Component Synthesis Method Research Articles

Methods of diagnostic meta-analysis: comparing the generalized linear mixed model and the split component synthesis model

Purpose of review Diagnostic meta-analyses combine data from several diagnostic test accuracy (DTA) studies to provide an in-depth assessment of a specific diagnostic test's performance across diverse populations and settings. Additionally, knowledge on common methods of diagnostic meta-analyses is crucial for researchers to make informed decisions on best practice for reporting analyses and results. This article provides an overview of commonly used methods of diagnostic meta-analyses using real-life and simulation data. Recent findings Advances in methods of diagnostic meta-analyses in recent years have increased uncertainty among researchers in relation to the most suitable method to be used. Currently, the most popular approaches for diagnostic evidence synthesis include hierarchical summary operating characteristic (HSROC) and bivariate random effects models though other methods such as the split component synthesis method have been proposed. In addition, different software modules exist for DTA meta-analyses. Summary This article presents a thorough evaluation of current frequentist DTA meta-analysis methods implementing both simulated and real-world data. By understanding the recent methods of diagnostic meta-analyses and their limitations, clinicians may better be equipped in selecting the optimum approach to improve clinical judgement and consequently better patient outcomes.

Diagnostic accuracy of stress CMR to evaluate chronic coronary syndromes: an updated meta-analysis

Abstract Background Stress cardiovascular magnetic resonance (CMR) imaging is utilised for the evaluation of patients with stable chest pain and intermediate or high pre-test likelihood of coronary artery disease (CAD). Purpose To provide an updated synthesis of diagnostic accuracy of stress CMR imaging for the diagnosis of anatomically and functionally significant CAD in patients with stable chest pain and suspected or known CAD. Methods After prospective registration and approval of the study protocol, we performed a systematic review and meta-analysis of studies published between 2000 through 2021, enrolling ≥100 patients, and reporting on the diagnostic accuracy of stress CMR imaging to diagnose anatomically and functionally significant CAD with invasive coronary angiography (ICA) or ICA and fractional flow reserve (FFR <0.80) as the reference standard. The novel split component synthesis method was used through the SCSmeta function in R. The meta-analysis yielded pooled diagnostic indicators including diagnostic odds ratio (DOR), sensitivity, specificity, positive likelihood ratio (pLR), negative likelihood ratio (nLR) and area under the curve (AUC). Results We identified a total of 32 studies pooling an overall population of 7,678 individuals (mean age 62 years, 70% males, CAD prevalence 52%). Compared with ICA (29 studies, 7,360 patients), stress CMR yielded a pooled DOR of 19.2 (95% CI: 12.5–29.4), a sensitivity of 84% (95% CI: 79–88%), a specificity of 79% (95% CI: 73–84%), a pLR of 3.9 (95% CI: 3.0–5.3), a nLR of 0.2 (95% CI: 0.2–0.3), and an AUC of 0.81 (95% CI: 0.78–0.84) for the detection of anatomically obstructive CAD. Compared with ICA and FFR (8 studies, 1,196 patients), stress CMR yielded a pooled DOR of 26.4 (95% CI: 10.6–65.9), a sensitivity of 81% (95% CI: 68–89), a specificity of 86% (95% CI: 75–93%), a pLR of 5.8 (95% CI: 3.0–11.4), a nLR of 0.2 (95% CI: 0.1–0.4), and an AUC of 0.84 (0.77–0.89) for the detection of functionally obstructive CAD. Higher diagnostic accuracy was observed for 3 Tesla myocardial perfusion imaging studies to detect both anatomically and functionally obstructive CAD, with pooled DORs of 24.3 and 33.2, respectively. Conclusions In patients with stable chest pain and known or suspected CAD, stress CMR imaging yields high diagnostic accuracy to detect both anatomically and functionally obstructive CAD. Stress CMR perfusion imaging at 3 Tesla is to be associated with overall greater diagnostic accuracy. Funding Acknowledgement Type of funding sources: None.

Active vibration suppression for flexible satellites using a novel component synthesis method

This paper is devoted to developing a closed-loop vibration suppression controller for a satellite with large flexible appendages based on component synthesis vibration suppression (CSVS) method. The dynamics model of a flexible satellite is firstly established by using the Newton–Euler methodology, and the dynamics model of the flywheel is also developed. A novel CSVS method is presented based on zero-vibration differentiator (ZVD), which can guarantee multi-order vibration suppression. Combined with the proposed CSVS method, traditional closed-loop controllers such as PD or sliding mode controllers can be applied to active vibration suppression. The stability of the proposed closed-loop CSVS controller is proved by the Lyapunov theory. Subsequently, the dynamic optimal control allocation algorithm is proposed for six flywheels, and a novel nonsingular fast terminal sliding mode controller is developed to obtain practical voltage control input for the flywheel drive control system. Finally, numerical simulations are carried out to validate the effectiveness of the proposed method.

