Spring Model Research Articles

An equivalent approach for modelling butterfly-hysteresis passive variable friction damper

This research work proposes an equivalent approach modelling the peculiar hysteretic behavior of passive variable friction damper, for engineers who call for a simplified way to simulate such damper in anti-earthquake engineering practice with acceptable accuracy. This approach models the special nonlinear behavior of the damper via paralleling 3 basic link elements that commonly built-in commercially available structural analysis software, instead of developing direct hysteretic model that demands for both post development functionality on software side and programming skill on engineer side. The mathematical derivation and analytical geometric equating work are comprehensively conducted. The numerical accuracy of analysis output yielded using equivalent model is digitally verified against the one yielded using generic FEM simulation of the same damper subject to several loading cases. Code-automated optimization workflow for yielding product-wise modelling parameters is developed that is convenient and straightforward for application by engineers without requirement of high expertise, which is demonstrated by generating optimized parameters to equivalently model tested specimen.Article highlightsPassive variable friction damper can be modelled by assembling friction spring, elastic spring and wen model into parallel.Code-automated optimization process can locate the most ideal modelling parameters combination in predefined numeral fields.Hysteretic behaviors yielded from equivalent modelling approach match well corresponding ones from generic FEA simulation.

Predicting the Elastic Modulus of Nanoparticle-Reinforced Polymer Matrix Composites Based on Digital Image Processing and Finite Elements

“Composite” means composition of two or more separate components. Composites are materials composed of two or more components that are chemically separated from each other on a macroscopic scale, and there are interfaces between these components. Conceptually, fiber-reinforced composites have existed since about 800 B.C. The aim of this paper is to predict the elastic modulus of nanoparticle-reinforced polymer matrix composites based on digital image processing and finite elements and to investigate the presence of interfaces in three-phase particle-reinforced composites. In this paper, the interfacial layer is designed as a spring model with the help of the effective modulus law, a statistical debonding criterion is proposed to represent the proceeding changes, and metallurgical methods are used to optimize the particles and prepare different composites with uniform dispersion. The experimental results of this paper show that the highest increase in tensile strength of the composites is about 8% and the highest increase in elastic modulus is 40% after the addition of nanoparticle materials, and the highest increase in tensile strength is 18% and the highest increase in elastic modulus is 50% after the addition of CNFs.

A locally resonant phononic crystal structure with low-frequency broad bandgap

The vibration induced by low-frequency elastic wave reduces the working accuracy of precision instruments. The locally resonant phononic crystal provides a feasible measure for low-frequency vibration isolation because of its bandgap characteristics. In this paper, a locally resonant phononic crystal structure with a broad bandgap is proposed, which consists of a periodic phononic crystal plate with double-sided steel stubs coated by rubber layers. Through finite element analysis, it can be found that the proposed structure can produce a bandgap with 355 Hz bandwidth within the range of 0–500 Hz and isolate vibration in the range of bandgap. By analyzing the local resonance modes of the proposed structure, we further propose the equivalent mass–spring model to predict its bandgap range. The predicted bandgap results from equivalent models of the proposed structure agree well with the results from the finite element analysis. These equivalent models provide an effective and simple method for bandgap optimization of the proposed phononic crystal structure.

Estimation of the interaction force between human and passive lower limb exoskeleton device during level ground walking

To develop sophisticated and efficient control strategies for exoskeleton devices, acquiring the information of interaction forces between the wearer and the wearable device is essential. However, obtaining the interaction force via conventional methods, such as direct measurement using force sensors, is problematic. This paper proposes a kinematic data-based estimation method to evaluate the interaction force between human lower limbs and passive exoskeleton links during level ground walking. Unlike conventional methods, the proposed method requires no force sensors and is computationally cheaper to obtain the calculation results. To obtain more accurate kinematic data, a marker refinement algorithm based on bilevel optimization framework is adopted. The interaction force is evaluated by a spring model, which is used to imitate the binding behavior between human limbs and the exoskeleton links. The deflection of the spring model is calculated based on the assumption that the phase delay between human limb and exoskeleton link can be presented by the sequence of frames of kinematic data. Experimental results of six subjects indicate that our proposed method can estimate the interaction forces during level ground walking. Moreover, a case study of bandage location optimization is conducted to demonstrate the usefulness of obtaining the interaction information.

