Simultaneous Layout Research Articles

Analysis on the Spatial Structure and Interaction of Aviation Network and Tourism Efficiency Network in Major Cities in China

Tourism efficiency is crucial for measuring sustainable tourism development. Examining the relationship between aviation and tourism efficiency networks is key to promoting their synergistic development in China's urban areas. This study employs various methods, such as complex network analysis method, entropy-weighted TOPSIS, tourism efficiency gravity model, and quadratic assignment procedure, to analyze the networks' spatial structure evolution characteristics and interaction effects. Results show that (1) China's major cities' aviation network has improved its organizational efficiency and formed a "double rhombus-single axis" spatial evolution pattern of the axis-spoke network. The number of intermediary networks and hub cities in the central and western regions has increased. (2) The tourism efficiency network adopts a "honeycomb" structure pattern with the simultaneous layout of "point-to-point" and "star" networks. The network's tourism efficiency follows "Pareto's Law," and tourism cities above the second level form a club group development. The tourism efficiency development potential area is shifting to the southwest. (3) The aviation and tourism efficiency networks exhibit a clear trend of synergistic evolution with a "path locking" phenomenon between them. Differences in tourism resource endowment, labor advantage, and capital advantage positively impact the aviation network's structure. Conversely, differences in revenue capacity and market scale negatively impact the structure. The aviation scale advantage, openness, intimacy, and influence exhibit decreasing positive effects on the tourism efficiency network's structure.

Simultaneous layout and size optimization of nonlinear viscous dampers for frame buildings under stochastic seismic excitation

Viscous dampers, as effective energy-dissipation devices, have been widely used for seismic mitigation of building structures. Due to the intrinsic uncertainties of structural parameters and earthquake ground motions, to obtain an optimal performance of structural control, the stochastic design optimization of viscous dampers for buildings is essential. This paper establishes a new dynamic reliability-based optimization framework to address the simultaneous layout and size design of nonlinear viscous dampers in frame buildings, considering the dual randomness of both nonstationary seismic excitations and uncertain structural model parameters. Firstly, a mixed integer optimization problem for nonlinear viscous dampers, including discrete and continuous design variables, is formulated, and the design target is to minimize the cost of the dampers subjected to performance constraints on dynamic reliability of building structures. Then, sequential approximate mixed integer programming with trust region is proposed to solve the optimization problem. Moreover, direct probability integral method is suggested to assess the dynamic reliability and its sensitivity with respect to design variables. Finally, accounting for both stochastic nonstationary seismic excitations and random structural parameters, the optimized results of two numerical examples indicate that the proposed method is a competitive choice for realizing the layout and size optimization of limiting types of nonlinear viscous dampers in frame buildings. To ensure the same target performance of buildings in terms of the probability of exceeding the target value of inter-story drift, the larger peak ground acceleration of stochastic ground motions is, the more cost of dampers is required for seismic protection of buildings.

Simultaneous layout design optimization with the scalable reconfigurable manufacturing system

Simultaneous layout design optimization with the scalable reconfigurable manufacturing system

JayaX Algorithm for Simultaneous Layout and Size Optimization of Grillages

JayaX Algorithm for Simultaneous Layout and Size Optimization of Grillages

Layout design of thin-walled structures with lattices and stiffeners using multi-material topology optimization

In this paper, the thin-walled structures with lattices and stiffeners manufactured by additive manufacturing are investigated. A design method based on the multi-material topology optimization is proposed for the simultaneous layout optimization of the lattices and stiffeners in thin-walled structures. First, the representative lattice units of the selected lattices are equivalent to the virtual homogeneous materials whose effective elastic matrixes are achieved by the energy-based homogenization method. Meanwhile, the stiffeners are modelled using the solid material. Subsequently, the multi-material topology optimization formulation is established for both the virtual homogeneous materials and solid material to minimize the structural compliance under mass constraint. Thus, the optimal layout of both the lattices and stiffeners could be simultaneously attained by the optimization procedure. Two applications, the aircraft panel structure and the equipment mounting plate, are dealt with to demonstrate the detailed design procedure and reveal the effect of the proposed method. According to numerical comparisons and experimental results, the thin-walled structures with lattices and stiffeners have significant advantages over the traditional stiffened thin-walled structures and lattice sandwich structures in terms of static, dynamic and anti-instability performance.

