Acquisition, representation and rule generation for procedural knowledge

Current research into the design and continuing development of a system for the acquisition of procedural knowledge, its representation in useful forms, and proposed methods for automated C Language Integrated Production System (CLIPS) rule generation is discussed. The Task Analysis and Rule Generation Tool (TARGET) is intended to permit experts, individually or collectively, to visually describe and refine procedural tasks. The system is designed to represent the acquired knowledge in the form of graphical objects with the capacity for generating production rules in CLIPS. The generated rules can then be integrated into applications such as NASA's Intelligent Computer Aided Training (ICAT) architecture. Also described are proposed methods for use in translating the graphical and intermediate knowledge representations into CLIPS rules

Scavenging Energy Sources Using Ferroelectric Materials

Ferroelectric materials have attracted interest for over a hundred years as a result of their spontaneous polarization and a polarization orientation that can be reversed by the application of an external electric field. In addition, the degree of polarization can be affected by external stimuli such as vibrations, stress, heat, and light. These properties enable ferroelectric materials to be used to fabricate nanogenerators, which are devices used in energy scavenging applications and provide an opportunity to obtain electrical energy from a variety of external stimuli. This review discusses the development of ferroelectric-based nanogenerators for scavenging mechanical, thermal, and solar energies through the piezoelectric effect, pyroelectric effect, and photovoltaic effect, respectively. The mechanisms of the effects and the pathways to optimize the output performance of the nanogenerators are analyzed in detail. Recent developments in energy harvesting using ferroelectric materials are discussed with the objective to motivate attention and efforts in this growing field.</p

Phase transition enhanced pyroelectric nanogenerators for self-powered temperature sensors

Pyroelectric materials are of interest for waste heat utilization and thermal detection. However, the low output current and inefficiency reduces their effectiveness. Here, we utilize the abrupt decrease in polarization of ferroelectric BaTiO3 materials around Curie temperature to improve the output performance of a pyroelectric nanogenerator. The variation of the polarization leads to a large change in the density of surface free charges, resulting in an increase of pyroelectric current. We have designed a temperature control and recording system to realize direct measurement of the pyroelectric output current. The pyroelectric current, power and energy conversion efficiency of the device near the Curie temperature were measured to be 15.6-fold, 18-fold and 15.8-fold higher than those acquired near room temperature. Moreover, the temperature induced current and charge density enhancement can be applied to detect temperature and temperature change. The responsivity of the self-powered temperature sensor near Tc is 120 nC/cm2∙K, which 4.8 times higher than that near room temperature (25.1 nC/cm2∙K). The results confirmed the ability to exploit a ferroelectric phase transition for pyroelectric performance enhancement.</p

Photocatalytic Properties of Commercially Available TiO2 Powders for Pollution Control

The photocatalytic properties of titanium dioxide have been widely studied over recent decades since the discovery of water photolysis by TiO2 electrodes in 1972. Titanium dioxide has three main crystal polymorphs; anatase, rutile and brookite and rutile is the most common as the metastable polymorph. Each polymorph has different band gap positions. Anatase’s band gap is 3.2 eV, higher than rutile’s which is 3.0 eV. This difference in the band gap will determine their optimum UV wavelength range to promote a photocatalytic process. There are different methods to assess the photocatalytic activity of a material. The most commonly used method is the degradation of a dye in aqueous solution under UV light, due to its simplicity. Under these conditions the decomposition rate of a suitable organic dye is used as a measure of activity. Physical properties such as particle size and surface area will determine the effective area that will interact and absorb the dye prior to degradation. The physical mechanisms involved in such aqueous based methods differ from gas phase reactions. More advanced techniques use mass spectrometers to evaluate photocatalytic activity of titanium dioxide in the gas phase. An effective photocatalyst for heterogeneous reactions in the gas phase is one which is efficient at creating radicals as a result of an absorbed photon

Understanding the Effects of Cross-Linking Density on the Self-Healing Performance of Epoxidized Natural Rubber and Natural Rubber

[Image: see text] The demand for self-healing elastomers is increasing due to the potential opportunities such materials offer in reducing down-time and cost through extended product lifetimes and reduction of waste. However, further understanding of self-healing mechanisms and processes is required in order to develop a wider range of commercially applicable materials with self-healing properties. Epoxidized natural rubber (ENR) is a derivative of polyisoprene. ENR25 and ENR50 are commercially available materials with 25 and 50 mol % epoxidation, respectively. Recently, reports of the use of ENR in self-healing materials have begun to emerge. However, to date, there has been limited analysis of the self-healing mechanism at the molecular level. The aim of this work is to gain understanding of the relevant self-healing mechanisms through systematic characterization and analysis of the effect of cross-linking on the self-healing performance of ENR and natural rubber (NR). In our study, cross-linking of ENR and NR with dicumyl peroxide and sulfur to provide realistic models of commercial rubber formulations is described, and a cross-linking density of 5 × 10(–5) mol cm(–3) in sulfur-cured ENR is demonstrated to achieve a healing efficiency of 143% for the tensile strength. This work provides the foundation for further modification of ENR, with the goal of understanding and controlling ENR’s self-healing ability for future applications

Experimental and Analytical Investigation of the Response of a Triboelectric Generator Under Different Operating Conditions

This article provides experimental and theoretical studies on the effect of operating conditions on the output response of triboelectric generators. The influence of specific parameters is examined in detail, including vibration frequency, impact separation distance, and the type of adhesive between the dielectric and the electrode for a single dielectric layer device operating in contact-separation mode, with Teflon and copper being the dielectric and electrode materials, respectively. A scotch-yoke mechanism is designed and fabricated in an effort to understand the effect of varying the operating conditions on the output voltage behavior. The voltage output is compared with an analytical capacitor model at drive frequencies ranging from 1 to 5 Hz and separation distances from 5 to 40 mm to evaluate the model's effectiveness in predicting generator output. The experimental results provide new insights into the behavior of triboelectric generators and how the type of adhesive between the dielectric material and the electrode affects the output signal.</p

Time Domain Multiplexing for Efficiency Enhanced Piezoelectric Energy Harvesting in MEMS

The conversion efficiency of piezoelectric energy harvesters (EH) have been improved by several approaches including frequency up-conversion (FUC) techniques that trigger the high-frequency (HF) piezoelectric resonators using low-frequency (LF) mechanical inputs. This work proposes a new time-domain multiplexing technique to further improve the harvesting efficiency for random mechanical impacts using commercially available microfabrication processes. The FUC is implemented by a slowly moving shuttle beam, which represents the LF mechanical inputs, that triggers the free ends of piezoelectric cantilever beams. Mechanical impacts by the LF shuttle lead to the cantilever beams vibrating at their higher natural resonance frequencies. In the proposed approach, resonators are exposed to the LF mechanical input at unequal distances, which results in sequential HF vibrations. As a result, the HF electrical outputs fit sequentially within the long period of the LF input. Analytical and experimental comparisons support the increased electrical output using time domain multiplexing.</p