Calculation Of Upper Bound Research Articles

A Giza Pyramids Construction metaheuristic approach based on upper bound calculation for solving the network reliability problem

Network reliability optimization is an optimization problem that focuses on finding an optimal solution for a reliable network design. In network reliability optimization, the goal is to maximize network reliability so that the overall cost of the network is reduced at the same time. The discussion of the reliability of various systems in the field of industry and engineering is of great importance, that's why reliability optimization has received a lot of attention in recent decades. Since this problem is included in the category of NP-Hard problems, the use of soft computing methods will be highly effective in solving it. In this paper, an approach based on the Giza Pyramids Construction (GPC) metaheuristic algorithm is proposed to solve the network reliability problem. For this purpose, two independent single objective functions with constraints are defined, and then the reliability of the network is calculated through optimistic estimation using the upper bound method. In order to compare the performance, 12 types of diverse and complex network models have been generated and the proposed algorithm has been compared with 10 popular and state-of-the-art algorithms. Statistical analysis has been used to find significant differences in the performance of algorithms. Also, a real model of the university network has been generated, investigated, and solved as a case study. The results of experiments, statistical analysis, and observations show that the proposed algorithm has a better performance than other metaheuristic algorithms and the proposed approach in solving reliability is an effective and low-cost approach.

New resource-constrained project scheduling instances for testing (meta-)heuristic scheduling algorithms

The resource-constrained project scheduling problem (RCPSP) is a well-known scheduling problem that has attracted attention since several decades. Despite the rapid progress of exact and (meta-)heuristic procedures, the problem can still not be solved to optimality for many problem instances of relatively small size. Due to the known complexity, many researchers have proposed fast and efficient meta-heuristic solution procedures that can solve the problem to near optimality. Despite the excellent results obtained in the last decades, little is known why some heuristics perform better than others. However, if researchers better understood why some meta-heuristic procedures generate good solutions for some project instances while still falling short for others, this could lead to insights to improve these meta-heuristics, ultimately leading to stronger algorithms and better overall solution quality.In this study, a new hardness indicator is proposed to measure the difficulty of providing near-optimal solutions for meta-heuristic procedures. The new indicator is based on a new concept that uses the σ distance metric to describe the solution space of the problem instance, and relies on current knowledge for lower and upper bound calculations for problem instances from five known datasets in the literature.This new indicator, which will be called the σD indicator, will be used not only to measure the hardness of existing project datasets, but also to generate a new benchmark dataset that can be used for future research purposes. The new dataset contains project instances with different values for the σD indicator, and it will be shown that the value of the σ distance metric actually describes the difficulty of the project instances through two fast and efficient meta-heuristic procedures from the literature.

NukCP: An Improved Local Search Algorithm for Maximum k-Club Problem

The maximum k-club problem (MkCP) is an important clique relaxation problem with wide applications. Previous MkCP algorithms only work on small-scale instances and are not applicable for large-scale instances. For solving instances with different scales, this paper develops an efficient local search algorithm named NukCP for the MkCP which mainly includes two novel ideas. First, we propose a dynamic reduction strategy, which makes a good balance between the time efficiency and the precision effectiveness of the upper bound calculation. Second, a stratified threshold configuration checking strategy is designed by giving different priorities for the neighborhood in the different levels. Experiments on a broad range of different scale instances show that NukCP significantly outperforms the state-of-the-art MkCP algorithms on most instances.

Computing tight upper bounds for Bhattacharyya parameters of binary polar code kernels with arbitrary dimension

Multi-kernel polar codes have recently received considerable attention since they can provide more flexible code lengths than do the original ones. The construction process of them can be simplified by obtaining the Bhattacharyya parameter bounds of the kernels employed. However, there has been currently no generic method for seeking such bounds. In this paper, therefore, we focus on the upper Bhattacharyya parameter bounds of the standard binary polar code kernels with an arbitrary dimension of lge 2. A calculation process composing of four steps, the common column binary tree construction for the channel inputs, the common factor extraction, the calculation feasibility testing, and the upper bound calculation based on pattern matching, is formulated with a computational complexity of O(2^l). It is theoretically proved that the upper bounds obtained by the proposed method are tight, which can lay the foundation to compare the reliability of the synthesized channels in polar codes.

