Bar Model Research Articles

B/PS bulges in DESI Legacy edge-on galaxies – I. Sample building

ABSTRACTWe present the biggest up-to-date sample of edge-on galaxies with boxy/peanut-shaped (B/PS) bulges and X-structures. The sample was prepared using images from the Dark Energy Spectroscopic Instrument (DESI) Legacy catalogue and contains about 2000 galaxies. To find suitable candidates in catalogue, we made the assumption that the residues (original images minus model) of galaxies with B/PS bulges should exhibit a characteristic X-shape. Galaxies with such features were selected by eye and then used as input data for a neural network training, which was applied to a bigger sample of edge-on galaxies. Using the available data and the photometric models from the literature, we investigated the observational and statistical properties of the sample created. Comparing the B/D ratios for galaxies with and without B/PS bulges, we found that the B/D ratio for galaxies from our sample is statistically higher, with typical values in the range ≈0.2–0.5 depending on the decomposition procedure. We studied how the opening angles φ of the X-structure and the length of its rays are distributed in the formed sample and found them to be consistent with previous measurements and predictions from N-body models, e.g. $\varphi \gtrsim 25{^\circ }$, but measured here for a much larger number of galaxies. We found a sharp increase in the B/PS bulge fraction for stellar masses log M⋆ ≳ 10.4, but for edge-on galaxies, which complements the results of previous works. The sample can be used in future work to test various bar models and their relationship with B/PS bulges, as well as to study their stability and evolution.

Monotonic and cyclic bond responses of steel bar with steel-polypropylene hybrid fiber reinforced recycled aggregate concrete

The bond failure between steel bars and concrete is the main reason for the strength degradation and deformation increase of structures in service. In this study, the bond behavior of steel bars with steel-polypropylene hybrid fiber reinforced recycled aggregate concrete (HFRAC) under monotonic and cyclic loadings was investigated. The acoustic emission (AE) technique was applied to monitor the bond response and the inner damage evolution of specimens during the loading process, and the microstructure of HFRAC was analyzed through the scanning electron microscope (SEM). The hysteresis curves, failure modes, bond strength degradation rate, and energy dissipation capacity, were systematically investigated by considering the effects of water-cement ratio, recycled aggregate replacement ratio, steel fiber volume fraction, and polypropylene fiber volume fraction. Experimental results demonstrated that there was more obvious degradation in the bond strength for the HFRAC specimens under cyclic loading, compared with that under monotonic loading. In the case of cyclic loading, the bond strength was degraded with the increase of the number of cycles, and the degradation rate increased quickly with the increase of the displacement amplitude. Moreover, the analysis of AE parameters measured on steel bar bonded recycled aggregate concrete (RAC) and HFRAC specimens, including the AE hits, AE energy, localization of AE events, and average frequency, was performed. Results showed that the AE technique could effectively monitor the bond damage of HFRAC specimens at different stages. A good correlation between the results of AE parameters analysis and the cracking process of specimens was confirmed. Based on the Weibull cumulative distribution function, the bond-slip models of steel bars with HFRAC under monotonic and cyclic loadings were proposed by considering the coupling effect of hybrid fibers and recycled coarse aggregates.

Novel Biodegradable 3D-Printed Analgesics-Eluting-Nanofibers Incorporated Nuss Bars for Therapy of Pectus Excavatum.

A novel hybrid biodegradable Nuss bar model was developed to surgically correct the pectus excavatum and reduce the associated pain during treatment. The scheme consisted of a three-dimensional (3D) printed biodegradable polylactide (PLA) Nuss bar as the surgical implant and electrospun polylactide–polyglycolide (PLGA) nanofibers loaded with lidocaine and ketorolac as the analgesic agents. The degradation rate and mechanical properties of the PLA Nuss bars were characterized after submersion in a buffered mixture for different time periods. In addition, the in vivo biocompatibility of the integrated PLA Nuss bars/analgesic-loaded PLGA nanofibers was assessed using a rabbit chest wall model. The outcomes of this work suggest that integration of PLA Nuss bar and PLGA/analgesic nanofibers could successfully enhance the results of pectus excavatum treatment in the animal model. The histological analysis also demonstrated good biocompatibility of the PLA Nuss bars with animal tissues. Eventually, the 3D printed biodegradable Nuss bars may have a potential role in pectus excavatum treatment in humans.

