Area Moment Research Articles

The study of the Sommerfeld phenomenon in the eccentric overhung shaft-disk system considering internal and external depreciation and shear deformations

As a basic component of many rotary systems, the overhung shaft-disk system is exposed to the Sommerfeld phenomenon. Owing to the interaction between the electric driving source and the vibration system, this destructive phenomenon appears as a dynamic jump around the natural frequencies of the vibration system. This dynamic effect causes instability in the system and impacts mechanical components. In this paper, first, the governing equations of the problem and the system response have been obtained by considering the effects of shear deformations, as well as internal and external damping, in an overhung shaft-disk system. Then, using the instantaneous power balance method in the complex form, the occurrence of the Sommerfeld phenomenon has been investigated based on the Timoshenko beam theory. Another innovation is the utilization of numerical solutions and stability graph analysis to prevent complicated calculations and facilitate the determination of the Sommerfeld effect. In order to validate the obtained results, the problem was simulated using ABAQUS software whereby it was observed that the findings obtained from finite element analysis are in good agreement with our results. In addition to considering various mechanical effects such as shear deformation, gyroscopic effects, area moment, and internal damping, the proposed method allows studying the Sommerfeld effect in similar systems, with thick shafts.

Center of mass and area moment of inertia of fractal circular lamina

Center of mass and area moment of inertia of fractal circular lamina

Digital Restoration of Separations Data.

In experimental separations, the acquired signal can have four common but unwanted elements: (i) high-frequency noise, (ii) drift, (iii) occasional periodic and pink noise, and (iv) a mixture of components traveling with close velocities. Additionally, separation scientists observe partially resolved peaks in chromatographic or capillary electrophoresis detector output. A protocol for digitally recovering the "true data" is provided with clear-cut details and open-access codes for formulating denoising, baseline correction, and peak resolution problems as linear or nonlinear optimizations. The smoother of Bohlmann-Whittaker denoises and preserves the total area of the signal. Fourier transform methods to detect and remove periodic noise are also proposed for erratic periodic noise problems. A peak width preserving filter, called the bilateral filter, is also given. This procedure is followed by two reliable baseline correction algorithms based on asymmetric reweighted least squares or curvature-based weights to deal with low-frequency signal variations. Once low- and high-frequency noise components are removed, a convenient peak mode location method is introduced, relying upon numerically stable second derivative calculation from Savitzky-Golay (SG) filter. Peak locations, area, height, and higher statistical moments can be derived from iterative curve fitting. The protocol shows two peak models that can model left or right skewed peaks. The new peak models are (i) a numerically stable version of the bi-directional exponentially modified Gaussian (EMG), suitable for a wide variety of real chromatograms, and (ii) the twice generalized normal model with third- and fourth-moment parameters built into it. The nonlinear least squares regression approach uses the trust-region reflective optimization method. The algorithm converges to a solution even with multiple peaks and approximate guesses of peak parameters. The protocol can be generalized to fit more than 200 peak functions in separation sciences available in literature by minor adaptations of the provided codes in the MATLAB environment.

Tapered insect (Acheta domesticus) antennae have rapid damped return with minimal oscillation after perturbation.

As tactile sensors, antennae must be flexible and responsive while maintaining shape and control of the structure. We evaluated the geometric and mechanical properties of cricket antennae, which we treat as bending cantilever beams. Flexural rigidity (EI) is the mechanical property that most significantly controls bending behavior. We determined that the flexural rigidity decreases steeply (proximal to distal) by evaluating the quasistatic bent shapes in response to obstacle contact at different points along the antennae. This steep decrease in flexural rigidity causes the antennae to bend readily only near the obstacle contact, in contrast to the curvature of a beam with uniform properties and cross-section (which bends closer to the base). This flexural rigidity gradient in the antennae is consistent with the morphology: a decreasing second moment of area calculated from the measured taper and the diminishing wall (cuticle) thickness. Cricket antennae recovered from a single localized perturbation quickly and with minimal to no oscillation, suggesting behavior close to critical damping (fastest return without oscillations). Bending primarily occurred in the portion of the flagellum near the obstacle contact, reducing the length of the flagellum that participated in the oscillating behavior (natural frequency ∼11 Hz). Forced sinusoidal vibrations generated a resonance frequency of ∼30 Hz with imperceptible movement in the proximal part of the flagellum while the distal part vibrated. The results suggest that tapering of an elongated mechanosensor may facilitate a rapid return to its original shape without oscillation, which is an advantageous attribute that may also inform biomimetic applications.

