The discovery that a nano-sized material behaves differently than its bulk material opened the door to many exciting opportunities. One such opportunity is the observed ignition of single-walled carbon nanotubes (SWCNTs) with a camera flash. In this paper, results from distributed ignition of fuels with SWCNTs are presented which motivated further investigation of dry SWCNT samples. Consequently, a major part of the paper focuses on ignition characteristics of SWCNTs with an ordinary camera flash. A preliminary result from graphene sheets is also presented. The primary objective of this work is to use nanostructured materials as means for distributed ignition and combustion improvement in propulsion applications. Examples are homogeneous-charged compression ignition (HCCI) engines, liquid rocket fuel sprays, and enhanced flame stabilization in gas turbine engines. The idea was originally proposed by the author in April 2003 and the first patent filed in July 2004 after initial investigations. Based on tests conducted so far, this new ignition method is considered as a potential enabling technology for volumetric and distributed ignition of liquid fuel sprays and gaseous fuel-air mixtures with the lowest incident power intensity possible. This means remote and spatial ignition within any desired region defined by the shape of the light from a pulsed light source. In this paper, effects of incident pulsedlight exposure duration and wavelength between 350-1500 nm on minimum ignition energy (MIE), effects of sample physical compression (i.e., packing) on ignition characteristics, and the impact of iron (Fe) nanoparticle content in dry (no fuel) SWCNTs samples are presented. Initial measurements of the sound pressure level (SPL) from the photoacoustic phenomenon as well as ignition of graphene oxide are also presented. It appears that the wavelength of the illumination source does not play an important role as compared to the flash duration, at least within the range studied here. Data suggest that a lower energy-per-pulse is needed to initiate ignition when a shorter flash pulse duration is used. For example, only 30-35 mJ/pulse is required at pulse width of ∼0.2ms to initiate ignition of the as-produced fluffy samples in standard air, whereas at 7ms duration, it needs 80-90 mJ/pulse. For lightly-compressed samples, MIE trend remains unchanged and similar to that of the as-produced batches; otherwise, it increases with the level of the compression. Samples with Fe (metallic nanoparticle) content as low as 18% by weight can be ignited in air with a camera flash. Averaged intensities between 10 to 150 W/cm2 are required for distributed ignition of SWCNTs. This is a factor of 80 less than cases where lasers (pulsed or cw) are used in coal particles. However, graphene oxide required much higher input energy, a disadvantage to keep in mind in applications.
A future mission to return to Titan after Cassini/Huygens has now a really high priority for planetary exploration. Recent Cassini discoveries have revolutionized our understanding of the Titan system and its potential for harboring the ingredients necessary for life. These discoveries reveal that Titan is one of the most exciting places in the solar system; data show a complex environment, both for the atmosphere and for the surface. The data obtained, enriched by continuing observations from the Cassini spacecraft, show hydrocarbon lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. All these features demonstrate that dynamic processes are present on Titan and have raised the scientific interest in a follow-up mission to Titan. A robotic lighter-than-air vehicle has been suggested as a possible platform for an extensive exploration of the moon. NASA centers and universities around the US, as well as the European Space Agency, are studying the possibility of sending, as part of the next mission to this giant moon of Saturn, a hot-air balloon or similar for further and more in-depth exploration. Several patents cover different aspects of airship subsystems, such as design, propulsion and energy production; here we discuss some critical aspects taking into account the outcomes of our work. Recent studies on airships have demonstrated the high capability of airships to be considered as scientific platforms for extended explorations, both in space and time, on planets with atmosphere. Here we analyze the dynamics of the airship in response to the encountered Titans environment. Possible trajectories for an extended survey of the moon are investigated; these allow us to have a precise quantitative analysis of the energy necessary for a journey on the moon. Analysis on stability is performed in order to check the possible scientific slot windows available for investigations. A 1.2 km x 1.4 km region is selected as baseline: time necessary for performing a complete survey is investigated. Investigations are conducted both in a quiet situation with no wind and in wind conditions. Trajectories are followed with airship at 1.5, 3, 5 and 7 m/s velocities; surface science ( < 100 m) scenarios are proposed. Considered winds are in the range 0.0 - 1 m/s parallel and orthogonal to the ground track.
This paper refers to recent patents in GPS-based clock estimation and synchronization and observes advances in estimation and steering of clock errors with the finite impulse response (FIR) technique. The problem one meets here is caused by the GPS time temporary uncertainty and non-Gaussian sawtooth noise induces in the commercially available GPS timing receivers. It is complicated with the clock colored noise (flicker and random walks) often making the Kalman filter low efficient and requiring weighted averaging. We examine applications of optimal FIR filtering, prediction, and smoothing for polynomial and state space clock models. Optimal and unbiased FIR estimators are observed in line with the ladder, thinning, and Kalman-like algorithms. It is noticed that, for large averaging horizons featured to highly oversampled and slowly changing with time clock models, simple unbiased FIR solutions become virtually optimal. The trade-off with the Kalman filter is also discussed and we show that the unbiased FIR estimator ignoring noise and initial conditions is a better choice in terms of accuracy, stability, and robustness in solving many of the clock problems.
Diffractive gratings are very important in astrophysics where they provide clues to the composition of and processes in stars and planetary atmospheres. Another field of application is in optical data processing where gratings play its role as a spatial light modulator in spectrometers for miniature space instruments and for space technology. This article is intended to review papers and patents which discuss several techniques for producing these gratings as well as the various materials used in their fabrication. Special attention will be devoted to a patent concerning the fabrication of diffractive gratings in low-cost glass substrates by laser ablation without mask and in one step.
In this paper we present a Trefftz method for solving steady and transient heat conduction problems in FGMs, including nonlinear FGMs whose properties are dependent on temperature. For the case of steady heat transfer, Tcomplete solutions of governing equation for nonlinear exponential FGMs are derived by Kirchhoff transformation and coordinate transformation, and then, they can be used to model the temperature fields. For transient case, the analog equation method is used to convert the original governing equation to an equivalent Poissons equation. Then, the homogeneous solution is obtained by linear combination of a set of T-complete solutions while the radial basis functions (RBF) are employed to approximate the inhomogeneous terms. Finally, by enforcing satisfaction of the governing equation and boundary conditions at collocation points of the original problem, in which the time domain is discretized by time-stepping method, a Trefftz-RBF scheme is established. The performance of the proposed methods are assessed through three numerical examples. The results are presented for illustrating the accuracy and efficacy of the proposed numerical models.
A terrain adaptive tracked mobile robot with variable configurations – LMA was developed with an enhanced maneuverability to travel over a variety of rough and unpredictable surfaces. The active terrain adaptability of the robot is achieved through a pair of flippers, i.e. track configuration-controlling mechanisms. The mechanism can change and control tracks configurations to adapt all terrains, provide the tracks with a continuously invariable spring force to tension tracks, and adjust the center of gravity of the robot system to prevent it turning over from slopes or obstacles. This technology has been used in the development of an innovative Micro-rover for the space exploration. Two U.S. Patents (US 7493976, US 7600592) and one Canadian patent (CA2555455) were awarded to Engineering Services Inc. (ESI) for the invention of this technology in the past two years.