A Heuristic Approach for Two-Dimensional Rectangular Cutting Stock Problem considering Balance for Material Utilization and Cutting Complexity

The common staged patterns are always required during the cutting process for separating a set of rectangular items from rectangular plates in manufacturing industries. Two-staged patterns can reduce cutting complexity at the expense of material utilization; three-staged patterns do the opposite. Combining these two types of staged patterns may be a good balance for two contradictory objectives of material utilization and cutting complexity. A heuristic approach is proposed to solve the two-dimensional rectangular cutting stock problem with a combination of two-staged general patterns (2SGP) and three-staged homogenous patterns (3SHP). Firstly, the 2SGP and 3SHP are constructed by using recursive techniques. The pattern with the larger value is selected as the candidate pattern. Then, the value of each item is corrected according to the current candidate pattern. A cutting plan accurately satisfying all items demand is obtained by using the sequential heuristic algorithm. Finally, the cutting plan with a minimum number of used plates is achieved by applying the iterative algorithm. The computational results indicate that the proposed heuristic approach is more effective in material utilization and cutting complexity than the two published algorithms with staged patterns.

Quaternion Codes in MIMO System of Dual-Polarized Antennas

The use of quaternion orthogonal designs (QODs) to describe point-to-point communication among dual-polarized antennas has the potential to provide higher rate orthogonal and quasi-orthogonal complex designs exploiting polarization diversity among space and time diversities. Furthermore, it is essential to have a space time block code (STBC) which offers a linear and decoupled decoder which quasi-orthogonal designs fail to attain. In this paper, we show how the realm of quaternions unexpectedly offers us a possible solution and codes obtained from quaternion designs mostly achieve both linear and decoupled decoders. This motivated us to perform an indispensable search for QODs such that the code rate is bounded below by 1/2 and does not sharply decrease as the number of transmit antennas increases. It is shown that three famous recursive techniques do not satisfy this criteria and their code rates decrease rather rapidly. Therefore, we propose another method of constructing quaternion designs suitable for any number of transmit antennas and verify that these attain linear and decoupled decoders with the system model based on quaternionic channel. It is shown that such designs outperform others in terms of transmit diversity, code rates and the optimality of the proposed decoder is validated through simulation results.

A Study of Recursive Techniques for Robust Identification of Time-Varying Electrical Equivalent Circuit Models of Li-Ion Batteries

This article presents results of a comparative study of recursive techniques for robust identification of time-varying electrical equivalent circuit models of li-ion batteries. Two such methods are studied, a direct continuous time system identification method and an indirect discrete time technique. The results of this study indicate that although both methods work equally well for identification of time-invariant circuit models from clean voltage-current data, the direct continuous time method outperforms indirect discrete time technique for identification of time-varying circuit models. Similar conclusions can also be drawn for identification of equivalent circuit models in the presence of noise and/or unmodeled dynamics.

Recursive Exercises to Help Students Engage and Recognize Sociological Shifts

Introductory sociology courses encourage students to shift from understanding social relations and inequalities through an individualistic lens toward a more sociological one. It is difficult for students to know how far they have advanced toward a sociological perspective if they do not have a good sense of where they began. This paper describes an approach intended to assess a sociological shift over the course of a semester by combining various recursive techniques that take place at the beginning and end of the semester: letters to oneself, social opinion surveys, and recorded small discussion groups. Although the shift was often not dramatic, the approach proved to be useful not only to help students keep track of their own developing sociological perspective but also as a way to improve teaching and assess student learning outcomes. Although ideal for small classes or discussion sections, I discuss ways to also adapt it for larger classes.

Digital Filter Designs for Recursive Frequency Analysis

Digital filters for recursively computing the discrete Fourier transform (DFT) and estimating the frequency spectrum of sampled signals are examined, with an emphasis on magnitude-response and numerical stability. In this tutorial-style treatment, existing recursive techniques are reviewed, explained and compared within a coherent framework; some fresh insights are provided and new enhancements/modifications are proposed. It is shown that the replacement of resonators by (non-recursive) modulators in sliding DFT (SDFT) analyzers with either a finite impulse response (FIR), or an infinite impulse response (IIR), does improve performance somewhat; however, stability is not guaranteed as the cancellation of marginally stable poles by zeros is still involved. The FIR deadbeat observer is shown to be more reliable than the SDFT methods, an IIR variant is presented, and ways of fine-tuning its response are discussed. A novel technique for stabilizing IIR SDFT analyzers with a fading memory, so that all poles are inside the unit circle, is also derived. Slepian and sum-of-cosine windows are adapted to improve the frequency responses for the various FIR and IIR DFT methods.

Dynamic Provisioning and Resource Management for Multi-Tier Cloud Based Applications

Dynamic capacity provisioning is a useful technique for handling the workload variations seen in cloud environment. In this paper, we propose a dynamic provisioning technique for multi-tier applications to allocate resources efficiently using queueing model. It dynamically increases the mean service rate of the virtual machines to avoid congestion in the multi-tier environments. An optimization model to minimize the total number of virtual machines for computing resources in each tier has been presented. Using the supplementary variable and the recursive techniques, we obtain the system-length distributions at pre-arrival and arbitrary epochs. Some important performance indicators such as blocking probability, request waiting time and number of tasks in the system and in the queue have also been investigated. Finally, computational results showing the effect of model parameters on key performance indicators are presented.

Systematic Dynamic Modeling and Simulation of Multibody Offshore Structures: Application to Wave Energy Converters

This article presents a framework to model and perform time domain dynamic simulations of offshore structures presenting several interconnected rigid bodies. Both fixed and 6 degree of freedom floating structures are considered. It uses a robotics formalism to parameterize the kinematic chain of the structures and is robust with respect to the number of bodies involved. Direct dynamics algorithms are given, using a consistent notation across offshore engineering and robotics fields. They use efficient recursive techniques based on Newton-Euler equations. The advantage of this framework is that tedious analytical developments are no longer needed. Instead of that, it is sufficient to provide a data parameter table as well as principal inertia parameters of each body to entirely describe the mechanical structure. An example of simulation is given, based on the 7 degree of freedom SEAREV Wave Energy Converter.

On calculation of recursive M- and GM-estimates in LQG control systems

The aim of the given paper is development of a parametric identification approach for a closedloop system when the parameters of a discrete-time linear time-invariant (LTI) dynamic system as well as that of LQG (Linear Quadratic Gaussian) controller are not known and ought to be calculated. The recursive techniques based on an the maximum likelihood(M) and generalized maximum likelihood(GM) estimator algorithms are applied here in the calculation of the system as well as noise filter parameters. Afterwards, the recursive parameter estimates are used in each current iteration to determine unknown parameters of the LQG-controller, too. The results of numerical simulation by computer are discussed.