bluuebunny/crossref_metadata_2025_split huggingface dataset:
Damage Detection in Rods Using Wave Propagation and Regression Analysis
Authors: Feroz K. T. , Oyadiji S. O. 
Published: February 2021

Abstract
The phenomena of wave propagation in rods was studied both numerically and experimentally. The finite element (FE) code ABAQUS was used for the numerical study while PZT (lead zirconium titanate) sensors and a 50 MHz transient recorder were used experimentally to monitor and to capture the propagation of stress pulses. For the study of damage detection in the rods the analyses and the experiments were repeated by introducing slots in a fixed axial location of the rod. A longitudinal wave was induced in the rod via collinear impact which was modelled in the FE analyses using the force-time history computed from the classical Hertz contact theory. In the experimental measurements this was achieved by a spherical ball impact at one plane end of the rods. It is shown that the predicted and measured strain-time histories for the defect-free rod and for the rods with defect correlate quite well. These results also show that defects can be located using the wave propagation phenomena. A regression analysis technique of the predicted and measured strain histories of the defect free rod and of the rod with defect was also performed. The results show that this technique is more efficient for smaller defects. In particular, it is shown that the area enclosed by the regression curve increases as the defect size increases.
Identification of a Nonlinear Vibration System Using Simulated Annealing, Genetic Algorithm and Programming
Authors: Sláma Lubomir , Balátě Mojmir , Krejsa Jiří , Slavík Jan 
Published: February 2021

Abstract
Application of genetic algorithm and genetic programming to identification of a nonlinear vibration system is presented. Both the theoretical groundwork and experimental results are included. The genetic algorithm is used for identification of parameters of nonlinear stiffness and friction damping characteristics of a single-degree-of-freedom model of a vibration isolation system. The genetic programming is used for identification of a functional form and parameters of a load-deflection characteristic of a rubber isolator. Obtained results from computational experiments are presented and discussed. Results of GA are compared to results obtained by using a simulated annealing method.
Design of Reduced Order H∞ Controller for Smart Structures
Authors: Moreira Fernando J. O. , Arruda José Roberto de França , Inman Daniel J. 
Published: February 2021

Abstract
In this paper the design of a low order controller for a high-order, smart structural system is presented. The application considered here is a model of a solar panel dynamically similar to those used on satellites. Smart structure refers here to the use of integrated piezoceramic materials as sensors and actuators in the structural system in order to implement the control. The theoretical contribution is made be extending well known robust control theory by relating the high frequency robustness condition to the residual uncertainty, removing a trial and error step in the normal robust control design. The procedure is applied experimentally to a one-meter long frame that is coupled in bending and torsion. Both numerical and experimental results are given.
Vibrations Analysis for Gun Systems by Multibody Dynamics
Authors: Wang Deshi , Xiao Renbin , Ouyang Guangyao 
Published: February 2021

Abstract
The multi-rigid-bodies model for the single barrel gun has been developed and the structure vibration of the gun has been analyzed though Lagrangian equations reduced by the software on microcomputer. It is shown that the deck stiffness is significant in the effect of the gun vibration, and then that design of a suitable equilibrium equipment and design of the elastic connection axle to increasing the flexibility in pitching movement can effectively decrease the vibration amplitudes of the tube end. The maximum amplitude, for example, could decay to ten percent of that when the measures mentioned above are adopted. It also indicates that entirely removing the vibration is impossible except relevant vibration absorbing measures are adopted. The method and results are also significant in checking the motions of the mechanisms designed in the guns.
Some Ideas on the Local Control of Nonlinear Systems With Time-Periodic Coefficients
Authors: Dávid Alexandra , Sinha S. C. 
Published: February 2021

