Comparison of Linear Level I Green-Naghdi Theory with Linear Wave Theory for Prediction of Hydroelastic Responses of VLFS

Very Large Floating Structures (VLFS) have drawn considerable attention recently due to their potential significance in the exploitation of ocean resources and in the utilization of ocean space. Efficient and accurate estimation of their hydroelastic responses to waves is very important for the design. Recently, an efficient numerical algorithm was developed by Ertekin and Kim (1999). However, in their analysis, the linear Level I Green-Naghdi (GN) theory is employed to describe fluid dynamics instead of the conventional linear wave (LW) theory of finite water depth. They claimed that this linear level I GN theory provided better predictions of the hydroelastic responses of VLFS than the linear wave theory. In this paper, a detailed derivation is given in the conventional linear wave theory framework with the same quantity as used in the linear level I GN theory framework. This allows a critical comparison between the linear wave theory and the linear level I GN theory. It is found that the linear level I GN theory can be regarded as an approximation to the linear wave theory of finite water depth. The consequences of the differences between these two theories in the predicted hydroelastic responses are studied quantitatively. And it is found that the linear level I GN theory is not superior to the linear wave theory. Finally, various factors affecting the hydroelastic response of VLFS are studied with the implemented algorithm.

Optimal design of butterfly-shaped linear ultrasonic motor using finite element method and response surface methodology

A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.

Transient Response Model of Standing Wave Piezoelectric Linear Ultrasonic Motor

A transient response model for describing the starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor was presented. Based on the contact dynamic model, the kinetic equation of the motor was derived. The starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor according to different loads, contact stiffness and inertia mass were described and analyzed, respectively. To validate the transient response model, a standing wave piezoelectric linear ultrasonic motor based on in-plane modes was used to carry out the simulation and experimental study. The corresponding results showed that the simulation of the motor performances based on the proposed model agreed well with the experimental results. This model will helpful to improve the stepping characteristics and the control flexibility of the standing wave piezoelectric linear ultrasonic motor.

Hormesis has emerged as a more common and fundamental dose-response model than the threshold or linear-no-threshold(LNT) models

在回顾传统的有阈和线性无阈的剂量-反应关系的基础上,分析此类该模型被毒理学领域认同的主要原因和其在预测低剂量效应中的缺陷,进而提出了高剂量接触呈现抑制效应,而低剂量却呈现促进或刺激作用这一全面的激效兴奋性剂量-反应关系,弥补了现有模型的不足,并充分论证这种激效性剂量-反应关系在不同种属、接触因素和生物学终点中的普遍性,并探讨了不同物质的激效兴奋作用的可能机制以及激效兴奋模型的三大优点,最后提出了激效模型谋求广泛接受的现实困难和发展趋势。

Estimation of Concrete Arch Dams Responses in Linear Domain Using Endurance Time Analysis Method

In this paper, Endurance Time Analysis （ETA） method which is a new time-history based dynamic pushover procedure is introduced and its application in linear analysis of concrete arch dams is investigated. In this method the structure is subjected to gradually intensifying acceleration functions and its performance is evaluated based on the length of the time duration that can satisfy required performance criteria. For this purpose Dez arch dam is selected as case study, fluid-structure interaction is taken into account and F.E. model of the system is excited in three performance levels. ETA method gives an approximation of maximum response at the equivalent target time, resulted from analyzing the system based on natural records. Extracted results are displacement, velocity and acceleration of the crest at crown cantilever. Results show using of ETA method can reduce at least 50% in number of analyses and 70% in total time of analyses at the current case. Furthermore, it is found that although the results of the ETA are not exactly consistent with the results of time-history analyses using real ground motions, errors are reasonable and ETA can identify performance levels of the dam with acceptable accuracy.