Bending and twisting with a pinch: Shape morphing of creased sheets

In this letter, we introduce a unique behavior seen in creased sheets where localized changes in the folding (i.e., a pinch) result in global bending and twisting deformations. Using isometric deformation theory, we identify the connections between pinching, crease curvature, and crease torsion that begin to explain the shape-morphing behavior. Given the limitations of isometric deformations, we expand our understanding of the behavior using a mechanics-based bar and hinge model of creased sheets, where the sheet is allowed to stretch. With this tool, we found that the increase in crease curvature and torsion due to pinching are proportional to the curvature of the crease before folding and that curved creases facilitate the bending and twisting. Additionally, we explored the bending and twisting of sheets with more than one crease. We found that sheets with an even number of creases generate more intense twisting than those with an odd number of creases and experience twisting even when the creases are straight. The number of creases had little effect on the pinch-induced bending of the origami. The stiffness of the sheets had little effect on the amount of bending and twisting, but greater spacing between the creases resulted in more bending with little effect on the twisting. Based on these results, we created a framework to design crease patterns to have desirable bending and twisting that can be coupled or not, and demonstrated this programmability with simulations and by pinching physical prototypes. Our findings enable shape morphing of creased sheets with a low-complexity input and a versatile output.

Mid-Channel Braid-Bar-Induced Turbulent Bursts: Analysis Using Octant Events Approach

In a laboratory, a model of a mid-channel bar is built to study the turbulent flow structures in its vicinity. The present study on the turbulent flow structure around a mid-channel bar is based on unravelling the fluvial fluxes triggered by the bar’s 3D turbulent burst phenomenon. To this end, the three-dimensional velocity components are measured with the help of acoustic doppler velocimetry (ADV). The results indicate that the transverse component of turbulent kinetic energy cannot be neglected when analyzing turbulent burst processes, since the dominant flow is three-dimensional around the mid-channel bar. Due to the three-dimensionality of flow, the octant events approach is used for analyzing the flow in the vicinity of the mid-channel bar. The aim is to develop functional relationships between the stable movements that are modelled in the present study. To find the best Markov chain order to present experimental datasets, the zero-, first-, and second-order Markov chains are analyzed using the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). The parameter transition ratio has evolved in this research to reflect the linkage of streambed elevation changes with stable transitional movements. For a better understanding of the temporal behaviors of stable transitional movements, the residence time vs. frequency graphs are also plotted for scouring as well as for depositional regions. The study outcome herein underlines the usefulness of the octant events approach for characterizing turbulent bursts around mid-channel bar formation, which is a precursor to the initiation of braiding configuration.

Assessment and Prediction Model of GFRP Bars’ Durability Performance in Seawater Environment

In this study, the performance degradation law and mechanism of glass fiber reinforced polymer (GFRP) bars were investigated by being immersed in natural seawater (denoted as SW), saline-alkali solution (SA), or wrapped with concrete, and then submerged in natural seawater (SWC). A series of short-beam shear tests were conducted to investigate the effects of aging temperature and time on the interlaminar shear strength (ILSS) of GFRP bars. Microstructure changes, glass transition temperature (Tg) difference, and hydrolysis degree of GFRP bars after aging in three environments for 183 days were analyzed using scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and Fourier transform infrared spectroscopy (FTIR). Test results demonstrated that the temperature could accelerate the strength degradation of GFRP bars significantly. After 183-day aging treatment at 60 °C, the ILSS retention rates of GFRP bars in the three environments of SW, SWC, and SA were 66.41%, 53.10%, and 45.36%, respectively; and Tg was 1.7%, 7.0%, 7.8% lower than that of unconditioned sample, respectively. Meanwhile different degrees of damage, such as separation between fiber and resin and few holes in the resin, were observed on the GFRP bars in the SWC and SA environments. It was also found that irreversible hydrolysis took place in some resins. The durability prediction model of GFRP bars serving in the Yellow Sea of China was established by using Arrhenius equation, and the correlation coefficient with the test data was not less than 0.94.

