Flexible Wall Research Articles

A Novel Landfill Liner Material for Solidified Lake Sediment Based on Industrial By-Product and Construction Waste: Engineering Behavior and Cr(VI) Breakdown Characteristics

Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 × 10−6 cm2/s–9.5 × 10−6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 × 10−8 to 4.13 × 10−7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills.

Impact of flexible walls of curved channel on biological flow of Reiner-Rivlin fluid

In this study, the Reiner-Rivlin fluid model is opted for examination as the complex dynamical fluid and is flowing on account of the waves travelling on the walls of flexible curved channel. The governing equations are solved analytically up to the first order to analyse the velocity profiles. As the governing equation is highly nonlinear, so the problem is solved by regular perturbation technique about small wave number. After the implication of regular perturbation, the second order Cauchy Euler ordinary differential equations are obtained for both the systems. A detailed analysis is conducted on the effects of diverse factors, such as the rheological properties of fluid, the curvature radius of the channel, the wave amplitude and the wall properties. The velocity of the fluid enhanced by increasing wall properties parameters, wave number, Reynolds number and the amplitude ratio parameter. It is also observed that the Reiner-Rivlin fluid flows slowly as compare to the Newtonian fluid, this type of findings can be helpful for the understanding of many physiological processes, like blood flow and food swallowing. This study enlightens the interaction between the curved nature of the channel and Reiner-Rivlin fluid flow in peristalsis that can be a great contribution for the designing of biomedical devices. Such types of problems have great significance in many physiological processes and engineering applications like microfluidic devices and drug delivery systems.

Predictive model for the instability of flexible formwork concrete wall in secondary mining of non-pillar coal mining

The secondary mining movement in non-pillar coal extraction causes significant overrun damage to flexible formwork concrete walls, leading to extensive deformation of roadway roof and bottom plates. This adversely affects working face efficiency and safety. The engineering context focuses on the non-pillar gob-side retaining walls in the 1315 working face of Zhaozhuang Coal Mine and the 23107 working face of Xiegou Coal Mine. Through on-site investigation, numerical simulation, theoretical analysis, and testing, we explore the stress migration law and destabilizing mechanism of the flexible formwork concrete wall influenced by the secondary mining movement of the coal-free pillar along the hollow wall. The research results showed that: (1) During the mining back process, the concrete wall formed with flexible formwork may experience stress concentration, leading to excessive damage and compromising mining safety. (2) Developing a predictive stress model for the concrete wall with flexible formwork is essential. If the stress surpasses the ultimate compressive strength during mining back, reinforcement becomes necessary.3) The length of damage overrun in the flexible formwork concrete wall exhibits two distinct stages as the distance back to mining increases. The first stage shows nearly linear growth, while the second stage indicates a decreasing growth rate, ultimately stabilizing. The application of Z6 concrete reinforcing agent effectively strengthens the flexible formwork concrete wall.

15 Years of Vacuum Bell Therapy for Pectus Excavatum: Long-term Outcomes and Influencing Factors

BackgroundLong-term results and factors affecting outcomes of vacuum bell therapy for pectus excavatum are relatively unknown. MethodsWe conducted a retrospective study on patients (<18y) treated with vacuum bell therapy between May 2008 and October 2021. Primary outcome was treatment success; secondary outcomes were analysis of daily time spent on treatment, treatment duration, complications, long-term follow-up, treatment for patients awaiting a Nuss procedure, treatment for female patients, and factors affecting outcomes. ResultsOf 259 patients treated with vacuum bell therapy, 18.9% (n = 49/259) were still being treated, 17.4% (n = 45/259) were lost to follow-up and 63.7% (n = 165/259) completed treatment, with a 52.1% (n = 86/165) success rate. Median follow-up was 64.0 months (interquartile range 48.0–87.0). More time spent daily on vacuum bell therapy, total treatment duration, and overnight use led to a higher success rate (P = 0.002, P < 0.001, P < 0.001 resp.). Complications (22.8%, n = 59/259) were minor, recurrence occurred in 2.3% (n = 2/86) of patients. Of the patients treated while awaiting a Nuss procedure, 26.7% (n = 4/15) no longer required the Nuss procedure. Breast growth made 39.3% (n = 11/28) of female patients quit treatment. Deeper deformities (P = 0.02, P = 0.009), flexible chest wall (P = 0.007) and symptomatic pectus excavatum (P = 0.02) resulted in lower success rates. ConclusionsVacuum bell therapy is successful in up to 52.1% of patients. Overnight vacuum bell use and treatment while awaiting a Nuss procedure should be encouraged. Older patients with a stiff chest wall can be successfully treated with prolonged treatment. For female patients watchful waiting or early treatment, to prevent challenges during breast growth, is preferred. Level of evidenceLevel II.

