Delayed resonator for complete vibration suppression of primary structures with nonlinear stiffness

Enhanced delayed resonator for complete single- and multiple-frequency vibration suppression: A hybrid feedforward-feedback control approach

The delayed resonator (DR) is known for its ideal vibration suppression and simple control logic, but its operable frequency range is also known limited due to stability issues and practical hardware constraints. To extend the limited operable frequency range, we inject an additional nondelayed control term into the feedback loop of the classic DR such that the equivalent natural frequency of the DR can be real-time tuned, so the creation of DR with virtual natural frequency adjustment (DRV). Besides, we take the difference between the adjustable natural frequency of the DRV and the excitation frequency as a control parameter to further enhance the vibration suppression leading to optionally tuned parameters for a given excitation. For this, we start with the complete stability analyses of the DRV and the associated coupled system following independent and purely analytical approaches, and the obtained nonconservative stability maps reveal DRV's greatly extended operable frequency range. Given the optional tuned parameters, an optimization procedure aiming for a faster transient process and stronger robustness is proposed to determine the optimal parameter composition. Finally, three numerical case studies are prepared to demonstrate the benefits of the DRV compared with the classic DR. In addition to extending the operable frequency range of the classic DR, this work simplifies the stability analysis of the existing DR investigations and provides a guideline for the tuned control parameter design if they are optional.

Horizontal Denture: A Prosthodontic Alternative for Severe Maxillary Atrophy

INTRODUCTION TO THE DUAL FREQUENCY FIXED DELAYED RESONATOR

Seismic response of submerged secondary systems in base-isolated structures

An active control system consists of three parts : the vibration system of the controlled object, sensors and actuators, and controllers. Control performance depends on the characteristics of the controllers. Therefore, we discuss control system design strategies and control performance for a typical design method of active structural control in detail. Although there are many control system design methods for active vibration control systems of structural control, we focus attention on a design method using modern and postmodern control theories, which is called robust control theory. We verify the control performances as benchmark problems for LQ control, LQG control, disturbance cancellation control, H2 control, H∞ control, μ control and sliding mode control. In this study, we use two vibration models : the active vibration absorber (AVA) model and the active dynamic vibration absorber (ADVA) model. Finally, we confirm that μ is superior to other control methods for linear structural control, and sliding mode is currently the best method for the nonlinear structural control system compared with other control methods in practical use.

Multiple-parallel-protease digestion coupled with high-resolution mass spectrometry: An approach towards comprehensive peptide mapping of therapeutic mAbs

Subject of Research. Algebraic Bayesian networks are referred to a class of probabilistic graphical models that are a representation of knowledge bases with uncertainty. The distinguishing feature of ABN is the availability of global structures. Among them there are primary and secondary structures that are directly used in various kinds of probabilistic logical inference as well as tertiary and quaternary involved in the problems of automatic synthesis and identification of the properties of the secondary structure and partially in the machine learning tasks within specified networks. Existing algorithms for quaternary structure changing require its complete rebuild when changing the primary structure. That feature slows down the whole global structures synthesis, dispels user’s attention who is forced to re-analyze the whole rebuilt structure instead of focusing on the changes that were directly caused by the limited modification of the original data. This fact reduces ABN attractiveness as a model for data processing in general. Scope of Research. This paper is aimed at speeding up the rebuild process and eliminating the shortage of the quaternary structure rebuild algorithms when adding and deleting vertices of primary structure expressed in excess rebuild of the entire structure. The task of algorithm incrementalization for quaternary structure rebuild is solved to achieve the goal. Method. The proposed approach is based on the properties of incremental algorithms that reduce the amount of computations due to the result obtained at the previous step of the algorithm. All the arguments used in the paper are expressed in a graph theory language to apply the established system of terms and classical results. Main Results. The paper presents incremental and decremental algorithms, complemented by a proof of correctness and listing. Given algorithms are based on the previously obtained incremental algorithms for tertiary structure. Moreover, a detailed analysis of the plurality of separators is carried out on each stage of the algorithms. Theoretical and Practical Relevance. These algorithms develop a global structure of algebraic Bayesian networks as well as the theory of probabilistic graphical models in general. Furthermore, they create the groundwork for creation of the secondary structure invariants that may be non-unique even if the primary structure is fixed unlike the current approach where connections are included in the secondary structure. The deletion of manipulation with a set of secondary structures considerably simplifies and makes foreseeable visualization of such complex object as ABN and may improve the computational characteristics of probabilistic logical inference algorithms. It also enables to reformulate the problem of ABN machine learning excluding any need for synthesis of many different objects with complex structure and virtually the same semantics. It also can be expected that the obtained incremental algorithms will accelerate computational processes of rebuilding and properties analysis for all four global ABN structures.