Fault zone mechanical response under co-exploitation of mine and geothermal energy: The combined effect of pore pressure and mining-induced stress

As the mine depth around the world increases, the temperature of the surrounding rock of the mining workface increases significantly. To control the heat hazards, the hot water in the mining floor is developed during mining to decrease the mining workface temperature while also developing geothermal energy. This method is called the co-exploitation of mine and geothermal energy (CMGE). The geothermal development may precipitate the large-scale failure of the nearby fault zone during the mining process. However, the evolution of shear slide and shear failure of fault under geothermal production/reinjection during mining is missing. Therefore, a fully-coupled hydraulic mechanism (HM) double-medium model for CMGE was developed based on the measured data of the Chensilou mine. A comparative analysis of the mechanical response of fault between CMGE and single mining was conducted. The disturbance of geothermal production pressure and reinjection pressure under mining on fault stability were respectively expounded. The results indicate that: (1) The disturbance of geothermal reinjection amplifies the disturbance of mining on fault stability. The amplified effect resulted in a normal stress drop of the fault, further leading to a substantial increase in shear slide distance, failure area, and cumulative seismic moment of fault compared with the single mining process. (2) As the distance of reinjection well to the fault decreases, the fault failure intensity increases. Setting the production well within the fault is advantageous for controlling fault stability under CMGE. (3) The essence of the combined disturbance of CMGE on the nearby fault is the overlay of tensile stress disturbance on the fault rock mass of the mining and geothermal reinjection. Though the geothermal reinjection causes a minor normal stress drop of fault, it can result in a more serious fault failure under CMGE. This paper supplies a significant gap in understanding the nearby faults failure under CMGE.

Locomotor adaptation in the hominoid clavicle through ontogeny.

Locomotor adaptation in the hominoid clavicle through ontogeny.

Relationship of Skeletal Muscle Mass, Length of Sports Experience, and Sexual Maturity with Bone Density and Geometry in Adolescent Athletes.

Relationship of Skeletal Muscle Mass, Length of Sports Experience, and Sexual Maturity with Bone Density and Geometry in Adolescent Athletes.

Towards a more objective and high-throughput spheroid invasion assay quantification method

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high‐throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high‐throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

Attention-based hybrid convolutional-long short-term memory network for bridge pier hysteresis and backbone curves prediction

This paper proposes a solution to the problem of automatically predicting hysteresis and backbone curves of bridge piers under seismic loads. The proposed solution utilizes a stacked hybrid Convolutional Neural Network-bidirectional Cuda Deep Neural Network Long Short Term Memory layer benefiting from the skip connections technique and incorporates a custom task-specific attention layer to enhance its performance. The proposed framework borrows the functional API provided by the Keras library in Python to construct a model taking into account horizontal and vertical ground accelerations, actuator loads in both horizontal and vertical directions, the effective pier height, the second moment of area, and the superstructure mass as input features. The deep learning model demands a substantial amount of data for effective training, validation, and testing. An error-sensitive analysis suggests that a comprehensive dataset should consist of a minimum of 12 sets of pier data for real-time hybrid simulations and 17 sets for cyclic experiments (10 for high-speed and seven for low-speed scenarios). This extensive dataset is deemed essential for the optimal performance of the model. The same deep learning framework and optimization of hyperparameters apply when training real-time hybrid simulations and conducting cyclic tests. After 5000 epochs, the proposed hybrid loss function, combining mean square and mean absolute errors, exhibits a steady and gradual decrease toward near-zero values within the datasets used for training and validation. Additionally, over 93% correlation exists between the predicted unseen time series responses and those derived from empirical measurements. Overall, the proposed deep learning model offers significant advantages, notably in terms of time and cost savings associated with experimental endeavors for new tests. By providing a rapid and accurate understanding of the hysteretic behavior of bridge piers, this model contributes to more efficient bridge design processes. Ultimately, it facilitates precision in design decisions, leading to enhanced accuracy and effectiveness in bridge engineering.

Bending properties of human cartilaginous ribs and costal cartilage material vary with age, sex, and calcification.