Discrete heating of turbulent FSI in a vented lid-driven enclosure

Heat dissipation from a segmental heat source confined in a vented cavity with a moving lid is investigated numerically. The left wall is made flexible with an opening to force the cooling fluid with Rein. The fluid is discharged out from another opening located in the opposite right wall. The lid of the cavity is driven by a speed four times greater than the inlet velocity, ReLid = 4Rein. The κ -ε turbulent model together with the interaction of the fluid with the flexible wall (FSI) are solved numerically using the method of finite element. The impacts of Reynolds, Richardson Ri and Prandtl Pr numbers, elasticity of the flexible wall and the location of the inlet ports are scrutinized. It is found that the location of the inlet port and the Prandtl number play crucial roles in improving the overall performance. It is found that the lower position of the inlet port gives better performance than the higher position, where the performance criterion is 1.69 at Ri = 100. Results reveal that the lower Prandtl number (0.71) gives higher Nusselt number, where at Ri = 100, setting Pr at 0.71 the Nusselt number increases by 125% more than Pr = 6.5. It is concluded that the flexible wall either promotes the Nusselt number or alleviates the pressure drop.

Effect of Flexible Tank Wall on Seismic Response of Horizontal Storage Tank

Horizontal storage tanks are integral to the petrochemical industry but pose significant risks during earthquakes, potentially causing severe secondary disasters. Current seismic designs predominantly assume rigid tank walls, which can lead to an underestimation of seismic responses. This study introduces a novel analysis method for assessing the dynamic response of flexible-walled horizontal storage tanks. By separating the liquid velocity potential into convective and impulsive components and integrating these with beam vibration theory, we developed a simplified mechanical model. A parameter analysis and dynamic response research were conducted using numerical methods. Results indicate that flexible tank walls amplify seismic responses, including liquid dynamic pressure peaks, base shear, and overturning bending moments, compared to rigid walls. Additionally, the impact of flexible walls is more pronounced in tanks with larger radii, aspect ratios, diameter–thickness ratios, and H/R ratios. These findings highlight the necessity for revised seismic design approaches that consider wall flexibility to enhance the safety and resilience of horizontal storage tanks.

Analysing the application of a flexible formwork pre-cast wall driving roadway along goaf in a large mining height face

The technology of building a retaining roadway along goaf or a protecting roadway with a small coal pillar has been developed and applied for many years, and a satisfactory supporting effect has been obtained in medium–thick coal seam and thin coal seam mining. However, the gob-side roadway or small coal pillar mining in a thick coal seam is still subjected to technical problems occasioned by factors such as high roadway, high support pressure beside roadway, and waste of coal resources. To solve these problems, the author proposes an innovative technology of coal-free mining: the technology of driving roadway along goaf with a flexible formwork pre-cast wall. The article utilizes the 3503 and 3505 working faces of Wangzhuang Coal Industry Group as the research background, and comprehensively introduces the principle of the technology and the overburden rock movement law. Through theoretical calculations and numerical simulations, the support resistance and support parameters of flexible formwork pre-cast walls have been determined and successfully performed in industrial practice. The results indicate that the combination of the flexible mould pre-cast wall coal pillar-free mining technology and roof cutting process is more conducive to the maintenance of the roadway in the lower working face, and effectively reduces the stress and deformation of the surrounding rock. The roof and floor of the drivage roadway move, and the deformation of the two sides is small; furthermore, the overall roadway retention effect is satisfactory, which meets the requirements of mining in the lower working face. The coal pillar pertaining to the 20 m section of the 5 m high mining height face was recovered for Wangzhuang Coal Mine, and the recovery rate of the coal resources and the driving speed of the roadway were improved. The proposed method can be popularised and applied in this mine and even in the mining of 15# large-height coal seams in the two cities.

