Showing papers by "Swedish Defence Research Agency published in 2001"

Analytical prediction of large mass impact damage in composite laminates

Abstract: Analytical models are suggested for prediction of impact damage initiation and growth during quasi-static response caused by large mass impactors. Comparisons with experiments are presented for different layups, geometries and boundary conditions. The critical load for delamination growth is found almost insensitive to geometry and boundary conditions. The critical energy for delamination growth is separated in bending, shear and indentation contributions. Further growth depends on the number of delaminations developing, and is in thin laminates limited by the early occurrence of penetration. Observed delamination sizes are compared with a suggested upper bound and predictions based on the observed number of delaminations.

Supernovae and the nature of the dark energy

Abstract: The use of Type Ia supernovae as calibrated standard candles is one of the most powerful tools to study the expansion history of the universe and thereby its energy components. While the analysis of some 50 supernovae at redshifts around z 0:5 has provided strong evidence for an energy component with negative pressure, \dark energy", more data is needed to enable an accurate estimate of the amount and nature of this energy. This might be accomplished by a dedicated space telescope, the SuperNova / Acceleration Probe (2000; SNAP), which aims at collecting a large number of supernovae with z< 2. In this paper we assess the ability of the SNAP mission to determine various properties of the \dark energy." To exemplify, we expect SNAP, if operated for three years to study Type Ia supernovae, to be able to determine the parameters in a linear equation of state w(z )= w0 +w1z to within a statistical uncertainty of0:04 for w0 and +0:15 0:17 for w1 assuming that the universe is known to be flat and an independent high precision (m =0 :015) measurement of the mass density m, is used to constrain the t. A further improvement can be obtained if, in addition to the high-z events, a large number of low-z supernovae are included in the sample.

Terrain modelling and analysis using laser scanner data

Abstract: Very detailed high-resolution (3D) digital terrain models can be obtained using airborne laser scanner data. However, laser scanning usually entails huge data sets even for moderate areas, making data management and analysis both complex and time consuming. For this reason, automatic terrain modelling and efficient storage structures supporting data access are needed. In this paper a number of methods supporting automatic construction of 3D digital terrain models, especially ground surface modelling and detection and measurement of individual trees will be discussed. Furthermore automatic and/or interactive terrain feature analysis will be discussed. A special data representation structure for the terrain model allowing efficient data storage and data access will be presented. Beside this, it is possible to create a symbolic information structure from the terrain model that can be used in queries for determination of different terrain features, such as ditches or ridges etc., but also for detection of changes in the terrain.

Supernovae and the Nature of the Dark Energy

Abstract: The use of Type Ia supernovae as calibrated standard candles is one of the most powerful tools to study the expansion history of the universe and thereby its energy components. While the analysis of some ~50 supernovae at redshifts around z~0.5 have provided strong evidence for an energy component with negative pressure, ``dark energy'', more data is needed to enable an accurate estimate of the amount and nature of this energy. This might be accomplished by a dedicated space telescope, the SuperNova / Acceleration Probe (2000; SNAP), which aims at collecting a large number of supernovae with z<2. In this paper we assess the ability of the SNAP mission to determine various properties of the ``dark energy.'' To exemplify, we expect SNAP, if operated for three years to study Type Ia supernovae, to be able to determine the parameters in a linear equation of state w(z)=w0 + w1 z to within a statistical uncertainty of +-0.04 for w0 and +0.15,-0.17 for w1 assuming that the universe is known to be flat and an independent high precision (sigma_{Omega_m}=0.015) measurement of the mass density Omega_m, is used to constrain the fit. An additional improvement can be obtained if a large number of low-z, as well as high-z, supernovae are included in the sample.

129I from the nuclear reprocessing facilities traced in precipitation and runoff in northern Europe.

Abstract: A huge amount of radioactive 129 I has been released into the environment from the nuclear energy industry, atomic weapon tests, and nuclear accidents. In this study, we present weekly and seasonal data on 129 I measured in precipitation and runoff of northern Europe during 1998 and 1999. The 129 I concentration is at 10 8 -10 9 atoms/L in precipitation and (2-5) x 10 8 atoms/L in runoff water, and it is 3-4 orders of magnitude higher than in the prenuclear era. Snow shows lower 129 I concentration than rain, and there is apparently a positive correlation between surface air temperature and 129 I. Precipitation chemistry, expressed as the content of Cl, SO 4 , and NO 3 and atmospheric ozone, exhibits weak negative correlation with 129 I values. Our 129 I data on precipitation suggest significant influence of the northern European atmosphere by the discharges from the nuclear reprocessing facilities at Sellafield and La Hague.