Upper bound limit analysis of blow-out failure mode of excavation face of shield tunnel considering groundwater seepage

The study of failure mode for the soil in front of a shield tunnel face is a key challenge for tunnel engineering, especially when drilling under the water table. This work aims to study face stability of a shield tunnel under the water table based on an blow-out failure mechanism in the framework of the upper bound theorem of limit analysis in conjunction with variational principle. The seepage force in the seepage field is derived, and seepage force is regarded as an external force which is introduced in the upper bound calculation. Based on the failure characteristic of the blow-out failure for the soil in front of a shield tunnel face, a upper bound failure mechanism is constructed. Using this mechanism, the equation of the failure surface is obtained and the shapes of the failure surfaces for different parameters are plotted. By studying the influence of various parameters on the shape of failure surfaces, the changing laws of the shape of the failure surface for different parameters are obtained.

An A⁎ search algorithm for the constrained longest common subsequence problem

The constrained longest common subsequence (CLCS) problem was introduced as a specific measure of similarity between molecules. It is a special case of the constrained sequence alignment problem and of the longest common subsequence (LCS) problem, which are both well-studied problems in the scientific literature. Finding similarities between sequences plays an important role in the fields of molecular biology, gene recognition, pattern matching, text analysis, and voice recognition, among others. The CLCS problem in particular represents an interesting measure of similarity for molecules that have a putative structure in common. This paper proposes an exact A⁎ search algorithm for effectively solving the CLCS problem. This A⁎ search is guided by a tight upper bound calculation for the cost-to-go for the LCS problem. Our computational study shows that on various artificial and real benchmark sets this algorithm scales better with growing instance size and requires significantly less computation time to prove optimality than earlier state-of-the-art approaches from the literature.

Upper bound solution for the bearing capacity of rock masses considering the embedment depth

The effect of the embedment depth is one of the most important issues in calculating the bearing capacity. The results of the previous studies show that in most cases, it was assumed that the footings are rested at the ground surface and the effect of the embedment depth was considered by applying an equivalent surcharge load to the ground surface. In this paper, the influence of the embedment of the footings on the bearing capacity of weak rock masses was investigated using the upper bound method of limit analysis. The modified Hoek–Brown failure criterion was used for the rock mass. The embedment depth of the footings was considered directly in the upper bound calculations. According to the obtained results, considering the embedment depth results in increasing the ultimate bearing capacity, which cannot be anticipated correctly in the methods which replace the embedment depth by an equivalent surcharge. The results of this paper were presented in the form of a design table that can be used easily in practical applications.

Value-Based Hierarchical Information Collection for AUV-Enabled Internet of Underwater Things

The Internet of Underwater Things (IoUT) shows great potential in realizing the smart ocean. Underwater acoustic sensor networks (UWASNs) are the main existing form of IoUT but face with reliable data transmission problems. To tackle this issue, this article considers using the autonomous underwater vehicle (AUV) as a mobile collector to construct a reliable hierarchical information collection system while the Value of Information (VoI) is used as a main metric to measure the Quality of Information (QoI). We first establish a realistic model for characterizing the behaviors of AUV and sensor nodes as well as the challenging environments. Then, to construct a hierarchical architecture, we design a sink node (SN) selection scheme by jointly considering VoI conservation and energy load balancing. After that, we focus on AUV path planning with the objective of maximizing the VoI of the total network. We formulate the problem as a combinatorial optimization problem and provide an integer linear programming (ILP) model for this problem. An optimal algorithm based on the branch-and-bound (BB) method is proposed for seeking for the optimal solution, in which the lower bound and upper bound calculation strategies are specifically designed. Two near-optimal heuristic algorithms based on the concepts of the ant colony algorithm (ACA) and the genetic algorithm (GA) are also provided for further reducing the computation complexity. Finally, simulations validate the effectiveness of the proposed algorithms.

