546 research outputs found
DNS of inertial wave attractors in a librating annulus with height-dependent gap width
No full textDirect numerical simulations (DNS) of inertial wave attractors have been carried out in a librating Taylor-Couette system with broken mirror symmetry in the radial-axial cross-section. The inertial wave excitation mechanism and its localisation at the edges was clarified by applying boundary layer theory. Additional resonance peaks in the simulated response spectra were found to agree with low-order wave attractors obtained by geometric ray tracing. Numerics and theory are in qualitative agreement with recent lab experiments
Griffiths (Birth, 1887-02-20)
No full textAddress: McMillan1038/Pg.25/1887/MW/Amer/Amer/I.D.& J.E. Jones, M.D.Original record filed in drawer labeled 'GRIESS-GROTE, H'
Capillary gas chromatography/Fourier transform infrared microspectrometry at subambient temperature
No full textIncreasing the differentiating power of chromatographic and spectroscopic techniques by interfacing them
together has been a long-recognized goal of analytical chemists (1). However, the marriage of gas chromatography (GC) and Fourier transform infrared (FT-IR) spectrometry has not always been synergistic because capillary GC has often required lower detection limits than FT-IR has been able to provide (2,3). The development of the light-pipe interface has been largely responsible for the success of gas chromatography/
Fourier transform infrared spectrometry. The key
component of this interface is usually a light-pipe gas cell
through which the effluent from a capillary column flows
continuously during the IR measurement. Typical sample
quantities required to yield identifiable spectra using a light
pipe with an internal diameter of 1 mm are between 5 and 25 ng, although a light-pipe interface based on the "counter-Jacquinot advantage" holds promise in reducing these identification limits by a factor of 2 or 3 (4). The need for a further reduction of the injected amount required to yield an identifiable spectrum by at least an order of magnitude has resulted in the development of alternative approaches to the light-pipe interface. Possibly the best approach to high-sensitivity GC/FT-IR has involved trapping each eluate in a matrix of argon at about 12 K (5,6). A device which is based on this principle, known as the Cryolect, was introduced commercially in 1984 (7,8). With this interface, identifiable spectra of compounds with average absorptivities can be obtained in the 200-400-pg range.
Such low limits of identification have been achieved primarily because of the very small area over which the sample is deposited, the effective thickness of a given amount of a GC eluate being inversely proportional to the area the sample occupies. Let us compare the band intensities of a given amount of material measured by matrix isolation and using a light pipe. With the Cryolect, each eluate can be deposited in a spot the diameter of which is as small as 0.25 mm (8). Neglecting the effect of the low-temperature matrix on the widths and peak absorbances of spectral bands, it can be readily seen that the intensity of the bands due to a given quantity of a GC eluate trapped in an argon matrix as a 0.25-mm-diameter spot should be 16 times greater than that of bands due to the same amount of the eluate held in a 1-mm-i.d. light pipe. For samples of this size, the - 1-mm-diameter image at the sample focus of a conventional 6X beam condenser is too large and the use of an infrared microscope is indicated (9). In an earlier note (IO), we showed that it is possible to trap a GC eluate of low volatility on a stationary infrared window held at ambient temperature. When this window was transferred to an infrared microscope, spectra of deposited materials were measured with 1-ng detection limits. In this paper, we report the feasibility of constructing an interface for real-time GC/FT-IR measurements based on this principle.
