SNAP Process Research Articles

Snapping of a viscoelastic cylindrical panel under loading with small volume compressed gas

The paper considers the dynamics of the process of a flat rectangular elastic panel having an initial deflection equal to the critical deflection of the static problem of panel stability. The panel is loaded with compressed gas enclosed in a small volume container. Using this value, the load acting on the panel during the snapping process will depend on the deflection of the panel as a result of the adiabatic expansion of the compressed gas. The main goal of the work is to investigate the stability region of a cylindrical panel when loaded with compressed gas. The problem is solved using a developed methodology based on the method of separating variable equations of mathematical physics. Based on calculations, it was found that when the panel is loaded with compressed gas enclosed in a small-volume container, a stabilizing effect appears, i.e. a certain deflection interval appears where the panel does not lose stability. The presence of external pressure makes it possible to expand this area, i.e. the external environment increases the “stabilizing” effect. Also, taking into account the viscoelastic properties of the material expands this area to 10%.

SNAP Process and Technology Improvement Grants (USDA)

Federal Grants & ContractsVolume 47, Issue 12 p. 8-8 Grants Alerts SNAP Process and Technology Improvement Grants (USDA) First published: 14 May 2023 https://doi.org/10.1002/fgc.33048Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume47, Issue1218 May 2023Pages 8-8 RelatedInformation

Bistable characteristics of unsymmetric cross-ply composite laminates considering different boundary shapes

The aim of this paper is to study the bistable characteristics of unsymmetric cross-ply composite laminates induced by thermal stress during the curing process when considering different boundary shapes. The changes in geometry for five types of planform shapes, have been focused, which are named rectangular planform (RP), elliptical planform (EP), trapezoidal planform (TP), diamond planform (DP) and cruciform planform (CP) respectively. The parameters that characterize the bistable performance of the laminates, including the principal curvature and snap load, were measured. The principal curvatures in different stable configurations were determined with analytical, numerical, and experimental methods, and the load-displacement curves in the snapping process were successfully obtained. Moreover, the boundary effect caused by the difference in planform shapes, which cause the local curvature of the bistable composite laminate to change, were also discussed. Predictions from an analytical shell model are verified through comparisons with nonlinear finite element simulations and experimental test results.

Dynamic snap-through instability and damped oscillation of a flat arch of hard magneto-active elastomers

In this paper, we investigated the dynamic responses of a hard magneto-active arch (HMAA) under three forms of external magnetic fields. An HMAA was fabricated by compressing a flat plate of hard magneto-active elastomers (HMAEs) to buckle. A theoretical model was formulated by using the Euler–Lagrange (E-L) equation and considering the damped oscillations. Our experiment and theory showed that the HMAA could achieve a dynamic snap-through instability at a magnitude of 63 Gs. The snapping process only took a few microseconds, and the HMAA had a speed of about 141 mm/s and a large displacement of about 10 mm. After the snap-through instability, the period of oscillation was about 60 ms. Especially, the HMAA subjected to a triangle magnetic field behaved as a bistable system. This paper is desired to help design robust devices of HMAEs by harnessing the rapid configuration change through the snap-through instability.

Effect of humic acid on the single-stage nitrogen removal using anammox and partial nitritation (SNAP) process: performance and bacterial communities

The present research investigated the effect of humic acid on nitrogen removal performance and microbial community structure in a single-stage nitrogen removal using anammox and partial nitrification (SNAP) reactor. The results showed that 576 mg·L−1 humic acid enhanced nitrogen removal efficiency maximally to 96% and nitrogen removal rate to 1.61 kgN·m−3·d−1. COD concentration (provided by humic acid) of 120–233 mg·L−1, the nitrogen removal rate (NRR) was 1.27 kgN·m−3·d−1. COD concentration (provided by humic acid) of 259–658 mg·L−1 enhanced the NRR above 1.5 kgN·m−3·d−1, and COD concentration increased to 691–1637 mg·L−1, the average NRR decreased to 1.45 kgN·m−3·d−1. The results indicated COD concentration of 691–1637 mg·L−1 has the strongest positive effect on the anammox reaction. The analysis of high throughput sequencing presented COD concentration of 500 mg·L−1 promoted the growth of Candidatus_brocadia, and 1500 mg·L−1 COD concentration improved Candidatus kuenenia growth. Functional genes from KEGG and COG database showed that the expressions of nitrate reductase and nitrite reductase were highly promoted with the increase of humic acid concentration, which proved the nitrification enhanced by humic acid. All findings in this study were inferred that humic acid enhanced nitrogen removal in SNAP reactor. This result will improve the practical and effective use of the SNAP process to treat landfill leachate in engineering application.