Anytime algorithms for the longest common palindromic subsequence problem

The longest common palindromic subsequence (LCPS) problem aims at finding a longest string that appears as a subsequence in each of a set of input strings and is a palindrome at the same time. The problem is a special variant of the well known longest common subsequence problem and has applications in particular in genomics and biology, where strings correspond to DNA or protein sequences and similarities among them shall be detected or quantified. We first present a more traditional A* search that makes use of an advanced upper bound calculation for partial solutions. This exact approach works well for instances with two input strings and, as shown in experiments, outperforms several other exact methods from the literature. However, the A* search also has natural limitations when a larger number of strings shall be considered due to the problem’s complexity. To effectively deal with this case in practice, anytime A* search variants are investigated, which are able to return a reasonable heuristic solution at almost any time and are expected to find better and better solutions until reaching a proven optimum when enough time given. In particular a novel approach is proposed in which Anytime Column Search (ACS) is interleaved with traditional A* node expansions. The ACS iterations are guided by a new heuristic function that approximates the expected length of an LCPS in subproblems usually much better than the available upper bound calculation. This A*+ACS hybrid is able to solve small to medium-sized LCPS instances to proven optimality while returning good heuristic solutions together with upper bounds for large instances. In rigorous experimental evaluations we compare A*+ACS to several other anytime A* search variants and observe its superiority.

Basal stability analysis of braced excavations with embedded walls in undrained clay using the upper bound theorem

The embedded wall has beneficial effects on the basal stability of braced excavation in clay. Conventional basal stability analysis methods cannot evaluate the lateral resistance afforded by the wall reasonably. This paper presents a new failure mechanism to evaluate the basal stability of excavations with embedded walls in undrained clay based the upper bound theorem. The proposed mechanism consists of a rigid block and three shear zones, and the horizontal reinforcing effects of wall penetration blow the excavation base are considered. The embedded wall is regarded as an elastic beam and deforms consistently with the velocities of adjacent soil in the shear zone. The elastic strain energy stored in the wall is incorporated in the upper bound calculation to increase the stability of excavation. The proposed mechanism has also been extended to the basal stability of excavations in anisotropic and non-homogeneous clay. The applicability of the proposed mechanism was validated by comparison with the results of numerical limit analysis and FEM, as well as five field cases near or at failure. Two failure field cases in anisotropic clay were also studied using the proposed mechanism. The results showed that the proposed method is capable to yield reasonable estimation by using both isotropic and anisotropic shear strength.

Upper bound of tunnel face stability using asymmetric yielding

Although significant advancement has been made over recent years with respect to three-dimensional upper bound calculations of tunnel facing, a considerable difference still exists between analytically and empirically based stability values. The current work suggests that the difference may well be the outcome of the traditional use of Tresca yield criterion for the upper bound calculations, which, by definition, does not distinguish among the shearing modes (compression, extension, plane strain). Consequently, this paper suggests and discusses a new yield function, which allows for asymmetric yielding. Such yielding is only beneficial in the case of three-dimensional and continuous velocity fields, and therefore a numerical procedure that generates relevant kinematically admissible fields for classical upper bound calculation is suggested. The procedure involves conversion from a load controlled boundary value problem to a velocity controlled problem at the limit state of collapse. The analysis results in significantly lower upper bound values than those presented earlier (for Tresca material), and the values are much closer to the stability curves of Kimura and Mair (1981), which are commonly used in design.

Vehicle lateral control in the presence of uncertainty for lane change maneuver using adaptive sliding mode control with fuzzy boundary layer

Recent researches on advanced driver-assistance systems indicate great advances in terms of safety and comfort in automated driving. Advanced driver-assistance systems use control systems to perform most of the maneuvers as performed by the driver in the past. One of the useful advanced driver-assistance systems is automatic lane change system in order to avoid accidents. This study designs the controller of an automatic lane change system for an autonomous vehicle. The control law in this study is adaptive sliding mode control. To avoid chattering in adaptive sliding mode control, fuzzy boundary layer is used. Also, adaptive law is used for sliding-based switching gain. This adaptive controlling law is used to avoid the calculation of upper bound of system uncertainties. In this study, based on the boundary conditions, the vehicle lane change path planning and different maneuver periods are evaluated. To simulate the designed controller, CarSim–Simulink joint simulation model is used. This linkage leads to a full non-linear vehicle model. The results of simulation show excellent tracking for dry road conditions and acceptable tracking in icy and wet roads in some maneuvers of above 4-s long.