Stiffness assessment of welded I-beam to RHS column connections

This present paper evaluates the initial stiffness of welded I-beam to RHS column connections loaded by in-plane bending moments. Currently, there is a need to find mechanisms to satisfactorily determine the stiffness of these joints, due to the vast diversity of geometric characteristics. In this context, a numerical and theoretical study was carried out to obtain the initial stiffness through numerical finite element models and the component method. Thus, with a validated numerical model, 36 different connections were evaluated with column face failure and with variations in column thickness, beam flange width, and beam height. The initial stiffness results were obtained for the numerical models and compared with results calculated by the component method. The formulations available in the literature were considered, since the normative prescriptions still do not include formulations for tubular connections. The adopted springs model was described, composed of three components that correspond to the characteristic efforts of the connection: column face in bending, column lateral face in tension or compression and column lateral face in shear. The component “column face in bending” contributed mainly to the determination of the initial stiffness. In the current normative prescription, there are no equations for the stiffness coefficient of this component. Thus, three different formulations from the literature were evaluated. Finally, an adjustment was proposed to satisfactorily represent the evaluated component and the initial stiffness of the connections.

Viscoelastic and Viscoplastic Glucose Theory (VGT #31): Applying VGT with Two Different CGM Sensor Measured 2-Hour Postprandial Plasma Glucose (PPG) values from 240 Liquid Egg Meals and 191 Solid Egg Meals as the Strain, along with the PPG Change Rate Multiplied by a Viscosity Factor of Average Carbs/ Sugar Amounts for Each Egg Meal Type as the Stress, and then

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake influences which have dealt with “time-dependency” issues. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. But, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. The postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via postmeal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept” of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #29): Applying viscoelastic Glucose Theory with CGM Sensor Measured Fasting Plasma Glucose (FPG) Values as the Strain along with the FPG Change Rate Multiplied by a Viscosity Factor as the Stress, and Finally Utilizing the Viscoelastic Perturbation Model to Calculate the Predicted FPG Values to Compare Against the Measured FPG Values Based on GH-Method:

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work to earn a master’s degree in Biomechanics under Professor James Andrews. At that time, he used the spring and dashpot models to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. He also took additional graduate courses in the field of fluid dynamics and thermodynamics. Since then, many advancements have been made in the biomechanics branch, especially with human body tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relaxation for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. The author’s research focuses on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. Fasting plasma glucose (FPG) has nothing to do with either diet or exercise during sleep hours and is mainly relying on the health condition of both liver and pancreatic beta cells, which produces glucose and releases insulin, to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #30): Applying VGT with Two Different CGM Sensor Measured 3-Hour Postprandial Plasma Glucose (PPG) Values from 240 Liquid Egg Meals and 191 Solid Egg Meals as the Strain, Along with the PPG Change Rate Multiplied by a Viscosity Factor of Average Carbs/Sugar Amounts for Each Egg Meal Type as the Stress, and then Applying

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work on UI campus to earn a master’s degree in Biomechanics under Professor James Andrews. At that time, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons in order to investigate the human-weapon interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. He also took additional graduate courses in the field of fluid dynamics and thermodynamics along the way of his schooling years. Since then, many advancements have been made in the biomechanics branch, especially with human body tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. The author’s research focuses on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. The postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept” of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #34): Applying VEGT and Viscoelastic Perturbation Model and Using Carbs/Sugar Intake Amount Along with Post-Meal Walking K-Steps as Two Constant Viscosity Factors to Predict Two LEGT PPG Values from 8/8/2018 to 2/26/2022 Based on GH-Method: MathPhysical Medicine (No. 615)

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa (UI). He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons, where he took some related courses at the UI School of Medicine, to investigate the soldier-weapon biophysical interactions during the Vietnam war era. Next, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake forces which deal with “time-dependent issues”. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that calf stretching exercises or wearing the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief from the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. However, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. It is nearly impossible to measure the material geometry or material properties to determine the viscosity of glucose, like in engineering research work. Although postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent upon the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, the author selects a combined value of (carbs/sugar grams and post-meal walking k-steps with respective weighting factors of GH-Modulus as the viscosity factor (η). Based on this knowledge, he applies the “concept” of viscoelasticity and viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #33): Applying VGT and Viscoelastic Perturbation Model and Using the Combined Values from Carbs/ Sugar Intake Amount with GH.p-Modulus and Post-Meal Walking k-Steps with GH.w-Modulus as the Constant Viscosity Factor to Predict the K-line PPG Values from 8/8/2018 to 2/25/2022 Based on GH-Method: Math-Physical Medicine (No. 614)

