Values Of Structural Parameters Research Articles

Effects of the Temperature and Salt Concentration on the Structural Characteristics of the Protein (PDB Code 1BBL).

The effect of the temperature and salt solution on the structural characteristics of the protein 1BBL was investigated by molecular dynamics simulations. The paper presents simulation results regarding the non-bonded energy and the structural stability of the protein immersed in salt solutions with different concentrations and temperatures. Our work demonstrates that the electrostatic potential energy and van der Waals energy of the system show the opposite changes with the influence of the external environment. Since the electrostatic potential energy changes more obviously, it is dominated in the non-bonding interactions. The structural parameters, such as the root mean square deviation and the radius of gyration, increased initially and decreased afterward with the increase of the salt concentration. The protein presented the loose structure with a relative low stability when it was immersed in a monovalent solution with a salt concentration of 0.8 mol/L. The salt concentration corresponding to the maximum value of structural parameters in the monovalent salt solution was double that in the divalent salt solution. It was also concluded that the protein presented a compact and stable structure when immersed in salt solutions with a high concentration of 2.3 mol/L. The analysis of the root mean square deviation and root mean square fluctuation of the protein sample also exhibited that the structural stability and chain flexibility are strongly guided by the effect of the temperature. These conclusions help us to understand the structural characteristics of the protein immersed in the salt solutions with different concentrations and temperatures.

A probabilistic approach to the description of the crack kinetics and fatigue failure of structural components with allowance for the effect of crack retardation after overloads

A probabilistic approach to assessing fatigue strength and cyclic life based on Wheeler’s model is presented. The approach provides the possibility of estimating the probability of failure of the structural component under consideration, with allowance for the effect of crack retardation after the overload. The initial crack size, the parameters of the Paris equation, and the exponent of the crack retardation power function are assumed random parameters. The kinetics of a fatigue crack is described by cycle-by-cycle integration of the Paris equation written in finite differences. The probabilistic estimate is performed using the Monte Carlo statistical simulation method by repeatedly solving the Cauchy problem for various combinations of the values of random model parameters that are generated under the adopted laws of the probability distributions of those parameters. The probabilistic distributions of random parameters are selected proceeding from the level of the uncertainty of the problem using available statistical data without taking into accounting for data on the actual state of a particular structural component in real operation conditions. A computer code in Matlab environment has been developed for statistical description of the fatigue crack growth in structural components which allows accounting for the effect of crack retardation. An example of assessing the probability of the fatigue failure of a pipeline component with a longitudinal crack on the inner surface loaded by the internal pressure which varies according to a periodic law with a constant amplitude is presented for single tensile overload of the pipeline component. The dependencies of the fatigue failure probability on the number of loading cycles for various combinations of model parameters were obtained. The sensitivity of the fatigue failure probability under a given number of loading cycles to changes of the values of structural parameters was assessed.

Kinematic calibration of a symmetric parallel kinematic machine using sensitivity-based iterative planning

Since kinematic calibration will induce variations in the structural parameter values, the forward kinematics may have multiple or no solutions after calibration. This paper proposes a novel kinematic calibration method to obtain the optimal solution and high accuracy after calibration. We use the closed-loop vector to represent the clearance and the concomitant motion and convert the angular to a dimensionless variable to simplify the kinematic calibration model. Thus, we can calculate the global sensitivity index (GSI) of the symmetric parallel kinematic machine (sPKM). Then, we present a sensitivity-based iterative planning method to ensure iterative convergence and obtain the optimal solution. Due to the large difference in magnitude between the position and orientation errors, we adopt a segmental calibration approach to calibrate the two types of errors to improve the calibration accuracy. Finally, the Levenberg-Marquard(L-M) iterative algorithm is used to obtain the parameter errors. Simulations and experiments are performed on a 3-PPR sPKM. The results show that the proposed method prevents the kinematics with multiple solutions or without solutions after the calibration and reduces the position and orientation errors by 89.74% and 90.71%, respectively.