First report of Sansabaina acicula, an organic-cemented siliceous agglutinated foraminifera from the Early Permian glaciomarine Pebbley Beach Formation, Southern Sydney Basin, southeastern Australia

A ca 6 cm-thick microfossil coquina bed dominated by plastically deformed and siliceous tubular test fragments is described for the first time from the Lower Permian (Artinskian) Pebbley Beach Formation of coastal and glacial marine origin in the southern Sydney Basin, southeastern Australia. The test fragments are mostly very large, straight, smooth, nearly cylindrical in shape, and the test walls are composed mainly of homogenous microcrystalline quartz grains. This homogeneous siliceous test-wall microstructure is interpreted to have resulted from diagenetic alteration of what might have been originally organic-cemented, flexible (not rigid) and siliceous agglutinated walls. As such, this microscopic tubular test is identified as Sansabaina acicula, an organic-cemented siliceous-agglutinated foraminifera originally described from the Kungurian Quinnanie Shale in the Carnarvon Basin of Western Australia. The discovery of Sansabaina acicula supports the previous interpretation of the studied strata being deposited in a stressed marine shelf environment. G. R. Shi [guang@uow.edu.au], Sangmin Lee* [lsam@uow.edu.au], Paul F. Carr [pcarr@uow.edu.au] and Brian G. Jones [briangj@uow.edu.au], School of Earth, Atmospheric and Life Sciences, University of Wollongong, Northfields Avenue, NSW 2522 Australia David W. Haig [david.haig@uwa.edu.au], Oceans Institute, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia.

Experimental research of a flexible retaining wall model in laboratory conditions

Introduction. The Russian standards determine the lateral earth pressure at the failure surface stage, which corresponds to the Coulomb’s theory. In this case, the limit values of earth pressure on the flexible wall remain independent from the nature and intensity of deformation of the retaining structure. Therefore, computational methods for retaining walls are to be improved considering the above-mentioned factors.Aim. To obtain experimental data in order to develop a computational method for determination of the active earth pressure on retaining structures depending on their deformations.Materials and methods. Experimental tests were carried out by physical simulation for various models of flexible retaining walls using a purpose-designed laboratory test bench. Medium sand was used as a model backfill soil; its physical properties were determined under laboratory conditions in accordance with State Standard 5180-2015.Results. The tests provided data on the character of backfill soil deformations within the wedge of failure for different kinematic conditions of the retaining wall model and, accordingly, justified the application of inclined block phenomenological model, used to develop a computational method for determining the active earth pressure on retaining walls.Conclusions. Experimental tests indicate the correlation between deformation nature of the backfill soil and accepted conditions of soil operation during the development of engineering method for determining the lateral earth pressure. The obtained experimental data can be used in adoption and verification of the suggested computational method that enables shoring of excavations to be designed more reasonably in mutual conformity with the actual earth pressure diagrams.

Real-time ultrasonic water level IoT sensor for in-situ soil permeability testing

Soil permeability tests require a time series of water level measurements to determine system losses, including both infiltration and evaporation. Laboratory measurements of flow are standardised by international regulations such as ASTM International, ISO or UNE, but field measurements are not as well described and in some cases may require definition and specification of test conditions. This is the case for geosynthetic clay liner (GCL) products, where permeability is assessed by a laboratory measurement using a flexible wall permeameter as defined in standard test method D 5887-04. This method is not able to evaluate the performance of such products in the field and therefore cannot guarantee their ability to be used for the repair of landfill liner overlays. For this reason, we have defined a field test in a confined steel ring and developed a real-time ultrasonic IoT device to evaluate water losses over a period of time. The test method was applied in Mallorca (Spain) and as a result the quality of a landfill cover repair solution was evaluated, the corresponding civil works were carried out and the basis for future field measurements of soil permeability tests on different materials and conditions was established.

Progress and challenges in designing dynamic in vitro gastric models to study food digestion.

Understanding the mechanisms involved in food breakdown in the human gastrointestinal (GI) tract is essential in food digestion research. Research to study food digestion in the human GI tract requires in vivo and in vitro approaches. In vivo methods involving human or animal subjects are often cost-prohibitive and raise ethical concerns. For these reasons, in vitro approaches are becoming more common. Several dynamic in vitro models that mimic one or more components of the GI tract have been developed at various research institutions and by commercial companies. While there is evidence of considerable novelty and innovation in the design of these models, there are many differences among them in how the mechanical breakdown of solid foods is accomplished. In some systems, modulating water pressure is used to achieve peristaltic contractions of the gastric antrum, whereas, in other models, the flexible walls of a gastric chamber are compressed by the movement of rollers or clamps outside the walls of the test chamber. Although much progress has been made in standardizing the biochemical environment appropriate to the food digestion process, there is a lack of standard protocols to measure mechanical forces that result in the breakdown of solid foods. Similarly, no standardized methods are available to evaluate the results obtained from in vitro trials for validation purposes. Due to the large variability in the design features of in vitro models used for food digestion studies, developing consensus-based standards for the mechanical aspects of food breakdown is needed.