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa (UI). He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons, where he took some related courses at the UI School of Medicine, to investigate the soldier-weapon biophysical interactions during the Vietnam war era. Next, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake forces which deal with “time-dependent issues”. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that calf stretching exercises or wearing the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief from the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. However, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. It is nearly impossible to measure the material geometry or material properties to determine the viscosity of glucose-like in engineering research work. Although postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar intake amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. Therefore, the author selects a combined value of (carbs/sugar grams and post-meal walking k-steps with weighting factors of GH-Modulus as the viscosity factor (η). Based on this knowledge, he applies the “concept” of viscoelasticity and viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

Viscoelastic and Viscoplastic Glucose Theory (VGT #32): A Step-By-Step Illustration of how to Apply VGT and Viscoelasticity Perturbation Model with the Average Value of normalized body weight and body temperature in early morning as the viscosity factor to predict average fasting plasma glucose values over 7-hours of sleep time based on GH-Method: math-physical medicine (No. 613)

The author has studied strength of materials and theory of elasticity through his undergraduate courses at the University of Iowa. He also conducted research work and earned a master’s degree in Biomechanics under Professor James Andrews. In 1970-1971, he used a combined spring and dashpot model to simulate the behaviors of human joints, bones, muscles, and tendons (which he took some related courses at School of Medicine at UI) in order to investigate the soldier-weapon biophysical interactions during the Vietnam war era. Later, he went to MIT to pursue his PhD study under Professor Norman Jones, who taught him theory of plasticity and dynamic plastic behaviors of various structure elements. To further his education, he took additional graduate courses in various fields of fluid dynamics, thermodynamics, bridge design using energy absorption pad, and soil mechanics under earthquake strike forces which deal with “time-dependency” issues. Since then, many advancements have been made in the biomechanics branch, especially with human body live tissues that possess certain viscoelastic characteristics, such as bones, muscles, cartilages, tendons (connect bone to muscle), ligaments (connect bone to bone), fascia, and skin. For example, the author suffered plantar fasciitis for many years. He understood that the night splint dorsiflexes forefoot, at the back of the foot, increases plantar fascia tension to offer stress-relief for the pain. This model where muscles and tendons connect the lower leg and foot is a form of viscoelastic study for medical problem solving. When dealing with human internal organs, it is not easy to conduct live experiments to obtain accurate measurements for the biomedical material properties. Blood itself is a viscous material (time-dependent) and its viscosity factor may fall between water, honey, syrup, or gel. However, the author’s research focus is on “glucose” where the blood sugar amount is produced by the liver and carried by red blood cells, not the blood itself. The postprandial plasma glucose (PPG) is strongly influenced by both energy input via carbs/sugar amount (~60%) and energy output via post-meal exercise level (~40%). Fundamentally, the PPG level is also dependent on the individual's health conditions in regard to liver cells and pancreatic beta cells, which produce glucose and release insulin to control the glucose level in blood. With regard to FPG, there are many influential factors. In this article, the author selects both body weight and body temperature as the inter-influential factors of FPG. Therefore, it is nearly impossible to measure the material geometry or material properties to determine the viscosity of “glucose” like in engineering research work. As a result, the best the author could do is to apply the “concept” of viscoelasticity and/or viscoplasticity” to construct an analogy model of time-dependent glucose behaviors.

A universal dynamical model of dual-chamber air springs with experimental validation

Experimentally and theoretically, this paper combines thermodynamics, aerodynamics and structural dynamics to give a universal dynamical model of dual-chamber air springs, with physical meanings of each stiffness and damping term. An indicator experiment was designed to verify the theory proposed in this paper. The experimental results show that the dynamic stiffness model can well reflect the hysteresis characteristics and the variable stiffness characteristics of the dual-chamber air spring. It can also clearly reveal the frequency dependence of the dynamic stiffness. Finally, based on the derived model, the influence regulation of each parameter term on the dynamic stiffness amplitude and hysteresis phase angle is given numerically. The results show that each term can influence different dynamic characteristic of the dual-chamber air springs. The conclusions of this article can provide positive guidance for the vehicle dynamics matching and design of air springs.