Measurements and Modeling of Optical Turbulence in the Coastal Environment

The goal of this study was to characterize optical turbulence in the near-coastal environment. Measurements to obtain the refractive index structure parameter and other meteorological data were taken over the course of a month along the shore of Monterey Bay. The results were compared to a new version of the Navy Vertical Surface Layer Model (NAVSLaM), a model of turbulence originally developed for maritime environments but now extended to terrestrial environments. The new version has not been previously validated by comparisons to experiments, particularly in a complex environment such as near the coastline. Our experimental results showed generally good agreement between measured and modeled levels of turbulence. Specifically, the differences between experimental and modeled values of the refractive index structure parameter were less than an order of magnitude in most conditions and followed the same diurnal trend. There were some greater differences during near-neutral conditions, but this is a known limitation of the model. Overall, this extended model appears to do a good job of predicting turbulence in this environment for the observed time period.

An Open-Source System for Generating and Computer Grading Traditional Non-Coding Assignments

One of the most time-consuming activities in higher education is reviewing and grading student evaluations. Rapid and effective feedback of evaluations, along with an appropriate assessment strategy, can significantly improve students’ performance. Furthermore, academic dishonesty is a major issue in higher education that has been aggravated by the limitations derived from the COVID-19 pandemic. One of the possible ways to mitigate this issue is to give different evaluations to each student, with the negative cost of increasing reviewing time. In this work, an open-source system developed in Python to automatically create and correct evaluations is presented. Using Jupyter Notebook as the graphical user interface, the system allows the creation of individual student question sheets, with the same structure and different parameter values, to send them to students, grade them, and send the final score back to the students. The proposed system requires little programming knowledge for the instructors to use it. The system was applied in Civil Engineering and Geological Engineering programs at the Universidad Católica de la Santísima Concepción, drastically reducing grading time while improving students’ performance.

The impact of magnetized cold plasma and its various properties in sensing applications

These analyses present a novel magnetized cold plasma-based 1D photonic crystal structure for detecting the refractive index of various bio-analytes. The proposed structure is designed with two photonic crystals composed of an alternating layer of right-hand polarization and left-hand polarization of the magnetized cold plasma material with a central defect layer. Transmittance characteristics of the structure are studied by employing the well-known transfer matrix method. Various geometrical parameters such as electron density, external magnetic field, thickness of odd and even layers of the multilayers, thickness of the sample layer, and incident angle are judiciously optimized to attain the best sensitivity, figure of merit, quality factor, signal-to-noise ratio, detection range and limit of detection. Finally, a maximum sensitivity of 25 GHz/RIU is accomplished with the optimized value of structure parameters, which can be considered as a noteworthy sensing performance.

Fragility curves for different classes of existing RC buildings under ground differential settlements

Existing reinforced concrete (RC) buildings can be affected by different actions that can induce permanent or transient effects on them. While applications concerning the seismic vulnerability of existing RC buildings have been largely proposed in literature, the evaluation of the structural vulnerability because of hazards different from earthquake has been less dealt with. The focus of this work is to estimate the probability that the simulated RC buildings stock could reach a given Limit State for a certain intensity of imposed monotonically increasing ground differential settlements. A set of simulated FEM models, considering the geometrical and mechanical uncertainties in the representation of the existing RC frame buildings designed only for gravitational loads, has been created. The structural frames differ from each other for geometrical features and mechanical materials properties, obtained through a simulation process. The non-linear behavior of columns and beams is considered by applying a modeling approach specifically elaborated for RC members with plain bars. A FEM model for each simulated structural frame has been developed using the Open Application Programming Interface by using the programming and numeric computing platform MATLAB to run the modelling software SAP2000. Time by time, by scaling up the amplitude of the imposed base displacements, a non-linear static incremental procedure has been implemented. At each step of the analysis, a code-based seismic safety assessment has been carried out with reference to a specific ultimate Limit State considered in the Italian and European codes. The goal of the analysis has been to find the values of the significative structural response parameters (identified in this work as the maximum differential settlement and the deflection ratio) at the onset of the selected Limit State by using the critical demand to capacity ratio. Considering that these values are lognormally distributed, the structural fragility is then derived, showing how the vulnerability of the considered RC buildings stock is affected by the impact of the geometrical features and by the application direction of the differential settlements.

