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Showing papers by "Fraunhofer Society published in 1995"


Journal ArticleDOI
TL;DR: A novel method for efficient image analysis that uses tuned matched Gabor filters that requires no a priori knowledge of the analyzed image so that the analysis is unsupervised.
Abstract: Recent studies have confirmed that the multichannel Gabor decomposition represents an excellent tool for image segmentation and boundary detection. Unfortunately, this approach when used for unsupervised image analysis tasks imposes excessive storage requirements due to the nonorthogonality of the basis functions and is computationally highly demanding. In this correspondence, we propose a novel method for efficient image analysis that uses tuned matched Gabor filters. The algorithmic determination of the parameters of the Gabor filters is based on the analysis of spectral feature contrasts obtained from iterative computation of pyramidal Gabor transforms with progressive dyadic decrease of elementary cell sizes. The method requires no a priori knowledge of the analyzed image so that the analysis is unsupervised. Computer simulations applied to different classes of textures illustrate the matching property of the tuned Gabor filters derived using our determination algorithm. Also, their capability to extract significant image information and thus enable an easy and efficient low-level image analysis will be demonstrated. >

206 citations


Journal ArticleDOI
TL;DR: In this paper, a wide range of pore and crystallite sizes can be formed easily due to the doping sensitivity of the porous silicon formation and the high surface-to-volume ratio.

183 citations


Journal ArticleDOI
TL;DR: In this article, a high performance forced air cooing scheme is theoretically and experimentally investigated which employs microchannel parallel plate-fin heat sinks and tubes to deliver the air to and optionally from the heat sink.
Abstract: In this paper, a high performance forced air cooing scheme is theoretically and experimentally investigated which employs microchannel parallel plate-fin heat sinks and tubes to deliver the air to and optionally from the heat sink. The performance of the cooling system is modeled in terms of thermal resistance, pressure drop, and pumping power. Optimizations are performed and design trade-offs discussed. Tubes are observed to have a significant impact on optimum heat sink design as well as operating point. Sample heat sinks with lateral dimensions of 5/spl times/5 cm/sup 2/ and fin lengths of 1.5 and 2.5 cm were fabricated from copper and aluminum foils using a simple assembly process. Fin thicknesses and channel widths of the heat sinks are on the order of 200 and 500 /spl mu/m, respectively. Thermal resistances as low as 0.2 R/W are measured. Results of the present study are compared to prior works dealing with direct air cooling. The thermal performances achievable using the investigated cooling approach are superior to those attainable using open air cooled heat sinks as well as those employing silicon microcoolers.

176 citations


Journal ArticleDOI
Maurus Tacke1
TL;DR: In this paper, the authors describe new developments driven by this use as well as potential new applications that in part do not depend on high spectral resolution, such as high-resolution spectroscopy with gas analysis.

161 citations


Journal ArticleDOI
TL;DR: In this article, the authors used an 85 μm polyacrylate fiber to extract 34 compounds from aqueous samples by SPME using a gas chromatograph and a nitrogen-phosphorus detector.
Abstract: Solid-phase microextraction (SPME) represents a very simple and rapid method for the extraction of organophosphorus, triazine and 2,6-dinitroaniline pesticides from aqueous samples without making use of any solvents. The same fiber can be used repeatedly. Moreover, a sample volume as small as 3 mL can be employed with no loss in sensitivity. 34 compounds have been extracted from aqueous samples by SPME using a 85 μm polyacrylate fiber. For organophosphorus pesticides, a 100 μm polydimethylsiloxane fiber has been used additionally for comparison. The fibers were directly introduced into the heated split/splitless injector of the gas chromatograph and determined using a nitrogen-phosphorus detector. The method was evaluated with respect to the limit of detection (LOD), linearity and precision. The limit of detection (LOD) depends on the compound and varies from 0.005–0.09 μg/L. The method is linear over at least three orders of magnitude with coefficients of correlation usually >0.999. For triazines and 2,6-dinitroanilines the coefficient of variation (precision) is <8% while for organophosphorus compounds it may reach values up to 18% (however, if the latter compounds are extracted using the polydimethylsiloxane phase considerably higher precision is achieved). The partitioning of the analyte between the aqueous phase and the polymeric phase depends on the hydrophobicity of the compound as expressed by the octanol/water partitioning coefficient (Pow). For triazines it was shown that there is a linear dependence of the logarithm of the analyte response on the log(Pow) i.e. the higher the hydrophobicity, the higher the affinity of the analytes to the polymeric phase of the fiber and the higher the response. Salt addition has a strong effect on the extraction efficiency. This effect increases with decreasing hydrophobicity (increasing polarity) of the compound. The triazines ametryn, atrazine, propazine, simazine and simetryn have been identified in a ground water well sample by SPMEGC/NPD.

