Energy transfer in Sm:Eu system in zinc sodium phosphate glasses

The mechanism of nonradiative energy transfer process in zinc sodium phosphate glass system co-doped with samarium and europium ion has been examined under cw laser excitation. Donor–acceptor distance and quantum efficiency of transfer have been evaluated using the relevant theoretical expressions. Transfer probabilities have been determined using the overlap integral and relative fluorescence methods. The Forster–Dexter theoretical predictions are found to be in excellent agreement with experimental results. The nonresonant energy transfer assisted by phonons is the dominant transfer mechanism in the concentration range taken. Excitation spectra and the decay profile of the samarium ion also support the energy transfer from samarium to europium.     

Role of phase key in the double random phase encoding technique: an error analysis

We perform a numerical analysis of the double random phase encryption-decryption technique to determine how, in the case of both amplitude and phase encoding, the two decryption keys (the image- and Fourier-plane keys) affect the output gray-scale image when they are in error. We perform perfect encryption and imperfect decryption. We introduce errors into the decrypting keys that correspond to the use of random distributions of incorrect pixel values. We quantify the effects that increasing amounts of error in the image-plane key, the Fourier-plane key, and both keys simultaneously have on the decrypted image. Quantization effects are also examined.     

A Dual Variable Approximation Based Heuristic for Dynamic Congestion Pricing

This work presents a heuristic combining dual variable approximation techniques and the method of successive average to determine the time-varying tolls in a general transportation network. The dual approximation techniques exploit the linear programming structure of the underlying assignment problem which uses the cell transmission model to propagate the traffic dynamics. Both the first best and second best time-varying tolls can be determined in a computationally efficient manner with the proposed heuristic. Numerical experiments are conducted on two networks of different sizes to show the efficacy of the heuristic. From the experiments conducted, the proposed heuristic obtains the solutions with the maximum optimality gap of 2.03%.     

Discovering Frequent Generalized Episodes When Events Persist for Different Durations

This paper is concerned with the framework of frequent episode discovery in event sequences. A new temporal pattern, called the generalized episode, is defined, which extends this framework by incorporating event duration constraints explicitly into the pattern's definition. This new formalism facilitates extension of the technique of episodes discovery to applications where data appears as a sequence of events that persist for different durations (rather than being instantaneous). We present efficient algorithms for episode discovery in this new framework. Through extensive simulations, we show the expressive power of the new formalism. We also show how the duration constraint possibilities can be used as a design choice to properly focus the episode discovery process. Finally, we briefly discuss some interesting results obtained on data from manufacturing plants of General Motors.     

Field and service applications - An infrastructure-free automated guided vehicle based on computer vision - An Effort to Make an Industrial Robot Vehicle that Can Operate without Supporting Infrastructure

Automated guided vehicles (AGVs) have been operating effectively in factories for decades. These vehicles have successfully used strategies of deliberately structuring the environment and adapting the process to the automation. The potential of computer vision technology to increase the intelligence and adaptability of AGVs is largely unexploited in contemporary commercially available vehicles. We developed an infrastructure-free AGV that uses four distinct vision systems. Three of them exploit naturally occurring visual cues instead of relying on infrastructure. When coupled with a highly capable trajectory generation algorithm, the system produces four visual servo controllers that guide the vehicle continuously in several contexts. These contexts range from gross motion in the facility to precision operations for lifting and mating parts racks and removing them from semi-trailers. To our knowledge, this is the first instance of an AGV that has operated successfully in a relevant environment for an extended period of time without relying on any infrastructure.     

Integrated Inventory Control and Facility Location Decisions in a Multi-Echelon Supply Chain Network with Hubs

This paper develops mathematical models to coordinate facility location and inventory control for a four-echelon supply chain network consisting of multiple suppliers, warehouses, hubs and retailers. The hubs help in reducing transportation costs by consolidating products from multiple warehouses and directing the larger shipments to the retailer. The integrated models studied in this paper simultaneously determines three types of decisions: (i) facility location—the number and location of warehouses and hubs, (ii) allocation—assignment of suppliers to located warehouses and retailers to located warehouses via the location hubs, and (iii) inventory control decisions at each located warehouse. The goal is to minimize the facility location, transportation and the inventory costs. A mixed integer nonlinear programming formulation is first presented. The nonlinear integer programming formulation is then transformed into a conic mixed integer program and a novel and compact conic mixed integer programming formulation. Computational runs are conducted using commercial solvers to compare the performance of the different formulations. The compact conic mixed integer programming formulation was found to significantly outperform the other formulations by achieving significant computational savings. The results demonstrate that large scale instances of certain multi-echelon supply chain network design problems can be solved using commercial solvers through intelligent reformulation of the model.     

Note on the stability of first-order p.w.m. systems

It is shown in this letter that the necessary and sufficient condition for stability of first-order pulse-width-modulated (p.w.m.) systems derived using exact analysis by Skoog and Blankenship1 is the same as that obtained by using a linearisation technique. This points to the accuracy of the linear model which is simple and easy to use.     

Threaded linear hierarchical quadtrees for computation of geometricproperties of binary images

A modification of the linear quadtree, the threaded linear hierarchical quadtree (TLHQT), is proposed for the computation of geometric properties of binary images. Since most of the algorithms used in connection with computation of geometric properties require frequent exploration of adjacencies, a structure that keeps permanently in memory some adjacency links is introduced. Some results obtained by using the TLHQT for labeling connected components and for evaluating the perimeter and Euler's number in a quadtree environment are presented. The performance of the TLHQT is discussed     

Deep learning architectures for land cover classification using red and near-infrared satellite images

Multimedia Tools and Applications - Classification of remotely sensed data requires the modelling of suitable image processing algorithms. The rise of machine learning systems upgraded the...     

Computational study on the influence of number of threads on the performance of single screw pump at high angular velocities

Fluid flow in a screw pump which rotates at very high angular velocity is numerically analyzed. In the present study, fluid flow in screw pumps under high Reynolds number, of the order of 10⁵, is considered. Screw pump has two major elements, a plain shroud which is a stationary element and a rotating hub with helical grooves contained within the shroud. In this paper, three variants of hubs with different number of thread starts numbering six, eight and twelve in combination with a plain shroud is studied. Each of the three possible combinations are analyzed on the basis of pressure rise developed, efficiency and shaft power. It was seen that pressure rise, efficiency and shaft power increases as the number of threads increases in the range of mass flow rates studied.