Extensive allelic variation among Francisella tularensis strains in a short-sequence tandem repeat region.

Abstract: Members of the genus Francisella and the species F. tularensis appear to be genetically very similar despite pronounced differences in virulence and geographic localization, and currently used typing methods do not allow discrimination of individual strains. Here we show that a number of short-sequence tandem repeat (SSTR) loci are present in F. tularensis genomes and that two of these loci, SSTR9 and SSTR16, are together highly discriminatory. Labeled PCR amplification products from the loci were identified by an automated DNA sequencer for size determination, and each allelic variant was sequenced. Simpson's index of diversity was 0.97 based on an analysis of 39 nonrelated F. tularensis isolates. The locus showing the highest discrimination, SSTR9, gave an index of diversity of 0.95. Thirty-two strains isolated from humans during five outbreaks of tularemia showed much less variation. For example, 11 of 12 strains isolated in the Ljusdal area, Sweden in 1995 and 1998 had identical allelic variants. Phenotypic variants of strains and extensively cultured replicates within strains did not differ, and, for example, the same allelic combination was present in 55 isolates of the live-vaccine strain of F. tularensis and another one was present in all 13 isolates of a strain passaged in animals. The analysis of short-sequence repeats of F. tularensis strains appears to be a powerful tool for discrimination of individual strains and may be useful for a detailed analysis of the epidemiology of this potent pathogen.

Soman-Induced Interleukin-1β mRNA and Protein in Rat Brain

Abstract: Exposure to high doses of the toxic organophosphate compound soman, also known as a chemical warfare agent, causes a progression of toxic symptoms including hyper-secretions, convulsions, respiratory depression, and finally death. In previous studies, we have demonstrated pronounced effects following soman intoxication in dopaminergic, GABAergic, and cholinergic systems in rat brain. The aim of this study was to investigate the effects on the pro-inflammatory cytokine interleukin-1beta (IL-1beta), indicated as mRNA and protein production, at different time intervals following soman intoxication. The peak levels of mRNA was observed 30 min following soman exposure, while a significant increase in the protein was observed at 6 h. Immunohistochemistry analysis revealed the presence of IL-1beta protein in astrocytes and endothelial cells. In addition to the previously observed effects of soman, there is an induction of IL-1beta in the brain. This effect, which is highly correlated to convulsions, implicates IL-1beta as a possible mediator for long-term brain damage observed after soman intoxication.

Vehicle size and orientation estimation using geometric fitting

Abstract: Over the years imaging laser radar systems have been developed for military and civilian applications. Among the applications we note collection of 3D data for terrain modeling and object recognition. One part of the object recognition process is to estimate the size and orientation of the object. This paper concerns a vehicle size and orientation estimation process based on scanning laser radar data. Methods for estimation of length and width of vehicles are proposed. The work is based on the assumption that from a top view most vehicles' edges are approximately of rectangular shape. Thus, we have a rectangle fitting problem. The first step in the process is sorting of data into lists containing object data and data from the ground closest to the object. Then a rectangle with minimal area is estimated based on object data only. We propose an algorithm for estimation of the minimum rectangle area containing the convex hull of the object data. From the rectangle estimate, estimates of the length and width of the object can be retrieved. The first rectangle estimate is then improved using least squares methods based on both object and ground data. Both linear and nonlinear least squares methods are described. These improved estimates of the length and width are less biased compared to the initial estimates. The methods are applied to both simulated and real laser radar data. The use of the minimum rectangle estimator to retrieve initial parameters for fitting of more complex shapes is discussed.

Construction of a reporter plasmid for screening in vivo promoter activity in Francisella tularensis.

Abstract: Francisella tularensis is a facultative intracellular bacterium that survives and multiplies inside macrophages. Here we constructed a new promoter probe plasmid denoted pKK214 by introduction of a promoter-less chloramphenicol acetyltransferase (cat) gene into the shuttle vector pKK202. A promoter library was created in F. tularensis strain LVS by cloning random chromosomal DNA fragments into pKK214. Approximately 15% of the recombinant bacteria showed chloramphenicol resistance in vitro. The promoter library was also used to infect macrophages in the presence of chloramphenicol and after two cycles of infection the library contained essentially only chloramphenicol resistance clones which shows that pKK214 can be used to monitor F. tularensis genes that are expressed during infection.

