A measurement strategy for non-dispersive ultra-violet detection of formaldehyde in indoor air: Spectral analysis and interferent gases

We have conducted an extensive review of published spectra in order to identify a region with potential for detection of formaldehyde in indoor air. 85 chemicals and chemical groups common to the indoor environment were identified, 32 of which had absorption spectra in the UV-vis region. Of these, 11 were found to overlap with the formaldehyde UV region. It was found that the region between 320 to 360 nm is relatively free from interference from indoor gases, with NO being the only major interferent. A method is proposed for a low resolution (3 nm) spectroscopic detection method, specifically targeted at formaldehyde absorption features at 327 nm with a reference at 334 nm. 32 ppb of NO was found to have a cross-sensitivity with equivalent magnitude to 100 ppb of formaldehyde. A second reference at 348 nm would reduce this cross-sensitivity.This work was funded by the Engineering and Physics Science Research Council (EPSRC) under grants GR/T18424, EP/P504880 and EP/H02252X. Enquiries for access to the data referred to in this article should be directed to [email protected]

Noise analysis for CCD-based ultraviolet and visible spectrophotometry

Full-text not yet available due to publisher embargo.We present the results of a detailed analysis of the noise behavior of two CCD spectrometers in common use, an AvaSpec-3648 CCD UV spectrometer and an Ocean Optics S2000 Vis spectrometer. Light sources used include a deuterium UV/Vis lamp and UV and visible LEDs. Common noise phenomena include source fluctuation noise, photoresponse nonuniformity, dark current noise, fixed pattern noise, and read noise. These were identified and characterized by varying light source, spectrometer settings, or temperature. A number of noise-limiting techniques are proposed, demonstrating a best-case spectroscopic noise equivalent absorbance of 3.5×10−4  AU for the AvaSpec-3648 and 5.6×10−4  AU for the Ocean Optics S2000 over a 30 s integration period. These techniques can be used on other CCD spectrometers to optimize performance

Formaldehyde sensor using non-dispersive UV spectroscopy at 340nm

Formaldehyde is a volatile organic compound that exists as a gas at room temperature. It is hazardous to human health causing irritation of the eyes, nose and throat, headaches, limited pulmonary function and is a potential human carcinogen. Sources include incomplete combustion, numerous modern building materials and vehicle fumes. Here we describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy for the first time. A two channel system has been developed, making use of a strong absorption peak at 339nm and a neighbouring region of negligible absorption at 336nm as a reference. Using a modulated UV LED as a light source and narrowband filters to select the desired spectral bands, a simple detection system was constructed that was specifically targeted at formaldehyde. A minimum detectable absorbance of 4.5 × 10-5 AU was estimated (as ΔI/I0), corresponding to a limit of detection of approximately 6.6 ppm for a 195mm gas cell, with a response time of 20s. However, thermally-induced drift in the LED spectral output caused this to deteriorate over longer time periods to around 30 ppm or 2 × 10-4 A

Design and analysis issues of integrated control systems for high-speed civil transports

A study was conducted to identify, rank, and define development plans for the critical guidance and control design and analysis issues as related to economically viable and environmentally acceptable high-speed civil transport. The issues were identified in a multistep process. First, pertinent literature on supersonic cruise aircraft was reviewed, and experts were consulted to establish the fundamental characteristics and problems inherent to supersonic cruise aircraft. Next, the advanced technologies and strategies being pursued for the high-speed civil transport were considered to determine any additional unique control problems the transport may have. Finally, existing technologies and methods were examined to determine their capabilities for the design and analysis of high-speed civil transport control systems and to identify the shortcomings and issues. Three priority levels - mandatory, highly beneficial, and desirable - were established. Within each of these levels, the issues were further ranked. Technology development plans for each issue were defined. Each plan contains a task breakdown and schedule

A content-theoretical model of educational change : the case of the new vocationalism.