Sensitivity Analysis of Holdback Bar Release Load during Catapult-Assisted Takeoff of Carrier-Based Aircraft

The release load of holdback bar will affect the safety of catapult-assisted takeoff of carrier-based aircraft, and the accurate control of releasing the load will ensure success. The magnitude and the control accuracy of release load are important parameters which impact the takeoff performance, therefore unstable release load and insufficient release precision are the main factors affecting the takeoff safety. In this paper, mechanical models of the carrier-based aircraft in the catapult-assisted takeoff tensioning state and gliding state after release are established based on multi-body dynamics, contact mechanics and tribological theory, and the influence of the release load of the holdback bar on the catapult-assisted takeoff performance is analyzed. Furthermore, a kinetic model of the holdback bar device is established, and the kinetic characteristics of the release process of the holdback bar are studied. Based on the kinetic model and friction model of the holdback bar, the influencing factors of the sensitivity of the holdback bar release load are analyzed and the structural parameters are optimized. The results show that the released load decreases slowly with the increase of the contact surface angle of the holdback bar structure and increases rapidly when that angle reaches the critical value; besides, the release load increases slowly with the increase of the friction coefficient of the contact surface and increases faster when the critical friction coefficient is reached.

Probabilistic structural performance of RC frames with corroded smooth bars subjected to near- and far-field ground motions

This paper investigates the seismic vulnerability of existing RC frames exposed to corrosion and subjected to near-field and far-field ground motions. A threefold approach for corrosion is adopted to illustrate the probabilistic framework and define time-dependent performance criteria for an accurate seismic fragility assessment. A bond-slip model is employed to simulate the fixed-end rotation and column-beam joints behaviour to account for the deficit in the bond strength of plain rebars. Such a model is calibrated using experimental studies from the literature and considering the effects of corrosion. An inelastic buckling model of steel bars is also incorporated in the finite element model through a hysteretic material to investigate its impact on the deformation capacity of RC members. The effects of near-field and far-field earthquakes are investigated through incremental dynamic analyses (IDA) and cloud analyses on a typical four-storey RC frame with plain bars. Results from the fragility analysis indicate that corrosion has significant effects on the seismic performance of such RC frames over time and near-field pulse-like motions are more destructive than both near-field no-pulse-like and far-field earthquakes.

Architectural Characteristics, Evolutionary Stages, and Sedimentary Models of Clastic Beach Bars

Architectural Characteristics, Evolutionary Stages, and Sedimentary Models of Clastic Beach Bars

Case study of testing different materials for seat belt retractor torsion bar by the means of finite element analysis

This paper examines the use of various materials for the force limiter torsion bar found in an automotive seat belt assembly. We have selected the following materials: carbon steel, cast stainless steel, cast low alloy steel and cast aluminium alloy. The primary method used for this study is finite element analysis (FEA) and the use of the named materials on a 3D model of the torsion bar, constructed using the dimensions of a standard part. The 3D models were created with a 3D CAD program and the FEA analysis was carried out with special software. For the input values, the torsion bar was fixed at one corner and a 360 degree rotation shift at the other corner. A fine mesh of 1.5 mm/element was also set to get a more accurate analysis. The results of this study are in the form of stress, strain, safety factor and displacement plots generated by the FEA analysis software showing the difference between the materials. The main outcome of the study is to determine the best overall material to manufacture the part in terms of performance and cost.

The effect of attachment types and implant level on the stress distribution in a mandibular overdenture: a 3D Finite Element Analysis

Objective: The objective of this study was to evaluate the stress distribution in bone-surrounding implants placedin different levels in a mandibular overdenture. Material and Methods: A Computerized Tomography (CT) scanof an edentulous mandible was used to generate the models. Two implants with an internal connection wereplaced perpendicular to the occlusal plane in the Canine sites of the mandible. The implant in the left side wasplaced 1mm higher than the other side. Dolder bar and ball attachments were designed. Loading was performedby clenching the teeth with reconstruction of the muscles. In the anterior loading condition, force was appliedto the central incisors and in the posterior loading conditions, it was applied to the molars and premolars. Thenthe Maximum Principal Stresses in the peri implant bone was evaluated with finite element analysis. Results:In both models, the highest stress values were recorded in the cortical bone surrounding the higher implantexcept in the ball model with unilateral load application on the right side (64.7 MPa). In almost all loadingconditions the stress value differences in models with bar and ball attachments were low. Only in the anteriorloading condition, the stress magnitude was higher in two implants of the ball model (60.5 MPa in the left sideand 21 MPa in the right side) compared to the bar model (54.5 MPa in the left side and 17.5 MPa in the rightside). Conclusion: The stress concentration did not affected considerably by the attachment system. High stressvalues were found adjacent the implant with a higher level. To reduce the amount of stress, bilateral balanceocclusion should be considered. KEYWORDSStress; Finite element analysis; Overdenture; Dental implants.