Concurrent multi-process graph-based design component synthesis: Framework and algorithm

Facing today’s increasingly complex and high-demanded design missions, the abundant and multifarious design components distributed in different disciplines and locations should be fully considered and elaborately synthesized. However, this involves a large amount of data processing workload which heavily restrains the application and development of the traditional graph-based synthesis methods. Therefore, a concurrent multi-process graph-based design component synthesis method is proposed to break the bottleneck. With this method, the heavy workload can be dynamically and efficiently decentralized and shared in a group of processes working simultaneously and concurrently. As an application, a software prototype is presented, and the design component synthesis of a biochemical heating system is completed with it.

Research on component synthesis active vibration suppression method for flexible spacecraft attitude maneuver with reaction jet actuators

Purpose The purpose of this paper is to design a component synthesis method to suppress the vibration of the flexible spacecraft, which has the constant amplitude force/moment actuator. Design/methodology/approach The authors proposed a method to construct constant amplitude of time delay and composite coefficient sequences based on the principles of the component synthesis vibration suppression (CSVS). The associated design strategy of the CSVS torque control is also developed. The dynamic model consisting of a single axis rotating rigid central body and a fixed flexibility panel is used to validate the proposed method. Constraint modal and free modal method are both tested to analyse the natural frequencies of the panel and dynamic properties of rigid–flexible decoupling system, under the conditions of known and unknown frequencies. The feasibility of constructing CSVS control force based on the constraint modal frequency is also analysed. Findings The proposed method can suppress multistage vibration and has arbitrary order robustness for each order frequencies simultaneously. Simulation results show that only the duration time of the actuator has to be set for the proposed method, reasonable vibration suppression effect can be achieved. Practical implications The method can be used in spacecraft, especially flexible spacecraft to suppress the vibration; the approach is convenient for engineering application and can be easily designed. Originality/value The authors proposed a method to construct constant amplitude of time delay and composite coefficient sequences based on the principles of the CSVS.

Component Synthesis Method for Transient Response of Nonproportionally Damped Structures

A component synthesis technique for calculating the transient response of nonproportionally damped structures is presented in this paper. The structure can be composed of nonproportionally damped components or proportionally damped components with different damping factors, and the components are joined by connecting elements at their boundaries. In the synthesis technique, the transient responses of the nonproportionally damped components are defined by a newly developed direct integration method, which keeps the analytical solution of the mode displacement superposition method for the proportionally damped structure with the interpolation of excitation forces as the input. The structural responses are obtained based on the geometric compatibility and the force equilibrium conditions of the connecting elements. The proposed method is most suitable for the recalculation of structural responses induced by modification of the connecting elements. Numerical examples are given to validate the correctness and to show the effectiveness of the proposed method.

モード合成法と出力フィードバックを用いた柔軟ロボットアームの制振制御

This paper presents a high accurate reduced-order model for the output feedback controller which is newly derived on the basis of the modal component synthesis method for the vibration suppression control of a flexible robot arm. The output feedback control law combined the reduced-order model and the Minimum Error. Excitation Method is designed in order to obtain the system stable condition.The presented control law gives the stable gain for the vibration suppression. From the comparison of the numerical simulation results with the experiment ones using a two flexible links robot arm, the proposed reduced-order model represents system response accurately. The validity of the proposed output feedback law to suppress the vibration of the robot arm is verified by carrying out the experiment.

Analyzing the normal mode dynamics of macromolecules by the component synthesis method: Residue clustering and multiple‐component approach

AbstractA study of the component synthesis method (CSM) for analyzing the normal mode dynamics of macromolecules is reported. The procedure involves a reduction of the dimensions of the normal mode problems for large molecular systems and the accurate extraction of the low‐frequency modes. A macromolecule is divided into small components based on a hierarchical clustering of the residues in the structure. Interactions between coupled components are treated by the method of static correlation. The normal modes of the components are obtained first, and a fraction of the low‐frequency normal modes of the components under mutual correlations are then used as a reduced basis for solving for the normal modes of the whole molecule. Multiple components are introduced for large macromolecules so that the dimensions of the eigenvalue problems at the component level are small. The method is applied to the protein crambin. In test calculations in which the dimensions of the eigenvalue equations are reduced to 1/6 of their natural size, the errors in the normal mode frequencies calculated by the CSM procedure are only about 1–2% when compared with the exact values. The rms fluctuations of all atoms in crambin calculated by the CSM procedure are basically identical to the exact results. The CSM procedure is shown to be accurate for calculating the normal modes of large macromolecules with a significant reduction of the size of the problem. © 1994 John Wiley & Sons, Inc.