Easy characterization of the etched Al5052 surfaces and its distinctive data correlation with the Al5052/PMMA bonding performance

Pore–creating of the metal surface is essential to the bonding performance of the metal/polymer laminate interface. This work made use of the high distinction of the mass variation and surface porosity (SP) values of every etched 5052 aluminum alloy (Al5052) sheet to characterize the porous surface, in order to set up distinctive data correlations between surface characterization and bonding performance of the Al5052/polymethyl methacrylate (PMMA) laminate. The obtained distinctive characterization–performance correlations indicate that in certain scattered plots regions (mass variation: 0–2.5%; SP: 0–25%/dm2 or 0–32%/cm3), parabola relations existed between the mass variation/SP and the bonding strength (BS), and linear relations existed between the mass variation/SP and the interface failure work (IFW), which was corroborated by analysis on a simplified springs model. In the discrete regions, the distinctive characterization–performance correlations also showed that the BS was limited between 6.25 and 8.25 MPa and the IFW fluctuated between 346 and 691 mJ/cm2. According to the data correlations, the SP limit of Al5052 in this work was 70%/dm2, which could help determine and control the degree of surface treatment.

Prediction of In-plane Stiffness for the Cold-formed Steel Frame of the Wall Panel Structure

The purpose of this research was to study the lateral deformation behavior of cold-formed steel wall panel structures using experimental tests, finite element analysis and analytical methods to study the lateral stiffness of these structures. The wall panel structures were tested by full-scale experiments the experimental results of which were verified by a 3D-finite element model. The verification results showed a good correlation between the experimental tests and a finite element model. The single-column spring model was proposed for an elastic lateral stiffness analysis of the cold-formed steel wall panel structures that were formed by combinations of a guide cantilever beam and springs connection. The spring constants were defined by using the stiffness of the stub-chord connection and the bending stiffness of the chord. The experiments tests and finite element analysis were used to verify this single-column spring model. The comparison results showed good agreement between the analytical prediction, finite element analysis and experimental data in the case of the primary type of cold-formed wall structure. The proposed procedure was an efficient method for elastic lateral deformation analysis of cold-formed wall panel structures which can be used for such configurations.

An Analytical Solution for Lateral-Torsional Buckling Resistance of Perforated Cold-Formed Steel Channel Beams with Circular Holes in Web

Perforated cold-formed steel (PCFS) beams are regarded as an economical option for steel construction industry owing to its various advantages. They can provide access for the facilities like electric wires and pipelines to penetrate the web so that extra building space could be saved. However, the web openings might change the web stress distribution as well as reduce the cross-sectional properties, which make the PCFS beams more susceptible to buckling and may have effect on their load-bearing capacity. In this paper, a simplified spring model was proposed based on the use of energy method, to predict the critical moment of lateral-torsional buckling of PCFS channel beams with circular holes in web subject to pure bending. The effect of hole sizes and lateral restraint at the tension flange was examined by using the derived analytical solution. In addition, eigenvalue buckling analysis was conducted by using finite-element package ANSYS to validate the accuracy of the proposed analytical model. The results demonstrated that the proposed analytical solution was reliable and the critical moment predicted can be used for the extension of DSM formulae for the design of PCFS beams when considering the failure caused by lateral-torsional buckling of the beams.

Drivers predicting biodiversity and community assembly of benthic diatoms in a karst spring environment

Geographical location, landscape heterogeneity, and their position at the edge of Quaternary glaciations are the major reasons why the river basins of the Western Carpathians are of the utmost importance for research on European aquatic biodiversity. Moreover, unlike streams, springs have several features determining their insularity in the river continuum. This study aimed to uncover the mechanism forming the diatom assemblages in the karst springs environment, using a two-dimensional approach, including taxonomic and trait data. Thus, (1) the congruence between observed and expected values of null models of taxonomic/functional diversity and functional dispersion and (2) Generalized mixed models and Variation partitioning were used to assess how taxonomic/functional diversity and composition were associated with the local conditions, regional affiliation and spatial springs distance. In 64 rheocrene karst springs (10 karst mountain ranges) of the Western Carpathians, 138 epilithic diatom taxa were found. Null model analyses did not uncover any clear evidence of non-random events forming the spring diatom community. Although, the observed functional diversity did not differ from the null model for most springs, most observed values were lower than the mean value of the null model, suggesting that, except for random events, environmental filtering was an important driver of community assembly. Substratum type, spring connectivity and phosphorus concentration drove the value of taxonomic richness, whereas functional diversity was controlled by silica and bicarbonate concentration as well as spring size. In both models, affiliation to the mountain range (defined as a random factor) was significant. The Variation Partitioning Analysis showed that diatom assemblage composition was mainly determined by local and regional environmental conditions, whilst the distance between springs had only a weak influence.