Enhancing Mathematical Word Problem Solving Skills: Using Bar Model Visualization Technique

The study purpose is to investigate the effect of Bar Model Visualization Technique on the word problem solving skills of elementary level students in mathematics. Following were the objectives of the study (i) to investigate the effect of Bar Model Visualization Technique on addition word problems-solving skills; (ii) to investigate the effect of Bar Model Visualization Technique on subtraction word problems solving skills; (iii) to investigate the effect of Bar Model Visualization Technique on multiplication word problems solving skills; (iv) to investigate the effect of Bar Model Visualization Technique on division word problems solving skills. The null hypotheses were designed to test the objectives as (i) there is no significant effect of Bar Model Visualization Technique on addition word problem solving skills; (ii) there is no significant effect of Bar Model Visualization Technique on subtraction word problem solving skills; (iii) there is no significant effect of Bar Model Visualization Technique on multiplication word problem solving skills; (iv) there is no significant effect of Bar Model Visualization Technique on division word problem solving skills. The nature of the study was experimental. Pre-test and post-test equivalent group design was used as a tool for data collection in this study. Sample of the study was 40 students (Male & Female) of Government Primary School No.2 Bab-e-Jadeed District Nowshera, Khyber Pakhtunkhwa. The sample students were divided on the basis of pretest scores by applying paired random technique in to experimental group and control group. Data were analyzed by mean, SD and t-test. It was concluded that the concepts of Bar Model Visualization Technique had significant effect on addition word problems and subtraction word problems but it has not significant effect on multiplication word problems neither division word problems. The results of the study show that Bar Model Visualization Technique had significant effect on Mathematical word problem solving skills and also the learner take interest in the subject. It provides alternative method for teacher to teach mathematics subject.

Analysis of Turbulent Flow Structure with Its Fluvial Processes around Mid-Channel Bar

Researchers have recognized that the successive growth of mid-channel bar deposits can be entertained as the raison d’être for the initiation of the braiding process, which is closely interlinked with the growth, decay, and vertical distribution of fluvial turbulent kinetic energy (TKE). Thus, focused analysis on the underlying mechanics of turbulent flow structures in the proximity of a bar deposit occurring in the middle of the channel can afford crucial scientific clues for insight into the initiating fluvial processes that give rise to braiding. In the study reported herein, a physical model of a mid-channel bar is constructed in an experimental flume to analyze the turbulence parameters in a region close to the bar. Notably, the flow velocity plays an important role in understanding the flow behavior in the scour-hole location in the upstream flow divergence zone as well as near the downstream zone of flow convergence in a mid-channel bar. Therefore, the fluctuating components of turbulent flow velocity are herein discussed and analyzed for the regions located close to the bar. In the present study, the impact of the mid-channel bar, as well as its growth in turbulent flow, on higher-order velocity fluctuation moments are investigated. For near-bed locations, the results show the dominance of ejection events in upstream zones and the dominance of sweep events at locations downstream of the mid-channel bar. In scour-hole sections, the negative value of the stream-wise flux of turbulent kinetic energy and the positive value of the vertical flux of turbulent kinetic energy indicate energy transport in downward and forward directions, respectively. The downward and forward energy transport processes lead to scouring at these locations. The maximum turbulent production rate occurs in the wake region of the bar. The high rate of turbulence production has occurred in that region, which can be ascribed to the process of shedding turbulent vortices. The results show that the impact of the presence of the bar is mainly restricted to the lower layers of flow. The turbulent dissipation rate monotonically decreases with an increase in the vertical distance from the bed. The turbulent production rate first increases and then decreases with successive increases in the vertical distance from the bed. The paper concludes with suggestions for the future potential use of the present research for the practical purpose of examining braid bar occurrences in alluvial rivers to develop an appropriate response through training measures.