Analyzing the normal mode dynamics of macromolecules by the component synthesis method.

This paper presents a general method for studying the harmonic dynamics of large biomolecules and molecular complexes. The performance and accuracy of the method applied to a number of molecules are also reported. The basic approach of the method is to divide a macromolecule into a number of smaller components. The local normal modes of the components are first calculated by treating individual components and the interactions between nearest neighboring components. The physical displacements of all atoms are then represented in the local normal mode space, in which a selected range of high-frequency local modes is neglected. The equation of motion of the molecule in the local normal mode space will then have a smaller dimension, and consequently the normal modes of the whole structure, particularly for large molecules, can be solved much more easily. The normal modes of two polypeptides--(Ala)6 and (Ala)12--and a double-helical DNA--d(ATATA).d(TATAT)--are analyzed with this method. Reductions on the dimensions of harmonic dynamic equations for these molecules have been made, with the fraction of the deleted high-frequency modes ranging from 1/2 to 5/6. The calculated low-frequency normal modes are found to be very accurate as compared to the exact solutions by standard procedure. The major advantage of the present approach on macromolecule harmonic dynamics is that the reduction on the dimensionality of the eigenvalue problems can be varied according to the size of molecules, so the method can be easily applied to large macromolecules with controlled accuracy.

Component synthesis method for system transient responses

The system may be formed by joining components through the connecting elements at the boundaries of the components. The transient responses of the system are calculated based on the geometric compatibility and force equilibrium equations. For the rigid and linear connecting elements at the joints, no iteration is required, and direct marching procedures are used to calculate the responses. For nonlinear connecting elements, the interconnecting force vectors at the joints are determined using iterative procedures, and the responses are computed subsequently

Block-Krylov component synthesis method for structural model reduction

A new analytical method is presented for generating component shape vectors, or Ritz vectors, for use in component synthesis. Based on the concept of a block-Krylov subspace, easily derived recurrence relations generate blocks of Ritz vectors for each component. The subspace spanned by the Ritz vectors is called a block-Krylov subspace. The synthesis uses the new Ritz vectors rather than component normal modes to reduce the order of large, finite-element component models. An advantage of the Ritz vectors is that they involve significantly less computation than component normal modes. Both 'free-interface' and 'fixed-interface' component models are derived. They yield block-Krylov formulations paralleling the concepts of free-interface and fixed-interface component modal synthesis. Additionally, block-Krylov reduced-order component models are shown to have special disturbability/observability properties. Consequently, the method is attractive in active structural control applications, such as large space structures. The new fixed-interface methodology is demonstrated by a numerical example. The accuracy is found to be comparable to that of fixed-interface component modal synthesis.

Investigation of the Transient Response of a Dual-Rotor System With Intershaft Squeeze-Film Damper

A method is presented for calculating the dynamics of a dual-rotor gas turbine engine equipped with a flexible intershaft squeeze-film damper. The method is based on the functional expansion component synthesis method. The transient response of the rotor due to a suddenly applied imbalance in the high-pressure turbine under different steady-speed operations is calculated. The damping effects of the intershaft damper and stability of the rotor system are investigated.

A modal synthesis method employing physical coordinates, free component modes, and residual flexibilities

For the solution of the eigenproblem of large dynamical MK systems a new component synthesis method incorporating residual flexibilities and free component modes is developed. The assembly procedure for this method is particularly simply, in fact the components can be linked to other components or elements like a conventional finite element by the direct stiffness approach, because the reduced component models employ the physical coordinates of the interface nodes among others. Therefore, the method may easily be integrated into an existing finite element code. Converence is outstanding because the residual flexibilities are considered at the interface degrees of freedom linking the individual substructures. It is believed that the method possesses potential computer applicablity because of the listed advantages.

Analysis of Vibration by Component Synthesis Method : 3rd Report, Analysis of Cylinder Block

有限要素法や伝達行列法などの従来の方法では解析が困難である複雑な機械構造物を振動解析する方法の一つとして, 著者らが提案した区分モード合成法を用いて, 4シリンダディーゼルエンジンのシリンダブロックの固有振動数, 固有モードおよび強制振動応答を解析する. 同時に調和励振により振動試験を行い, その結果と計算結果を比較する. 両者は良く一致し, 区分モード合成法の有用性を例証できた.