On three soft rectangle packing problems with guillotine constraints

We investigate how to partition a rectangular region of length $L_1$ and height $L_2$ into $n$ rectangles of given areas $(a_1, \dots, a_n)$ using two-stage guillotine cuts, so as to minimize either (i) the sum of the perimeters, (ii) the largest perimeter, or (iii) the maximum aspect ratio of the rectangles. These problems play an important role in the ongoing Vietnamese land-allocation reform, as well as in the optimization of matrix multiplication algorithms. We show that the first problem can be solved to optimality in $\mathcal{O}(n \log n)$, while the two others are NP-hard. We propose mixed integer programming (MIP) formulations and a binary search-based approach for solving the NP-hard problems. Experimental analyses are conducted to compare the solution approaches in terms of computational efficiency and solution quality, for different objectives

Modelling and solving complex combinatorial optimization problems : quorumcast routing, elementary shortest path, elementary longest path and agricultural land allocation

The feasible solution set of a Combinatorial Optimization Problem (COP) is discrete and finite. Solving a COP is to find optimal solutions in the set of feasible solutions such that the value of a given cost function is minimized or maximized. In the literature, there exist both complete and incomplete methods for solving COPs. The complete (or exact) methods return the optimal solutions with the proof of the optimality, for example the branch-and-cut search. The incomplete methods try to find hight-quality solutions which are as close to the optimal solutions as possible, for example local search. In this thesis we focus on solving four distinct COPs: the Quorumcast Routing Problem (QRP), the Elementary Shortest Path Problem on graphs with negative-cost cycles (ESPP), the Elementary Longest Path Problem on graphs with positive-cost cycles (ELPP), and the Agricultural Land Allocation Problem (ALAP). In order to solve these problems with the complete methods, we use the Branch-and-Infer search, the Branch-and-Cut search, and the Branch-and-Price search. We also solve ALAP by the incomplete methods, such as Local Search, Tabu Search, Constraints-Based Local Search that combine with metaheuristics. The experimental evaluations on well-known benchmarks show that all proposed algorithms for all the first three COPs (QRP, ESPP and ELPP) are better than the-state-the art algorithms. Specially, we describe ALAP, formulate it as a combination of three COPs, and propose several complete and incomplete algorithms for these COPs.(FSA - Sciences de l'ingénieur) -- UCL, 201

Failure of rammed earth walls: from observations to quantifications

International audienceNowadays, rammed earth construction is attracting renewed interest throughout the world thanks to its "green" characteristics in the context of sustainable development. Firstly, using a local material (soil on site or near the site), rammed earth constructions have very low embodied energy. Secondly, rammed earth houses have an attractive appearance and present advantageous living comfort due to substantial thermal inertia and the "natural regulator of moisture" of rammed earth walls. This is why several research studies have been carried out recently to study the mechanical and thermal characteristics of rammed earth. However, to our knowledge, there are not yet sufficient studies on the tensile strength and the shear strength of rammed earth. The tensile strength of rammed earth is neglected in general due to its very low value, but in extreme conditions (e.g., seismic conditions), knowing the tensile strength is necessary for structural design. Moreover, the shear strength is required in many cases to check the local failure of rammed earth quickly, which has been observed in old structures (especially those submitted to concentrated loads). This paper presents experimental results on tensile strengths and the Poisson ratio of rammed earth specimens. Local failure tests were also conducted on 1 m × 1 m × 0.3 m wallettes manufactured in the laboratory. The shear strength was then identified using a simple method based on compressive strength, tensile strength and Mohr's circle theory. The approach proposed was validated by tests on the wallettes. Finite Element (FE) modeling was also carried out to confirm the results. Last, the method presented was validated for stabilized rammed earth lintels presented in the literature

ANALYZING AND OPTIMIZING OF A PFLUGER COLUMN

ABSTRACTThe optimal shape of a Pfluger column is determined  by using Pontryagin’s maximum principle (PMP). The governing equation of the problem is reduced to a boundary-value problem for a single second order nonlinear differential equation. The results of the analysis problem are obtained by Spectral method. Necessary conditions for the maximum value of the first eigenvalue corresponding to given column volume areestablished to determine the optimal distribution of cross-sectional area along the column axis. Keywords: optimal shape; Pontryagin’s maximum principle

Smart Shopping Assistant: A Multimedia and Social Media Augmented System with Mobile Devices to Enhance Customers’ Experience and Interaction

Multimedia, social media content, and interaction are common means to attract customers in shopping. However these features are not always fully available for customers when they go shopping in physical shopping centers. The authors propose Smart Shopping Assistant, a multimedia and social media augmented system on mobile devices to enhance users’ experience and interaction in shopping. Smart Shopping turns a regular mobile device into a special prism so that a customer can enjoy multimedia, get useful social media related to a product, give feedbacks or make actions on a product during shopping. The system is specified as a flexible framework to take advantages of different visual descriptors and web information extraction modules. Experimental results show that Smart Shopping can process and provide augmented data in a realtime-manner. Smart Shopping can be used to attract more customers and to build an online social community of customers to share their interests in shopping

BoMb-OT: On Batch of Mini-batches Optimal Transport

Mini-batch optimal transport (m-OT) has been successfully used in practical applications that involve probability measures with intractable density, or probability measures with a very high number of supports. The m-OT solves several sparser optimal transport problems and then returns the average of their costs and transportation plans. Despite its scalability advantage, the m-OT does not consider the relationship between mini-batches which leads to undesirable estimation. Moreover, the m-OT does not approximate a proper metric between probability measures since the identity property is not satisfied. To address these problems, we propose a novel mini-batching scheme for optimal transport, named Batch of Mini-batches Optimal Transport (BoMb-OT), that finds the optimal coupling between mini-batches and it can be seen as an approximation to a well-defined distance on the space of probability measures. Furthermore, we show that the m-OT is a limit of the entropic regularized version of the BoMb-OT when the regularized parameter goes to infinity. Finally, we carry out extensive experiments to show that the BoMb-OT can estimate a better transportation plan between two original measures than the m-OT. It leads to a favorable performance of the BoMb-OT in the matching and color transfer tasks. Furthermore, we observe that the BoMb-OT also provides a better objective loss than the m-OT for doing approximate Bayesian computation, estimating parameters of interest in parametric generative models, and learning non-parametric generative models with gradient flow.Comment: 36 pages, 20 figure

Solving Min-Max Capacitated Vehicle Routing Problem by Local Search

Vehicle routing is a class of combinatorial optimization problems in transportation and logistics. Min-max capacitated vehicle routing is a problem of this class in which the length of the longest route must be minimized. This paper investigates local search approach for solving the min-max capacitated vehicle routing problem with different neighborhood structures. We also propose a combined function instead of the objective function itself for controlling the local search. Experimental results on different datasets show the efficiency of our proposed algorithms compared to previous techniques

Criblage virtuel sur grille de composés isolés au Vietnam

Criblage virtuel sur grille de composés isolés au Vietna

Influence of ASE Noise on Performance of DWDM Networks Using Low-power Pumped Raman Amplifiers

We present the results of investigation  for  influence of amplified spontaneous emission (ASE) noise, noise figure (NF) and  chromatic dispersion on the performance of middle-distance Dense-wavelength-division-multiplexing (DWDM) networks using low-power pumped distributed Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role for improving network performance by decrease of noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and low noise figure were obtained, when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment. These results conclude that DRA with low pump power  ($1$~W) is the promising key technology for short-- and/or middle-distance DWDM transmission networks