Method to identify if torsional mode of a building is its first mode

Torsionally flexible buildings (that have torsional mode as fundamental mode) twist during earthquake shaking, and may collapse partially or completely depending upon the direction and level of shaking. The problem is aggravated when the building is torsionally unsymmetrical. Some design codes (like Eurocode, Indian Code) explicitly prohibit the design of such buildings. This paper presents a simple approximate method to identify torsionally flexible RC Moment Frame and RC Structural Wall buildings at the initial proportioning stage itself without carrying out a detailed structural analysis. It is possible to identify whether or not the first mode is torsional mode of a building (i.e., torsionally flexible building) if Natural Period Ratio τ&gt;1 by modelling the building with rigid diaphragm and distribution of mass &amp; stiffness along the height of building, and estimating: (1) radius of gyration of rotational mass rm of each floor plan geometry by lumping the masses of slabs, beams and all vertical elements at each nodes, (2) radius of gyration of twisting stiffness rKθ of all vertical elements using their translational and torsional stiffnesses (considering flexibility of adjoining beams and vertical elements accounting for both flexural and shear deformations), and (iv) τ (=rm/rKθ). The method is validated with 3D Modal Analysis (using τ =Tθ/T, where Tθ is Uncoupled Torsional Natural Period and T Uncoupled Translational Natural Period) of hypothetical buildings using a commercial structural analysis software. Also, parameters are identified that lead to τ&gt;1, and solutions suggested to avoid torsional flexibility in buildings. Further, the method helps identify vertical stiffness irregularity in buildings. Draft provisions are suggested for inclusion in seismic codes. Also, poor performance of multi-storey building (with τ&gt;1) is demonstrated using nonlinear static and nonlinear time history analyses.

Numerical Investigation of Seismic Behaviour for a Flexible Cantilever Retaining Wall with Cohesive Backfill

In the seismic design of flexible cantilever walls retaining cohesive backfill soil, the common practice is to neglect the cohesion effect. Dynamic lateral earth pressure is typically evaluated based on approaches primarily intended for cohesionless soils or through analytical pseudo-static methods. Nevertheless, both experimental and theoretical evidence has demonstrated significant effects due to soil cohesion that are not accounted for by these methods. This study involved finite element modeling (FE) of a flexible cantilever wall with a height of 5.4m, supporting homogeneous cohesive backfill under initial static and seismic loadings. The calculated active earth thrust was then compared with values obtained experimentally and through conventional analytical methods. The obtained results indicate that the presence of soil cohesion significantly reduces seismic demands on flexible cantilever retaining walls, resulting in a substantial reduction of seismic active earth pressures and total seismic thrust by up to 50% and 52%, respectively. It enhances also the overall stability of the system by shifting the point of application of seismic thrust toward the base of the wall, thereby increasing the safety margin. In addition, it significantly decreases the wall displacement at the stem top, with reductions of up to 104% compared with the case involving cohesionless backfill. It was observed that the conventional methods recommended by some seismic regulations largely underestimate seismic active pressure.

Mixed convection in a variable size cavity: Effect of flexible wall characteristics

Boosting the mixed convection in vented cavities using a moving wall results in a disturbed strong circulation. This study investigates the mitigation of the disturbed circulation to promote the transfer of heat by providing additional size to the circulation. The use of deformable walls with different thicknesses, lengths and modulus of elasticity is suggested for this problem. The top wall of the cavity is adiabatic and moves in the positive direction, and four speeds were studied; 0.5, 1, 2 and 4 times the fluid velocity at the inlet vent. The ratio of the natural to forced convection is controlled by ranging Richardson number by 0.01 ≤ Ri ≤ 100. Three aspect ratios are studied; AR = 0.5 (horizontal cavity), 1 and 2 (tall cavity). The problem is treated numerically using the finite element method. Results indicate that the fluid flow inside the vented square cavity changes from major single vortices into multi vortices at high (Ri = 100). Results affirm that a flexible wall yields a higher Nusselt number than the rigid wall, it's about 12 %, and 20 % for Ri = 0.01 and 10, respectively. A thicker flexible wall augments the Nusselt number for Ri ≤ 10. For specified conditions, the Nusselt number of the horizontal cavity is 17.7 % greater than the tall cavity. The lid speed of uLid = 4 uin exhibits a competent role in raising the Nusselt number for low Richardson number.

