH· through a peroxone process. The addition of the reactive nitrogen species increases the disinfection efficiency of the hydroxyl radicals and other oxygen species. Hence, plasma activation of a low concentration hydrogen peroxide solution, using a hand-held flexible DBD device results in a dramatic improvement in disinfection.

Effect of inkjet-printed flexible dielectric barrier discharge plasma on reduction of pathogen and quality changes on sliced cheese

The objective of this study was to investigate pathogen reduction and quality changes in sliced cheddar cheese treated with inkjet-printed flexible dielectric barrier discharge (FXDBD) plasma. The samples were treated with plasma for 0, 5, 10, 15, and 20 min. The surviving populations of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were significantly reduced by 2.65, 2.80, and 2.03 log CFU/g, respectively, after 20 min. The main reactive species that could be involved in bacterial inactivation were ozone (O3) and nitrogen oxides (NOx), which were produced at concentrations of 298.19 and 28.08 ppm, respectively, after 20 min plasma treatment. The pH of the plasma-treated sample was lower than that in the control group (P < 0.05), whereas there was no significant difference among treatment times. With increasing plasma treatment time, the L* value decreased, while the b*, total color difference, and 2-thiobarbituric acid reactive substances values increased (P < 0.05) while the redness (a*) value remained unchanged. These results indicate that inkjet-printed FXDBD plasma can effectively inactivate pathogens in cheese; however, it causes an increase in lipid oxidation. Plasma treatment with newly developed inkjet-printed FXDBD showed improved microbiological safety with minimal effects to the physicochemical quality of cheese.

Antibacterial and safety tests of a flexible cold atmospheric plasma device for the stimulation of wound healing

Cold atmospheric plasma (CAP) devices generate an ionized gas with highly reactive species and electric fields at ambient air pressure and temperature. A flexible dielectric barrier discharge (DBD) was developed as an alternative antimicrobial treatment for chronic wounds. Treatment of Staphylococcus aureus in collagen-elastin matrices with CAP for 2 min resulted in a 4 log reduction. CAP treatment was less effective on S. aureus on dermal samples. CAP did not affect cellular activity or DNA integrity of human dermal samples when used for up to 2 min. Repeated daily CAP treatments for 2 min lowered cellular activity of dermal samples to 80% after 2 to 4 days, but this was not significant. Repeated treatment of ex vivo human burn wound models with CAP for 2 min did not affect re-epithelialization. Intact skin of 25 healthy volunteers was treated with CAP for 3× 20” to determine safety. Although participants reported moderate pain scores (numerical rating scale 3.3), all volunteers considered the procedure to be acceptable. Severe adverse events did not occur. CAP treatment resulted in a temporarily increased local skin temperature (≈3.4°C) and increased erythema. Lowering the plasma power resulted in a significantly lower erythema increase. Good log reduction (2.9) of bacterial load was reached in 14/15 volunteers artificially contaminated with Pseudomonas aeruginosa. This study demonstrated the in vitro and in vivo safety and efficacy in bacterial reduction of a flexible cold plasma device. Trial registration number NCT03007264, January 2, 2017Key Points• CAP strongly reduced bacterial numbers both in vitro and in vivo.• Re-epithelialization of burn wound models was not affected by repeated CAP.• CAP treatment of intact skin was well tolerated in volunteers.

Rational design of vapor‐deposited self‐crosslinking polymer for transparent flexible oxygen barrier coatings

AbstractTransparent flexible barrier coatings consisting of a copolymer of 2‐isocyanatoethyl methacrylate and 4‐aminostyrene were fabricated using a facile vapor‐based initiated chemical vapor deposition (iCVD) method. The isocyanate and amino groups were well reserved during deposition and reacted on the substrate surface, inducing self‐crosslinking. The resultant coating showed a fairly smooth pinhole‐free surface with more than 99% light transmittance across the visible range. With a proper compositional ratio, the synthesized coating demonstrated oxygen permeability 26 and 8 times lower than commercial PET and PVDF barrier films, respectively. The achieved barrier performance is attributed to the designed molecular structure, where interchain crosslinks are produced between a combination of both rigid and flexible side chains. Such combination enabled efficient packing of space while avoiding loose structures with low permeation resistance. The crosslinked network with rather flexible urea linkages also imparted excellent mechanical strength and high flexibility to the coating. Furthermore, the reported method is compatible with current industrial manufacturing process, thus expecting great potential in flexible electronics encapsulation.

Debris flow impact on a flexible barrier: laboratory flume experiments and force-based mechanical model validation

Nowadays, hydrogeological instability is a very critical issue because of its impact on population, infrastructures and economic and productive sectors. This makes essential to use advanced and reliable defense technologies, which are able to guarantee high performance and reliability. Flexible and permeable structures are ideal for stopping natural phenomena like debris flow, thanks to their high deformation capacity and their water permeability. This study presents some results obtained from laboratory tests related to the impact of a simulated debris flow against a scaled physical model of the barrier. A granular flow composed of aggregates of known size particle was released in a channel with variable inclination and known length and height. Using this experimental setup, several tests were carried out by varying the inclination of the channel and the geometry of the barrier. The results obtained were correlated with data deriving from a simplified analytical model; the comparison between the measured and calculated values made possible to assess the good prediction capability of the model, providing a simple and innovative tool to design and assess the safety of deformable protection barriers.