NONLINEAR TRANSIENT RESPONSE OF STAY CABLE WITH VISCOELASTICITY DAMPER IN CABLE-STAYED BRIDGE

Taking the bending stiffness, static sag, and geometric non-linearity into consideration, the space nonlinear vibration partial differential equations were derived. The partical differential equations were discretized in space by finite center difference approximation, then the nonlinear ordinal differential equations were obtained. A hybrid method involving the combination of the Newmark method and the pseudo-force strategy was proposed to analyze the nonlinear transient response of the inclined cable-dampers system subjected to arbitrary dynamic loading. As an example, two typical stay cables were calculated by the present method. The results reveal both the validity and the deficiency of the viscoelasticity damper for vibration control of stay cables. The efficiency and accuracy of the proposed method is also verified by comparing the results with those obtained by using Runge-Kutta direct integration technique. A new time history analysis method is provided for the research on the stay cable vibration control.

Lattice dynamics properties of chalcopyrite ZnSnP_2:Density-functional calculations by using a linear response theory

We present a first-principles study of the structural,dielectric,and lattice dynamical properties for chalcopyrite semiconductor ZnSnP2.The structural properties are calculated using a plane-wave pseudopotential method of densityfunctional theory.A linear response theory is used to derive Born effective charge tensors for each atom,dielectric constants in low and high frequency limits,and phonon frequencies.We calculate all zone-center phonon modes,identify Raman and infrared active modes,and report LO-TO splitting of the infrared modes.The results show an excellent agreement with experiment and propose several predictive behaviors.

Subharmonic response of single-degree-of-freedom linear vibroimpact system to narrow-band random excitation

The subharmonic response of a single-degree-of-freedom linear vibroimpact oscillator with a one-sided barrier to the narrow-band random excitation is investigated.The analysis is based on a special Zhuravlev transformation,which reduces the system to the one without impacts or velocity jumps,and thereby permits the applications of asymptotic averaging over the period for slowly varying the inphase and quadrature responses.The averaged stochastic equations are exactly solved by the method of moments for the mean square response amplitude for the case of zero offset.A perturbation-based moment closure scheme is proposed for the case of nonzero offset.The effects of damping,detuning,and bandwidth and magnitudes of the random excitations are analyzed.The theoretical analyses are verified by the numerical results.The theoretical analyses and numerical simulations show that the peak amplitudes can be strongly reduced at the large detunings.

A Study on Stochastic Resonance in Biased Subdiffusive Smoluchowski Systems within Linear Response Range

The method of matrix continued fraction is used to investigate stochastic resonance (SR) in the biasedsubdiffusive Smoluchowski system within linear response range.Numerical results of linear dynamic susceptibility andspectral amplification factor are presented and discussed in two-well potential and mono-well potential with differentsubdiffusion exponents.Following our observation,the introduction of a bias in the potential weakens the SR effect inthe subdiffusive system just as in the normal diffusive case.Our observation also discloses that the subdiffusion inhibitsthe low-frequency SR,but it enhances the high-frequency SR in the biased Smoluchowski system,which should reflect a'flattening' influence of the subdiffusion on the linear susceptibility.

Analysis of the variability of auditory brainstem response components through linear regression

The analysis of the Auditory Brainstem Response (ABR) is of fundamental importance to the investigation of the auditory system behavior, though its interpretation has a subjective nature because of the manual process employed in its study and the clinical experience required for its analysis. When analyzing the ABR, clinicians are often interested in the identification of ABR signal components referred to as Jewett waves. In particular, the detection and study of the time when these waves occur (i.e., the wave latency) is a practical tool for the diagnosis of disorders affecting the auditory system. In this context, the aim of this research is to compare ABR manual/visual analysis provided by different examiners. Methods: The ABR data were collected from 10 normal-hearing subjects (5 men and 5 women, from 20 to 52 years). A total of 160 data samples were analyzed and a pair- wise comparison between four distinct examiners was executed. We carried out a statistical study aiming to identify significant differences between assessments provided by the examiners. For this, we used Linear Regression in conjunction with Bootstrap, as a method for evaluating the relation between the responses given by the examiners. Results: The analysis suggests agreement among examiners however reveals differences between assessments of the variability of the waves. We quantified the magnitude of the obtained wave latency differences and 18% of the investigated waves presented substantial differences (large and moderate) and of these 3.79% were considered not acceptable for the clinical practice. Conclusions: Our results characterize the variability of the manual analysis of ABR data and the necessity of establishing unified standards and protocols for the analysis of these data. These results may also contribute to the validation and development of automatic systems that are employed in the early diagnosis of hearing loss.