Abstract
In this paper ideas on local control of linear and nonlinear time-periodic systems are presented. Our first goal is to stabilize the system far away from bifurcation points. In this case, the classical linear state feedback stabilization based on pole placement is generalized such that it is applicable to time-periodic systems. The linear state-feedback controller design involves computation of the fundamental solution matrix of the system in a symbolic form as function of the control parameters.
Next, we focus on the bifurcation control of time-periodic systems. When the linearized system is in a critical case of stability (i.e. when it has Floquet multipliers on the unit circle of the complex plane) and the critical modes are uncontrollable in the linear sense, then a purely nonlinear state-feedback controller is designed to stabilize the equilibrium at the bifurcation point and ensure the stability of the bifurcated nontrivial solution. When the linearized system is linearly controllable, then it is shown that an appropriately chosen linear state-feedback control can also modify the nonlinear features of the bifurcations, such as stability or size of the limit cycles or quasi-periodic limit sets. The control techniques are based on a series of transformations that convert the system into a time-invariant form. First, the Lyapunov-Floquet transformation is used to make the linear part of the periodic system time-invariant. Then, time-periodic center manifold reduction and time-dependent normal form theory are applied to obtain the simplest nonlinear form of a system undergoing bifurcation. For most codimension one bifurcations the normal form is completely time-invariant and therefore, it is a rather simple task to choose the appropriate control gains. These ideas are illustrated by an example of a parametrically excited simple pendulum undergoing symmetry breaking bifurcation.
Parametric Instability of a Leipholz Column Under Periodic Excitation
Authors: Kang Bongsu , Tan Chin An 
Published: February 2021

Abstract
In this paper, the parametric instability of a Leipholz column under four boundary conditions is studied. The distributed, follower-type axial load is assumed to be uniform and periodic. Instability regions are obtained and the existence of combination resonance of sum and difference types is discussed for each set of boundary conditions. It is found that combination resonance of sum type exists in all the cases of boundary conditions considered, but the difference type exists only in the cases of clamped-simply supported and clamped-free boundary conditions. The combination resonance is shown to be as important as the simple parametric resonance. Results, when compared to a column under a periodic end load, show that the instability characteristics of these two columns are considerably different.
Nonlinear Shape Control of Shells and Plates
Authors: Tzou H. S. , Bao Y. , Chou C. S. 
Published: February 2021

Abstract
Adaptive shape control is essential in many high-performance engineering systems, such as nozzles, airplane wings, helicopter blades, etc. Recent development of smart structures and structronic systems offers new alternatives to shape control with inherent and embedded actuator components. Imposed shape control often involves large deformations implying that the conventional linear theory is no longer applicable. This study is to explore a new structural control concept based on nonlinear theories. Nonlinear piezoelectric shell equations are derived based on von Karman geometric nonlinearity. Physical significance and application are discussed. As to compare the linear and nonlinear theories, a zero-curvature shell–plate is investigated. Analytical results suggest that the linear theory is indeed invalid when large deformation shape control is considered. Differences between the two theories are presented. Control effects of the plate with polymeric and ceramic piezoelectric actuators are compared.
Reduction of Noise Inside a Cavity by Piezoelectric Actuators
Authors: Hagiwara Ichiro , Rao Zhushi , Shi Qinzhong 
Published: February 2021

Abstract
A new analytical model is developed for the reduction of noise inside a cavity using distributed piezoelectric actuators. The cavity is modeled with four rigid walls and two flexible panels, panel on the top is excited by disturbing point forces and thus radiating structure borne noise into the cavity, and the other panel which is on the bottom is bonded with actuators to control the noise inside the cavity. Modal coupling method is used to establish the governing equations of motion of the fully coupled acoustics-structure-piezoelectric patch system. Two performance functions relating ‘global’ and ‘local’ optimal control of sound pressure levels (SPL) respectively are applied to obtain the control laws. Numerical investigations into the effect of number of actuators, error sensors as well as disturbing point forces on SPL’s are presented. Based on the studies, it is found that the number of actuators has a significant influence on SPL’s for local control case, while for global control case, this influence is quite limited. The discussions on associated control mechanism show that both the mechanisms of modal amplitude suppression and modal rearrangement may sometimes coexist in the implementation of optimal noise control.
Benchmark Problems for the Analysis of Piezoelectric Controlled Smart Structures
Authors: Gabbert U. , Görnandt A. , Köppe H. , Seeger F. 
Published: February 2021