Semi-Reliability Probability Damage Assessment of GFRP Bars Embedded in Steam-Curing Concrete Beams Based on the Multiple Factors Related Moisture Absorption Model.

GFRP bars will be damaged due to a series of irreversible hygroscopic chemical reactions under humid and hot curing environmental conditions. The multiple factors related to the moisture absorption model were established through the moisture absorption test of GFRP bars embedded in steam-curing concrete, which considered different curing temperatures, different thicknesses of the protective layer, and different diameters of GFRP bars. Semi-reliability probability damage assessment of GFRP bars embedded in steam-curing concrete was described by introducing the reliability and stochastic theory. Subsequently, the tensile test of GFRP bars was carried out to verify the feasibility of the damage assessment. The results showed that the moisture absorption curves of GFRP bars were basically in line with Fick’s law. In addition, the influences of the curing temperature, the thickness of the protective layer, and the diameter on moisture absorption performance were presented. The semi-reliability probability damage assessment model of GFRP bars embedded in steam-curing concrete beams adequately considered the multiple factors related to moisture absorption and the uncertainty and randomness of the influencing factors during the process of moisture absorption.

KESAN KAEDAH MODEL BAR TERHADAP KEMAHIRAN BERFIKIR ALGEBRA PELAJAR DALAM PENYELESAIAN MASALAH ALGEBRA

Algebraic thinking skills are one of the elements emphasized in the benchmarking of PISA (Program for International Student Assessment). However, the algebraic thinking skills among students were found to be still at a very weak level. The purpose of this study was to look at the effect of the bar model method on students’ algebraic thinking skills. Pre-test and post -test were used as research instruments. The study was an experimental study conducted on 90 Form One students from a school in Tuaran District, Sabah. This study used a quasi-experimental design of pre-and post-test. The sample was divided into 3 groups, namely the group of learning methods i) Bar Model (MB, n = 30), ii) Bar Model and Cooperative Learning (MBPK, n = 30), and conventional (TR, n = 30). Statistical inference test, One-way Analysis of Variances Test (ANOVA) was used to analyze the findings of this study. The results of one-way ANOVA analysis showed that there was a significant difference in the mean score of the post-test between the MB group, MBPK group, and TR group (F (2, 87) = 9.316, p <.05). Significant differences in mean scores for post-test could only be seen between TR group with MB group (P = 0.019) and between TR group with MBPK group (P = 0.000) while insignificant differences were shown between MB and MBPK group (P = 0.304). Therefore, it is suggested that mathematics teachers use the Bar Model as a teaching aid to improve students' algebraic thinking skills.

Experimental Study on SSRC under Eccentric Compression

The use of stainless steel bars can improve the durability and sustainability of building materials. Through the static performance test, this research analyzes the failure pattern and bearing performance of bias stainless steel reinforced concrete (SSRC) column. The influence of reinforcement ratio of longitudinal bars and eccentricity on the mechanical performance of specimens was studied. Different constitutive models of stainless steel bars were used to calculate the ultimate bearing capacity of the section of the column under eccentric compression column. Based on the experimental results, a method to modify the expression of the design specification is proposed. And, the results were compared with the test results. The results showed that the damage patterns and failure modes of SSRC columns are essentially the same as those of traditional reinforced concrete columns. The bearing capacity of SSRC columns rises with the increase in the longitudinal reinforcement ratio, and the ductility of the specimens is enhanced. The ultimate load of the specimen decreases with the rise in eccentricity but the deflection increases gradually. The strain distribution of the mid-span section of the SSRC column conforms to the plane section assumption. The bearing capacity of the specimen can be analyzed by referring to the calculation method of the specification, and some parameters in the calculation formula of the specification are modified to adapt to the design and calculation of the SSRC column.

