Hybrid Global Search Algorithm Research Articles

A Hybrid Distribution Algorithm Based on Membrane Computing for Solving the Multiobjective Multiple Traveling Salesman Problem

The multiobjective multiple traveling salesman problem (MmTSP), in which multiple salesmen and objectives are involved in a route, is known to be NP-hard. The MmTSP is more appropriate for real-life applications than the classical traveling salesman problem (TSP), however it has not received the same amount of attention. Due to the high complexity of the MmTSP, a promising algorithm for solving it must be based on a global search procedure. This paper proposes a hybrid global search algorithm, that belongs to the membrane computing framework. The search behavior of the algorithm is enhanced by a communication mechanism. The multichromosome representation is considered to reduce the excess runtime. The effectiveness of the proposed algorithm is tested on the MmTSP with disparately-scaled objective functions, salesmen and problem sizes. The experimental results are compared with the NSGA-II and several evolutionary strategies with decomposition, including simulated annealing algorithm, hill climbing method, pure evolutionary algorithm, and genetic algorithm.

Optimal Scheduling for Highway Emergency Repairs Under Large-Scale Supply–Demand Perturbations

In this paper, we develop a model for emergency repair problems under large-scale supply-demand perturbations. The model formulation proposed in this paper has the following key features. First, a novel time-space network flow technique is adopted to generate detailed schedules for repair teams and allow dynamic updates of the network due to perturbations. Second, the original schedules prior to the perturbations are considered by controlling the total difference between the original schedule and the adjusted schedule. Third, to reduce computational complexity, the model is formulated with different levels of detail (individual teams versus a team group). The model is also formulated as a special mixed-integer network flow problem with side constraints, which is characterized as NP-hard. An ant-colony-system-based hybrid global search algorithm is developed to efficiently solve large-scale problems. To test how well the model formulation and the heuristic algorithm may perform in actual operations, we conduct a case study using actual data from the 1999 Chi-Chi earthquake in Taiwan. The results show that the proposed model and solution algorithm perform very well and thus have great potential for assisting with the making of emergency repair decisions in the event of disasters given large-scale perturbations in supply and demand.

A decorrelation-based hybrid global search algorithm for inversion of 1D magnetotelluric data

An efficient algorithm is presented in this paper to improve the perturbation efficiency of the adaptive downhill simplex simulated annealing (ASSA) method for magnetotelluric inversion with oblique correlated misfit valleys. The correlated model space is rotated to a less dependent space which is defined by the eigenvectors of the parameter covariance updated progressively by the inversion itself. The downhill simplex step and rotation work together to decorrelate the correlated model space. The application to two synthetic cases and real data indicates that ASSA in the rotated space generally has a better convergence and efficient behaviour than ASSA without rotation. In the rotated space, the high rejection rates, which occurred in the unrotated space, are avoided. At low temperature, the estimated covariance can be used to approximate the global covariance. For all cases, ASSA in the rotated space gives better inversion results.

A particle swarm optimization-based hybrid algorithm for minimum concave cost network flow problems

Traditionally, minimum cost transshipment problems have been simplified as linear cost problems, which are not practical in real applications. Some advanced local search algorithms have been developed to solve concave cost bipartite network problems. These have been found to be more effective than the traditional linear approximation methods and local search methods. Recently, a genetic algorithm and an ant colony system algorithm were employed to develop two global search algorithms for solving concave cost transshipment problems. These two global search algorithms were found to be more effective than the advanced local search algorithms for solving concave cost transshipment problems. Although the particle swarm optimization algorithm has been used to obtain good results in many applications, to the best of our knowledge, it has not yet been applied in minimum concave cost network flow problems. Thus, in this study, we employ an arc-based particle swarm optimization algorithm, coupled with some genetic algorithm and threshold accepting method techniques, as well as concave cost network heuristics, to develop a hybrid global search algorithm for efficiently solving minimum cost network flow problems with concave arc costs. The proposed algorithm is evaluated by solving several randomly generated network flow problems. The results indicate that the proposed algorithm is more effective than several other recently designed methods, such as local search algorithms, genetic algorithms and ant colony system algorithms, for solving minimum cost network flow problems with concave arc costs.

March 19, 1996 Artux Xinjiang Earthquake: A Simple Unilateral Rupture Event

AbstractUsing the Global Digital Seismograph Network (GDSN) broadband P wave records and the adaptive hybrid global search algorithm, the rupture process of the 19 March, 1996 Artux, Xinjiang earthquake(MS6.9) is examined. Aftershock data and results of geological and seismic field investigation are applied to constrain the real fault plane. This event occurred in the western part of the Keping Fault zone and is a unilateral‐rupture thrust event with a small strike slip component. The fault plane has a strike of 252° and a dip of 30°. The rupture duration was 15 s and the focal depth was 13 km. The inferred slip distribution contains two major slip sources. A sub‐event with a slip amplitude of 0.3m and a risetime of 0.8 s is located at the hypocenter. The maximum slip amplitude of 1.0m is associated with a 3.5 s risetime subevent located to the east of the first major slip source. The distance between the two major slip sources is about 25 km, and corresponds with the 30 km difference between the instrumental and macroseismic epicenters.