RANDOM RESPONSES OF A TWO-DEGREE-OF-FREEDOM STRUCTURE WITH STRONGLY NONLINEAR COUPLING AND PARAMETRIC INTERACTION

This paper investigates the random responses of a TDOF structure with strongly nonlinear coupling and parametric vibration. With the nonlinear cou- pling of inertia in the equations of motion of the system being removed by successive elimination, the non-Gaussian moment equation method (NGM) is applied and 69 moment equations are integrated with central cumulative truncation technique. The stochastic central difference-cum-statistical linearization method(SCD-SL) and the digital simulation method(DSM) are also used. A comparison of results by different methods are given and the SCD-SL method is the most efficient method.

Linear analysis of the dynamic response of a riser subject to internal solitary waves

The flow field induced by internal solitary waves(ISWs)is peculiar wherein water motion occurs in the whole water depth,and the strong shear near the pycnocline can be generated due to the opposite flow direction between the upper and lower layers,which is a potential threat to marine risers.In this paper,the flow field of ISWs is obtained with the Korteweg-de Vries(Kd V)equation for a two-layer fluid system.Then,a linear analysis is performed for the dynamic response of a riser with its two ends simply supported under the action of ISWs.The explicit expressions of the deflection and the moment of the riser are deduced based on the modal superposition method.The applicable conditions of the theoretical expressions are discussed.Through comparisons with the finite element simulations for nonlinear dynamic responses,it is proved that the theoretical expressions can roughly reveal the nonlinear dynamic response of risers under ISWs when the approximation for the linear analysis is relaxed to some extent.

Dynamics Response and Non⁃linear Characteristics Analysis of Complex Planar 2⁃DOF Mechanism with Revolute Clearances

There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.

A Study on Simple Prediction Method of Heat Load： A Use of Linear Approximation Indicial Response in Basements

This study was conducted to establish a predictable method for a heat load of an underground structure with sufficient accuracy. As the first step, our previous paper reported the measurement results of field experiments on an underground experimental basement under internal heat generation conditions. Also, it presented the results of numerical analyses on the heat and moisture behavior and the influence of internal heat generation of the experimental basement and ground. However, it is practically impossible to utilize the model of simultaneous heat and moisture transfer at the design phase because the prediction by the model of simultaneous heat and moisture transfer requires a long calculation time. In this paper, the authors present the simple load calculation technique, using a linearized approximation indicial response of the inner surface heat flux in a basement to outdoor air temperature change. In addition, the approximation indicial responses for each part of the single-walled concrete drawn using this technique are arranged. The heat load calculation example of application to the basement of the optional size by this technique is shown.

Frequency responses of immersing tunnel element under wave actions

The immersion of large-scale tunnel elements is one of the most important working procedures in the construction of an underwater immersed tunnel. To investigate the dynamic characteristics of tunnel element in the process of immersion, based on the twin-barge immersing operation method, the frequency-domain analysis of the tunnel element motions under wave actions was made. The linear wave diffraction theory and the three-dimensional source distribution method were applied to calculate the wave loads and motion responses of the tunnel element under different incident wave conditions. In the study, movement of the two barges in the water was assumed to be small and was ignored. Cable tension was computed by the static method. On the basis of the above theories, a computer program was made, and two cases were taken to check the validity of the program. The results showed that wave loads acting on the immersed tunnel element are relatively large near the water surface, and they decrease with the increase of immersing depth of the tunnel element. Wave loads first increase, then decrease, with the increase of wave period. The motion responses of the tunnel element are also generally large near the water surface and decrease as the immersing depth increases.

