Correction to: Classifying MOOC forum posts using corpora semantic similarities: a study on transferability across different courses

Neural Computing and Applications - A correction to this paper has been published: https://doi.org/10.1007/s00521-021-05904-z     

Microbiological quality of tomatoes and peppers produced under the good agricultural practices protocol AGRO 2-1 & 2-2 in Crete, Greece

The efficiency of the good agricultural practices (GAP) protocol AGRO 2-1 & 2-2, in advancing microbiological-quality of tomatoes and peppers, was studied in greenhouses at Ierapetra, Crete, Greece. The 240 tested vegetables-samples, produced under AGRO 2-1 & 2-2, showed satisfactory quality: Listeria monocytogenes absent per 25 g; Escherichia coli < 20 Colony Forming Units per gram (CFU/g); total coliforms 4.37–4.68 log CFU/g; aerobic plate counts 5.78–5.92 log CFU/g. Based on actual results and practices evaluation, we conclude that AGRO 2-1 & 2-2 can reduce microbial hazards for consumers and furthermore can establish practices in compliance to basic Euro-Retailer-Produce GAP (EUREPGAP) requirements.     

Autonomous stair-climbing with miniature jumping robots.

The problem of vision-guided control of miniature mobile robots is investigated. Untethered mobile robots with small physical dimensions of around 10 cm or less do not permit powerful onboard computers because of size and power constraints. These challenges have, in the past, reduced the functionality of such devices to that of a complex remote control vehicle with fancy sensors. With the help of a computationally more powerful entity such as a larger companion robot, the control loop can be closed. Using the miniature robot's video transmission or that of an observer to localize it in the world, control commands can be computed and relayed to the inept robot. The result is a system that exhibits autonomous capabilities. The framework presented here solves the problem of climbing stairs with the miniature Scout robot. The robot's unique locomotion mode, the jump, is employed to hop one step at a time. Methods for externally tracking the Scout are developed. A large number of real-world experiments are conducted and the results discussed.     

Variational stability of infinite-dimensional optimal control problems

In this paper we examine the variational stability of infinite-dimensional optimal control problems governed by nonlinear evolution equations. Our tools are the Kuratowski—Mosco convergence of sets and the corresponding τ-convergence of functions. We prove the τ-convergence of cost functional and the convergence of the values of the problems, and we examine the variational stability of the solution and reachable sets. These results are then applied to a sequence of nonlinear parabolic distributed-parameter optimal control problems     

Molecular simulation studies of adsorption of hydrogen cyanide and methyl ethyl ketone on zeolite NaX and activated carbon

In the present research study the primary aim is to understand and characterize the physical adsorption of polar molecules namely, hydrogen cyanide and methyl ethyl ketone (MEK) in zeolite NaX, and activated carbon through detailed Monte-Carlo simulations and computational quantum chemistry techniques. The sorption capacity and affinity of the zeolite is compared with activated carbon with different acid site concentrations, type of acid site, and pore sizes by simulating single component isotherms and Henry's constant at 25 degrees C. The role/contribution of certain types of electrostatic interactions namely charge-dipole, charge-induced dipole with zeolite NaX and activated carbon, as well as dipole-dipole interactions among polar molecules is analyzed and discussed.     

Experimental Validation of a Helicopter Autopilot Design using Model-Based PID Control

Autonomous helicopter flight provides a challenging control problem. In order to evaluate control designs, an experimental platform must be developed in order to conduct flight tests. However, the literature describing existing platforms focuses on the hardware details, while little information is given regarding software design and control algorithm implementation. This paper presents the design, implementation, and validation of an experimental helicopter platform with a primary focus on a software framework optimized for controller development. In order to validate the operation of this platform and provide a basis for comparison with more sophisticated nonlinear designs, a PID controller with feedforward gravity compensation is derived using the generally accepted small helicopter model and tested experimentally.     

A strange convergence property of the lobatto-chebyshev method for the numerical determination of stress intensity factors

The Lobatto-Chebyshev method for the numerical solution of the Cauchy type singular integral equation of crack problems in two-dimensional elasticity, plates and shells and the determination of the values of the stress intensity factors at the crack tips is shown to converge for non-differentiable Hölder-continuous or even discontinuous loading distributions as far as the values of the stress intensity factors are concerned. Moreover, in all cases of differentiable loading distributions it is shown to converge more rapidly than believed up to now. The problems of a simple straight crack and a periodic array of cracks loaded by three non-differentiable loading distributions are used for the application of the present results. The displayed numerical results for these problems verify and further corroborate the theoretical results. The extension of the present results to the Gauss-Chebyshev method is also quite possible.     

An architecture for managing virtual circuit and virtual path services in ATM networks

ATM networks rely on the Virtual Circuit (VC) and Virtual Path (VP) concepts to provide unicast connection-oriented services with Quality of Service (QoS) guarantees. This paper presents a model for managing the configuration and performance of the VC and VP services in these networks. The model consists of a connection management architecture that provides the services and is instrumented for network management purposes, and a network management architecture that uses the OSI management model to provide access to the appropriate service monitoring and control functions. The network management architecture proposes complete managed object definitions that achieve a variety of monitoring and control objectives: service configuration, service performance at the call and cell level, and service control. The latter includes the capability to establish VPs and control their allocated networking capacity and also control parameters of the signaling system that affect the performance of the VC service. The architecture was implemented in its entirety on the Xunet ATM testbed, and several experiments were conducted to illustrate the trade-off between the throughput of the VC service and the allocation of capacity to VPs. The experiments further demonstrated that the signaling system can create throughput bottlenecks in the absence of VPs in the network, and therefore, the network operator can increase performance by controlling the VP distribution.     

Heuristic collision-free path planning for an autonomous platform

In this paper, a heuristic and learning, algorithmic scheme for collision-free navigation is presented. This scheme determines an optimum collision-free navigation path of an autonomous platform by using a trial and error process, past navigation knowledge and current information extracted from the generated surrounding environment.     

Spot addressing for microarray images structured in hexagonal grids

In this work, an efficient method for spot addressing in images, which are generated by the scanning of hexagonal structured microarrays, is proposed. Initially, the blocks of the image are separated using the projections of the image. Next, all the blocks of the image are processed separately for the detection of each spot. The spot addressing procedure begins with the detection of the high intensity objects, which are probably the spots of the image. Next, the Growing Concentric Hexagon algorithm, which uses the properties of the hexagonal grid, is introduced for the detection of the non-hybridized spots. Finally, the Voronoi diagram is applied to the centers of the detected spots for the gridding of the image. The method is evaluated using spots generated from the scanning of the Beadchip of Illumina, which is used for the detection of Single Nucleotide Polymorphisms in the human genome, and uses hexagonal structure for the location of the spots. For the evaluation, the detected centers for each of the spot in the image are compared to the centers of the annotation, obtaining up to 98% accuracy for the spot addressing procedure.