Abstract
In the paper at first the theoretical basis for the simulation of piezothermoelastic smart structures is discussed briefly. Then an overview about our finite element simulation tool for smart structures is given. During the development of this analysis tool several test examples have been solved and compared with theoretical results from the literature as well as experimental results. During this process of software verification and qualification we were tackled with several problems, such as incomplete and incorrect data from literature, especially missing material data, incorrect boundary and load conditions, etc. Consequently, a collection of well documented benchmark examples should be created for smart structures. The selection of suited examples should follow the guidelines of the well established NAFEMS benchmarks in other fields of mechanics. In the paper a first collection of some smart structures benchmark problems is proposed and discussed.
A New Integrated Algorithm of Structure Determination and Parameter Estimation for Nonlinear Systems Identification
Authors: Wang Wang Xiao , Xie Jianyin 
Published: February 2021

Abstract
A new integrated algorithm of structure determination and parameter estimation is proposed for nonlinear systems identification in this paper, which is based on the Householder Transformation (HT), Givens and Modified Gram-Schmidt (MGS) algorithms. While being used for the polynomial and rational NARMAX model identification, it can select the model terms while deleting the unimportant ones from the assumed full model, avoiding the storage difficulty as the CGS identification algorithm does which is proposed by Billings et. al., and is numerically more stable. Combining the H algorithm with the modified bidiagonalization least squares (MBLS) algorithm and the singular value decomposition (SVD) method respectively, two algorithms referred to as the MBLSHT and SVDHT ones are proposed for the polynomial and rational NARMAX model identification. They are all numerically more stable than the HT or Givens or MGS algorithm given in this paper, and the MBLSHT algorithm has the best performance. A higher precision for the parameter estimation can thus be obtained by them, as supported b simulation results.
Joint Design and Application of Adaptive Filter and Optimal Control
Authors: Ren Yu Hong , Jing Zhong Liang 
Published: February 2021

Abstract
Kaiman filter is well suited for application to the problems of missile guidance and control. In this paper, we make use of the Kaiman filter theory to develop an efficient scheme for estimating the current states of maneuvering targets, and optimal guidance law is applied in order for a high performance index of miss distance. This scheme is designed to suit for tracking several types of target if aircraft can not provide much known information regarding maneuvering targets before launching missile. It is shown how an adaptive filter based on Current Statistical Model can be applied in conjunction with the optimal guidance law to improve system attacking performance and to relax the requirements of maneuvering target acceleration information during tracking and attacking.
Air-to-Air Attack Based Performance Analysis of Integrated Avionics Systems
Authors: Xu Yi , Jing Zhongliang , Jin Dekun 
Published: February 2021

Abstract
This paper proposes the advanced techniques used by Integrated Avionics System to track and attack the maneuvering target effectively, develops the parameter sensitivity analysis, and then point out the primary factors and the secondary factors affecting the attack effectiveness. First of all, mathematical models are provided, including the kinematic model, the airborne radar tracking model, the fire control model, the pilot-manipulation model and the fire logic. With the use of self-adaptive Kaiman filter, the algorithm for the maneuvering target tracking is suggested. By means of the forced singular perturbation, the suboptimal strategy for three-dimensional pursuit-evasion differential game problem is developed. Secondly, based on the models, the algorithm and the strategy above, the simulation flow chart is proposed, which is in accordance with the actual air-to-air attack. Thirdly, in the light of the relative sensibility function, the values of system parameter sensibility about several parameters are calculated. Fourthly, appropriate parameter selections for improving and updating the attack capability are suggested. Finally, the imaginary air-to-air scenario is simulated to analyze the performance of Integrated Avionics System. The simulation results show that the system can track the maneuvering target reliably and attack it accurately with the longer locking time, and the burden of numerical calculation is lightened considerably.
Application of a Five-Axis Robot Manipulator to Maintenance Operations
Authors: Lacagnina Michele , Petrone Francesco , Sinatra Rosario 
Published: February 2021