Snap behaviors of bistable unsymmetric cross-ply composite cylindrical shells with different thicknesses

Bistable composite structures have a wide application prospect in the design of deformable structures. In this study, the snap behaviors of unsymmetric cross-ply bistable composites with different thicknesses are investigated. Besides the experiments, the relationships between load and displacement during the snap process are also analyzed by finite element (FE) methods. The load-displacement curves of composite shell with four layers and two layers are completely different. The results of the two-layer cylindrical shell with resin layer are in good agreement with the experimental results. The resin layer has great influence on the snap behaviors of the two-layer bistable cylindrical shell, although it has little effect on the four-layer cylindrical shell. So it cannot be ignored in the analyzing of two-layer bistable shell. The cause of experimental errors is also analyzed. The research results of this paper have reference value for the engineering design of bistable composite structures.

Flow-induced periodic snap-through dynamics

Abstract

Tristable behaviour of cross-shaped unsymmetric fibre-reinforced laminates with concave–convex boundaries

This paper presents cross-shaped unsymmetric fibre-reinforced cross-ply laminates with concave–convex boundaries, which have three stable configurations. The third stable equilibrium configuration is a transition state which occurs in the snap process from the first to second equilibrium configurations. The snap processes, including the first–third–second and second–third–first, between the different stable equilibrium configurations of tristable cross-shaped unsymmetric laminates were investigated by experimental and numerical methods, and the parameters that characterise the tristable performance of the laminates, including the principal curvature, snap load, and displacement, were measured. The principal curvatures in different stable configurations were determined with analytical, experimental, and numerical methods, and the load–displacement curves and buckling phenomena in the snapping process were successfully recorded. Moreover, the influences of the reinforcement material, thickness of the single layer, and geometric parameters on the tristable performance of the cross-shaped unsymmetric fibre-reinforced cross-ply laminates were discussed. According to the results, the analytical, experimental, and numerical results agree well.

Non-Uniform Curvature Model and Numerical Simulation for Anti-symmetric Cylindrical Bistable Polymer Composite Shells.

The bistability of anti-symmetric thin shallow cylindrical polymer composite shells, made of carbon fiber/epoxy resin, has already been investigated based on the uniform curvature and inextensible deformation assumptions by researchers in detail. In this paper, a non-uniform curvature model that considers the extensible deformations is proposed. Furthermore, a parametric modeling and automatic postprocessing plug-in component for the bistability analysis of polymer composite cylindrical shells is established by means of ABAQUS-software, by which the equilibrium configurations and the load-displacement curves during the snap process can be easily obtained. The presented analytical model is validated by the numerical simulation and literature models, while the factors affecting the bistability of anti-symmetric cylindrical shells are revisited. In addition, the planform effects of anti-symmetric cylindrical shells with rectangular, elliptical and trapezoidal planform are discussed. The results show that the presented analytical model improves the accuracy of the prediction of the principal curvature of second equilibrium configuration and agree well with the numerical results.