Eluates are trapped on an infrared-transparent plate which
is either held at ambient temperature or is termoelectrically cooled to temperatures as low as -45 "C. This window is located in the focal plane of an FT-IR microscope so that each eluate passes through the beam shortly after it is deposited. Although the sensitivity of this device for GC/FT-IR is not quite as high as that of the Cryolect, detection limits appear
to be approximately 1 order of magnitude lower than those of corresponding spectra measured with a light-pipe interface. The fact that this device operates near ambient conditions means that its cost should be considerably less than that of matrix-isolation GC/FT-IR interfaces
Remark on Applied Statistics Algorithm AS030 Half-Normal Plotting
No full textWe provide a Fortran 77 version of the Applied Statistics Algorithm AS30 `Half-Normal Plotting'' originally appearing in the book `Applied Statistics Algorithms'' by P. Griffiths and I.D. Hill. We believe that the new code offers improvements both in readability and maintainability. [The file /pub/misc/statlib/apstat/as030.sh contains the Fortran 77 source code, example driver codes, data and sample results as a Unix shar file. It is available via anonymous ftp from unix.hensa.ac.uk
Remark on Applied Statistics Algorithm AS057 Printing Multidimensional Tables
No full textWe provide a Fortran 77 version of the Applied Statistics Algorithm AS57 `Printing Multidimensional Tables'' originally appearing in the book `Applied Statistics Algorithms'' by P. Griffiths and I.D. Hill. We believe that the new code offers improvements both in readability and maintainability. [The file /pub/misc/statlib/apstat/as057.sh contains the Fortran 77 source code, example driver code, data and sample results as a Unix shar file. It is available via anonymous ftp from unix.hensa.ac.uk
Intradermal immunization with a bovine herpesvirus-1 DNA vaccine induces protective immunity in cattle
No full textAlthough intramuscular (i.m.) injection of DNA encoding glycoprotein D (gD) of bovine herpesvirus-1 (BHV-1) induces immune responses in cattle, this route of delivery is inefficient. Here we assessed three parameters that may enhance the efficacy of a gD DNA vaccine in cattle. First, the immune response generated by i.m. injected plasmid expressing a secreted form of gD (tgD) was determined and found to be very similar in magnitude to the response induced by gD-expressing plasmid. Secondly, gD- and tgD-expressing plasmids were administered by intradermal (i.d.) immunization, which resulted in a superior immune response to the secreted form, but no improvement in the response to the membrane-associated form. However, the form of gD used for immunization did not influence the immunoglobulin subtype, the ratio of antigen-specific IgG1 to IgG2 being approximately 4:1. Finally, the effect of promoter strength was assessed by replacing the Rous sarcoma virus (RSV) promoter, which was used in the original experiments, with the human cytomegalovirus immediate early promoter and first intron A (HCMV/IA). Although upon transfection in vitro the HCMV/IA promoter appeared to be stronger than the RSV promoter, there was only a 2-fold higher antibody response in vivo upon i.d. injection of cattle. Protection against virus challenge was obtained in the calves immunized i.d. with tgD-encoding plasmid, as shown by a significant reduction in weight loss, virus excretion, temperature response and clinical disease. No significant protection was observed in the animals vaccinated i.d. with the gD-expressing plasmid, which correlates with the lower level of immunity pre-challenge.ID: 3643; LR: 20081121; JID: 0077340; 0 (Antibodies, Viral); 0 (Immunoglobulin G); 0 (Vaccines, DNA); 0 (Viral Proteins); 0 (Viral Vaccines); 0 (bovine herpesvirus type-1 glycoproteins); 82115-62-6 (Interferon-gamma); ppublishSource type: Electronic(1
Gas path analysis for the MTT micro turbine
No full textGas turbine diagnostics is as old as the gas turbine itself. Over the years, performance based diagnostics allowed for a shift from time-based maintenance to more economical condition based maintenance playing a fundamental role in enhancing the availability and reliability of gas turbines. By monitoring the condition of the engine over time, maintenance actions can be taken based on information collected from the field. MTT (Micro Turbine Technology) is currently developing a low cost 3kWe micro-turbine CHP (Combined Heat and Power)-system by using off-the-shelf technologies. Once the system will be launched on the market an organized, cost-effective maintenance procedure will be required. The objective of this M. Sc. thesis project was to develop and demonstrate a Gas Path Analysis diagnostic concept for the micro-turbine. Gas Path Analysis (GPA) is a method to assess the condition of the gas turbine by using performance measurements from the gas path. The feasibility of the diagnostic concept was demonstrated by some case studies using data from the first generation field test units. After reviewing a number of gas turbine diagnostic techniques, a non-linear model based gas path analysis approach was chosen. For the development of the diagnostic concept, a non-linear model of a healthy reference engine was used to simulate the off-design behaviour of the engine and derive healthy performance parameter baselines. These baselines are used to compare the performance of field engines against. A component based modelling environment called GSP or the Gas turbine Simulation Program was used to simulate the effect of ambient conditions and deterioration on performance. The diagnostic concept relies on the principle that deterioration causes corrected measurement parameters to shift from the healthy reference baselines. Measurement performance parameters are first corrected to standard ISA conditions before being compared against the healthy baselines. By modelling specific types of deterioration in GSP, signature parameter shifts could be recorded for each of the deterioration modes. These signature parameter shifts are used to compare shifts in performance parameters against and determine the closest pattern-match which can be used to identify the most probable cause of deterioration. The proposed concept is capable of performing engine level diagnostics and partially component level diagnostics. Multiple fault diagnostics and quantifying the level of deterioration are more difficult due to the limited number of sensors and the relatively large impact of second-order effects such as heat-loss, auxiliary power take-off, mechanical losses, etc. The performance parameter baselines together with the derived rulesets can easily be implemented in a maintenance tool making the concept flexible and easy to use.MastersFlight performance and propulsionAerospace Engineerin
Parallel implementation of interior-point methods for semidefinite optimization
No full textElectrical Engineering, Mathematics and Computer Scienc
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