Simultaneous Layout and Topology Optimization of Curved Stiffened Panels

Simultaneous layout and topology optimization of stiffened panels is investigated in this paper using a new level-set-based method. Specifically, plate elements are used to construct a stiffened panel structure. The level set method is then used to manipulate the stiffener layout, with curved members allowed. A free-form mesh deformation method with a control mesh is used to adjust the finite element mesh. The level set method is also used to optimize the internal topologies of the stiffeners. Both mass minimization with buckling constraint and critical buckling load factor maximization with mass constraint are investigated. A semi-analytical sensitivity analysis is performed, and the optimization algorithm is outlined. For the buckling-constrained problem, the -norm function is used to aggregate multiple buckling modes and a gradient-based optimizer is used with an adaptive scaling method to enforce exact control of the buckling limit. Numerical investigations demonstrate and validate the proposed method.

A Unified Framework for Simultaneous Layout Decomposition and Mask Optimization

In advanced technology nodes, layout decomposition (LD) and mask optimization (MO) are two key stages in integrated circuit design. Due to the inconsistency of the objectives of these two stages, the performance of conventional layout and MO may be suboptimal. To tackle this problem, in this article, we propose a unified framework, which seamlessly integrates LD and MO. We propose a gradient-based approach to solve the unified mathematical formulation, as well as a set of discrete optimization techniques to avoid being stuck in local optimum. The conventional optimization process can be accelerated as some inferior decomposition results can be smartly pruned in early stages. The experimental results show that the proposed unified framework can achieve more than $34\times $ speed-up compared with the conventional two-stage flow, meanwhile, it can dramatically reduce EPE violations by more than $8\times $ , and thus maintain better design quality.

A local mesh reconstruction method for layout and scantling optimization of FPSO internal turret area structure

This paper proposes a local mesh reconstruction method designed for generating the finite element (FE) analysis model in the context of simultaneous layout and scantling optimization. The FE model is automatically built by inheriting the topology and property information of the prepared initial finite element (FE) analysis model. A framework of optimization integrating the mesh reconstruction process is set up through the ISIGHT platform based on MATLAB code and MSC.PATRAN&NASTRAN. The capability and effectiveness of the method are demonstrated on the optimization of a typical internal turret area for the mooring system of FPSO. The thickness of plates and the layout of web-frames are optimized to minimize the structural weight of the turret area subjected to yield stress constraints. The optimization result presents the potential application of the proposed method in layout and scantling optimization of the FPSO internal turret area structure.

Sewer network design: Heuristic algorithm for hydraulic optimisation

For a given sewer network layout and choice of pipe material, the total installed cost of the network is determined mainly by the pipe diameters and slopes. Hydraulic design optimisation is the task of determining suitable pipe diameters and slopes so as to minimise the installed cost of the network. This is a complex problem for which numerous solution approaches have been proposed. Recently the use of metaheuristic algorithms, like Ant Colony Optimisation (ACO) for example, has gained popularity, and they perform well for a given static layout. However, their computational complexity precludes their use in simultaneous layout and hydraulic optimisation, where a complete hydraulic optimisation has to be performed for each layout. This paper proposes a computationally efficient method for near optimal hydraulic design of a gravity sewer network. It makes use of required minimum slope information to heuristically determine optimal pipe sizes and slopes. The method is used to solve two benchmark problems and is shown to obtain good solutions while being computationally extremely efficient. Therefore it is ideally suited to be used in combination with a metaheuristic algorithm aimed at optimising the network layout.

New Discrete Particle Swarm Optimization Applied to the Design of Pressurized Irrigation Networks

AbstractPipe size of pressurized irrigation networks that usually have a branched layout had been optimized by assuming a predetermined layout. Few researches have considered simultaneous layout and pipe size optimization. In this study, a hybrid approach that is a combination of pipe size optimizer and layout optimizer is adapted for simultaneous layout and pipe size optimization. Once the solutions (specific layouts) are developed, a modified version of Labye’s iterative discontinuous method (LIDM) is applied to optimize pipe sizes. After the layout optimizer rearranges, the solutions and the process continues. Two versions of a new discrete particle swarm optimization (PSO) are used as tree layout optimizer, namely, original jumping PSO (JPSO) and tree growing JPSO (TG-JPSO). In the original JPSO, a loop model network is considered first, and a spanning tree is produced by using JPSO for eliminating certain branches. Tree growing JPSO without producing a loop model directly deals with branched layout. ...

