The Impact of Metastable Intermolrecular Nanocomposite Particles on Kinetic Decomposition of Heterocyclic Nitramines Using Advanced Solid‐Phase Decomposition Models

Journal of Inorganic and Organometallic Polymers and Materials - Surface oxygen of oxide catalyst has low coordination number; they are negatively charged. Surface oxygen can act active site for...     

Model-based testing of a real-time adaptive motion planning system

Abstract

To enable effective and safe operations of autonomous robots in environments with unknowns and unpredictability, a key practical problem is how to test the functionality and assess the performance of real-time motion planning systems. This is a challenge because the underlying algorithms are real-time, sensing-based, and often non-deterministic. These systems’ performance depends on task environments, which can vary in countless ways. Existing testing techniques are designed heavily based on testers’ experience and hardly provide a good coverage of possible test scenarios. This paper introduces a systematic model-based testing (MBT) approach to evaluate the functionality and performance of a real-time adaptive motion planning (RAMP) system. The MBT approach uses the formal communicating extended finite state machine model to model RAMP’s concurrent components and leverage graph traversal algorithms to systematically generate behavioral test cases. First, component integration is considered by modeling the RAMP components and their interactions. Next, system-level testing is considered by modeling mobile obstacles of unpredictable motion behavior. The behavior models are leveraged to generate Abstract Behavioral Test Cases, which are transformed by test data into executable test cases. The test results demonstrate the effectiveness of applying the systematic MBT approach to the evaluation of real-time robotic systems.     

Transient Investigation of the Critical Abstraction Rates in Coastal Aquifers: Numerical and Experimental Study

This research investigated the transient saltwater upconing in response to pumping from a well in a laboratory-scale coastal aquifer. Laboratory experiments were completed in a 2D flow tank for a homogeneous aquifer where the time evolution of the saltwater wedge was analysed during the upconing and the receding phase. The SEAWAT code was used for validation purposes and to thereafter examine the sensitivity of the critical pumping rate and the critical time (the time needed for the saltwater to reach the well) to the well design and hydrogeological parameters. Results showed that the critical pumping rate and the critical time were more sensitive to the variations of the well location than the well depth. The critical time increased with increasing the location and depth ratios following a relatively linear equation. For all the configurations tested, the lowest critical pumping rate was found for the lower hydraulic conductivity, which reflects the vulnerability of low permeability aquifers to salinization of pumping wells. In addition, higher saltwater densities led to smaller critical pumping rate and shorter critical time. The influence of the saltwater density on the critical time was more significant for wells located farther away from the initial position of the interface. Moreover, increasing the dispersivity induced negligible effects on the critical pumping rate, but reduced the critical time for a fixed pumping rate.     

The study on radiation grafting of acrylic acid onto fluorine-containing polymers. III. Kinetic study of preirradiation grafting onto poly(tetrafluoroethylene–hexafluoropropylene)

A kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–hexafluoropropylene) (FEP) film. The effect of grafting conditions was investigated. The dependencies of the grafting rate on preirradiation dose and monomer concentration were found to be 0.58 and 1.25 order, respectively. The overall activation energy for the graft polymerization was 7.4 kcal/mol. The final degree of grafting increased with preirradiation dose and monomer concentration and slightly decreased as the grafting temperature was elevated. The relationship between the grafting rate and film thickness gave a negative first-order dependency, which is in agreement with that obtained for polytetrafluoroethylene—AAc grafting system. It was reasonably concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.     

Low-cost,rapid-prototyping of digital microfluidics devices

An innovative and simple microfabrication method for digital microfluidics is presented. In this method, devices are formed from copper substrates or gold compact disks using rapid marker masking to replace photolithography. The new method is capable of forming devices with inter-electrode gaps as small as 50 μm. Saran™ wrap (polyethylene film) and commercial water repellants were used as dielectric and hydrophobic coatings, respectively, to replace commonly used and more expensive materials such as parylene-C and Teflon-AF. Devices formed by the new method enabled single- and two-plate actuation of droplets with volumes of 1–12 μL. Fabricated devices were successfully tested for droplet manipulation, merging and splitting. We anticipate that this fabrication method will bring digital microfluidics within the reach of any laboratory with minimal facilities. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of waste-derived MA spinel on sintering and stabilization behavior of partially stabilized double phase zirconia