Study on hydraulic conductivity of dredged sediment-attapulgite vertical cutoff walls under confining pressure

Landfills require effective containment systems to prevent the leakage of leachate into the underground environment. Cutoff walls are commonly employed for this purpose, with options including rigid and flexible designs. In areas where structural strength is not a primary concern, flexible cutoff walls offer lower permeability and environmental benefits due to their lack of cement content, thereby reducing CO2 emissions. This study investigates the use of dredged sediment and attapulgite as materials for flexible cutoff walls. Through analyses of bound water content, free water content, hydraulic conductivity, and scanning electron microscopy, we explore the impact of confining pressures on cutoff wall permeability.Our findings reveal that the consolidation induced by confining pressure does not significantly alter the bound water content within the cutoff wall. Instead, changes in water content are predominantly attributed to variations in free water content. Under identical confining pressures, we observe a positive correlation between permeability and hydraulic gradient, with permeability increasing as the hydraulic gradient rises, and anti-permeability decreasing accordingly. Additionally, when holding the hydraulic gradient constant, increasing confining pressure leads to a continuous decrease in permeability. Microscopic analyses highlight that high confining pressure not only compresses pore diameter but also alters pore morphology, thereby influencing permeability.This study contributes to the understanding of cutoff wall behavior under different conditions. Our results demonstrate that increasing confining pressure during soil consolidation effectively reduces cutoff wall permeability to meet design standards. However, the influence of high leachate head on permeability should also be considered. These findings provide a more environmentally friendly and lower permeability option for landfill sites, which is significant for the design and enhancement of containment systems in landfill sites.

Cochlear implant electrode design for safe and effective treatment.

The optimal placement of a cochlear implant (CI) electrode inside the scala tympani compartment to create an effective electrode-neural interface is the base for a successful CI treatment. The characteristics of an effective electrode design include (a) electrode matching every possible variation in the inner ear size, shape, and anatomy, (b) electrically covering most of the neuronal elements, and (c) preserving intra-cochlear structures, even in non-hearing preservation surgeries. Flexible electrode arrays of various lengths are required to reach an angular insertion depth of 680° to which neuronal cell bodies are angularly distributed and to minimize the rate of electrode scalar deviation. At the time of writing this article, the current scientific evidence indicates that straight lateral wall electrode outperforms perimodiolar electrode by preventing electrode tip fold-over and scalar deviation. Most of the available literature on electrode insertion depth and hearing outcomes supports the practice of physically placing an electrode to cover both the basal and middle turns of the cochlea. This is only achievable with longer straight lateral wall electrodes as single-sized and pre-shaped perimodiolar electrodes have limitations in reaching beyond the basal turn of the cochlea and in offering consistent modiolar hugging placement in every cochlea. For malformed inner ear anatomies that lack a central modiolar trunk, the perimodiolar electrode is not an effective electrode choice. Most of the literature has failed to demonstrate superiority in hearing outcomes when comparing perimodiolar electrodes with straight lateral wall electrodes from single CI manufacturers. In summary, flexible and straight lateral wall electrode type is reported to be gentle to intra-cochlear structures and has the potential to electrically stimulate most of the neuronal elements, which are necessary in bringing full benefit of the CI device to recipients.

An insight into laboratory column experiments for microplastic transport in soil

Plastic litter, most of which is landfilled or improperly disposed to aquatic and terrestrial environments, is a global environmental concern. Large-sized plastics can fragment into smaller pieces due to abrasion or weathering effects generating microplastics (MPs) which are tiny plastic debris smaller than 5 mm. In the aquatic environment, particularly oceans, MPs have been well documented in terms of their occurrence and toxicity. Soils have been shown to be an important sink of MPs, but the latter's fate and transport in the subsurface are not well understood. Laboratory studies have so far mostly employed rigid-wall columns to investigate MP transport through porous media, with a vast majority focusing on glass beads and predominantly sandy soils. Much less knowledge is available on MP transport in clay soils and minerals where transport mechanisms are much slower and the potential for chemical reactivity higher. There is hence a need for establishing experimental protocols for conducting such experiments. The paper presents preliminary results for an investigation assessing whether flexible wall permeameters (FWP) are suitable for the study of the transport of MPs in clayey soils. Key advantages of FWP are that they are widely available and commonly used and that they allow the control of effective stress in the sample. Two key questions addressed in this paper are whether the instruments themselves act as sink for MPs or as source of material that may interfere with the measurement of MPs in the effluent.