The May 23 and 24, 1994 Taiwan earthquakes: comparison of source process between the two events

Inversion for the seismic fault rupture history is an important way to study the nature of the earthquake source. In this paper, we have selected two Taiwan earthquakes that occurred closely in time and located in the same region, inversed the distribution of the slip amplitudes, rakes, risetimes and the rupture times on the fault planes by using GDSN broad-band and long-period records and the adaptive hybrid global search algorithm, and compared the two events. The slip rate of every subfault calculated provides information about the distribution of tectonic stress and fault strength. To the former event (MS=6.0), the maximum slip amplitude 2.4 m and the minimum risetime 1.2 s are both located at the hypocentre. The latter earthquake (MS=6.6) consisted of two subevents and the second source has 4 s delay. The maximum slip amplitude 0.9 m located near hypocentre is corresponding to the minimum risetime 1.4 s, and the corresponding maximum slip rate 0.7 m·s−1 is similar to the peak value of other large slip rate areas. We consider that the latter event has more complicated temporal-spatial distribution than the former.

The 16 September 1994 Taiwan Strait earthquake: a simple rupture event starting as a break of asperity

In this paper we give a detailed study of the 16 September 1994 Taiwan Strait earthquake using a broad-band body-waveform inversion. An adaptive hybrid global search algorithm was used to solve the nonlinear problems of inverting the spatial distributions of slip amplitude, rake, slip duration and rupture time on a finite fault. The best-fitting solution reveals that the largest slip of 14 m took place in the hypocentre region, in which the rise time is short. The slip amplitude decreases and the rise time increases from the initiation point outward. A suggested mechanism is that the rupture initiated as a breaking of a strong asperity with low dynamic friction and was arrested by large friction around the asperity. The hypocentre is a region of high frequency radiation. We examined the sensitivity by comparing the inversion solutions utilizing varied parameterizations and constraints. These numerical tests show that the major features of the rupture model are better resolved.

The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high‐frequency radiation

A hybrid global search algorithm is used to solve the nonlinear problem of calculating slip amplitude, rake, risetime, and rupture time on a finite fault. Thirty‐five strong motion velocity records are inverted by this method over the frequency band from 0.1 to 1.0 Hz for the Northridge earthquake. Four regions of larger‐amplitude slip are identified: one near the hypocenter at a depth of 17 km, a second west of the hypocenter at about the same depth, a third updip from the hypocenter at a depth of 10 km, and a fourth updip from the hypocenter and to the northwest. The results further show an initial fast rupture with a velocity of 2.8 to 3.0 km/s followed by a slow termination of the rupture with velocities of 2.0 to 2.5 km/s. The initial energetic rupture phase lasts for 3 s, extending out 10 km from the hypocenter. Slip near the hypocenter has a short risetime of 0.5 s, which increases to 1.5 s for the major slip areas removed from the hypocentral region. The energetic rupture phase is also shown to be the primary source of high‐frequency radiation (1–15 Hz) by an inversion of acceleration envelopes. The same global search algorithm is used in the envelope inversion to calculate high‐frequency radiation intensity on the fault and rupture time. The rupture timing from the low‐ and high‐frequency inversions is similar, indicating that the high frequencies are produced primarily at the mainshock rupture front. Two major sources of high‐frequency radiation are identified within the energetic rupture phase, one at the hypocenter and another deep source to the west of the hypocenter. The source at the hypocenter is associated with the initiation of rupture and the breaking of a high‐stress‐drop asperity and the second is associated with stopping of the rupture in a westerly direction.

Calculation of earthquake rupture histories using a hybrid global search algorithm: application to the 1992 Landers, California, earthquake

A method is presented for the simultaneous calculation of slip amplitudes and rupture times for a finite fault using a hybrid global search algorithm. The method we use combines simulated annealing with the downhill simplex method to produce a more efficient search algorithm then either of the two constituent parts. This formulation has advantages over traditional iterative or linearized approaches to the problem because it is able to escape local minima in its search through model space for the global optimum. We apply this global search method to the calculation of the rupture history for the Landers, California, earthquake. The rupture is modeled using three separate finite-fault planes to represent the three main fault segments that failed during this earthquake. Both the slip amplitude and the time of slip are calculated for a grid work of subfaults. The data used consist of digital, teleseismic P and SH body waves. Long-period, broadband, and short-period records are utilized to obtain a wideband characterization of the source. The results of the global search inversion are compared with a more traditional linear-least-squares inversion for only slip amplitudes. We use a multi-time-window linear analysis to relax the constraints on rupture time and rise time in the least-squares inversion. Both inversions produce similar slip distributions, although the linear-least-squares solution has a 10% larger moment (7.3 × 10 26 dyne-cm compared with 6.6 × 10 26 dyne-cm). Both inversions fit the data equally well and point out the importance of (1) using a parameterization with sufficient spatial and temporal flexibility to encompass likely complexities in the rupture process, (2) including suitable physically based constraints on the inversion to reduce instabilities in the solution, and (3) focusing on those robust rupture characteristics that rise above the details of the parameterization and data set.

Non-linear multiparameter inversion using a hybrid global search algorithm: applications in reflection seismology

SUMMARY Many interesting inverse problems in geophysics are non-linear and multimodal. Parametrization of these problems leads to an objective function, or measure of agreement between data and model predictions, that has a complex topography with many local minima. Optimization algorithms that rely on local gradients in the objective function or that search the model space locally may become trapped in these local minima. By combining simulated annealing with the downhill simplex method, a hybrid global search algorithm is presented in this paper for non-linear, multimodal, inverse problems. The hybrid algorithm shares the advantages of both local search methods that perform well if the local model is suitable, and global methods that are able to explore efficiently the full model space. The hybrid algorithm also utilizes a larger and more complex memory to store information on the objective function than simulated annealing algorithms. The effectiveness of this new scheme is evaluated in three problems: minimization of the multidimensional Rosenbrock function, non-linear, 1 -D, acoustic waveform inversion, and residual statics. The performance of the hybrid algorithm is compared with simulated annealing and genetic algorithms and is shown to converge more rapidly and to have a higher success rate of locating the global minimum for the cases investigated.