Structural Dynamic Effects Research Articles

Structural analysis and application of wind loads to solar arrays

Evaluation of a solar array subjected to wind requires knowledge of the aerodynamics of the array as well as the structural response of the array to wind pressures that vary with time and location. Boundary layer wind tunnel testing using pressure-tap models is effective for measuring these pressures. However at the small scale necessary for such testing, particularly when modeling rooftop arrays, it is difficult to create aeroelastic models that can accurately capture the structural response. Nonlinear wind response-history analysis can account for dynamic effects in lieu of aeroelastic testing, with some advantages and limitations. Response-history analysis is a means for investigating the effects of structural dynamics on the behavior of solar arrays and the appropriateness of equivalent static analysis procedures. Key aspects in the implementation of response-history analysis include the effects of damping, nonlinear modeling assumptions, and initial conditions of the analysis. Findings from an investigation using response-history analysis indicate that a solar array support system that is flexible under uplift can resist code design-level winds provided there is adequate structural interconnection and sufficient ballast weight or attachments, particularly at the edges and corners of the array.

Effect of Structural Dynamics and Base Pair Sequence on the Nature of Excited States in DNA Hairpins

In this article, a theoretical study of the electronic and spectroscopic properties of well-defined DNA hairpins is presented. The excited states in the hairpins are described in terms of an exciton Hamiltonan model, and the structural dynamics of the DNA model systems is explicitly taken into account by molecular dynamics simulations. The results show that the model reproduces the experimentally observed absorption and circular dichroism spectra accurately in most cases. It is shown that structural disorder leads to excited states that are largely localized on a single base pair, even for regular DNA sequences consisting only of AT base pairs. Variations in the base pair sequence have a significant effect on the appearance of the spectra but also on the degree of delocalization of the excited state.

Nonlinear finite element model for 3D Galfenol systems

This work addresses the development of an advanced modeling tool which describes the fullnonlinear coupling in three-dimensional (3D) Galfenol transducers to provide system levelinput–output relationships. Maxwell’s equations for electromagnetics and Navier’sequations for mechanical systems are formulated in weak form. The constitutive behavior ofGalfenol is described through a nonlinear discrete energy-averaged model. The overallsystem is approximated hierarchically; first, piecewise linearization is used to describequasi-static responses and magnetic bias calculations. A linear dynamic solution withpiezomagnetic coefficients computed at a given magnetic bias describes the systemdynamics for moderate inputs. Dynamic responses at large input fields and stresses arequantified through an implicit dynamic solution based on the trapezoidal rule.The model simultaneously incorporates the effects of eddy currents, flux leakage,structural dynamics and nonlinear material behavior. A case study on a Galfenolunimorph actuator validates the model in quasistatic and dynamic conditions.

Dynamic Response of Intraocular Pressure and Biomechanical Effects of the Eye Considering Fluid-Structure Interaction

The vibration characteristics of shell structures such as eyes have been shown to vary with intraocular pressure (IOP). Therefore, vibration characteristics of the eye have the potential to provide improved correlation to IOP over traditional IOP measurements. As background to examine an improved IOP correlation, this paper develops a finite element model of an eye subject to vibration. The eye is modeled as a shell structure filled with inviscid pressurized fluid in which there is no mean flow. This model solves a problem of a fluid with coupled structural interactions of a generally spherically shaped shell system. The model is verified by comparing its vibrational characteristics with an experimental modal analysis of an elastic spherical shell filled with water. The structural dynamic effects due to change in pressure of the fluid are examined. It is shown that the frequency response of this fluid-solid coupled system has a clear increase in natural frequency as the fluid pressure rises. The fluid and structure interaction is important for accurate prediction of system dynamics. This model is then extended to improve its accuracy in modeling the eye by including the effect of the lens to study corneal vibration. The effect of biomechanical parameters such as the thicknesses of different parts of the eye and eye dimensions in altering measured natural frequencies is investigated and compared to the influence of biomechanical parameters in Goldmann applanation tonometry models. The dynamic response of the eye is found to be less sensitive to biomechanical parameters than the applanation tonometry model.