Rapid start-up of single-stage nitrogen removal using anammox and partial nitritation (SNAP) process in a sequencing batch biofilm reactor (SBBR) inoculated with conventional activated sludge

The long initiation period of the single-stage nitrogen removal using the anammox and partial nitritation (SNAP) process is a major hindrance to its practical application. In this study, the SNAP process was initiated in a sequencing batch biofilm reactor (SBBR) inoculated with conventional activated sludge within 46 days when the ammonium removal efficiency (ARE) and total nitrogen removal efficiency (TNRE) reached 86.9% and 76.8%, respectively. After the 46 days, ARE of 93.7 ± 2.8% and TNRE 77.5 ± 2.3% were achieved. The rapid initiation of the SNAP process could be attributed to biomass retention provided by biofilm and regulation of parameters including dissolved oxygen (DO), pH, temperature, organic matter, inorganic carbon (IC), free ammonium (FA), and free nitrite acid (FNA). The microbial analysis suggested that microbial richness of biomass increased while the microbial diversity reduced during the initiation of the SNAP process. Nitrosomonas and Candidatus Brocadia were the main ammonium oxidizing bacteria (AOB) and anammox bacteria (AnAOB), respectively, and were found to be enriched. Nitrospira was the main nitrite oxidizing bacteria (NOB) and relative abundance of it was decreased. The heterotrophic denitrification established rapidly and then gradually declined during the start-up of the SNAP process.

Fast start-up of the single-stage nitrogen removal using anammox and partial nitritation (SNAP) from conventional activated sludge in a membrane-aerated biofilm reactor

The single-stage nitrogen removal using anammox and partial nitritation (SNAP) is a promising alternative for low-cost ammonium removal from wastewaters. This study aimed to evaluate the anammox biomass enrichment and SNAP process start-up in a laboratory-scale membrane-aerated biofilm reactor (MABR) at nitrogen loading rates of 50 g N.m−3.d−1 (period 1) and 100 g N.m−3.d−1 (period 2). Anammox activity was observed after 48 days, and the SNAP process was stable after 80 days. In period 1, the average total nitrogen (TN) removal was 78 ± 6%, and the maximum removal was 84%. In period 2, the average TN removal was 61 ± 5%, and the maximum was 69%. Higher dissolved oxygen levels may have caused imbalances in the microbial community in period 2, decreasing the reactor performance. These results demonstrated the potential of the MABR for the fast implementation of the single-stage partial nitritation and anammox processes.

Hygroscopic influence on bistable characteristics of antisymmetric composite cylindrical shells: An experimental study

This paper investigates the effect of moisture on bistable characteristics of antisymmetric composite cylindrical by using experimental and finite element method. The bistable characteristics are characterized by the curvatures of antisymmetric composite cylindrical shells in different stable states and snap processes between the two stable states which are indicated by the load–displacement curve and snap load. The manufactured specimens after dried in the oven are immersed in distilled water to full saturation and the saturated salt solutions (MgCl2) to full saturation. The specimen achieves different moisture that is immersed in distilled water at the different period until full saturation and in the saturated salt solution (MgCl2) with the same period of saturation in distilled water. Specimens with different moisture are then mechanically loaded on a testing machine to transform between two stable states. Load–displacement curves are recorded in the computer, from which the snap loads can be found. After the test, the principal and twisting curvatures are captured by a digital image processing. The results are contrasted with hygroscopic influence on another kind of bistable composite structure (asymmetric cross-ply laminates) in this paper. The results show that the shapes and snap loads of antisymmetric composite cylindrical shells are influenced by the moisture increasing.

Simultaneous nitrogen and phosphorus removal by combined anammox and denitrifying phosphorus removal process

AbstractBACKGROUNDSingle‐stage nitrogen removal using anammox and partial nitrification process (SNAP process) is a promising process to treat low C/N wastewater relying on ammonia‐oxidizing bacteria (AOB) and anaerobic ammonium oxidation (anammox) bacteria. However, excess nitrate (NO3−) in effluent is a common problem for the SNAP process. The denitrifying phosphorus removal (DPAO) process using NO3− as electron acceptor was adopted to reduce nitrate in effluent from the SNAP process, while phosphorus removal was also achieved simultaneously. Thus, a novel combined process (DPAO‐SNAP process) was established to achieve nitrogen and phosphorus removal simultaneously.RESULTSThe DPAO‐SNAP process achieved average 95.7% chemical oxygen demand, 98.2% total nitrogen and 97.8% total phosphorus removal efficiencies during stable stages. Furthermore, Candidatus Kuenenia and Nitrosomonas were identified as the dominant genus for anammox bacteria and AOB, respectively. Defluviicoccus was enriched as the glycogen‐accumulating microorganism (GAOs) for the DPAO process with acetate as the carbon source, while Rhodocyclales was the dominant genus in the DPAO process with mixed carbon source.CONCLUSIONThis DPAO‐SNAP process could not only resolve the problem of effluent NO3− in the SNAP process but also simultaneously achieved high removal efficiency of COD, TN and TP with a low need for carbon sources (COD/N/P=25:15:1). © 2017 Society of Chemical Industry