The design and optimization of novel elliptic cylindrical through‐silicon via and its temperature characterization

AbstractThrough‐silicon via (TSV) technology is a key technology to realize multi‐layer chips and its structure model and transmission characteristics have attracted much attention. With the continuous reduction of chip size, higher requirements are put forward for the model and transmission characteristics of TSV. A novel elliptic cylindrical TSV structure model is proposed. The influence of axial length ratio, height, dielectric layer thickness, and spacing on the transmission characteristics of TSV is further studied by HFSS software. The results show that the transmission of TSV is facilitated by the decrease of axial length ratio, the decrease of height, the increase of dielectric layer thickness, and the increase of TSV spacing. The TSV structural parameter values are optimized by a single variable method. The optimized TSV structure is compared with the original TSV, traditional cylindrical and conical TSV, and coaxial TSV. It is concluded that the elliptic cylindrical TSV structure has better transmission performance. The temperature characteristics of the elliptic cylindrical TSV are simulated. It is indicated that the transmission characteristics of the elliptic cylindrical TSV are poor at low frequency and better at high frequency when the temperature rises.

Pозрахункова математична модель руху частинок вороху при вібраційному очищенні картоплі від домішок

Goal. To substantiate rational constructive and kinematic parameters of the V-shaped distributor of potato heap of the offered design of the combined digging and separating the working body of the potato harvester. Methods. Theoretical research was conducted using the basic principles of higher mathematics and theoretical mechanics. Numerical calculations and graphical dependencies are obtained using a PC based on developed and standard programs. Results. The movement of the potato heap on the wing surface of the V-shaped heap distributor in the process of its distribution over the entire width of the separating conveyor was studied. An equivalent scheme of interaction of the potato heap particle with the surface of the distributor wing is constructed, based on which differential equations of its motion on the specified surface are made, which take into account the main structural and kinematic parameters of the separating conveyor and V-like distributor. Based on the integration of this system of differential equations in quadratures, analytical expressions are obtained that describe the laws of change of velocity and displacement of potato heap particles in time at different values of structural and kinematic parameters of distributor and separating conveyor. Based on the obtained analytical expressions, calculations were performed on a PC and graphical dependences of the heap velocity along the distributor wing on time at different values of the angle of the distributor wings taking into account the oscillations of the separating conveyor blade were obtained. Conclusions. The allowable speed of movement of the heap along the wing of the distributor is determined, provided that the equality of supply of the heap to the distributor and its ascent from the distributor is maintained. The specified speed is 1.62 m·s–1. Analysis of graphical relationships shows that the speed of the heap along the wing of the distributor decreases with increasing angle of inclination of the wing. If the speed is reduced to less than the allowable value, the heap will be unloaded on the wings of the distributor, which will lead to a violation of the technological process of the potato harvester. With the allowable time of movement of the heap along the distributor wing, the maximum allowable values of the deflection of the distributor wing are in the range of 40–45°.

How to derive expected values of structural equation model parameters when treating discrete data as continuous

ABSTRACT This tutorial presents an analytical derivation of univariate and bivariate moments of numerically weighted ordinal variables, implied by their latent responses’ covariance matrix and thresholds. Fitting a SEM to those moments yields population-level SEM parameters when discrete data are treated as continuous, which is less computationally intensive than Monte Carlo simulation to calculate transformation (discretization) error. A real-data example demonstrates how this method could help inform researchers how best to treat their discrete data, and a simulation replication demonstrates the potential of this method to add value to a Monte Carlo study comparing estimators that make different assumptions about discrete data.