Long-time durability of GFRP bars in the alkaline concrete environment for eight years

The long-term durability of glass fiber reinforced polymer (GFRP) bars under different conditioning environments is investigated in this paper. A batch of GFRP bars exposed to alkaline accelerated corrosion concrete environment for 8 years is studied. The long-term tensile strength degradation law/micro deterioration mechanism are analyzed, and the tensile strength prediction model of GFRP bars is established. By comparing the estimated results with the long-term experimental data, it is found that the prediction model fits the first stage degradation data of GFRP bars well and has high accuracy. However, the long-term durability of GFRP bars is significantly underestimated based on the prediction results in the second stage, so an improved long-term tensile strength prediction model is proposed. Finally, the 8-year residual tensile strength of GFRP bars is evaluated according to three current codes.

In-Depth Verification of a Numerical Model for an Axisymmetric RC Dome

The designers of civil engineering structures often have to face the problem of the reliability of complex computational analyses performed most often with the Finite Element Method (FEM). Any assessment of reliability of such analyses is difficult and can only be approximate. The present paper puts forward a new method of verification and validation of the structural analyses upon an illustrative example of a dome strengthened by circumferential ribs along the upper and lower edges. Four computational systems were used, namely Abaqus, Autodesk Robot, Dlubal RFEM, and FEAS. Different models were also analyzed—two-dimensional (2D) and three-dimensional (3D) ones using continuum, bar, and shell finite elements. The results of the static (with two kinds of load—self-weight and load distributed along the upper ring) and modal analyses are presented. A detailed comparison between the systems’ and models’ predictions was made. In general, the spatial models predicted a less stiff behavior of the analyzed dome than the planar models. The good agreement between different models and systems was obtained for the first natural frequency with axisymmetric eigenmodes (except from the Autodesk Robot system). The presented approach to the verification of complex shell–bar models can be effectively applied by structural designers.

Investigation on the static fracture mechanical characteristics of marble subjected to impact damage based on the FDM-DEM coupled simulation

To investigate the mechanical characteristics of static fracture of marble subjected to dynamic damage after cyclic impacts, based on the modeling technology of the finite difference method (FDM) and the discrete element method (DEM) coupling, a three-dimensional numerical model of the split Hopkinson pressure bar (SHPB) was constructed, and the bar system and rock sample were modeled using FLAC3D and PFC3D programs, respectively. The numerical cyclic impact loading tests were carried out on notched semi-circular bend (NSCB) samples at a constant impact velocity, and then the static three-point bending fracture tests were simulated on these damaged samples. The coordinate data of the particles on fracture surfaces of the sample were extracted by compiling the Fish program, and then the fracture surface was reconstructed and the surface roughness was calculated quantitatively. The rationality and reliability of the numerical analysis were verified by comparison with the results of relevant laboratory tests. The results show that in the cyclic impact loading test, the stress-strain curve rebounds, resulting from the release of part of the stored strain energy during the unloading period. With the increase of the impact number n, the numbers of cracks and fragments generated increase. The connected force field becomes more and more chaotic and the number of broken force chains displays an increasing trend. The breakage of the force chains is the root cause of the deterioration of mechanical properties of the sample. The static fracture toughness of the sample after 5 times of impact is 53.35% lower than that of the natural sample, while the failure displacement increases. In the static loading process, more and more cracks and fragments generate as n increases. This is proof that the internal structure of the sample has been damaged in the cyclic impacts. The fracture surface roughness increases as the impact number increases. The research conclusions can provide certain guidance for the engineering practice.

Split Invariant Curves in Rotating Bar Potentials

Abstract Invariant curves are generally closed curves in Poincaré's surface of section. Here we study an interesting dynamical phenomenon, first discovered by Binney et al. in a rotating Kepler potential, where an invariant curve of the surface of section can split into two disconnected line segments under certain conditions, which is distinctively different from the islands of resonant orbits. We first demonstrate the existence of split invariant curves in the Freeman bar model, where all orbits can be described analytically. We find that the split phenomenon occurs when orbits are nearly tangent to the minor/major axis of the bar potential. Moreover, the split phenomenon seems “necessary” to avoid invariant curves intersecting with each other. Such a phenomenon appears only in rotating potentials, and we demonstrate its universal existence in other general rotating bar potentials. It also implies that actions are no longer proportional to the area bounded by an invariant curve if the split occurs, but they can still be computed by other means.