Output-only modal analysis of linear time-periodic systems with application to wind turbine simulation data

Many important systems, such as wind turbines, helicopters and turbomachinery, must be modeled with linear time-periodic equations of motion to correctly predict resonance phenomena. Time periodic effects in wind turbines might arise due to blade-to-blade manufacturing variations, stratification in the velocity of the wind with height and changes in the aerodynamics of the blades as they pass the tower. These effects may cause parametric resonance or other unexpected phenomena, so it is important to properly characterize them so that these machines can be designed to achieve high reliability, safety, and to produce economical power. This work presents a system identification methodology that can be used to identify models for linear, periodically time-varying systems when the input forces are unmeasured, broadband and random. The methodology is demonstrated for the well-known Mathieu oscillator and then used to interrogate simulated measurements from a rotating wind turbine. The measurements were simulated for a 5MW turbine modeled in the HAWC2 simulation code, which includes both structural dynamic and aerodynamic effects. This simulated system identification provides insights into the test and measurement requirements and the potential pitfalls, and simulated experiments such as this may be useful to obtain a set of time-periodic equations of motion from a numerical model, since a closed form model is not readily available by other means due to the way in which the aeroelastic effects are treated in the simulation code.

Prediction and Analysis of Main Rotor Loads in a Prescribed Pull-Up Maneuver

This paper predicts and analyzes main rotor airloads, structural loads, and swashplate servo loads in a prescribed high-g pull-up maneuver. A multibody finite-element structural model is coupled with a transient lifting-line aerodynamic model. The structural model includes a swashplate model to calculate servo loads. The lifting-line model combines airfoil tables, a Weissinger-L near-wake time-marching free wake, and a semiempirical dynamic stall model. The maneuver data were taken from the Army/NASA UH-60A Airloads Program Flight Counter 11029. The primary objective of this paper is to isolate the effects of structural dynamics, free wake, dynamic stall, and pitch control angles in order to determine the key loads mechanisms in this flight. The structural loads are first calculated using airloads measured in flight. The measured airloads are then replaced with a lifting-line coupled analysis, which is ideally suited to isolate the effects of free wake and dynamic stall. It is concluded that the maneuver is almost entirely dominated by stall, with little or no wake-induced effect on blade loads, even though the wake cuts through the disk twice during the maneuver. At the peak of the maneuver, almost 75 % of the operating envelope of a typical airfoil lies beyond stall. The mechanism of dynamic stall, in the analysis, consists of multiple cycles within a wide disk area. The peak-to-peak structural loads prediction from the lifting-line analysis shows an underprediction of 10-20% in flap and chord bending moments and 50% in torsion loads. The errors stem from the prediction of four-and five-revolution stall loads. Swashplate dynamics appear to have a significant impact on the servo loads (unlike in level flight), with a more than 50% variation in peak loads.

2P050 1E1435 障害性T細胞の機能にヒト主要組織適合複合体の揺らぎが与える影響について(蛋白質-物性(安定性,折れたたみなど),第48回日本生物物理学会年会)

2P050 1E1435 障害性T細胞の機能にヒト主要組織適合複合体の揺らぎが与える影響について(蛋白質-物性(安定性,折れたたみなど),第48回日本生物物理学会年会)

Different selves, different values: Effects of self‐construals on value activation and use

AbstractThree experiments demonstrated structural properties and dynamic effects of self‐construal on the processing and use of values. In Study 1, it was found that self‐focus during encoding caused spontaneous cognitive clustering of individualistic versus relational values. Study 2 demonstrated that self‐construal affected the implicit weight of a value‐related attribute in a multi‐attribute choice task. In Study 3, behavioral intentions were better predicted by personal values than social norms when the personal self was primed, whereas social norms predicted better when the collective self was primed. The effects of manipulated self‐construal were mimicked when comparing participants with an individualistic versus collectivistic cultural background. No interaction was found between priming and cultural background. Taken together, the studies demonstrated that different domains of the self are associated with different values, which may instigate different cognitive and behavioral processes when activated. Copyright © 2008 John Wiley & Sons, Ltd.

Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate

Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of I exp, obeys a simple exponential law with the rate constant (alpha I_{exp } ; + ;k_{text{rec}} ) , in which α is a parameter relating the light intensity, measured in mW/cm2, to a corresponding theoretical rate in units of reciprocal seconds, and k rec is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the α parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer–Lambert–Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation.

On the role of protein structural dynamics in the catalytic activity and thermostability of serine protease subtilisin Carlsberg

The effect of structural dynamics on enzyme activity and thermostability has thus far only been investigated in detail for the serine protease alpha-chymotrypsin (for a recent review see Solá et al., Cell Mol Life Sci 2007, 64(16): 2133-2152). Herein, we extend this type of study to a structurally unrelated serine protease, specifically, subtilisin Carlsberg. The protease was incrementally glycosylated with chemically activated lactose to obtain various subtilisin glycoconjugates which were biophysically characterized. Near UV-CD spectroscopy revealed that the tertiary structure was unaffected by the glycosylation procedure. H/D exchange FT-IR spectroscopy was performed to assess the changes in structural dynamics of the enzyme. It was found that increasing the level of glycosylation caused a linearly dependent reduction in structural dynamics. This led to an increase in thermostability and a decrease in the catalytic turnover rate for both, the enzyme acylation and deacylation steps. These results highlight the possibility that a structural dynamics-activity relationship might be a phenomenon generally found in serine proteases.