Assessing design and manufacturing quality of tractor gearboxes by their vibration characteristics

The paper deals with the development of a vibration-based technique for assessing quality and detecting design and manufacturing defects of tractor gearboxes. It highlights full-scale experimental studies of vibro-diagnostic characteristics of tractor gearboxes including carrying out vibration measurement and spectrum analysis; identifying statistical limit values of structural vibration parameters and their dependence on the technical condition of tractors; and comparing the vibration characteristics with acceptable vibrations which do not affect the acceleration of the process of tractor gearbox wear. All studies were conducted for tractor gearboxes of wheeled tractors T-150K, KhTZ-170, and T-17221 produced by Kharkiv Tractor Plant and equipped with identical tractor gearboxes of the same manufacturer. It has been determined that the vibration levels of gearboxes at the manufacturing stage exceed the acceptable vibrations by 10–30 dB. The main reason for the accelerated development of faults and decrease in the lifetime of most gearbox mechanisms is an increase in vibration loading by 2.5–31.6 times over the acceptable levels. The practical significance of the results obtained is in solving the problem of improving the design and manufacturing of tractor gearboxes T-150k through the use of the developed criteria for permissible vibration by methods of reducing the vibration level of detected defects. All the above mentioned makes it possible to create a complex of normative and technical, and methodological documentation to improve the reliability of tractors.

Wander of a Gaussian-Beam Wave Propagating through Kolmogorov and Non-Kolmogorov Turbulence along Laser-Satellite Communication Uplink

It is accepted that there exists two kinds of atmospheric turbulence in the Earth’s aerosphere—Kolmogorov and non-Kolmogorov turbulence; therefore, it is important to research their combined impacts on laser-satellite communications. In this paper, the exponential power spectra of refractive-index fluctuations for non-Kolmogorov turbulence in the free troposphere and stratosphere are proposed, respectively. Based on these two spectra, using the Markov approximation, beam wander displacement variances of a Gaussian-beam wave are derived, respectively, which are valid under weak turbulent fluctuations condition. On this basis, using a three-layer altitude-dependent turbulent spectrum model for vertical/slant path, the combined influence of a three-layer atmospheric turbulence on wander of a Gaussian-beam wave as the carrier wave in laser-satellite communication is studied. This three-layer spectrum is more accurate than a two-layer model. Moreover, the variations of beam wander displacement with beam radius, zenith angles, and nominal value of the refractive-index structure parameter on the ground are estimated. The theory of optical wave propagation through non-Kolmogorov atmospheric turbulence is further enriched and a theoretical model of a three-layer atmospheric turbulence beam wander for a satellite-ground laser communication uplink is established.

On the scattering and radiation of water waves by a finite dock floating over a rectangular trench

In this study, the scattering and radiation of surface water waves by a finite dock floating over an asymmetric rectangular trench-type bottom topography are analyzed. The boundary value problems are handled for solutions analytically using a matched eigenfunction expansion method and numerically using the boundary element method. Various physical quantities associated with the scattering and radiation problems are studied for various values of wave and structural parameters. The results demonstrate that the scattering coefficients are significantly influenced due to the variation in dock length and depth ratios of the bottom trench. In the case of radiation problems, the dock length plays a crucial role in analyzing the radiation coefficients and wave excitation forces associated with each mode of motion. On the other hand, the effect of depth ratios of the bottom trench is negligible on the radiation coefficients. The present study reveals that the scattering of water waves by a floating dock over an abrupt change in bottom topography plays an important role in the construction of floating structures having more durability to resist harsh wave environments and reduce the wave impact near the seashore.

Structural and magnetic analysis of nanostructured Barium Hexaferrite

In this work, we have examined the room temperature magnetic behavior of nanostructured BaFe12O19 synthesized using sol–gel auto-combustion method. As prepared sample, have undergone through X-ray diffraction at room temperature justifying its monophase composition along with its profile well indexed for p63/mmc space group having hexagonal crystal structure. Further structural details are calculated through Rietveld refinement of XRD data thereby providing values of several structural parameters using which its crystal structure is being emphasized at VESTA software. On engineering the XRD data using Scherrer, modified Scherrer and W-H method the crystallite size was estimated to be around 60 nm. The atomic occupation and bond distribution is presented from their charge density plot based on refined structural parameters. The presence of hard magnetic phase is justified by M−H curve showing its saturation magnetization and coercivity to be 63.3 emu/g and 3642 Oe respectively under applied field of ± 20 kOe. The squareness ratio was also found to be in permissible range for uniaxial anisotropy opening path for its use in magnetic devices especially permanent magnets and data storage.