Abstract
This paper describes the application of a five-axis manipulator with a particular architecture containing only revolute joints to the performance of maintenance operations on the concrete spire of the “Madonna delle Lacrime” church, in Siracusa, Italy. The kinematics model is derived and a computation of the joint coordinates and their time rates are calculated by the least-squares approximation, as proposed by Angeles. The Newton-Eulero algorithm is implemented for a simulation of the inverse dynamics of a not-simple trajectory in Cartesian space required to perform the maintenance task.
Racing and Training Physiology of an Elite Ultra-Endurance Cyclist: Case Study of 2 Record-Setting Performances
Authors: Rothschild Jeffrey A. , Delcourt Matthieu , Maunder Ed , Plews Daniel J. 
Published: February 2021

Purpose: To present a case report of an elite ultra-endurance cyclist, who was the winner and course record holder of 2 distinct races within a 4-month span: a 24-hour solo cycling race and a 2-man team multiday race (Race Across America). Methods: The athlete’s raw data (cycling power, heart rate [HR], speed, and distance) were obtained and analyzed for 2 ultra-endurance races and 11 weeks of training in between. Results: For the 24-hour race, the athlete completed 861.6 km (average speed 35.9 km·h−1, average power 210 W [2.8 W·kg−1], average HR 121 beats per minute) with a 37% decrease in power and a 22% decrease in HR throughout the race. During the 11 weeks between the 24-hour race and Race Across America, training intensity distribution (Zone 1/2/3) based on HR was 51%/39%/10%. For the Race Across America, total team time to complete the 4939-km race was 6 days, 10 hours, 39 minutes, at an average speed of 31.9 km·h−1. Of this, the athlete featured in this case study rode 75.2 hours, completing 2532 km (average speed 33.7 km·h−1, average power 203 W [2.7 W·kg−1]), with a 12% decrease in power throughout the race. Power during daytime segments was greater than nighttime (212 [25] vs 189 [18] W, P < .001, ). Conclusions: This case report highlights the performance requirements of elite ultra-endurance cycling. Although average power was similar when riding for 24 hours continuously and 75 hours intermittently over 6.5 days, there were large differences in pacing strategies and within-day power-output changes.
Inherited lithospheric structures control arc-continent collisional heterogeneity
Authors: Miller M.S. , Zhang P. , Dahlquist M.P. , West A.J. , Becker T.W. , Harris C.W. 
Published: February 2021

Abstract
From west to east along the Sunda-Banda arc, convergence of the Indo-Australian plate transitions from subduction of oceanic lithosphere to arc-continent collision. This region of eastern Indonesia and Timor-Leste provides an opportunity for unraveling the processes that occur during collision between a continent and a volcanic arc, and it can be viewed as the temporal transition of this process along strike. We collected a range of complementary geological and geophysical data to place constraints on the geometry and history of arc-continent collision. Utilizing ∼4 yr of new broadband seismic data, we imaged the structure of the crust through the uppermost mantle. Ambient noise tomography shows velocity anomalies along strike and across the arc that are attributed to the inherited structure of the incoming and colliding Australian plate. The pattern of anomalies at depth resembles the system of salients and embayments that is present offshore western Australia, which formed during rifting of east Gondwana. Previously identified changes in geochemistry of volcanics from Pb isotope anomalies from the inner arc islands correlate with newly identified velocity structures representing the underthrusted and subducted Indo-Australian plate. Reconstruction of uplift from river profiles from the outer arc islands suggests rapid uplift at the ends of the islands of Timor and western Sumba, which coincide with the edges of the volcanic-margin protrusions as inferred from the tomography. These findings suggest that the tectonic evolution of this region is defined by inherited structure of the Gondwana rifted continental margin of the incoming plate. Therefore, the initial template of plate structure controls orogenesis.
Biomineralization of the Cambrian chancelloriids
Authors: Yun Hao , Zhang Xingliang , Brock Glenn A. , Li Luoyang , Li Guoxiang 
Published: February 2021