Effect of Structural Dynamics on Charge Transfer in DNA Hairpins

We present a theoretical study of the positive charge transfer in stilbene-linked DNA hairpins containing only AT base pairs using a tight-binding model that includes a description of structural fluctuations. The parameters are the charge transfer integral between neighboring units and the site energies. Fluctuations in these parameters were studied by a combination of molecular dynamics simulations of the structural dynamics and density functional theory calculations of charge transfer integrals and orbital energies. The fluctuations in both parameters were found to be substantial and to occur on subpicosecond time scales. Tight-binding calculations of the dynamics of charge transfer show that for short DNA hairpins (<4 base pairs) the charge moves by a single-step superexchange mechanism with a relatively strong distance dependence. For longer hairpins, a crossover to a fluctuation-assisted incoherent mechanism was found. Analysis of the charge distribution during the charge transfer process indicates that for longer bridges substantial charge density builds up on the bridge, but this charge density is mostly confined to the adenine next to the hole donor. This is caused by the electrostatic interaction between the hole on the AT bridge and the negative charge on the hole donor. We conclude both that the relatively strong distance dependence for short bridges is mostly due to this electrostatic interaction and that structural fluctuations play a critical role in the charge transfer, especially for longer bridge lengths.

The Effects of Space on Inter-State Growth Dynamics and Income Disparities in India - Modeling the Simultaneous Growth of a System of Spatial Units

This dissertation examines the effects of spatial-specific conditions on trends in inter-state disparities in a sample of 17 Indian states. It employs an extended Lotka-Volterra model to estimate the magnitude and direction of inter-state growth dynamics and the long run collective behavior of this system of states. The study evaluates the estimates of growth effects or inter-state growth dynamics and offers meaningful insights into their association with the varying levels and rates of growth of income per capita of states in the sample. It also models and compares growth effects that are driven by geographical proximity with those that are driven by structures that are equivalent. There are several significant contributions of this dissertation. First, it develops a new methodology that makes it possible to model spatial and, more significantly, structural dynamic spillover effects among spatial units. Second, it provides new insight into the relationship between divergent tendencies in the Indian economy (despite a long history of India's attempt to deploy a generally balanced growth policy) and both their spatial and structural relations. And third, the empirical findings show that the methodology enables a deeper insight into potential policy prescriptions for the nation, its states and combinations of states.

Efficient calculation of wave-induced ship responses considering structural dynamic effects

This paper presents a new method for efficient calculation of wave-induced linear and nonlinear load effects in flexible ships. It is a combination of a modal superposition and the conventional load evaluation approach based on a rigid body model, and implies reduced computation effort in time-domain motion and load simulations. It is applied to a 270 m long containership (SL-7 class) as an example to demonstrate its efficiency. The method can also be used for other long flexible marine structures.

Changes in structural dynamics of the Grb2 adaptor protein upon binding of phosphotyrosine ligand to its SH2 domain

Growth factor receptor-bound protein 2 (Grb2) is an extensively studied adaptor protein involved in cell signaling. Grb2 is a highly flexible protein composed of a single SH2 domain flanked by two SH3 domains. Here we report on the structural dynamic effects upon interaction of a phosphopeptide ligand derived from the recognition sequence of the Shc adaptor protein with (i) the isolated SH2 domain of Grb2 (Grb2 SH2) and (ii) the full-length Grb2 protein. From kinetic studies using surface plasmon resonance, it was deduced that a conformation change occurred in the SH2 protein as well as the full-length Grb2 after binding. Measurements of hydrogen/deuterium exchange (HDX) in the isolated SH2 domain and full-length Grb2 protein as monitored by electrospray mass spectrometry, showed that binding reduces the overall flexibility of the proteins, possibly via slightly different mechanisms for the single SH2 domain and the full-length Grb2 protein.

Probing the dark state tertiary structure in the cytoplasmic domain of rhodopsin: proximities between amino acids deduced from spontaneous disulfide bond formation between cysteine pairs engineered in cytoplasmic loops 1, 3, and 4.