Evaluasi Kinerja Struktur Gedung Bertingkat Menggunakan Pendekatan Desain Berbasis Kinerja

In Indonesia, earthquake-resistant structures are governed by SNI as design codes, which are updated on a regular basis. As a result, existing buildings with outdated requirements must be reviewed so that the building's performance may be assessed in light of the most recent codes. Pushover analysis and direct displacement-based design are used to characterize the real condition of the building in order to assess its performance. The 7-story reinforced concrete building structure in this study was designed according to SNI 03-2847-2002 and SNI-1726-2002. This structure will be evaluated utilizing the FEMA 440 and FEMA 356 procedures, as well as SNI 1726:2019. The results show that the structure meets the minimal performance limit criteria (which is life safety) in terms of displacement and drift values from the pushover analysis, based on FEMA 356 and FEMA 440 performance levels. The evaluation indicates better structural response parameter values (R, Ω0, and Cd) than that of SNI 1726:2019, indicating that the building performance is good and capable of withstanding the design earthquake load.

Stiffness Modification-Based Bayesian Finite Element Model Updating to Solve Coupling Effect of Structural Parameters: Formulations

The Bayesian model updating approach (BMUA) benefits from identifying the most probable values of structural parameters and providing uncertainty quantification. However, the traditional BMUA is often used to update stiffness only with the assumption of well-known mass, which allows unidentifiable cases induced by the coupling effect of mass and stiffness to be circumvented and may not be optimal for structures experiencing damages in both mass and stiffness. In this paper, the new BMUA tailored to estimating both mass and stiffness is presented by using two measurement states (original and modified systems). A new eigenequation with a stiffness-modified system is formulated to address the coupling effect of mass and stiffness. The posterior function is treated using an asymptotic approximation method, giving the new objective functions with stiffness modification. Analytical formulations of modal parameters and structural parameters are then derived by a linear optimization method. In addition, the covariance matrix of uncertain parameters is determined by the inverse of the Hessian matrix of the objective function. The performance of the proposed BMUA is evaluated through two numerical examples in this study; a probabilistic damage estimation is also implemented. The results show the proposed BMUA is superior to the traditional one in mass and stiffness updating.

Novel Photonic Bio-Chip Sensor Based on Strained Graphene Sheets for Blood Cell Sorting.

A photonic biochip with a tunable response in the visible range is suggested for blood cell sorting applications. Multi-layers of ZnS and Ge slabs (as the main building blocks), hosting a cell in which bio-sample could be injected, are considered as the core of the sensor. In order to increase the sensitivity of the chip, the bio-cell is capsulated inside air slabs, and its walls are coated with graphene sheets. Paying special attention to white and red blood components, the optimum values for structural parameters are extracted first. Tunability of the sensor detectivity is then explored by finding the role of the probe light incident angle, as well as its polarization. The strain of the graphene layer and angle in which it is applied are also suggested to further improve the performance tunability. Results reflect that the biochip can effectively identify selected components through their induced different optical features, besides of the different figure of merit and sensitivity amounts that are recorded for them by the sensor.

Abnormal Bone Tissue Organization and Osteocyte Lacunocanalicular Network in Early-Onset Osteoporosis Due to SGMS2 Mutations.

