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Negative stiffness dampers (NSDs) have garnered significant attention in the research of base-isolated structures (BIS). This study proposes a tuned negative stiffness viscous mass damper (TNSVMD), which includes a tuning spring in series with the NSD and an inerter, to enhance the seismic control effect of the BIS. An analytical model of a BIS with the TNSVMD is initially established, followed by an investigation into frequency response analysis. The analytical expressions for the stochastic responses of the BIS with TNSVMD are derived, and further exploration is conducted on the influences of the negative stiffness ratio, dashpot damping ratio, and inerter mass ratio on the stochastic responses of the BIS. The mechanisms responsible for the damping enhancement and energy dissipation enhancement of the BIS with the TNSVMD are elucidated through the derivation of the analytical solution for the effective damping ratio and dissipated energy of the BIS with the TNSVMD. Two principles are utilized to determine the optimal parameters of the TNSVMD. These principles involve minimizing the earthquake input energy ratio of the BIS and minimizing the stochastic displacement response of the BIS. Finally, the effectiveness of the TNSVMD is validated through a design example using 100 ground motions. The results indicate that the displacement and acceleration responses of the BIS can be simultaneously controlled due to the weakening of stiffness and enhancement of the effective damping ratio, leading to higher energy dissipation efficiency of the TNSVMD. The increase in the inertial mass ratio enhances the seismic mitigation effect and reduces the optimal negative stiffness ratio and optimal dashpot damping ratio. Therefore, it raises the possibility of implementing the TNSVMD. The inherent damping ratio of the BIS has a significant impact on the control efficiency of the TNSVMD. For BIS systems with relatively small inherent damping ratios, the TNSVMD can achieve better control effectiveness.

In applying the boundary element method to an acoustic interior problem modeled as a single domain, even a small change of the cavity geometry affects the whole system matrix. Thus, calculating sensitivities for each intermediate shape is performed independently during iterations for an optimum shape. By utilizing the sub-domain modularization capability of the MBEM, however, the matrix inversion task is performed only once for the initial shape during whole iterations. This can reduce the total computational costs of finding an optimum shape design and the computational efficiency increases as the number of iterations increases. A demonstration example is given by a two-dimensional automotive interior cavity.

Presented herein are four different methods for the optimum design of structures subject to multiple natural frequency constraints. During the optimization process the optimum cross-sectional dimensions of elements are determined. These methods are robust and efficient in terms of the number of eigenvalue analyses required, as well as the overall computational time for the optimum design. A new third order approximate function is presented for the structural response quantities, as functions of the cross-sectional properties, and four different methods for the optimum design are defined based on this approximate function. The main features of the proposed function are that only the diagonal terms of higher order derivative matrices are employed, and these derivatives are established by the available first order derivatives. The first order exact derivatives are obtained from a sensitivity analysis at the previous design points. We show that this approximate function creates high quality approximations of the structural responses, such as the frequencies. Examples are presented and the efficiency and quality of the proposed methods are discussed and compared.

This paper introduces a mathematical model for optimizing the dynamic performance of thin-walled functionally graded box beams with closed cross-sections. The objective function is to maximize the natural frequencies and place them at their target values to avoid the occurrence of large amplitudes of vibration. The variables considered include fiber volume fraction, fiber orientation angle and ply thickness distributions. Various power-law expressions describing the distribution of the fiber volume fraction have been implemented, where the power exponent was taken as the main optimization variable. The mass of the beam is kept equal to that of a known reference beam. Side constraints are also imposed on the design variables in order to avoid having unacceptable optimal solutions. The mathematical formulation is carried out in dimensionless quantities, enabling the generalization to include models with different cross-sectional types and beam configurations. The optimization problem is solved by invoking the MatLab optimization ToolBox routines, along with structural dynamic analysis and eigenvalue calculation routines. A case study on the optimization of a cantilevered, single-cell spar beam made of carbon/epoxy composite is considered. The results for the basic case of uncoupled bending motion are given. Conspicuous design charts are developed, showing the optimum design trends for the mathematical models implemented in the study. It is concluded that the natural frequencies, even though expressed in implicit functions, are well-behaved, monotonic and can be treated as explicit functions in the design variables. Finally, the developed models can be suitably used in the global optimization of typical composite, functionally graded, thin-walled beam structures.

This paper proposes using spatially distributed TMD-type counterweights for the multiple-mode vibration control of irregular bridges subjected to wind loads. In particular, the governing equations of the bridge with TMD-type counterweights that are spatially distributed at any transverse and/or longitudinal positions of the bridge girder are established. Four objective functions are formulated and compared, and an optimum design method is developed to obtain the optimal design parameters of the TMD-type counterweights for each objective. Subsequently, an irregular cable-stayed bridge equipped with counterweight blocks is chosen as the prototype to demonstrate the control effectiveness of TMD-type counterweights. The results show that the proposed method is feasible for the multiple-mode vibration control of irregular bridges, and TMD-type counterweights show good control efficiency and robustness performance, providing an attractive alternative to traditional counterweights in the vibration control, especially multiple-mode vibration control, of irregular bridges.