Saturated permeability and water retention capacity in biochar-methanotrophs-clay for new landfill cover system

A new landfill cover system, biochar-methanotrophs-clay (BMC) cover is recommended for reducing methane emissions at landfills. It also contributes to decreasing soil permeability and improving soil water retention in a long time, due to highly porous structure of biochar and the growth metabolism of methanotrophs. To determine the effects of biochar content, oxidation aging times and methane-filled days on hydraulic properties, a total of 60 groups of experiments were conducted. The saturated hydraulic conductivity (ksat) was obtained by flexible wall permeameter with controllable hydraulic head pressure. The results showed that the ksat of BMC increased with increasing biochar content and oxidation aging times, while decreased with adding methane-filled days. The soil-water characteristic curves (SWCCs) were obtained with soil suction measured by the filter paper method. The results indicated the water retention capacity of MBC reduced with increasing oxidation aging times but increased with adding methane-filled days. Detected by mercury intrusion porosimetry (MIP), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), the differences displayed the changes of pore structures and extracellular polymeric substances (EPS). The oxidation aging of biochar increased the volume of pores, resulting in the increased ksat and the decreased water retention capacity. However, the growing of methanotrophs decreased the volume of pores, resulting in the ksat decreased and the water retention capacity increased due to EPS. No matter how many times the oxidation aging process was experienced, the BMC with longer methane-filled days exhibited relatively lower ksat and better water retention capacity. This implied a more stable barrier capacity to reduce water infiltration in the long term. By combing a series of macro and micro experiments, this paper provides theoretical guidance for the application of biochar-methanotroph-clay mixture to landfill covers.

Electrically evoked compound action potentials are associated with the site of intracochlear stimulation

ObjectivesObjective measurements to predict the position of a cochlear electrode during cochlear implantation surgery may serve to improve the surgical technique and postoperative speech outcome. There is evidence that electrically evoked compound action potentials (ECAP) are a suitable approach to provide information about the site of stimulation. This study aims to contribute to the knowledge about the association between the intraoperative intracochlear ECAP characteristics and the site of stimulation.MethodsIn a retrospective cohort study, patients undergoing cochlear implant surgery with flexible lateral wall electrode arrays (12 stimulating channels) between 2020 and 2022 were analyzed. The CDL was measured using a CT-based clinical planning software. ECAP were measured for all electrode contacts and associated to the CDL as well as to the site of stimulation in degree.ResultsSignificant differences among the amplitudes and slopes for the individual stimulated electrode contacts at the stimulation sites of 90°, 180°, 270°, 360°, 450° and 540° were found. The values showed a trend for linearity among the single electrodes.ConclusionsECAP characteristics correlate with the electrode’s position inside the cochlea. In the future, ECAP may be applied to assess the intracochlear position inside the cochlea and support anatomy-based fitting.

Current design of rectangular steel silos: limitations and improvement

This study proposes a modification for the current design approach for square and rectangular silos that accounts for silos’ wall flexibility. First, the authors investigated the effect of wall stiffness symbolized by the wall width-to-thickness ratio (a/t) and silo’s dimensions, on the wall-filling pressure using a recently validated 3D finite element model (FEM). The model was then employed to predict the pressures acting on silos’ walls accounting for the stress state in stored granular materials. Most design formulas and guidelines assume silos’ walls to be rigid. This assumption is acceptable for the case of rigid wall concrete silos; however, it is questionable for semi-rigid, flexible wall metal silos. Consequentially, it is crucial to determine the minimum wall stiffness necessary to secure the applicability of the current design rigid wall assumptions and to propose a way to deal with semi-rigid and flexible walls. To this end, several wall pressure distributions that correspond to filling steel silos with varied wall thicknesses were studied. A new adjustment to the Janssen technique was proposed for a better estimate of the wall-filling pressures for square and rectangular silos. In the case of prismatic silos, the Eurocode uses the Janssen equation together with an equivalent radius of a corresponding circular silo (with the same hydraulic radius) to determine the wall pressure. This method predicts pressure values that are practically accurate for rigid-wall silos, but its accuracy decreases for semi-rigid and flexible-wall silos. As an enhancement, the Janssen equation was modified in this research to generate more accurate pressure estimates based on the equivalent volume concept. The finite element results of several developed models with the same granular material were compared to the estimations of the newly established approach to verify the broad range of its applicability.