Synchrony measure for a neuron driven by excitatory and inhibitory inputs and its adaptation to experimentally-recorded data

The aim of the current work is twofold: firstly to adapt an existing method measuring the input synchrony of a neuron driven only by excitatory inputs in such a way so as to account for inhibitory inputs as well and secondly to further appropriately adapt this measure so as to be correctly utilised on experimentally-recorded data. The existing method uses the normalized pre-spike slope (NPSS) of the membrane potential, resulting from observing the slope of depolarization of the membrane potential of a neuron prior to the moment of crossing the threshold within a short period of time, to identify the response-relevant input synchrony and through it to infer the operational mode of a neuron. The first adaptation of NPSS is made such that its upper bound calculation accommodates for the higher possible slope values caused by the lower average and minimum membrane potential values due to inhibitory inputs. Results indicate that when the input spike trains arrive randomly, the modified NPSS works as expected inferring that the neuron is operating as a temporal integrator. When the input spike trains arrive in perfect synchrony though, the modified NPSS works as expected only when the level of inhibition is much higher than the level of excitation. This suggests that calculation of the upper bound of the NPSS should be a function of the ratio between excitatory and inhibitory inputs in order to be able to correctly capture perfect synchrony at a neuron's input. In addition, we effectively demonstrate a process which has to be followed when aiming to use the NPSS on real neuron recordings. This process, which relies on empirical observations of the slope of depolarisation for estimating the bounds for the range of observed interspike interval lengths, is successfully applied to experimentally-recorded data showing that through it both a real neuron's operational mode and the amount of input synchrony that caused its firing can be inferred.

Computation of worst-case spacing errors of vehicle platoons based on a skew-μ method

A numerical method is presented for the computation of spacing error bounds in vehicle platoons. The resulted bounds can be applied to evaluate performance of specific platoon control algorithms. The upper bound calculation is based on the computation of worst-case induced L2-gains of systems defined between the disturbance inputs to the leader vehicle and the spacing errors of the follower vehicles. The worst-case is defined subject to heterogeneity in the vehicle dynamics. The method is applicable both in the frequency- and the time-domain. The latter enables the extension of robustness analysis to a wider class of uncertainties and communication topologies. The method is illustrated on a numerical example with leader and predecessor following control architecture.

Analysis of Inclined Strip Anchors in Sand Based on the Block Set Mechanism

Anchors are widely used in foundation systems for structures requiring uplift resistance. As demonstrated by numerous theoretical and experimental studies on the subject, uncertainty remains as to both the theoretical uplift capacity of anchors in idealised soils and the suitability of the various modelling assumptions in capturing the responses observed during tests. This study, which deals exclusively with the theoretical uplift capacity, presents newly obtained predictions of uplift capacities and the corresponding collapse mechanisms for inclined strip anchors in sand. The analysis is based on the upper bound (kinematic) method of limit analysis and the so-called block set mechanism, in which a collapse mechanism consisting of sliding rigid blocks is optimised with respect to interior angles and edges of the blocks. It is demonstrated that the method provides lower (better) estimates of uplift capacity in some cases compared to previous upper bound calculations. Also, variations in the predicted collapse mechanism with changes in embedment and inclination are assessed in detail.

Undrained limiting lateral soil pressure on a row of piles

The displacement finite element, lower and upper bound finite element limit analysis and analytical upper bound plasticity methods are employed to investigate the undrained limiting lateral resistance of piles in a pile row. Numerical analyses and analytical calculations are presented for various pile spacings and pile–soil adhesion factors. The numerical results are shown to be in excellent agreement with each other and also with the theoretical upper bounds produced by the analytical upper bound calculations. Based on the numerical and analytical results, an empirical equation is proposed for the calculation of the ultimate undrained lateral bearing capacity factor. This equation is subsequently used to calculate p-multipliers applicable to the lower part of piles in pile rows, which are compared to multipliers available in the literature (that are constant with depth). The comparison shows significant differences, indicating that the amount of reduction in lateral resistance due to group effects is not constant with depth as routinely assumed in practice.

