[en] Low-power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference [1]. By combining these data with the corresponding acoustic signal, we've demonstrated an almost 10-fold bandwidth reduction in speech compression, compared to a standard 2.4 kbps LPC10 protocol used in the STU-III (Secure Terminal Unit, third generation) telephone. This paper describes a potential EM sensor/acoustic based vocoder implementation

[en] Low power Electromagnetic (EM) Wave sensors can measure general properties of human speech articulator motions, as speech is produced. See Holzrichter, Burnett, Ng, and Lea, J.Acoust.Soc.Am. 103 (1) 622 (1998). Experiments have demonstrated extremely accurate pitch measurements ( and lt; 1 Hz per pitch cycle) and accurate onset of voiced speech. Recent measurements of pressure-induced tracheal motions enable very good spectra and amplitude estimates of a voiced excitation function. The use of the measured excitation functions and pitch synchronous processing enable the determination of each pitch cycle of an accurate transfer function and, indirectly, of the corresponding articulator motions. In addition, direct measurements have been made of EM wave reflections from articulator interfaces, including jaw, tongue, and palate, simultaneously with acoustic and glottal open/close signals. While several types of EM sensors are suitable for speech articulator measurements, the homodyne sensor has been found to provide good spatial and temporal resolution for several applications

[en] The differential photocalorimetric technique was used to study the rates of photopolymerisation initiated by donor/acceptor pairs with N-vinylpyrrolidinone (NVP) as the donor, and the acceptors were a series of N-hydroxy alkylmaleimides including N-hydroxymethyl maleimide (HMMI), N-(2-hydroxy) ethylmaleimide (HEMI), N-(3-hydroxy) propylmaleimide (HPrMI) and N-(5-hydroxy) pentylmaleimide (HPMI). HPMI/NVP system displays the highest rate of polymerisation followed by HMMI/NVP and then HPrMI/NVP, with HEMI/NVP giving the lowest rate. These donor/acceptor pair systems were subsequently used to initiate the polymerisation of NVP under the influence of UV radiation. With the exception of the HEMI/NVP system, the other three systems produced polymers with characteristics pertaining to that of hydrogel. A previously proposed mechanism (Proceedings of the RadTech Asia '01 Conference, Kunming, China, 2001, pp. 182-201) was used to explain such phenomenon

[en] Parameters influencing the grafting of a typical charge transfer (CT) complex, maleic anhydride /triethylene glycol divinyl ether, to representative substrates, cellulose and polypropylene, initiated by UV and ionising radiation have been investigated. The variables studied include effect of solvent, role of donor involving the type of ether and the nature of the acceptor including the use of common monomers like methyl methacrylate. A novel application of this CT grafting work is reported involving hydrogel formation with subsequent controlled release of incorporated reagent

[en] Effect of monomer structure in photografting charge transfer (CT) complexes to typical substrates like wool, cellulose and polypropylene is reported. The importance of photoinitiators in these processes is examined. Maleic anhydride (MA) with triethylene glycol divinyl ether (DVE-3) is used as reference CT complex in this work. The additional monomers studied include the esters of MA as acceptors and vinyl acetate as donor. The role of solvent in these reactions is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation systems, is discussed

[en] Full text: Detailed studies on the accelerative effect of novel additives in radiation grafting and curing using acrylated monomer/oligomer systems have been performed in the presence of ionising radiation and UV as sources. Methyl methacrylate (MMA) is used as typical monomer for these grafting studies in the presence of the additives with model backbone polymers, cellulose and propropylene. Additives which have been found to accelerate these grafting processes are: mineral acid, occlusion compounds like urea, thermal initiators and photoinitiators as well as multifunctional monomers such as multifunctional acrylates. The results from irradiation with gamma rays have also been compared with irradiation from a 90W UV lamp. The role of the above additives in accelerating the analogous process of radiation curing has been investigated. Acrylated urethanes, epoxies and polyesters are used as oligomers together with acrylated monomers in this work with uv lamps of 300 watts/inch as radiation source. In the UV curing process bonding between film and substrate is usually due to physical forces. In the present work the presence of additives are shown to influence the occurrence of concurrent grafting during cure thus affecting the nature of the bonding of the cured film. The conditions under which concurrent grafting with UV can occur will be examined. A mechanism for accelerative effect of these additives in both grafting and curing processes has been proposed involving radiation effects and partitioning phenomena