Cubic-stabilized zirconia ceramic composites have been synthesized by conventional sintering, starting from commercial m-ZrO₂, Y₂O₃, and waste-derived magnesium aluminate spinel (MA) powders. In this work, the effect of sintering temperature and MA content on stabilization and densification properties of YSZ have been duly considered. MA-free YSZ0 composite sintered at 1600°C-1700°C revealed m- and t-ZrO₂ dual-phase structure where its m-ZrO₂ was partially stabilized upon temperature rising into tetragonal phase by Y³⁺ diffusion inside zirconia structure. YSZ10-50 composites containing 10-50 wt% MA demonstrated dissimilar behavior where their m-ZrO₂ was transformed and stabilized into a cubic form by diffusion of Y³⁺, Mg⁺², and Al⁺³ inside zirconia lattice. Furthermore, densification of YSZ10-50 powder mixtures by conventional sintering at 1600°C for 2 hours resulted in fully dense compacts with micrometer-sized grains. The outcomes indicate that MA has a significant effect on m-ZrO₂ stabilization into the cubic phase structure at room temperature. In this respect, this study offers huge potentials for developing fully stabilized c-ZrO₂ ceramics that could be possibly used as industrial ceramics for structural applications of harsh chemical and thermal environmental conditions.     

Effect of TGO thickness,pores, and creep on the developed residual stresses in thermal barrier coatings under cyclic loading using SEM image-based finite element model

Thermal barrier coatings (TBC) allow the metallic internal components of gas turbine engines to operate at elevated temperatures near its melting points. Formation of thermally grown oxide (TGO) layers at the top coat (TC) and bond coat (BC) interface induces cracks in the TC that may lead to complete TBC failure due to spallation. An SEM image-based finite element (FE) model is developed using commercial finite element package ABAQUS to investigate the development of residual stresses resulting from cyclic loading of TBCs. The model includes thermo-mechanical material properties and considers the real interface between the coating layers. The model includes real pores based on an SEM image, taking advantage of image processing techniques. Effect of TC surface roughness and pores on the developed residual stresses during thermal cycling is investigated with respect to different TGO thicknesses. The analysis shows that presence of TC roughness causes stress concentration sites during heating that may force horizontal cracks to initiate and propagate with stress values that are indifferent to the TGO thickness. The pores are found to shift stress concentration regions from the TC/TGO interface to the vicinity of the pores during cooling, and that may cause horizontal cracks to start from within the TC with stresses that increase with TGO thickness. Moreover, the effect of creep for all layers on the generated residual stresses is studied. Considering creep gives lower stresses at the end of cooling, however, stress distribution remains the same with and without creep.     

Measurement of functional impairments in human locomotion using pattern analysis

The authors have developed a measurement methodology for the efficient and reliable analysis of human gait dynamics at a level that quantifies variations from morphometrically adjusted normal in three dimensions and in real-time. The large quantities of acquired kinetic, kinematic and electromyographic data are dealt with as aggregate information granules, enabling an efficient partition of input space and more rapid analysis. The process of data aggregation or granulation is predicted on an understanding and application of the functional relationships of human movement and are expressed in an implication table. This implication table is the basis of a fuzzy relational matrix, a feature pattern, established between the dynamic activities during locomotion.The performance and efficiency of the system have been evaluated using two case studies of gait impairments involving two patients each with cerebral palsy and with multiple sclerosis, respectively.     

MICROCHANNEL HEAT SINKS: AN OVERVIEW OF THE STATE-OF-THE-ART

Computers are rapidly becoming faster and more versatile, and as a result, high-powered integrated circuits have been produced in order to meet this need. However, these high-speed circuits are expected to generate heat fluxes that exceed the circuit's allowable operating temperature, and so an innovative cooling device is needed to solve this problem. Microchannel heat sinks were introduced in the early 1980s to be used as a means of cooling integrated circuits. Since then, many studies have been conducted in the field of these microchannel heat sinks. Earlier research used mainly single-phase coolants in their heat sinks, but two-phase coolants are now the focus of more recent research. The purpose of this article is to present a state-of-the art literature review of the progress of research in the field of microchannel heat sinks. This literature will focus mainly on the most recent research, starting with the latter half of the 1990s.