A novel control strategy approach to optimally design a wind farm layout

Recently wind energy has become one of the most important alternative energy sources and is growing at a rapid rate because of its renewability and abundancy. For the clustered wind turbines in a wind farm, significant wind power losses have been observed due to wake interactions of the air flow induced by the upstream turbines to the downstream turbines. One approach to reduce power losses caused by the wake interactions is through the optimization of wind farm layout, which determine the wind turbine positions and control strategy, which determine the wind turbine operations. In this paper, a new approach named simultaneous layout plus control optimization is developed. The effectiveness is studied by comparison to two other approaches (layout optimization and control optimization). The results of different optimizations, using both grid based and unrestricted coordinate wind farm design methods, are compared for both ideal and realistic wind conditions. Even though the simultaneous layout plus control optimization is theoretically superior to the others, it is prone to the local minima. Through the parametric study of crossover and mutation probabilities of the optimization algorithm, the results of the approach are generally satisfactory. For both simple and realistic wind conditions, the wind farm with the optimized control strategy yield 1–3 kW more power per turbine than that with the self-optimum control strategy, and the unrestricted coordinate method yield 1–2 kW more power per turbine than the grid based method.

Coupled Topology and Pipe Size Optimization of Water Distribution Systems

This paper describes a new multi-objective evolutionary optimization approach to the simultaneous layout and pipe size design of water distribution systems. Pressure-deficient and topologically infeasible solutions are fully incorporated in the genetic algorithm without recourse to constraint violation penalties or tournaments. The proposed approach is demonstrated by solving three benchmark problems taken from the literature. New optimal layouts and/or new feasible solutions that are cheaper than the best solutions in the literature were found for both branched and looped network configurations. Specifically, a new best solution was generated for each of the above-mentioned benchmark problems. In addition, the case of the looped design of a hitherto branched network in the literature was considered. Detailed results are included that show that the proposed approach achieves good solutions efficiently and consistently.

Constrained Ant Colony Optimisation Algorithm for the layout and size optimisation of sanitary sewer networks

The incremental solution building capability of Ant Colony Optimisation Algorithm (ACOA) is used in this paper for the efficient layout and pipe size optimisation of sanitary sewer network. Layout and pipe size optimisation of sanitary sewer networks requires optimal determination of pipe locations, pipe diameters and pipe slopes leading to a highly constrained mixed-integer nonlinear programming (MINLP) problem presenting a challenge even to the modern heuristic search methods. A constrained version of ACOA equipped with a Tree Growing Algorithm (TGA) is proposed in this paper for the simultaneous layout and pipe size determination of sewer networks. The method is based on the assumption that a base layout including all possible links of the network is available. The TGA algorithm is used in an incremental manner to construct feasible tree-like layouts out of the base layout, while the constrained ACOA is used to optimally determine the cover depths of the constructed layout. Proposed formulation is used to solve three hypothetical test examples of different scales and the results are presented and compared with those produced by a conventional application of ACOA in which an ad-hoc engineering concept is used for layout determination. The results indicate the effectiveness and efficiency of the proposed method to optimally solve the problem of layout and size determination of sewer networks.

Density estimation of sympatric carnivores using spatially explicit capture–recapture methods and standard trapping grid

Population density is an important state variable in ecology and monitoring of wildlife populations. In the study of large carnivores, traditional density estimation methods have relied on camera trapping to collect capture–recapture data using sampling designs suited to a single target species and ad hoc methods to calculate the effective trapping area. We describe an application of spatially explicit capture–recapture analysis to estimate density for four sympatric carnivore species using a standard spatial sampling grid, camera trap sampling, and maximum-likelihood estimation methods. We used camera traps deployed in four adjacent, sequential camera arrays to construct capture histories for leopard, aardwolf, spotted hyena, and striped hyena in an African savanna/scrub ecosystem. We considered two methods of constructing trapping histories: (1) a simultaneous layout in which all cameras are deployed and active for 21 trapping intervals of 24 h each; and (2) an incomplete layout in which cameras are considered deployed for 84 sampling intervals, but with only a fraction of traps active for a given sampling interval. We estimated density and confidence or profile likelihood intervals for each species using a mean maximum distance moved method and maximum-likelihood estimation procedures with model averaging. Maximum-likelihood densities ranged from 4.93/100 km2 for spotted hyena to 12.03/100 km2 for leopard. Estimates did not differ between simultaneous and incomplete trap layouts. Our approach demonstrates the utility and cost effectiveness of using maximum-likelihood density estimation methods in studies of sympatric species that are individually recognizable.