Costal cartilage plays an important functional role in the rib cage, but its mechanical properties have not been well characterized. The objective of this study is to characterize the properties of human costal cartilage and examine the effects of age, sex, rib level, and degree of calcification. We obtained cadaveric costal cartilage samples of ribs 3-6 with intact perichondrium from 24 donors (12 females and 12 males) evenly distributed by age (range 47-94yr). Peripheral QCT scans were used to quantify geometric properties (area moments) and tissue calcification (as volume, length, and classified as central, peripheral, and mixed). Four-point bending tests were performed on each sample, and bending stiffness and modulus outcomes were evaluated by fitting data from mechanical testing with non-linear pseudo-elastic models (composed of linear and cubic components, separated into loading and unloading regimes). Effects of sex, age, rib level, and cartilage calcification on bending stiffness and modulus outcomes were assessed with mixed-effects regression models. Cartilage size (area moment) was larger in males than females and positively associated with age, while there was more calcification volume in cartilage of females than males. During loading, stiffness (linear and cubic) was larger in males, while modulus (linear and cubic) was larger in females. Linear stiffness and modulus were both negatively associated with age, positively associated with calcification, and varied between rib levels. Cubic (nonlinear) components of stiffness and modulus were positively associated with calcification and varied by rib, while modulus (but not stiffness) was negatively associated with age. During unloading, the linear stiffness and modulus values were much lower, though some similar associations were found. Overall, this study adds to our understanding of the behavior of costal cartilage as a nonlinear visco-elastic material, and the effects of sex, aging, and calcification on mechanical behavior.

Bending, torsion and flexural-torsional buckling of back-to-back cold-formed steel channels

The bending moment resistance of cold-formed steel channels can be improved by combining two channel sections with a pair of screw fasteners in the webs spaced intermediately along the member. By combining the two channels in this way, the moment capacity of the beam can be increased beyond the capacity of two single channels. Another advantage of this type of section is the coincidence of the centroid and shear centre which reduces the effects of stresses due to eccentric load and torsion. Most research on back-to-back channels in bending has focused on local and distortional buckling while data on flexural-torsional buckling is scarce. The flexural-torsional buckling resistance of a beam depends on various section properties which include the minor axis second moment of area, and the torsion and warping constants of the section. Although the flexural-torsional buckling moment can be easily determined for a single channel section because these section properties are relatively straightforward to calculate, the calculation of the flexural-torsional buckling moment for back-to-back channels with intermediately spaced screw fasteners is much more complicated due to the discontinuity of the cross-section along the length of the beam. In this paper, the shear stiffness of the screw fasteners connecting the channels is obtained from test results. The shear stiffness is then used to model the screw fasteners in a finite element analysis to analyse a beam composed of back-to-back channels under bending and torsion. The results are compared with two single channel sections and with back-to-back channels assuming full composite action. The effect of different screw fastener spacings is also investigated. Simple relationships between the bending and torsion section properties for single channels and back-to-back channels are presented. Suggestions for the design of back-to-back channels in bending are also proposed.

Machine learning-based axial compressive capacity estimation of cold-formed steel build-up sections

Machine learning-based axial compressive capacity estimation of cold-formed steel build-up sections

Bone turnover markers, and growth and bone parameters in infants participating in a vitamin D intervention study.

Amino-terminal propeptide of type 1 procollagen (P1NP) and carboxy-terminal crosslinked telopeptide of type 1 collagen (CTX-I) are markers of bone metabolism. We examined the effect of vitamin D3 supplementation on these markers and their relationship with growth and bone parameters in 12-month-old infants. In a randomized, double-blinded, vitamin D intervention in infants (VIDI) study, 987 infants received daily vitamin D3 supplementation of 10 μg (group-10) or 30 μg (group-30) from age 2 weeks to 24 months. We conducted a secondary analysis of the original VIDI trial. At 12 months of age, P1NP (n = 812) and CTX-I (n = 786) concentrations were analyzed, and anthropometrics and total bone mineral content, volumetric bone mineral density, cross-sectional area and polar moment of inertia of tibia were measured by peripheral quantitative computed tomography. The growth rate in weight and length was calculated from birth to 12 months. The vitamin D dose did not influence mean (SD) levels of CTX-I (group-10: 0.90 (0.31); group-30: 0.89 (0.31) (P > 0.53)). The mean difference of P1NP (CI 95%) comparing group-10 with group-30 was 35 (-103, 33) ng/mL (P = 0.31) in boys and -63 (-4, 130) ng/mL (P = 0.064) in girls. In group-10, girls had higher mean (SD) value of P1NP (1509 (362) ng/mL) than boys (1407 (297) ng/mL) (P = 0.003); no sex differences were observed in group-30 (girls: 1446 (359); boys: 1442 (359), P = 0.91) or CTX-I. P1NP associated positively with the growth rate in length (B (CI 95%) 0.0003 (0.0001, 0.001), P = 0.022) in the whole cohort but not in subgroups divided by the intervention group or sex, adjusted for birth size and parental heights and corrected for multiple testing. P1NP associated positively with the growth rate in weight (0.01 (0.0003, 0.01), P < 0.001). An inverse association was observed between CTX-I and length (cm) in the whole cohort (-0.90 (-1.40, -0.40), P = 0.005) and in group-30 (-1.05 (-1.72, -0.39), P = 0.011). Furthermore, CTX-I associated negatively with weight (SDS) in the whole cohort (-0.33 (-0.55, -0.12), P = 0.015) and the growth rate in weight (-0.43 (-0.66, -0.20), P = 0.005), persisting in group-30 and in boys but not in group-10 or in girls. Neither marker was associated with bone parameters. The observed sex difference in P1NP might suggest that a higher vitamin D dose resulted in a small decrease in bone collagen matrix formation in girls but not in boys. P1NP and CTX-I associate with growth and body size but not with bone mineralization in infancy.