Abstract
As extinct animals that flourished during the Cambrian explosion, chancelloriids have a unique body plan lacking guts but with a flexible integument and a suite of star-shaped, hollow sclerites. Due to this body plan, along with the paucity of knowledge on sclerite biomineralization, the phylogenetic position of chancelloriids within the Metazoa is still controversial. Integration of analyses of diverse fossils from Cambrian stage 2 to the Wuliuan Stage of China and Australia indicates that chancelloriid sclerites possess an encasement-like organic layer and a fibrous aragonitic layer. The organic layer is inferred to be a specialized trait derived from the epidermal integument of the animal body. The sclerites were likely biomineralized by using the outer organic layer as a template to absorb cations and precipitate crystal nuclei, reflecting a strategy adopted by a range of eumetazoans with a developed epidermis. Therefore, the hypothesis that chancelloriids represent an epitheliozoan-grade animal and an early explorer of template-based biomineralization is supported.
Wide-blocky veins explained by dependency of crystal growth rate on fracture surface type: Insights from phase-field modeling
Authors: Spruženiece Liene , Späth Michael , Urai Janos L. , Ukar Estibalitz , Selzer Michael , Nestler Britta 
Published: February 2021

AbstractVein microstructures contain a wealth of information on coupled chemical and mechanical processes of fracturing, fluid transport, and crystal growth. Numerical simulations have been used for exploring the factors controlling the development of vein microstructures; however, they have not been quantitatively validated against natural veins. Here we combined phase-field modeling with microtextural analysis of previously unexplained wide-blocky calcite veins in natural limestone and of the fresh fracture surface in this limestone. Results show that the wide-blocky vein textures can only be reproduced if ∼10%–20% of crystals grow faster than the rest. This fraction corresponds to the amount of transgranularly broken grains that were observed on the experimental fracture surfaces, which are dominantly intergranular. We hypothesize that transgranular fractures allow faster growth of vein minerals due to the lack of clay coatings and other nucleation discontinuities that are common along intergranular cracks. Our simulation results show remarkable similarity to the natural veins and reproduce the nonlinear relationship between vein crystal width and vein aperture. This allows accurate simulations of crystal growth processes and related permeability evolution in fractured rocks.
Gulf of Aden spreading does not conform to triple-junction formation
Authors: Almalki Khalid A. , Betts Peter G. 
Published: February 2021

AbstractThe Gulf of Aden represents an evolving example of a juvenile ocean system and is considered the most evolved rift arm of the Afar triple junction. We have undertaken analysis of recent coupled satellite and marine potential-field data to understand the first-order crustal architecture along the entire length of the gulf. Our interpretation suggests the Gulf of Aden has three domains with distinct free-air gravity and magnetic characteristics. These domains record a progression from active seafloor spreading in the eastern domain, through isolated and discontinuous spreading segments in the central domain, to active continental rifting in the western domain immediately adjacent to the Afar triple junction. Forward models suggest the presence of transitional crust, which displays linear magnetic stripe–like anomalies that bound oceanic stripes in the central domain and covering the majority of the western domain. Magnetic anomalies differ from magnetic stripes sensu stricto because they are discontinuous and cannot be correlated along the length of the gulf. Detection of northwest-southeast extension in the central domain based on magnetic stripe orientation is inconsistent with the regional northeast-southwest extension. Our observations reflect heterogeneous opening of the Gulf of Aden basins, in which spreading is migrating toward Afar as a series of isolated spreading segments, rather than initiating at the junction as proposed by classical plate-tectonic theory. This mechanism of ocean initiation is inconsistent with transtensional models that involve wholesale tearing of continental crust and contradicts conceptual models that rely on the Afar plume in initiating or driving the extension.