Simultaneous Layout Migration and Decomposition for Double Patterning Technology

Double patterning technology (DPT) and layout migration (LM) are two closely related problems on design for manufacturability in the nanometer era. DPT decomposes a layout into two masks and applies double exposure patterning to increase pitch size and, thus, printability. In this paper, we present the first algorithm in the literature for the simultaneous layout migration and decomposition (SMD) problem. Our algorithm first constructs a potential conflict graph and DPT-aware constraint graphs, and then applies integer linear programming (ILP) corresponding to the graphs to obtain a decomposed and migrated layout. We further present an effective graph-based reduction technique to prune the ILP solution space, which maintains the same DPT conflicts. We also present a new DPT-aware objective for the SMD problem to minimize the difference between the original and migrated layouts while considering the DPT effects. In addition, we present an approach to generate DPT-aware standard cells by considering the DPT effects on the cell boundaries; this technique improves the layout printability and facilitates electronic design automation tools to consider DPT. Experimental results show that our algorithms can effectively generate conflict-free migrated layouts with 11% smaller layout areas and 21% smaller layout changes, compared with the traditional method of layout decomposition followed by LM. In particular, our reduction technique reduces the ILP variables by 45.7%, the ILP constraints by 58.5%, and the DPT edges by 79.9% over the basic ILP formulation, leading to a substantial speedup. For example, it can reduce the runtimes for the test cases from more than one day to only seconds.

Closure to “Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach” by M. H. Afshar, M. Akbari, and M. A. Marino

Closure to “Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach” by M. H. Afshar, M. Akbari, and M. A. Marino

Discussion of “Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach” by M. H. Afshar, M. Akbari, and M. A. Marino

Discussion of “Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach” by M. H. Afshar, M. Akbari, and M. A. Marino

Layout and size optimization of tree-like pipe networks by incremental solution building ants

Application of an ant colony optimization algorithm (ACOA) for simultaneous layout and size optimization of tree-like pipe networks is described in this paper using two different formulations. In the first formulation, each link of the base graph is considered as the decision point of the problem. Each decision point is considered in turn and the ants are then required to choose any of the available options at the current decision point. The list of available pipe diameters with the null option included for each link constitutes the available options in this formulation. In the second approach, the network nodes are considered as the decision points of the problem. The available options in this formulation are represented by the list of allowable pipe diameters for all plausible links such that the resulting network is a tree network. The plausible links at each decision point are provided by a tree-growing algorithm. This formulation leads to a very small search space compared with the first algorithm, as each ant is now forced to create a feasible solution regarding the layout geometry of the network. This approach fully exploits the sequential nature of the ACOA in building solutions, which is believed to be one of the main advantages of these algorithms compared with other general metaheuristics. The proposed methods are applied to find the optimal layout of two benchmark examples in the published literature and the results are presented and compared with the existing results.

Application of a max–min ant system to joint layout and size optimization of pipe networks

The application of a max–min ant algorithm to the layout and size optimization of pipe networks is described in this paper. The formulation conventionally used for the pipe size optimization of networks with fixed layout is extended to account for the layout determination of the networks. This is achieved by including new constraints regarding the reliability of the network and modifying some of the constraints of the optimization problem. A deterministic concept of reliability is used in which the number of independent paths from source nodes to each of the demand nodes is considered as a measure of reliability. The method starts with a predefined layout which includes all possible links. The method is capable of designing the layout and pipe sizes of water distribution networks of predefined reliability including tree-like and looped networks. It is also shown that a layout optimization of a network followed by size optimization does not lead to an optimal or a near-optimal solution. This emphasizes the need for simultaneous layout and size optimization of networks if an optimal or near-optimal solution is desired. The performance of the method for layout and pipe size optimization of pipe networks is tested against two benchmark examples in the literature and the results are presented. The first example is considered to show the necessity of joint layout and size optimization even for the simple tree networks while the second example is considered to illustrate the efficiency of the proposed method for layout and size optimization of real-world networks with different levels of reliability.

Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach

A heuristic method is presented for the simultaneous layout and component size optimization of water distribution networks. The method is based on the engineering concept of reliability in which the number of independent paths from source nodes to each of the consumption nodes is considered as a measure of reliability. The method starts with a predefined maximum layout which includes all possible and useful connections. An iterative design-float procedure is then used to move from the current to a cheaper layout satisfying a predetermined reliability set by the user. This is achieved via identifying the hydraulically least important pipes and floating the one which would lead to the cheapest layout. A pipe is floated by relaxing its minimum diameter constraint requirement so that the optimization process could eliminate the pipe from the layout by assigning a zero value to its diameter if required. An iterative penalty method is used for design purpose at each iteration. Three different floating procedures are developed and their efficiencies are tested. A heuristic method is also developed to convert the continuous pipe size solution to a set of discrete solutions. The performance of the method for layout optimization of pipe networks is tested against the benchmark example in the literature and the results are presented.