Pathological variants in SGMS2, encoding sphingomyelin synthase 2 (SMS2), result in a rare autosomal dominant skeletal disorder with cranial doughnut lesions. The disease manifests as early‐onset osteoporosis or a more severe skeletal dysplasia with low bone mineral density, frequent fractures, long‐bone deformities, and multiple sclerotic cranial lesions. The exact underlying molecular features and skeletal consequences, however, remain elusive. This study investigated bone tissue characteristics in two adult males with a heterozygous SGMS2 mutation p.Arg50* and significant bone fragility. Transiliac bone biopsy samples from both (patient 1: 61 years; patient 2: 29 years) were analyzed by bone histomorphometry, confocal laser scanning microscopy, and quantitative backscattered electron imaging (qBEI). Bone histomorphometry portrayed largely normal values for structural and turnover parameters, but in both patient 1 and patient 2, respectively, osteoid thickness (−1.80 SD, −1.37 SD) and mineralizing surface (−1.03 SD, −2.73 SD) were reduced and osteoid surface increased (+9.03 SD, +0.98 SD), leading to elevated mineralization lag time (+8.16 SD, +4.10 SD). qBEI showed low and heterogeneous matrix mineralization (CaPeak −2.41 SD, −3.72 SD; CaWidth +7.47 SD, +4.41 SD) with a chaotic arrangement of collagenous fibrils under polarized light. Last, osteocyte lacunae appeared abnormally large and round in shape and the canalicular network severely disturbed with short‐spanned canaliculi lacking any orderliness or continuity. Taken together, these data underline a central role for functional SMS2 in bone matrix organization and mineralization, lacunocanalicular network, and in maintaining skeletal strength and integrity. These data bring new knowledge on changes in bone histology resulting from abnormal sphingomyelin metabolism and aid en route to better understanding of sphingolipid‐related skeletal disorders. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Anisotropic SST turbulence model for shock-boundary layer interaction

Menter SST k-ω is a Reynolds-averaged Navier–Stokes based two-equation turbulence model routinely used in industry for predicting aerodynamic flows. It shows excellent performance for low-speed flows, but gives inconsistent predictions for high-speed shock-induced separated flows. The model assumption of using a constant value of 0.31 for the structure parameter contradicts experimental observations. The model is also unable to predict Reynolds stress anisotropy generated by shock waves. In this work, we augment the SST model with quadratic eddy viscosity formulation of an explicit algebraic Reynolds stress model. A new relation for the structure parameter is proposed, making it a function of the local strain-rates and is no longer a constant in the regions of shock/turbulent boundary layer interaction (SBLI). Additional shock-physics is introduced using (Sinha et al., 2003) shock-unsteadiness model and an upper limit to the value of structure parameter is set in regions of shock waves. The new model, termed as SUQ-SST, is validated using a number of SBLI test cases ranging from supersonic to hypersonic speeds and near-incipient to fully-separated flows. Results show that the modifications do not alter the boundary layer prediction capability of the SST model. On the other hand, the new model gives significant improvement in predicting Reynolds stress anisotropy, flow separation, and surface properties in a wide range of SBLI flows.

Testing of linear models for optimal control of second-order dynamical system based on model-reality differences

In this paper, the testing of linear models with different parameter values is conducted for solving the optimal control problem of a second-order dynamical system. The purpose of this testing is to provide the solution with the same structure but different parameter values in the model used. For doing so, the adjusted parameters are added to each model in order to measure the differences between the model used and the plant dynamics. On this basis, an expanded optimal control problem, which combines system optimization and parameter estimation, is introduced. Then, the Hamiltonian function is defined and a set of the necessary conditions is derived. Consequently, a modified model-based optimal control problem has resulted. Follow from this, an equivalent optimization problem without constraints is formulated. During the calculation procedure, the conjugate gradient algorithm is employed to solve the optimization problem, in turn, to update the adjusted parameters repeatedly for obtaining the optimal solution of the model used. Within a given tolerance, the iterative solution of the model used approximates the correct optimal solution of the original linear optimal control problem despite model-reality differences. The results obtained show the applicability of models with the same structures and different parameter values for solving the original linear optimal control problem. In conclusion, the efficiency of the approach proposed is highly verified.