To probe proximities between amino acids in the cytoplasmic domain by using mutants containing engineered cysteine pairs, three sets of rhodopsin mutants have been prepared. In the first two sets, a cysteine was placed, one at a time, at positions 311-314 in helix VIII, while the second cysteine was fixed at position 246 (set I) and at position 250 (set II) at the cytoplasmic end of helix VI. In the third set, one cysteine was fixed at position 65 while the second cysteine was varied between amino acid positions 306 and 321 located at the cytoplasmic end of helix VII and throughout in helix VIII. Rapid disulfide bond formation in the dark was found between the cysteine pairs in mutants A246C/Q312C,A246C/K311C and in mutants H65C/C316, H65C/315C and H65C/312C. Disulfide bond formation at much lower rates was found in mutants A246C/F313C, V250C/Q312C, H65C/N310C, H65C/K311C, H65C/F313C, and H65C/R314C; the remaining mutants showed no significant disulfide bond formation. Comparisons of the results from disulfide bond formation in solution with the distances observed in the rhodopsin crystal structure showed that the rates of disulfide bond formation in most cases were consistent with the amino acid proximities as revealed in crystal structure. However, deviations were also found, in particular, in the set containing fixed cysteine at position Cys246 and cysteines at positions 311-314. The results implicate significant effects of structural dynamics on disulfide bond formation in solution.

Hysteresis in magnetic materials: the role of structural disorder, thermal relaxation, and dynamic effects

An overview is given of the present understanding of hysteresis phenomena in magnetic materials. The problem is addressed from three approximate viewpoints: the connection between rate-independent hysteresis and micromagnetics; the modifications brought into this picture by thermal relaxation effects; the role of rate-dependent magnetization mechanisms, like eddy-current-damped domain wall motion.

Structural Dynamic Effects on Interface Response: Formulation and Simulation Under Partial Slipping Conditions

A new formulation for dynamic sliding contact problems with partial slipping is presented and used to investigate the influence of structural dynamic response on interface behavior. The mixed differential-algebraic equation (MDAE) approach uses differential equations to describe the slipping dynamics and algebraic (constraint) equations to model interfacial sticking. An efficient method for solving the case of partial interface slipping has been developed, and special consideration has been given to the changing equations of motion (at the transition from stick-to-slip and slip-to-stick). An example is presented for the case of an elastic block pressed into a rigid foundation and loaded with cyclic tangential tractions at the top of the block. The full elastodynamic transient simulations illustrate that interface slip response is a strong function of loading frequency, reaching a maximum when the external loading frequency is near the theoretical (shear-mode) natural frequency of the structure. [S0021-8936(00)02204-2]

Effects of Conformational Diversity and Structural Dynamics on the Optical Properties of Diazoluminomelanin

ABSTRACTDiazoluminomelanin (DALM) is a luminescent polymer belonging to the broader class of conjugated polyphenylene materials, which has shown significant optical activity in response to perturbing fields. In this paper we use semiempirical electronic structure calculations and molecular dynamics simulations to investigate the molecular structure and absorption characteristics of model phenolic oligomers. Molecular dynamics simulations show the polymer backbone can be extremely flexible depending upon the ionization state of the phenolic hydroxyl groups. The interring torsion angle is a critical variable as it relates charge localization effects and electronic excitation energies. Comparison with experimental data demonstrates the need for a multistate basis to describe the absorption properties of this system.

The past and present roles of computer-aided engineering in DASD design

At the heart of today's computer-aided engineering (CAE) revolution is finite element modeling (FEM). This paper presents a brief history of how FEM simulations interact with and have significant impact on the design process of storage devices. The discussion is limited to structural static and dynamic effects on head/disk assemblies (HDAs) and components. FEM is integral to the design process; it is primarily a predictive/diagnostic design tool that provides engineers with detailed information on the performance of a design. FEM is most effective during the concept phase, where it can sort out many performance issues before the design parameters are constrained. Also, FEM can help to optimize critical structures within the system. As a diagnostic tool, FEM supplements testing by predicting in advance the properties and behavior of the device. A three-piece suspension design is presented as an example of how FEM and design work in harmony. An FEM of the entire structure was built to verify design and to fine-tune dimensions. Areas that required reinforcement and frequencies that seemed too low were identified, and the structure was modified. This process was repeated several times until the design satisfied the requirements. In addition to the suspension design example, a thermal deformation problem with a 3.5-in. actuator comb assembly is discussed.

Experimental study of the natural frequencies of rotating thin-walled composite blades

The paper presents an experimental method for detecting the natural frequencies of helicopter-like thin-walled rotating composite blades, and a study of their dependency in the lamination angles and in the rotor angular velocity. The tests were carried out in a vacuum chamber which allowed the isolation of the structural dynamic effects. Both symmetric and antisymmetric box-beam specimens were tested. The blades were excited by an impulse force during rotation and the time history of the resulting strain distributions were recorded. Natural frequencies have been obtained by numerical analysis of the time response. The results demonstrate high repeatability and clear trends of the natural frequencies variation as a function of the blade lamination modes and their angular velocity.