This thesis is concerned with theorising educational change. This involves\ud the identification of a distinct theoretical object; the conceptualisation of a\ud dynamic of educational change and the delimitation of the fundamental units of\ud analysis. Together, these provide the basis for the development in Part One of\ud the thesis of a content-theoretical model.\ud Working within a Marxist Reproduction problematic, power and domination\ud are theorised in terms of Social Forms - wage, state and civil-forms - which\ud are the product of the social relations of production within the Capitalist\ud Mode of Production. The education system is taken to be the most public and\ud formal site of their reproduction. Since social forms are a feature of the\ud social structure, including the education system, a 'translation effect' can be\ud identified between different levels of analysis. This approach therefore entails\ud recognition of the fact that reproduction is contested and has a political\ud aspect. The object of analysis has been to reveal this political aspect by\ud delineating the relationship between the economic and the political ( the wage\ud and state-forms), thereby demonstrating how 'the political' makes possible the\ud reproductive role of the education system.\ud In Part Two of the thesis, this content-theoretical model is employed in\ud an analysis of the introduction of the 'new vocationalism' into Further\ud Education. Focussing upon the FE teachers' trade union organisation NATFHE,\ud this analysis reveals that, faced with the introduction of the new vocationalism\ud in the shape of the Youth Training Scheme, a 'strategy of opportunism' has\ud been the dominant logic informing their collective action. Such a strategy is\ud shown to contribute to the proletarianisation of FE teachers, thereby rendering\ud their opposition to the new vocationalism ineffective

Smart cable for design of high density metallic cross connect systems

The present invention to provide a smart cable system for high density metallic cross connect systems. In particular, this invention relates to the physical structure of cables and associated hardware needed to form the smart cable system for interconnecting cards in shelves and racks of high density metallic cross connect switching systems. This invention provides the cable installer the ability to connect cables to cards with minimal errors by using visual indicators. The visual indicators guide the cable installer such that he/she can properly install the cables into the appropriate connectors. The present invention also provides a means for detecting when and where the cables are connected within the cross connect system

The tear behaviour of some tri-block copolymer elastomers.

Four SBS block copolymers were subjected to extensive chemical examination to determine block molecular weights and styrene fractions.Casting from different solvent systems into sheet form resulted in a range of microstructural formations for the normally dispersed styrene phase. These morphological details were studied using transmission electron microscopy and low angle X-ray scattering.Dynamic mechanical tests, on sheet material cast from different solvent systems, in both shear and tension over a wide temperature range, and static tensile tests at +20°C, revealed significant differences in viscoelastic properties between the materials. These differences were related to changes in morphological detail by the use of a model for composite materials. The large strain behaviour at +20°C is modelled by the inverse Langevin function and a debonding parameter which is related to void growth in the material.The conventional analysis of tear behaviour, developed originally for vulcanised rubbers, whilst ranking SBS block copolymers alongside the most tear resistant vulcanised materials over wide ranges of temperature and tearing rate, was found to be suspect for this class of materials. An alternative interpretation, however, succeeds in relating tear strength to tensile properties for the temperatures and tear rates studied, and also relates the tearing behaviour of these elastomers to that of a wide variety of other materials

Development and Testing of Control Laws for the Active Aeroelastic Wing Program

The Active Aeroelastic Wing research program was a joint program between the U.S. Air Force Research Laboratory and NASA established to investigate the characteristics of an aeroelastic wing and the technique of using wing twist for roll control. The flight test program employed the use of an F/A-18 aircraft modified by reducing the wing torsional stiffness and adding a custom research flight control system. The research flight control system was optimized to maximize roll rate using only wing surfaces to twist the wing while simultaneously maintaining design load limits, stability margins, and handling qualities. NASA Dryden Flight Research Center developed control laws using the software design tool called CONDUIT, which employs a multi-objective function optimization to tune selected control system design parameters. Modifications were made to the Active Aeroelastic Wing implementation in this new software design tool to incorporate the NASA Dryden Flight Research Center nonlinear F/A-18 simulation for time history analysis. This paper describes the design process, including how the control law requirements were incorporated into constraints for the optimization of this specific software design tool. Predicted performance is also compared to results from flight

Flight Test of the F/A-18 Active Aeroelastic Wing Airplane

Successful flight-testing of the Active Aeroelastic Wing airplane was completed in March 2005. This program, which started in 1996, was a joint activity sponsored by NASA, Air Force Research Laboratory, and industry contractors. The test program contained two flight test phases conducted in early 2003 and early 2005. During the first phase of flight test, aerodynamic models and load models of the wing control surfaces and wing structure were developed. Design teams built new research control laws for the Active Aeroelastic Wing airplane using these flight-validated models; and throughout the final phase of flight test, these new control laws were demonstrated. The control laws were designed to optimize strategies for moving the wing control surfaces to maximize roll rates in the transonic and supersonic flight regimes. Control surface hinge moments and wing loads were constrained to remain within hydraulic and load limits. This paper describes briefly the flight control system architecture as well as the design approach used by Active Aeroelastic Wing project engineers to develop flight control system gains. Additionally, this paper presents flight test techniques and comparison between flight test results and predictions