Evaluation of the flexural stiffness of a lattice girder composite slab at the construction stage according to the lattice girder shape

Evaluation of the flexural stiffness of a lattice girder composite slab at the construction stage according to the lattice girder shape

Towards a More Objective and High-throughput Spheroid Invasion Assay Quantification Method.

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high-throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high-throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

Probing morphology-dependent PDI/g-C3N4 heterostructures for co-production of H2O2 and 2,5-diformylfuran

Probing morphology-dependent PDI/g-C3N4 heterostructures for co-production of H2O2 and 2,5-diformylfuran

Strategies to improve fairness in artificial intelligence:A systematic literature review

Decisions based on artificial intelligence can reproduce biases or prejudices present in biased historical data and poorly formulated systems, presenting serious social consequences for underrepresented groups of individuals. This paper presents a systematic literature review of technical, feasible, and practicable solutions to improve fairness in artificial intelligence classified according to different perspectives: fairness metrics, moment of intervention (pre-processing, processing, or post-processing), research area, datasets, and algorithms used in the research. The main contribution of this paper is to establish common ground regarding the techniques to be used to improve fairness in artificial intelligence, defined as the absence of bias or discrimination in the decisions made by artificial intelligence systems.

Cross-sectional size, shape, and estimated strength of the tibia, fibula and second metatarsal in female collegiate-level cross-country runners and soccer players

Cross-sectional size, shape, and estimated strength of the tibia, fibula and second metatarsal in female collegiate-level cross-country runners and soccer players

The path less traveled: Using structural equation modeling to investigate factors influencing bone functional morphology.

The relationship between an organism's mechanical environment and its bone strength has been long established by experimental research. Multiple intrinsic and extrinsic factors, including body mass, muscle strength, genetic background, and nutritional and/or hormonal status, are likely to influence bone deposition and resorption throughout the lifespan, complicating this relationship. Structural equation modeling (SEM) is uniquely positioned to parse this complex set of influences. Data from the Third National Health and Nutrition Examination Survey, including sex, total body mass, lean body mass, exercise frequency, peak body mass, and age, were analyzed using SEM to determine how they affect bone strength both individually and combined. Body mass is typically the driver of cross-sectional area, but body mass and lean mass have similar effects on the polar moment of area (J). Peak body mass had a strong direct effect on J, despite decreasing strongly with increases in lean mass. Exercise also did not confer a large direct effect on cross-sectional area or J but did modify body mass and lean mass. In females, intentional weight loss was associated with decreased exercise levels. SEM is a useful tool for parsing complex systems in bone functional morphology and has the potential to uncover causal links in the study of skeletal remodeling, including factors like weight loss or exercise that may have secondary effects.

Flexural–torsional modal interaction in MEMS actuators initiated by minuscule asymmetry

AbstractAn efficient actuation technique for electrostatic MEMS actuators exploiting electro-mechanical-mechanical modal interactions is proposed. The flexural–torsional equations of motion are established, and we manifest that the initiation of a 2:1 autoparametric modal interaction between in-plane bending and torsional modes of the actuator that is supposed to be symmetrical with respect to its axis of rotation is contingent upon the presence of a quadratic stiffness term, which arises from the existence of non-zero first moments of area of the actual cross-section in prismatic microbeams. In order to efficiently reduce the AC voltage value required to reach the activation of the 2:1 mechanical modal interaction, the electrical resonant frequency is syntonized to half of the natural frequency of the in-plane bending mode. The results indicate that the amplitude of the in-plane motion saturates upon the initiation of an energy exchange between the bending and torsional motions. Through suitable tuning of the AC frequency, the amplitude of the in-plane motion is minimized, while the amplitude of the torsional motion, the indirectly excited mode, is maximized. Our results demonstrate that the actuator's torsional motion, when subjected to a 1:2:1 electro-flexural–torsional modal interactions, is triggered by applying a maximum voltage of 10 V, resulting in about 20 degrees rotational angle. Furthermore, prolific frequency combs are generated as a result of secondary Hopf bifurcations along the large-amplitude response branches, inducing quasi-periodicity in the MEMS dynamics.