Three-dimensional laser radar modeling

Abstract: Laser radars have the unique capability to give intensity and full 3-D images of an object. Doppler lidars can give velocity and vibration characteristics of an objects. These systems have many civilian and military applications such as terrain modelling, depth sounding, object detection and classification as well as object positioning. In order to derive the signal waveform from the object one has to account for the laser pulse time characteristics, media effects such as the atmospheric attenuation and turbulence effects or scattering properties, the target shape and reflection (BRDF), speckle noise together with the receiver and background noise. Finally the type of waveform processing (peak detection, leading edge etc.) is needed to model the sensor output to be compared with observations. We have developed a computer model which models performance of a 3-D laser radar. We will give examples of signal waveforms generated from model different targets calculated by integrating the laser beam profile in space and time over the target including reflection characteristics during different speckle and turbulence conditions. The result will be of help when designing and using new laser radar systems. The importance of different type of signal processing of the waveform in order to fulfil performance goals will be shown.

Biomonitoring of continuous microbial community adaptation towards more efficient phenol-degradation in a fed-batch bioreactor

Abstract: The anaerobic degradation of phenol was studied in a fed-batch culture. Nitrate was added as electron acceptor and phenol was provided three times, to a final concentration of 200 mg/l. Randomly amplified polymorphic DNA (RAPD) and terminal fraction fragment length polymorphism (T-RFLP) were used and compared in order to monitor the microbial succession in the reactor. Phenol degradation started after an initial lag phase of 14 days and was then completed within a few days. In addition, the duration of the lag phase was shortened and the degradation rate was increased after each phenol amendment. Nitrate reduction correlated with microbial growth and phenol depletion, confirming that the degradation was carried out anaerobically. Results from the DNA analysis showed that the structure of the microbial community changed after each phenol amendment. This study confirms the potential for anaerobic degradation of environmental pollutants and also confirms that microbial acclimation towards faster degradation rates occurred upon repeated substrate amendments. Furthermore, both of the DNA-based techniques described the phenol degradation-linked community shifts with similar general results. RAPD is a faster, simpler technique that gives a higher resolution and consequently reflects the shifts in the microbial community structure better, whereas T-RFLP is more suitable for phylogenetic studies.

Quasi-static behaviour of composite joints with countersunk composite and metal fasteners

Abstract: An experimental study of the quasi-static behaviour of composite joints has been carried out. Composite plates were joined by six fasteners of three different types: composite, titanium Torque-set, and titanium Huck-comp. Specimens were quasi-statically tested to obtain results of the joint tensile and compressive strength. Strain gauge and extensometer measurements were used to investigate the static behaviour of the joints. Strain gauge measurements were carried out to analyse strain distribution and load transfer between bolt rows. Extensometer measurements were done in order to observe bolt-movement behaviour. Generally, composite joints with titanium fasteners have a higher quasi-static strength than that with composite fasteners.

Determination of vapor pressure of low-volatility compounds using a method to obtain saturated vapor with coated capillary columns.

Abstract: The vapor pressures of O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX), O-isobutyl S-2-diethylaminoethyl methylphosphonothiolate (RVX), and 2,4-dinitrotoluene (2,4-DNT) were determined with the gas saturation method in temperatures ranging from -12 to 103 degrees C The saturated vapor was generated using a fused-silica column coated with the compound This column was placed in a gas chromatograph, and the vapor pressure was determined directly from the detector signal or by sampling on Tenax tubes that were subsequently analyzed From the linear relationships obtained by plotting log P vs 1/T, the enthalpies of vaporization (deltaHvap) and the vapor pressures at selected temperatures were determined The vapor pressure of VX at 25 degrees C was 0110 Pa and the deltaHvap 779 kJ x mol(-1) The corresponding results for RVX were 0082 Pa and 766 kJ x mol(-1) The vapor pressure of 2,4-DNT at 72 degrees C (melting point) was determined to 60 Pa, and the enthalpies of the solid and the liquid state were 942 and 753 kJ x mol(-1), respectively Using capillary columns to generate saturated vapors has three major advantages: short equilibrium time, low consumption of sample, and safe handling of toxic compounds

