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In this paper, three different variants of the canonical particle swarm optimization (PSO) algorithm are compared in terms of their optimal solutions to engineering optimization problems. The PSO often face to premature convergence due to its weak capability in local exploitation, which leads to a low optimization precision or even failure. Moreover, the computational burden is also one of the obstacles for the PSO when solving complex problems. To overcome these drawbacks, the original PSO algorithm is integrated with the knowledge sharing and auxiliary mechanisms of comprehensive learning (CL) and Gaussian local search (GLS) strategies to form the so-called GLS-PSO, CLPSO, and GLS-CLPSO algorithms. To demonstrate the accuracy and robustness of the three variants, their performance is tested on a benchmark spatial truss structure with continuous variables. The obtained optimization results are then compared with those by other PSO variants in the literature.

This paper presents an iterative limit analysis scheme modeled within a three-node node-based smoothed finite element framework incorporating a so-called modified elastic compensation method to determine the ultimate bearing capacity of ductile structures. More explicitly, the approach iteratively reduces those elemental Young’s modulus associated with a high-stress intensity such that the inelastic behavior of the elastic-perfectly plastic material model is taken into account. The approach provides good accuracy and convergence of solution through a series of standard linear elastic analyses that make possible the application in large-scale engineering structures, even the one with complex geometric configurations, and hence eminently accessible to structural engineers. As a result, complex inelastic analyses are eliminated and computational cost is significantly reduced. Several benchmark examples, one of which reported, illustrates the efficiency and robustness of the iterative limit analysis approach in tracing the load multipliers of in-plane ductile structures from the beginning until convergence of collapse load solution or failure state occurs. The yield areas at the ultimate state gradually appear in the graph of elastic modulus distribution.

generally account for a significant proportion of the total cost of the fences. Therefore, to reduce the number of energy absorbers and achieve lower cost while maintaining performance, energy absorbers are installed only at the end posts in the new type of fence. The new type of rock fence is examined in full-scale experiments carried out using a falling reinforced-concrete (RC) block that rolls down a natural slope without a navigation system for the block. In preparation for these tests, laboratory pre-tests on such components as energy absorbers, posts, and wire ropes were conducted to confirm their load-carrying capacities and structural behaviors. Furthermore, an experimental control system is introduced to investigate the impact force during collision. Moreover, numerical simulation was performed employing finite element code, LS-DYNA, to clarify the impact behavior by comparing numerical results with those obtained in actual-scale tests. ABSTRACT: To protect existing structures in mountainous areas against rockfall, various protection methods have been developed. A new type of rockfall protection fence is constructed of posts, wire ropes, and wire netting. To verify the performance of this rock fence, both experiments and numerical analysis based on finite element code were conducted. Collision tests were performed, in which a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. The performance of energy absorbers, which are effective in preventing wire ropes from breaking, was investigated. To measure the acceleration of a reinforced-concrete block rolling down a steep slope, a new system of measuring instruments was developed.

There are various protection measures against rockfalls. An embankment is effective in rockfall hazard mitigation at a dangerous slope end. The slope rockfall tests on full-scale embankments have been carried out. These embankments are made of sandy soil reinforced with geogrids. The cushioning layers which are made of geocells filled with crushed stones of 5-13 mm in diameter are also placed on the mountain side of the embankment. A boulder, i.e., RC block rolls down the test-site slope, and hits against the embankment. A new system of measuring instruments is employed in order to evaluate the impact force and the impact energy. One of important observations is a possibility that a rolling boulder carries it toward the top of an embankment because of its rolling momentum. The experimental results, especially the relationship between impact force and impact energy is discussed in this paper. © 2011, International Journal of GEOMATE.

The kinetics of the bone remodeling sequence in the rat has been studied using a system in which well-synchronized remodeling units were induced along the periosteum of rat mandibles. Remodeling of the periosteal surface of the mandibles was induced according to Tran Van (1979) by extraction of the opposing row of teeth; namely, the right maxillary molars were extracted under light ether anesthesia, therefore allowing the right mandibular molars to egress; this, in turn, induced a wave of remodeling activity on the buccal side of the periosteal surface of the alveolar bone. The quantification of the different cellular activities involved in bone remodeling has been performed up to 16 days after induction. This allowed us to demonstrate the sequential activity of the different cell types involved in bone remodeling, to study the cellular kinetics of this sequence of events, and to directly measure the duration of each phase of the bone remodeling sequence. A single wave of osteoclasts appeared 3 days after induction, reached a peak at 4–5 days, and then decreased sharply. This was followed by a single wave of mononuclear cells (Baron et al., 1980) within remodeling sites during the reversal phase; they appeared 4 days after induction, reached a peak by day 7, and then decreased sharply. This reversal activity was then followed by osteoblasts forming new bone on top of a reversal cement line in the remodeling sites, starting 6 days after induction and increasing until the end of the experiment. In addition, the synchronization of the system used in this study allowed direct measurement of the duration of the successive steps of the remodeling sequence. The directly measured values have then been compared to previous data calculated from other systems.