Rights protection of trajectory datasets with nearest-neighbor preservation

Companies frequently outsource datasets to mining firms, and academic institutions create repositories or share datasets in the interest of promoting research collaboration. Still, many practitioners have reservations about sharing or outsourcing datasets, primarily because of fear of losing the principal rights over the dataset. This work presents a way of convincingly claiming ownership rights over a trajectory dataset, without, at the same time, destroying the salient dataset characteristics, which are important for accurate search operations and data-mining tasks. The digital watermarking methodology that we present distorts imperceptibly a collection of sequences, effectively embedding a secret key, while retaining as well as possible the neighborhood of each object, which is vital for operations such as similarity search, classification, or clustering. A key contribution in this methodology is a technique for discovering the maximum distortion that still maintains such desirable properties. We demonstrate both analytically and empirically that the proposed dataset marking techniques can withstand a number of attacks (such a translation, rotation, noise addition, etc) and therefore can provide a robust framework for facilitating the secure dissemination of trajectory datasets.     

A system dynamics model for dynamic capacity planning of remanufacturing in closed-loop supply chains

Product recovery operations in reverse supply chains face continually and rapidly changing product demand characterized by an ever increasing number of product offerings with reduced lifecycles due to both technological advancements and environmental concerns. Capacity planning is a strategic issue of increased complexity importance for the profitability of reverse supply chains due to their highly variable return flows. In this work we tackle the development of efficient capacity planning policies for remanufacturing facilities in reverse supply chains, taking into account not only economic but also environmental issues, such as the take-back obligation imposed by legislation and the “green image” effect on customer demand. The behavior of the generic system under study is analyzed through a simulation model based on the principles of the system dynamics methodology. The simulation model provides an experimental tool, which can be used to evaluate alternative long-term capacity planning policies (“what-if” analysis) using total supply chain profit as measure of policy effectiveness. Validation and numerical experimentation further illustrate the applicability of the developed methodology, while providing additional intuitively sound insights.     

Understanding the differences between microporous and mesoporous synthesis through the phase behavior of silica

The link between M41S mesoporous silicates and all-silica zeolites during the initial stages of synthesis is analyzed with small-angle scattering and conductivity experiments. The phase behavior of silica in aqueous solutions is studied for a family of quaternary ammonium hydroxides, from tetramethylammonium to dodecyltrimethylammonium. All solutions exhibit a critical aggregation concentration at a 1:1 SiO₂:[OH⁻]_initial molar ratio with solutions containing short chain compounds forming optically transparent (clear) nanoparticle suspensions, and solutions of long chain compounds phase separating into a solid and a liquid phase. The solid phase is analyzed with X-ray diffraction and thermogravimetric analysis and is found to have a hexagonal structure similar to MCM-41. Mid-sized chain length compounds form solutions containing both the phase separated solid and nanoparticles. In addition to studying phase behavior, the role of attractive hydrophobic interactions is studied using water/ethanol solutions. In ethanolic solutions, the entire family of quarternary ammonium compounds are found to form stable nanoparticle suspensions.     

On transmission control protocol synchronization in optical burst switching

This article studies the transmission control protocol (TCP) synchronization effect in optical burst switched networks. Synchronization of TCP flows appears when optical bursts with segments from different flows inside are dropped in the network causing flow congestion windows decreasing simultaneously. In this article, this imminent effect is studied with different assembly schemes and network scenarios. Different metrics are applied to quantitatively assess synchronization with classical assembly schemes. A new burst assembly scheme is proposed that statically or dynamically allocates flows to multiple assembly queues to control flow aggregation within the assembly cycle. The effectiveness of the scheme has been evaluated, showing a good improvement in optical link utilization.     

PDSW: A program for the calculation of photon energy distribution resulting from radioactive elements in seawater

Photons, when emitted from radioactive sources in seawater, are subsequent to multiple scattering mechanisms, namely the photoelectric effect, the Compton scattering and the pair production effect. Thus, the monoenergetic emission of photons in seawater will result in equilibrium in a distribution of photons with different energies. PDSW is a MATLAB program which calculates this distribution and can be found useful for the characterization of measured spectra obtained by gamma detectors such as NaI(Tl). PDSW has been developed as an autonomous MATLAB function in order to make possible to integrate it in other applications. All calculations are performed using a typical value for seawater salinity (3.5%).

Program summary

Title of program: PDSWCatalogue identifier: ADWWProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWWProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: x86Operating systems: WindowsProgramming language used: MATLABMemory required: 10 MbNumber of bits in a word: 32Number of processors used: 1Vectorized or parallelized?: noNumber of bytes in distributed program, including test data, etc.: 16 378Number of lines in distributed program, including test data, etc.: 3004Distribution format:tar.gzCPC Program Library subprograms used: noneNature of physical problem: Calculation of photon energy distribution in seawater taking into account the photoelectric effect, the Compton scattering and the pair production effect.Method of solution: Analytical calculation of the continuity equation for photon energy distribution in seawater and numerical integration of this equation in equilibrium.Restrictions on the complexity of the program: Very small resolution results in large memory requirements and high execution time.Typical running time: (Maximum energy-minimum resolution) 20 sUnusual features of the program: none     

Multiple mini-robots navigation using a collaborative multiagent reinforcement learning framework

In this work we investigate the use of a reinforcement learning (RL) framework for the autonomous navigation of a group of mini-robots in a multi-agent collaborative environment. Each mini-robot is driven by inertial forces provided by two vibration motors that are controlled by a simple and efficient low-level speed controller. The action of the RL agent is the direction of each mini-robot, and it is based on the position of each mini-robot, the distance between them and the sign of the distance gradient between each mini-robot and the nearest one. Each mini-robot is considered a moving obstacle that must be avoided by the others. We propose suitable state space and reward function that result in an efficient collaborative RL framework. The classical and the double Q-learning algorithms are employed, where the latter is considered to learn optimal policies of mini-robots that offers more stable and reliable learning process. A simulation environment is created, using the ROS framework, that include a group of four mini-robots. The dynamic model of each mini-robot and of the vibration motors is also included. Several application scenarios are simulated and the results are presented to demonstrate the performance of the proposed approach.     

Development of a real-time visual and force environment for a haptic medical training simulator

In this article, a real-time, visual and force environment for a 5-dof haptic urological training simulator is presented that deals with a low-force, high-deformation environment. A real-time graphical representation of the male urethra during the insertion of an endoscope is developed. Smooth urethra deformations are produced by a mesh of piece-wise Bézier interpolations, while its inner wall is simulated by realistic tissue textures. Efficient real-time techniques are developed that introduce endoscope camera depth-of-field effects. A novel particle-based model computes in real-time the forces fed to the haptic device. A 13 fps refresh rate is achieved on a 2-GHz computer with the depth-of-field effect activated, while the rate is doubled to 26 fps with this feature disabled. It is expected that the simulator will contribute to ethical, efficient, and modern surgical training.     

The roles of catalysis and reaction engineering in overcoming the energy and the environment crisis

An overview of the environmental and energy problems is given with emphasis on the challenges and opportunities for the catalysis and reaction engineering community. Important research directions, entailing the hydrogen economy, process intensification, enhanced efficiency, transformation of underutilized energy resources (e.g., natural gas from remote and offshore locations), and biomass conversion with novel processing schemes, are outlined. Recommendations for future research needs are made.