An Analysis of the Correlation between the Changes in Sa-tellite DNA Methylation Patterns and Plant Cell Responses to the Stress

The differences in satellite DNA methylation pattern of corn seedlings with various spontaneous chromosome aberration yields and changes in methylation pattern of these DNA sequences under different exposure modes of acute UV-C and chronic gamma-irradiations have been investigated. The obtained experimental data and the conducted correlation analysis demonstrated the significant correlation between the satellite DNA methylation pattern varieties and chromosome aberration yields under various stress exposure modes. The role of satellite DNA methylation pattern variability and its changing in key responses to stress such as mobile elements’ activation, cell’s passage of checkpoints, and homological repair was discussed.

Response Process of Oceanto AtmosphericForcing and Optimal Response Frequency in the CZ Ocean Model

Ocean response to atmospheric forcing in the CZ ocean model is analyzed.The results show that Nino 3 indexfrom the CZ ocean model driven by linear composite of biennial,ENSO and even annual time scale wind stressanomalies is consistent well with composite of responding two or three components of observed Nino 3 index duringthe EI Nino period while the La Nina phenomena cannot be reproduced by the linear composite.It implies that linearresponse process for ocean response to atmospheric forcing is dominated during the EI Nino period while nonlinearresponse might be main process during the La Nina period.Simulated results also suggest that optimal response frequency of the CZ ocean model is the frequency lowerthan annual variability and ocean response to the atmospheric forcing with annual time scale can give rise to incorrectsignal-errors in the simulated SSTA field.

Hybrid Analysis Approach for Stochastic Response of Offshore Jacket Platforms

The dynamic response of offshore platforms is more serious in hostile sea environment than in shallow sea. In this paper, a hybrid solution combined with analytical and numerical method is proposed to compute the stochastic response of fixed offshore platforms to random waves, considering wave-structure interaction and non-linear drag force. The simulation program includes two steps: the first step is the eigenanalysis aspects associated the structure and the second step is response estimation based on spectral equations. The eigenanalysis could be done through conventional finite element method conveniently and its natural frequency and mode shapes obtained. In the second part of the process, the solution of the offshore structural response is obtained by iteration of a series of coupled spectral equations. Considering the third-order term in the drag force, the evaluation of the three-fold convolution should be demanded for nonlinear stochastic response analysis. To demonstrate this method, a numerical analysis is carried out for both linear and non-linear platform motions. The final response spectra have the typical two peaks in agreement with reality, indicating that the hybrid method is effective and can be applied to offshore engineering.

Controlling optical responses through local dielectric resonance in nanometre metallic clusters

Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances ε1 and ε2. Through varying the difference admittance ratio η[= （ε2 - ε0）/（ε1 - ε0）], we find that their optical responses are determined by the local resonance. There is a blueshift of absorption peaks with the increase of η- Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances, we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-component composites εe=ε0 （1＋∑^n n=1[（γn1＋ηγn2）/（ε0（s-sn））]） and the sum rule of cross sections：∑^n n=1（γn1＋ηγn2）=Nh1＋Nh2,, where Nh1and Nh2 are the numbers of εl and ε2 bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.

A Novel Approach for Evaluating Nonstationary Response of Dynamic Systems to Stochastic Excitation

The transient state of a dynamic system,such as offshore structures,to random excitation is always nonstationary.Many studies have contributed to evaluating response covariances at the transient state of a linear multi-degree-of-freedom(MDOF)system to random excitations,but a closed-form solution was not available unless the excitation was assumed to be a physically unrealizable white noise process.This study derives explicit,closed-form solutions for the response covariances at the transient state by using a pole-residue(PR)approach operated in the Laplace domain when the excitations are assumed to be stationary random processes described by physically realizable spectral density functions.By using the PR method,we can analytically solve the triple integral in evaluating the nonstationary response covariance.As this approach uses the poles and residues of system transfer functions,rather than the conventional mode superposition technique,the method is applicable to MDOF systems with non-classical damping models.Particular application of the proposed method is demonstrated for multi-story shear buildings to stochastic ground acceleration characterized by the Kanai–Tajimi spectral density function model,and a numerical example is provided to illustrate the detailed steps.No numerical integrations are required for computing the response covariances as the exact closed-form solution has been derived.The correctness of the proposed method is numerically verified by Monte Carlo simulations.