Dempster-Shafer clustering using Potts spin mean field theory

Abstract: In this article we investigate a problem within Dempster–Shafer theory where 2 q −1 pieces of evidence are clustered into q clusters by minimizing a metaconflict function, or equivalently, by minimizing the sum of weight of conflict over all clusters. Previously one of us developed a method based on a Hopfield and Tank model. However, for very large problems we need a method with lower computational complexity. We demonstrate that the weight of conflict of evidence can, as an approximation, be linearized and mapped to an antiferromagnetic Potts spin model. This facilitates efficient numerical solution, even for large problem sizes. Optimal or nearly optimal solutions are found for Dempster–Shafer clustering benchmark tests with a time complexity of approximately O(N 2log2 N). Furthermore, an isomorphism between the antiferromagnetic Potts spin model and a graph optimization problem is shown. The graph model has dynamic variables living on the links, which have a priori probabilities that are directly related to the pairwise conflict between pieces of evidence. Hence, the relations between three different models are shown.

Synthesis, characterization and optical power limiting behaviour of phenylazo- and 4-nitrophenylazo-tetrahydroxytetrathiacalix[4]arene

Abstract: p-Tetrakis(4-nitrophenylazo)tetrahydroxytetrathiacalix[4]arene and p-tetrakis(phenylazo)tetrahydroxytetrathiacalix[4]arene were prepared and fully characterized using 1H and 13C NMR, mass spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The solid-state structure of p-tetrakis(4-nitrophenylazo)tetrahydroxytetrathiacalix[4]arene was investigated by single crystal X-ray diffraction. It crystallized in the triclinic system (space group: P). z-Scan experiments were performed on the p-tetrakis(4-nitrophenylazo)tetrahydroxytetrathiacalix[4]arene showing non linear absorption due to two photon absorption with a TPA cross-section of about 50 × 10−50 cm4 s per photon. Optical power limiting measurements on the p-tetrakis(phenylazo)tetrahydroxytetrathiacalix[4]arene at 532 nm (48% linear transmission) was found to limit the energy to ∼9 µJ.

Assessing camouflage methods using textural features

Abstract: Developments in the area of signature suppression make it progressively more difficult to recognize targets. The emphasis has been on the reduction of distinct features, like hot spots in the infrared band. Thus, to obtain a low false alarm rate, threat sensors have to utilize more information, i.e., spatial and spectral properties. The purpose of our work is to develop a general tool for camouflage assessment. The approach proposed applies texture descriptors to quantify the similarity between different parts of an image. In addition, other descriptors are used to distinguish man-made object characteristics. The selection of an appropriate set of features is discussed. The assumption is that an area containing observable targets has different statistics than other areas. Statistical properties along with detected target specific features have to be combined with methods used in data fusion. An experiment with a dataset of 44 reference images has been carried out, using a recently developed computer program called Terrtex. High correlation with perception experiments is achieved using only one or two texture features. The importance of a careful selection of background area size is finally discussed. (C) 2001 Society of Photo-optical instrumentation Engineers.

Novel passive polymer waveguides integrated with electro-optically active ferroelectric liquid crystals

Abstract: We report the preparation and characterization of novel isotropic polymer slab waveguides made by photochemical crosslinking, and their integration with a ferroelectric liquid crystal in an integra ...

Multivariate data analysis of fluorescence signals from biological aerosols

Abstract: This paper describes the use of multivariate data analysis of multiwavelength fluorescence measurements of biological aerosols collected by an air to liquid cyclone sampler. The enriched aerosol suspension was analyzed in a flow cell by a commercial spectrofluorometer at eight different wavelength combinations. The data were obtained from the disseminations of biological simulants at the 6th Joint Field Trials at Defence Research Establishment Suffield, Ralston, Alberta, Canada. The measurement concept was to use intrinsic biological fluorescence to distinguish between the different simulants as well as to distinguish them from interfering particles such as smoke and dust. Fluorescence data were analyzed using principal component analysis. © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 171–176, 2001

Syntheses and Analyses of N,N′‐Dinitrourea

Abstract: N,N H-Dinitrourea was prepared through nitration of urea at low temperature in mixed acids in 67 % yield. The prepared material was pure and found to be stable at room temperature. The properties of N,N H-dinitrourea were analysed by: TG, DSC, ignition test in Wood's metal bath, NMR, MS, FT-IR, gaspycnometry and BAM impact and friction sensitivity tests. N,N H-Dinitrourea was found to have a very high density and positive oxygene balance. It was, however, found to be sensitive both to impact and friction.