Modelling and testing of the snap-through process of bi-stable cross-ply composites

Bi-stable response of cross-ply composites is modelled when snap processes are trigged by a vertical force and the laminate is supported at four points. The model is based on the Rayleigh–Ritz technique. Non-linear von Kármán strains, non-uniform curvatures and uniform through-the-thickness normal strain are included in the analysis. The analysis has been carried out step by step, by small increments of the applied load. Experiments in four [0/90]T carbon/epoxy laminates have been carried out for comparison in a test configuration that fulfils the requirements of the model. The multi-event snap-through and intermediate equilibrium positions have been experimentally observed and recorded. The initial snap-through and snap-back load–displacement curves have been experimentally determined and compared to those corresponding to the proposed model.

Start-up and bacterial communities of single-stage nitrogen removal using anammox and partial nitritation (SNAP) for treatment of high strength ammonia wastewater

In this study, a lab-scale sequencing batch biofilm reactor (SBBR) was used to start up the single-stage nitrogen removal system using anammox and partial nitritation (SNAP) process seeding from surplus activated sludge. The volumetric nitrogen loading rate (vNLR) was firstly 0.075kgNm−3d−1 and then gradually increased to 0.60kgNm−3d−1. A maximal total nitrogen (TN) removal rate of 0.54kgNm−3d−1 was achieved by the SNAP process after 132days operation with NH4+-N and TN removal efficiency of 99.4% and 90.5%, respectively. This reactor may have applications for the SNAP process treating high strength ammonia wastewater. And dewatered surplus activated sludge was recommended as the seed sludge for engineering applications. The dominant bacterial strains were Xanthomonas campestris, Nitrosomonas europaea and Ignavibacterium album, corresponding to the percentage of 24%, 22% and 20%, respectively, based on the 16S rDNA amplicon pyrosequencing of the SNAP sludge.

Systematic experimental and numerical study of bistable snap processes for anti-symmetric cylindrical shells

Anti-symmetric cylindrical shell as a novel bistable composite structure, offers wide applications in many fields. The entire snap-through and snap-back processes of the anti-symmetric cylindrical shell are systematically studied through experimental investigation and numerical simulation. The experimental and numerical results are also compared with the analytical predictions. The parameters used to characterize the bistable performances of the shells, including coiled-up radii, stress distributions of the shell in the second stable state, and snap load are measured. Load–displacement curves and buckling phenomena in the snapping process are successfully captured. The influences of the geometrical sizes and layup conditions on the bistable performance of anti-symmetric cylindrical shells are discussed in detail. Comprehensive experimental and numerical results indicate that the initial mid-plane transverse radius and ply angle are two key factors that affect bistable behaviors in the same environmental conditions, which is accordant with theoretical predictions, whereas the number of plies and longitudinal length of the shell only influence on the snap load and stress distribution. The angle of embrace is demonstrated of no influence on bistable performance of anti-symmetric cylindrical shells.

Rapid startup and high rate nitrogen removal from anaerobic sludge digester liquor using a SNAP process

In this study, a single-stage autotrophic nitrogen removal reactor, packed with a novel acrylic fiber biomass carrier material (Biofix), was applied for nitrogen removal from sludge digester liquor. For rapid start-up, conventional activated sludge was added to the reactor soon after the attachment of anammox biomass on the Biofix carriers, which allowed conventional activated sludge to form a protective layer of biofilm around the anammox biomass. The Nitrogen removal efficiency reached 75% within 1week at a nitrogen loading rate of 0.46 kg-N/m(3)/day for synthetic wastewater treatment. By the end of the synthetic wastewater treatment period, the maximum nitrogen removal rate had increased to 0.92 kg-N/m(3)/day at a nitrogen loading rate of 1.0 kg-N/m(3)/day. High nitrogen removal rate was also achieved during the actual raw digester liquor treatment with the highest nitrogen removal rate being 0.83 kg-N/m(3)/day at a nitrogen loading rate of 0.93 kg-N/m(3)/day. The thick biofilm on Biofix carriers allowed anammox bacteria to survive under high DO concentration of 5-6 mg/l resulting in stable and high nitrogen removal performance. FISH and CLSM analysis demonstrated that anammox bacteria coexisted and surrounded by ammonium oxidizing bacteria.