[en] Full text: The processes of radiation curing and grafting have been extensively investigated since 1950. In curing, the bonding between the polymeric film and the surface of the substrate involves the weak Van der Waals or London dispersion forces, whereas in grafting, covalent carbon-carbon bonds are formed between the polymer film and the substrate. The main application in radiation curing is in coating. A problem associated with this type of work is the possible occurrence of delamination of the coating from the substrate after curing which can be caused by the shrinkage of the coating due to the fast rate of polymerisation. Thus it is obvious that the occurrence of concurrent curing and grafting is important since this would increase in the bonding efficiency between the cured film and the substrate. Commercially, radiation curing processes predominantly involve UV initiated systems which involved the use of free radical formation photoinitiators (PIs). Besides being expensive, PI fragments may be released in the cured film and act as contaminants are of considerable concern. The recent development of PI free curing systems involving charge-transfer (CT) complexes is important in terms of the possible occurrence of grafting during UV curing of such materials. The current work involves the study of the effect of solvents on the radiation initiated concurrent curing and grafting of the CT complex formed between and triethylene glycol divinyl ether (DVE-3) and maleic anhydride (MA) onto polar naturally occurring substrates including wool and cellulose and a non-polar synthetic substrate, polypropylene. UV and gamma radiation are the radiation sources used in this study. Vinyl ethers are reactive comonomers for free radical polymerisations and have been used as an alternative to acrylate monomers. In the presence of radiation, the vinyl ether electron-rich double bond associates with highly electron-deficient maleates leading to the formation of CT complexes which are applicable to grafting processes. Solvents used in this study vary from polar to non-polar and they include THF, methanol, DMSO, CH₂CI₂, CH₃CI, CCI₄, acetonitrile and toluene. It has to be realised that the influence of polar and non-polar solvents on different types of monomer systems may in some cases reduce energies needed for reaction to proceed. Solvent molecules could form radicals and enter into reactivity of the system. Additionally, polar solvents can act as electron-donating species thus acting as radical donors. Various ratios of MA:DVE-3 were used in the study and the effect of MA:DVE-3 concentration on grafting yield examined. The most effective grafting system was observed when chlorinated solvents and THF were utilised. The least reactive solvents were DMSO, DMF and methanol. A mechanism for the grafting process is proposed

[en] Recent vibrational studies of CO and alkali metals coadsorbed on various transition metal surfaces have measured C-O stretching frequencies far below that observed on most clean metal surfaces. HREELS results from CO and potassium coadsorbed on Pt(111) suggest the presence of long range CO-potassium interactions. Recently, C-O vibrational frequencies characteristic of known alkali-CO ionic complexes have been reported for CO coadsorbed with potassium on Cu-(110), and are representative of short-range interactional effects. Long range interactions are observed at low potassium coverages while short range interactions are observed at high potassium coverages. All of the vibrational measurements reported to date for CO-alkali interactions have involved spectroscopic resolution which is low (between 40 and 80 cm^-1). In this paper, the authors clearly distinguish both short range and long range interactions for CO and potassium coadsorbed on Ni(111) at both low and high potassium coverages using Infrared Reflection-Absorption Spectroscopy (IRAS) at a resolution of 7cm^-1

[en] (High resolution) electron energy loss spectroscopy [(HR)EELS] has been used successfully to provide direct spectroscopic evidence regarding details of the molecular fragmentation of methoxy (CH₃O) on Al(111) caused by energetic electron and ion beams. Chemisorbed methoxy on Al(111) is produced by heating of adsorbed CH₃OH. Irradiation of CH₃O(a) by either energetic (∼300 eV) electrons or Ar⁺ ions results in C--O and C--H bond scission with simultaneous formation of Al--O and Al--C bonds. During electron stimulated desorption the CH₃O(a) species undergo sequential fragmentation first to CH/sub x/ groups that are captured by the surface and in the final decay process to adsorbed carbon. C--O bonds in CH₃O(a) are depleted preferentially compared to C--H bonds in CH/sub x/(a) species. The electron induced sequential fragmentation of the parent CH₃ group (from methoxy) to resultant CH/sub x/(a) occurs with an efficiency ∼3 orders of magnitude greater then the subsequent process of CH/sub x/(a) →C(a). Cross sections for various bond scission processes in electron and ion bombardment have been estimated

[en] This paper updates the on-going effort at Lawrence Livermore National Laboratory to develop autonomous, agile micro-satellites (MicroSats). The objective of this development effort is to develop MicroSats weighing only a few tens of kilograms, that are able to autonomously perform precision maneuvers and can be used telerobotically in a variety of mission modes. The required capabilities include satellite rendezvous, inspection, proximity-operations, docking, and servicing. The MicroSat carries an integrated proximity-operations sensor-suite incorporating advanced avionics. A new self-pressurizing propulsion system utilizing a miniaturized pump and non-toxic mono-propellant hydrogen peroxide was successfully tested. This system can provide a nominal 25 kg MicroSat with 200-300 m/s delta-v including a warm-gas attitude control system. The avionics is based on the latest PowerPC processor using a CompactPCI bus architecture, which is modular, high-performance and processor-independent. This leverages commercial-off-the-shelf (COTS) technologies and minimizes the effects of future changes in processors. The MicroSat software development environment uses the Vx-Works real-time operating system (RTOS) that provides a rapid development environment for integration of new software modules, allowing early integration and test. We will summarize results of recent integrated ground flight testing of our latest non-toxic pumped propulsion MicroSat testbed vehicle operated on our unique dynamic air-rail