Real life engineering problems usually require the satisfaction of different, potentially conflicting criteria. Design optimization, on the other hand, based on the conventional Taguchi method cannot accommodate more than one response. However, by the use of the overall evaluation criterion approach, the method can be applied to multiple-criteria optimization problems. This paper presents the use of different utility function methods as well as a multiple attribute decision-making model in the multiple-criteria optimization of a cold heading process. Different aspects of each method are discussed and compared.

This paper presents an improved version of the traction method that was proposed as a solution to shape optimization problems of domain boundaries in which boundary value problems of partial differential equations are defined. The principle of the traction method is presented based on the theory of the gradient method in Hilbert space. Based on this principle, a new method is proposed by selecting another bounded coercive bilinear form from the previous method. The proposed method obtains domain variation with a solution to a boundary value problem with the Robin condition by using the shape gradient.

This paper presents a numerical analysis method for solving the shape identification problems of thermoelastic fields. The square error integral between the actual thermal deformation distributions and the prescribed thermal deformation distributions on the prescribed sub-boundaries is used as the objective functional. The shape gradient of the shape identification problems is derived theoretically using the adjoint variable method, the Lagrange multiplier method and the formulae of the material derivative. Reshaping is accomplished using a traction method that was proposed as a solution to domain optimization problems. In addition, a new numerical procedure for the shape identification is proposed. The validity of the proposed method is confirmed based on the results of 2D numerical analysis.

An optimum design approach to reverse-flow cyclones based on the concept of optimizing cyclone dimensions is introduced in this paper. This approach involves optimizing cyclone dimensions by categories, calculating cyclone performance by correlating similitude numbers and optimizing the combination of four cyclone parameters, D, K_A, and v_i, which has been proven to be applicable not only for single-stage cyclone, but also for multistage cyclone separators. Applications of the designed cyclones in FCC units and acrylonitrile reactors are also presented.

In this paper, employing an analytical method, optimum design of multi-layer compound cylinders is investigated. To this end, considering Tresca criterion, maximum shear stress in each layer is minimized. Analytical relations for optimum values of a layer dimension, residual pressures and radial interferences are derived. A technique for shrink-fitting of layers is also proposed and relationships for radial interferences, residual pressures and required temperature differences during the shrink-fitting process are derived. Three different examples are presented to show the effectiveness of the proposed method. It is shown that increasing the number of layers makes shear stress distribution near to uniform. As a result, with specified maximum shear stress and inner radius, the weight of compound cylinder is decreased when the number of layers is increased. Moreover, compound cylinders with more layers have lower maximum shear stress for a specified weight. It is also concluded that if the ratio of outer to inner radii be larger, increasing the number of layers is more effective.

In this paper, using an analytical optimization method, optimum design of multi-layer compound cylinders with different materials in layers is investigated. For this purpose, considering Tresca criterion, maximum shear stress in each layer is minimized. At the optimum condition, the maximum shear stress at all layers occurs simultaneously. The general analytical relations for optimum dimension of layers, residual pressures and radial interferences are derived. The existence condition of the optimum solution is also investigated and the constraints for materials selection are derived too. It is shown that the allowable shear stress ratio of materials must be close to their geometric mean value. An optimization method is then presented to minimize different objective functions (weight, cost, etc.) by finding the optimum arrangement of layers. Several examples with different number of layers and different materials are presented to show the effectiveness of the proposed method. For compound cylinders with different materials, it is shown that the objective function is minimized when the materials that have higher cost values are used in inner layers. Moreover, it is shown that the shear stress distribution becomes near to uniform across the wall thickness when the number of layers is increased.

Tendons are frequently injured by direct trauma. Tendon adhesions were a common sequel of tendon repair and are one of the most challenging problems in hand surgery.

The concept of “controlled motion” gradually replaced “total immobilization” in the treatment of flexor tendon injuries and today represents a standard of care for all primary repaired flexor tendon injury. Use of controlled motion splints during the early stages of stages of tendon recovery in crease tendon gliding. However, how best to achieve passive motion and the effect of passive motion on tendon gliding have remained controversial subjects. Based on a series of recent experiments, the concept of “dynamic synergistic wrist motion splint” was established and evaluated. It was found that this synergistic wrist motion increases the tendon excursion due to eliminating the laxity and buckling of tendon in the regions between pulleys without introduce excessive amount of tension.

The purpose of this study is to design and fabricate a dynamic splint based on this concept and define the nature coordinated motion between the wrist and finger joints due to the passive tension of the muscles in vivo.

Parametric analysis will be conducted to achieve an optimum design with the consideration of anatomic constraints. Clinical trial of using such dynamic splint will be evaluated in the future.

To find the optimum design of ply orientation for composite material structure, we proposed a method based on genetic algorithm and executed on a composite frame case. Firstly we gave the descriptions of the structure including solid model and mechanical property of the material and then created the finite element model of composite frame and set a static load step to get the displacement of cared node. Then we created the optimization mathematical model and used genetic algorithm to find the global optimal solution of the optimization problem, and finally achieved the best layer angle of the composite material case. The ply orientation optimum design made a good performance as the results showed that the objective function dropped by 16.6%. This case can might provide a reference for ply orientation optimum design of similar composite structure.