141 citations


Journal ArticleDOI
TL;DR: At a target limit of detection below 100 ng/L, SPME-GC/MS represents a very simple, fast, selective, and solvent-free multimethod for the extraction and determination of these nitrogen- and phosphorous-containing pesticides from aqueous samples.

120 citations


Proceedings ArticleDOI
25 Sep 1995
TL;DR: In this contribution optical flow vectors are estimated from spatio-temporal derivatives of the gray value function which are computed at video frame rate by the custom-designed hardware MiniVISTA to eliminate outliers and to speed up obstacle detection by data reduction.
Abstract: Optical flow contains information about the motion of a camera relative to its environment and about the three-dimensional structure of the imaged scene. In this contribution we use that information to detect obstacles in front of a moving vehicle. Since the detection is based on motion no a-priori knowledge about obstacle shape is required. Optical flow vectors are estimated from spatio-temporal derivatives of the gray value function which are computed at video frame rate by the custom-designed hardware MiniVISTA. To eliminate outliers and to speed up obstacle detection by data reduction the estimated vectors are clustered before they are passed to the obstacle test. The purpose of the obstacle test is to separate moving objects from the stationary environment and to separate elevated objects from the ground plane. In continuation of our previous work, obstacle detection is regarded as a state estimation problem. This enables us to enlarge the motion stereo basis by applying a Kalman filter to track optical flow vectors over subsequent image frames. Experimental results obtained from image sequences recorded with our experimental vehicle are presented.

116 citations


Journal ArticleDOI
TL;DR: The present aproach attempts some news approaches to the presentation of bibliometric macro-level indicators as well as some new ideas on how to improve the quality of these indicators.
Abstract: The present aproach attempts some news approaches to the presentation of bibliometric macro-level indicators

113 citations


Journal ArticleDOI
TL;DR: This work aims to develop techniques for 3D reconstruction of parts during routine examinations to improve the quality of the reconstruction, reduce the required manual input, and increase the computational speed as well as availability for a wide range of standard platforms in order to provide a system that is usable under clinical conditions.
Abstract: The "noisy and blurry" nature of biomedical ultrasonic data makes the rendering of 3D models difficult. The volume rendering system described in this article generates high-quality images in seconds on desktop systems. Our work aims to develop techniques for 3D reconstruction of parts during routine examinations. We intend to improve the quality of the reconstruction, reduce the required manual input, and increase the computational speed as well as availability for a wide range of standard platforms in order to provide a system that is usable under clinical conditions. This case study focuses particularly on off-line filtering and semiautomatic segmentation methods. >

110 citations


Proceedings ArticleDOI
15 Sep 1995
TL;DR: An improved surface-extraction volume rendering procedure is introduced, applied on the original data within the ROI areas for visualizing high quality images within a few seconds on a normal workstation, or even on a PC, thus making the complete system suitable for routine clinical applications.
Abstract: Rendering 3D models from 3D-ultrasonic data is a complicated task due to the noisy, fuzzy nature of ultrasound imaging containing a lot of artifacts, speckle etc. In the method presented in this paper we first apply several filtering techniques (low-pass, mathematical morphology, multi-resolution analysis) to separate the areas of low coherency containing mostly noise and speckle from those of useful information. Our novel BLTP filtering can be applied at interactive times on-the-fly under user control & feed-back. Goal of this processing is to create a ’region-of-interest’ (ROI) mask, whereas the data itself remains unaltered. Secondly,we examine several alternatives to the original Levoy contouring method. Finally we introduce an improved surface-extraction volume rendering procedure, applied on the original data within the ROI areas for visualizing high quality images within a few seconds on a normal workstation, or even on a PC, thus making the complete system suitable for routine clinical applications. CR Descriptors: General Terms: Algorithms. I.3.3 [Computer Graphics]: Picture/image generation; I.3.8 [Computer Graphics]: Applications; I.4.3 [Image Processing]: Enhancement, Smoothing, Filtering; I.4.6 [Image Processing]: Segmentation, Edge and Feature Detection, Pixel Classification; J.3 [Life and Medical Sciences]. Additional

102 citations


Journal ArticleDOI
TL;DR: In this paper, the lateral supramolecular order of a variety of native and man-made cellulosics was investigated using wide-angle X-ray scattering (WAXS) techniques.
Abstract: This paper gives an overview of our recent research activities on the lateral supramolecular order of a variety of native and man-made cellulosics considering respective results from the literature. Wide-angle X-ray scattering (WAXS) was the main investigation technique used. Lateral root mean squared lattice strains between 2 and 3% were determined for the materials investigated. Crystallite sizes obtained without considering lattice distortions usually do not deviate by much more than −10% from the real, i.e. fully corrected values. This means that it is sufficient to use the simple Scherrer equation for determining lateral crystallite sizes for most routine investigations of cellulosic materials. The possible superposition of WAXS peaks of the triclinic Iα and monoclinic Iβ lattice types, however, has to be considered in crystallite size determinations for Valonia cellulose. It could be shown that neglecting this fact can lead to crystallite sizes being about 20% below the true ones. Lateral crystallite dimaensions for native celluloses vary between 4nm (dissolving pulps) and 10-15 nm (Valonia). Except for bacterial cellulose, the WAXS crystallite sizes are distinctly smaller than the microfibril dimensions obtained from electron microscopy. The man-made fibres investigated showed lateral crystallite dimensions between 3 and 5nm. The importance of lateral crystallite dimensions for the properties of man-made fibres and for the alkalization process of native cellulose id demonstrated.