Dynamic analysis of double-walled carbon nanotubes embedded in elastic medium under a nanoparticle delivery

Dynamic behaviors of double-walled carbon nanotubes (DWCNTs) embedded to elastic foundation under a moving nanoparticle are studied based on the nonlocal elasticity theory. The DWCNTs embedded an elastic medium are considered as two-scale shell model coupled with the van der Waals (vdW) interaction between two adjacent nanotubes. The elastic medium surrounding DWCNTs is formulated as Winkler spring model. Using the proposed models and solutions, we investigate the influences of various parameters on the mechanical properties, such as the nanoparticle delivery, the elastic foundation, and nonlocal coefficient. The dynamic response of DWCNTs depends largely by the moving velocity of nanoparticle, the stiffness of the elastic medium, and the nonlocal coefficient. The results show that increasing constant of elastic medium causes deceases in the dynamic deflection of DWCNTs due to the improved stiffness property. The influence of the nonlocal scaling parameter on the dynamic response of the flexural displacement is enhanced with increasing nanoparticle velocity.

Flexural Wave Band Gaps in Periodic Bi-Directionally Orthogonal Stiffened Plates with Holes

Plate frame structure with holes is a novel candidate to reduce the weight and strengthen the architectural structures to fulfill the requirements of practical engineering applications. The designed periodic hole structure can generate a band gap from the perspective of the frequency spectrum. In this study, a new band gap calculation method was proposed under the basic energy method framework for the analysis of hole periodic structures. Gaussian wavelet function with a good localization characteristic was adopted to overcome the inaccurately assumed displacement filed function due to the introduced hole issue. The entire plate structure was divided into cell elements and an artificial spring model was introduced to satisfy the cell coupling conditions. The coupling constraints were converted into elastic potential energy to be added to the energy functional for the entire system. The dispersion curves obtained by this method are in excellent agreement with the results of the finite element method. It was observed that periodic hole plates lead to the generation of complete and directional flexural wave band gaps. By introducing bi-directionally orthogonal stiffeners, the band gap of periodic hole plates could be significantly lengthened and complete band gaps could be successfully generated. Furthermore, geometrical parametric studies on flexural wave band gaps were analyzed. A wide and complete band gap could be realized by increasing the width of the stiffener to a certain extent, but not fully proportional.

Dynamic Simulation of Automotive Vehicle Suspension Using MATLAB Simulink

This work focuses on obtaining the natural frequencies and simulation of dynamic modes of a typical four wheeler SUV suspension spring. A mathematical model of the suspension spring is developed in MATLAB assuming 4 DOF considering half car model of the vehicle. Lagrange's method is used to solve the motion equations and extract the predominant dynamic mode frequencies in MATLAB. Further, Simulink is utilised for validation the results determined in MATLAB by constructing the Power Spectral Density curves of the dynamic response depending on one of the eigenvectors of the suspension system under consideration.

Flexible kirigami with local cylindrical shell design for stretchable microstrip antenna

This paper proposes a flexible kirigami structure. It has rotating rigid squares and cylindrical shells to improve the flexibility of the structure and produce snap-through instability. First, a mechanical spring model based on a quarter of unit cell was established to predict the mechanical characteristics of its deployment. The elastic deformation energy stored in the mechanical system was calculated, and the applied force was obtained after deriving the displacement. By assuming that the rotational stiffness of the spring is related to the length, elastic modulus, and thickness of the cylindrical shell, the coefficients used to quantify the stiffness of the rotational spring were obtained through a finite element calculation and the mechanical characteristics of the structure were obtained. The accuracy was verified through experiments and the finite element method. Then, the deployment mechanism and parameterization of the structure were analyzed. The snap-through characteristics of the cylindrical shell were analyzed, and the curvature of the second steady state was obtained using the minimum potential energy. The influence of the geometric parameters of the unit cell, such as its length, thickness, and the center angle of the cylindrical shell, on the snap-through instability was analyzed. By stretching or compressing it at different positions, different mechanical characteristics of the deployment were obtained. Finally, based on the designed structure, a stretchable microstrip antenna was designed to achieve high gain while the center frequency remained fixed. An antenna was fabricated and measured, and the test results are in good agreement with the simulated results. This work may provide theoretical guidance for the design and application of deformable structures.