The paper provides an experimental study on the feasibility of base isolation for seismic protection of nonstructural secondary system such as sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission systems housed in nonisolated primary structures. Damages to these secondary systems may result in significant social chaos and costly economic loss. A one-sixth-scaled three-story building model with a single-degree-of-freedom secondary system placed on its third floor is employed in this study. The secondary system is base-isolated by a laminated rubber bearing (LRB) base isolation system from the supporting floor. The ground motion input is simulated by a shaking table which generates three different types of signal including sweeping harmonic sinusoidal, the S00E component of the 1940 E1 Centro earthquake, and the simulated white noise. The experimental results demonstrate significant reduction in both displacement and acceleration responses of the secondary system by using the base isolation. Effects of parameters of the base isolation such as damping ratio and mass on its performance are also investigated. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Hou et al., 2001). Secondary systems in a structure can be divided into two categories: structural and nonstructural. A thorough review of these types of systems and their response behavior under seismic loading has been presented by (Chen and Soong, 1988). In this paper, only nonstructural secondary systems are the subject of the study. These systems include sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission system that reside within a primary structure system. The huge investment made, the mission, and the critical role played by secondary systems in modern day warrant an effective protection strategy against earthquake-induced vibrations. Studies on employing base isolation techniques to protect primary structures have shown the ability of such techniques to limit dynamic response of structures in seismic disturbance (Kelley, 1986; and Ahmadi, 1988); this paper proposes the adoption of a base isolation mechanism for seismic protection of secondary systems and presents the experimental results achieved with this strategy in a scaled-down system designed without primary structural isolation. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Ghantous, 1991; and Samaha, 1992).

Effect of the primary structure on the seismic response of the cable-net façade

Rotational nonlinear energy sinks (NESs) have been proposed to mitigate the response of underlying primary structures subjected to shock loading. This type of NES, which is composed of a passive mass that is free to rotate, has the potential to be easier to realize and more compact than other types of NESs. Like other types of NESs, these devices engage in targeted energy transfer, which allows for the broadband transfer of energy from the primary structure to the NES where it can be rapidly dissipated. Additionally, these devices can couple the dynamics of the primary structure and facilitate the transfer of energy from lower modes to higher modes, where it can be dissipated at a faster rate. This paper experimentally investigates the performance of this type of NES by using the results from tests of a rotational NES attached to a small-scale two-story structure. For these experiments, a shock load is provided to the primary structure using a shake-table-produced impulse-like ground motion. Additionally, by varying the amplitude of the input ground motion, the energy dependency of the performance of these devices can be investigated. The results of these experiments show that this type of NES can attenuate the response of a structure by responding in a highly effective rotational mode.