Development of single-stage nitrogen removal using anammox and partial nitritation (SNAP) and its treatment performances

Single-stage Nitrogen removal using Anammox and Partial nitritation (SNAP) process was newly developed as an economical nitrogen removal process for ammonium rich wastewaters. The experimental studies for the evaluation of SNAP process were carried out using a novel biofilm reactor, in which hydrophilic net-type acryl fiber biomass carrier was applied. This SNAP reactor was operated under operational conditions of pH 7.5-7.7, 35 degrees C and DO 2-3 mg/L, and 60 to 80% of influent NH4-N was removed under loading rate of 0.48 kg-N/m3/d. Through the DNA analysis of the attached sludge, it was made clear that ammonium oxidizing bacteria (AOB) and anammox bacteria coexisted in the attach-immobilized sludge on the acryl fiber biomass carrier. Favorable conditions for the growth of anammox bacteria were created inside attach-immobilized nitrifying sludge. Two kinds of anammox bacteria and two kinds of AOB were detected in the SNAP sludge. Existence ratios of anammox and AOB were estimated to be 15% and 8.7%, respectively, based on the obtained clone numbers. This coexisting condition was confirmed by the FISH image of SNAP sludge and its confocal laser scanning microscope.

On the post-buckling behavior of bilaterally constrained plates

A combined experimental/analytical effort is carried out to elucidate the post-buckling response of bilaterally constrained columns and plates under monotonically increasing edge displacement. Real-time observations of the outward deformation of the plate via the shadow moire technique facilitate deep insight into the behavior of this class of problems. The lateral constraints lead to a sequential plate snapping process that arise from secondary buckling of a contact zone(s) in the plate. The critical load for mode transition is evaluated systematically as a function of the confining gap, the plate aspect ratio and other system parameters. The results generally exhibit significant scatter that is attributed to the inherent asymmetry of the deformation pattern in such systems. A large-deformation finite element analysis incorporating frictional contact algorithm is used to model the problem. The deformation patterns as well as the critical loads predicted from this analysis generally agree well with the experimental results. A simple analytic expression, based on the linear theory of beams, is developed for the critical loads. The experimental data are found to be well contained by lower and upper bounds from this analysis once the plate surface interacts with the two confining planes. The results of this work may serve as a basis for multilaminate design possessing unique mechanical response and superior energy absorption capability.

Superconductive thin-film devices for microwave applications

At IEN, two types of superconductive microwave sensors have been developed. Nb microbridge bolometers, working in the frequency range between 26 and 40 GHz, have been fabricated on polyimide substrates. For these devices we have measured a responsivity of 7 X 103 V/W. With a careful choice of device parameters, it is possible to achieve a noise equivalent power (NEP) of about 10-12\(W/\sqrt {Hz} \), 3 orders of magnitude lower than that obtained with conventional bolometers. SIS mixers for radioastronomical observations at 94 GHz based on Nb/Al-AlOx/Nb Josephson tunnel junctions have been also realized. Josephson junctions, both single and two junctions stacks, have been fabricated using a SNAP process where liquid anodization is used not only for insulation and area patterning, but also for trimming the junction dimensions at a micrometer level. In order to use these junctions as SIS mixers for astrophysical observations at 94 GHz and possibly at higher frequencies, we have fabricated junctions with an area of a few square micrometer and current densities up to 104 A/cm2. The junctions are integrated with a low-pass filter made with a stripline technique, designed by means of a 3D electromagnetic simulator. The reflection coefficient of the filter has been evaluated to be 0.2 in the best case.