Assessing camouflage using textural features

Abstract: Developments in the area of signature suppression make it progressively more difficult to recognize targets. The emphasis has been on the reduction of distinct features, like hot spots in the infrared band. Thus, in order to obtain a low false alarm rate, threat sensors have to utilize more information, i.e. spatial and spectral properties. The purpose of our work is to develop a general tool for camouflage assessment. The approach proposed in this paper is to apply texture descriptors to quantify the similarity between different parts of an image. In addition, other descriptors are used to distinguish man-made object characteristics. The selection of an appropriate set of features is discussed. The assumption is that an area containing observable targets has different statistics than other areas. Statistical properties along with detected target specific features have to be combined with methods used in data fusion. An experiment with a data set of 44 reference images has been carried out, using a recently developed computer program called Terrtex. High correlation with perception experiments was achieved using only one or two texture features. The importance of a careful selection of background area size is finally discussed.

Microwave coupling into a generic object. Properties of measured angular receiving pattern and its significance for testing

Abstract: Results from extensive microwave coupling measurements on a generic missile are presented. Angular resolved plane wave coupling and coupling in the statistically isotropic environment of a reverberation chamber is studied. The former yields the angular and frequency resolution necessary to include the most susceptible directions and frequencies in testing. Typical differences of 10 - 15 dB between the maximum and average plane wave coupling are shown, the average being equal to isotropic coupling. This is of crucial importance for susceptibility testing, particularly concerning the relationship between the anechoic and reverberation chamber. An evaluation of a numerical simulation of the object is also presented.

Suppressed ambiguity in range by phase-coded waveforms

Abstract: In Doppler radar for surveillance and remote sensing, the ambiguities in range/Doppler are usually solved by varying the pulse repetition frequency. In this paper, two alternative methods are discussed based on phase-coding and orthogonal waveforms. The first one distributes a phase code over a pulse sequence with only one phase step per pulse. The received pulses are correlated with the phase code sequence, and by varying the delay of the phase code, the subintervals in range are scanned and reflector responses outside the focused range interval become highly suppressed. The alternative method that was studied applies a set of near-orthogonal phase codes, which modulate the pulses transmitted. In the receiver, the different subintervals in range are scanned, or detected in parallel, by correlating the signal from the scene by the delayed code sequence of the pulse transmitted. Because orthogonal codes are used, a strong suppression is achieved for signals originating outside the focused subinterval in range.

Response mechanisms of thermionic detectors with enhanced nitrogen selectivity.

Abstract: The response mechanisms of a thermionic detector with enhanced nitrogen selectivity operating in an inert gas environment were investigated. According to accepted theory, the analyte has to contain electronegative functional groups in order for negative ions to be formed by the extraction of electrons from the thermionic source. This leads to a selective detector response for compounds containing nitro groups or multiple halogens. However, in the tests described here, polycyclic aromatic nitrogen hydrocarbons (PANHs), acridines, and carbazoles were used as reference substances. These compounds contain no electronegative functional groups. None of the investigated acridines exhibited any response from the detector, but carbazoles generated a strong structure-related detector response. By examining partial charges for all hydrogens of all individual carbazoles and acridine, it was demonstrated that the acidic hydrogen atom attached to the nitrogen heteroatom of the carbazoles has a strong influence on the detector response. Ionization of carbazoles may occur by dissociation of the nitrogen-hydrogen bond during contact with the thermionic surface. Support for this theory was provided by the linear relationship between the relative detector response and the deprotonization energy of the carbazoles (coefficients of determination of 0.90 and 0.98 for linear and quadratic models, respectively, were obtained). Further, there appeared to be no linear relationship between the detector response and electron affinity of the carbazoles, (R2 value, 0.32). Thus, the mechanism involved in ionization of the carbazoles is probably not direct electron transfer from the thermionic surface to the carbazoles. Principal component analysis (PCA) showed that the thermal conductivity of chemically inert detector gases also has an influence on the detector response. The investigated gases were helium, neon, nitrogen, carbon dioxide, and argon. It was found that thermal conductivity can be used to rank the detector response for the carbazoles, and there was no discernible response when helium, which has the highest thermal conductivity, was used as the detector gas.