Introduction

In this article the syntactic synonyms as one the characteristics of the author’s idiostyle are defined as the co(n)textually preferential options formed in the continuum language → discourse as a result of the phased phenomenological cognitive polyoperations at the levels of primary and secondary consciousness: destruction and reconstruction of being and its structures and categories → sublinguistic schemes → primary (pivotal) structures → secondary reduced, extended and quantitatively equacomponential one-basis and two-basis synonymic transforms. Transformational processes and the primary structure are revealed by means of the procedure of inverse reconstruction (discourse → language). The author’s idiostyle is considered as the correlation of different degree of individual and collective cognitive spaces that conditions the choice and actualization of some synonymic structures. Three types of author’s idiostyle are distinguished: 1) diffuse (dominance of the collective cognitive space over the individual one which is revealed through the realization of synonymic structures characteristic to a certain epoch; 2) personal (prevalence of the individual cognitive space over the collective one, that is the actualization of grammaticalized synonymic utterances appropriate for another epoch, of typical agrammaticalized synonymic structures characteristic to another epoch or non-characteristic to the described epoch, of non-typical agrammaticalized synonymic structures. The french writer’s idiostyle of the XXth – the beginning of the XXIst centuries is analyzed using the examples of different semantic-structural types of synonymic preferential options (reduced mono- and polypredicative constructions with the participial and gerundial head lexemes, asyndetic conditional structures and extended with the predicates and presentatives synonymic structures) and it is proved the coexistence of two phenomena: reduction and extension in the modern French fiction despite of the general tendency of the economy of means of expression of author’s thought

Dynamic interaction between primary and secondary structures can alter the response of buildings, bridges and other civil engineering structures to external stressors such as earthquakes and windstorms. TMDs (tuned mass dampers) are a well-known example of passive control devices that exploit this concept. A TMD consists of a secondary mass attached to the primary structure through a linear or nonlinear link. Various formulations exist to optimize the performance of TMDs, depending on the chosen criterion. Typically, the TMD is optimized considering the steady-state amplitude of motion of the primary structure, e.g., when subjected to monochromatic harmonic excitation (H∞ criterion) or white noise input (H2 criterion). Several closed-form analytical solutions have been formulated for linear TMDs with elastic and viscoelastic damping. However, the available expressions only cover the case of constitutive laws described by two or three parameters, e.g., the Kelvin-Voight model (an elastic spring in parallel with a viscous dashpot) and the standard linear solid (SLS) model (an elastic spring in parallel with a single Maxwell element). Furthermore, the inherent damping of the primary system is usually neglected, even though it can drastically affect the performance of the TMD. Similarly, the effects of coloured excitations, e.g., the Kanai-Tajimi model of ground shaking, are often disregarded, leading to sub-optimal designs. Aimed at overcoming these limitations, a new stochastic approach is proposed. The only assumptions are: i) the salient dynamic features of the TMD-controlled structure can be captured with a linear 2-DoF (degree of freedom) system; ii) the dynamic action can be represented as a stationary Gaussian process.

Nonlinear energy sink (NES) as a new type of dynamic absorber has received widespread attention due to its broadband vibration suppression capability, but it has a certain requirement of energy triggering threshold. In this work, a bistable NES-based piezoelectric system with combined damping (BCPNES) and low threshold requirement is proposed. Electromechanical-coupled equations for the nonlinear oscillator coupled with BCPNES (NO-BCPNES) are established. The vibration suppression and vibration energy harvesting performance for the coupled system are investigated numerically and analytically. The frequency–energy plots of the conservative system are investigated using the complex-variable averaging method and the electromechanical decoupling method. The influence of circuit parameters on the target energy transfer threshold and harvested energy is discussed through the equivalent stiffness and damping of the circuit. The vibration suppression performance and the target energy transfer characteristics are analyzed in terms of the time–history response, the time–frequency response and the slowly varying dynamic flow, respectively. The results show that the electromechanical coupling coefficient affects the skeleton curve of frequency–energy plots in the form of equivalent stiffness. The NO-BCPNES system exhibits higher energy dissipation performance and better targeted energy transfer form under various excitations. From the phase perspective, NES-based piezoelectric system achieves vibration suppression of the main structure through the phase locking phenomenon. The mechanism of the influence of piezoelectric device parameters on the energy harvesting performance of the systems is clarified.