Lateral bearing capacity of rigid piles near clay slopes

Analytical equations were derived to determine the undrained lateral bearing capacity of rigid piles in cohesive soil. Piles in level ground and piles placed at a distance from the crest of a slope were examined, taking account of the effect of the adhesion at the pile–soil interface. The derived analytical solutions were used to develop charts relating the lateral pile capacity to the pile length/diameter ratio, the pile–soil adhesion, the distance of the point of load application from the ground to the pile diameter ratio, the inclination of the slope and the distance of the pile from the crest of the slope to the pile diameter ratio. They were also used to derive a reduction factor which, when multiplied by the lateral bearing capacity for level ground, gives the bearing capacity of the same pile near a slope. In addition, a critical non-dimensional distance between the pile and the crest of the slope, at which the bearing capacity approaches that for a level ground, was determined. The bearing capacity charts obtained for level ground were compared to the classic Broms' charts and to others derived using several different lateral earth pressure distributions along the pile. Comparisons were also made between the results of the proposed method for piles near slopes and those obtained from charts based on upper bound calculations. Finally, the proposed new method was validated through a comparison with the results of a large number of pile load tests, in which a remarkable agreement was observed between the analytical results and the measurements.

A Branch and Bound Algorithm to Minimize the Total Weighed Number of Tardy Jobs and Delivery Costs

This paper addresses the production and delivery scheduling integration problem; a manufacturer receives − orders from one customer while the orders need to be processed on one or two machines and be sent to the customer in batches. Sending several jobs in batches will reduce the transportation cost but it may increase the number of tardy jobs. The objective is to minimize the sum of the total weighted number of tardy jobs and the delivery costs. The structural properties of the problem for a single machine and special cases of the two-machine flow shop problem are investigated and used to set up a new branch and bound algorithm. A heuristic algorithm for upper bound calculation and two approaches for lower bound calculation are also introduced. Results of computational tests show significant improvement over an existing dynamic programming method.

Explosion Shear-Wave Generation in High-Velocity Source Media

We evaluate the mechanisms responsible for generation of shear waves by explosions in high‐velocity source media by identifying, quantifying, and modeling observations that can distinguish between commonly suggested mechanisms. We review the literature to identify regional observations that have been or can be used to distinguish between two or more mechanisms. We supplement these historical observations with new measurements of the Semipalatinsk test site (STS) event Lg and P amplitudes at Borovoye and model the observations with nonlinear source models, Rg ‐to‐ Lg upper bound calculations, and wavenumber integration synthetic seismograms for point explosions and CLVDs. Direct generation of shear waves by the nonspherical component of the source volume is consistent with the regional Lg amplitude versus yield relationship, while S * and Rg ‐to‐ Lg scattering are not. We also analyze and model a large set of Degelen explosion records from approximately 10 to 90 km. The local Sg spectral corner frequency is lower than the Pg corner frequency by approximately the source P ‐to‐ S velocity ratio, which is consistent with shear waves directly generated by the source, and inconsistent with Sg being the result of pS , S *, or Rg ‐to‐ Lg scattering. The local Sg and Rg spectra are distinctly different. Taken together, results from previous work and new observations presented here support the conclusion that explosions in high‐velocity source media dominantly generate shear waves directly, through the nonspherical part of the nonlinearly deforming source volume.

Model Tests and Analyses of Bearing Capacity of Strip Footing on Stiff Ground with Voids

A series of 1G loading tests under the plane-strain condition were conducted on stiff ground with continuous square voids with the view of shallow foundation on calcareous sediment rocks, which contain voids because of their susceptibility to water dissolution. Detailed experimental observation revealed three types of failure modes for a single void: bearing failure without void failure, bearing failure with void failure, and void failure without bearing failure, depending on the location of the void as well as the size of the void. Upper-bound calculations were presented to interpret the changes of bearing capacity observed because of the existence of a void.