Journal ArticleDOI
TL;DR: In this article, a home-built free programmable multipotentiostat was used to measure the signal amplification of reversible redox molecules using an IDA microelectrodes with width and space between 1 and 2 μm and between 300 nm and 1 μm, respectively.

Journal ArticleDOI
Bernhard Wagner1, Hans Joachim Quenzer1, W. Henke1, W. Hoppe, W. Pilz1 
TL;DR: In this paper, a study of a methodology for fabrication of relief shaped microstructures using technologies common to standard IC manufacturing processes is presented, with particular emphasis on the design and use of halftone transmission masks for the lithography step required in the fabrication process of mechanical, optical or electronic components.
Abstract: This paper reports on a study of a methodology for fabrication of relief shaped microstructures using technologies common to standard IC manufacturing processes. Particular emphasis is put on the design and use of halftone transmission masks for the lithography step required in the fabrication process of mechanical, optical or electronic components. The design and experimental investigation of grey-tone masks is supported by lithography simulation. Results are presented for both, simulated grey-tone patterns as well as experimental profiles.

Journal ArticleDOI
TL;DR: In this article, the authors describe the result of the interdisciplinary cooperation of traumatologists of the Berufsgenossenschaftliche Unfallklinik (BGU) in Frankfurt am Main and a team of computer graphics scientists of the Fraunhofer Institute for Computer Graphics in Darmstadt.

Proceedings ArticleDOI
25 Jun 1995
TL;DR: In this article, a monolithic potentiostat for chemical and biochemical sensors is presented, which allows measurements that use two or three clectrode configurations in amperometric and voltammetric mode.
Abstract: A monolithic potentiostat for chemical and biochemical sensors is presented. It allows measurements that use two- or three-clectrode-configurations in amperometric and voltammetric mode. The amplification part converts the electrode current with an input range from +/-0.1 InA up to +/-0.5/splmu/A. The microchip is fabricated in a 1/spl mu/m/5V Low Power Silicon-Gate CMOS process. The small chip size allows the assembly of the potentiostat together with monolithic microelectrodes on the same substrate. This way the distortion of the electrode signal is minimized, and the resulting rnicrosystem can be used as a low cost mass product for selective analysis, e.g. in very narrow passages.

Journal ArticleDOI
TL;DR: In this article, a review is presented of the activity of our research group in the area of mid-infrared (MIR) fiber-optical chemical sensing systems based on the new generation of infrared-transparent fiber materials such as chalcogenide (AsSeTe) and silver halide (AgBrAgCl).
Abstract: A review is presented of the activity of our research group in the area of mid-infrared (MIR) fiber-optical chemical sensing systems based on the new generation of infrared-transparent fiber materials such as chalcogenide (AsSeTe) and silver halide (AgBrAgCl). The availability of these fiber materials extends the optical window utilizable for chemical-sensor systems significantly into the MIR range (2–20 μm). The increasing number of publications on this topic during recent years attests to the modified IR-transparent fibers as chemical IR sensors for the on-line analysis of IR-active compounds in aqueous solutions (chlorinated hydrocarbons, glucose) and in the gas phase (chlorofluorohydrocarbons) as developed in our laboratory.

Journal ArticleDOI
TL;DR: In this paper, a five-pulse sequence for two-dimensional exchange 2H NMR is presented, together with the phase cycle necessary to eliminate unwanted signal contributions, and the scheme of the three-dimensional Fourier transformation to yield pure-absorption-mode three dimensional NMR spectra is presented.

Journal ArticleDOI
TL;DR: In this paper, an absolute interferometrical distance measurement technique using a tunable semiconductor laser which, by virtue of its external cavity, has extremely small linewidth and, therefore, considerable coherence length, is discussed.

Journal ArticleDOI
TL;DR: In this paper, the evolution, spread and decay of the aerosol cloud had formed in the stratosphere after the explosive eruption of the Philippine volcano Pinatubo in mid-June 1991.
Abstract: Three lidar systems at the northern hemisphere sites of Naha and Tsukuba, both in Japan, and Garmisch-Partenkirchen, Germany, have been observing the evolution, spread and decay of the aerosol cloud which had formed in the stratosphere after the explosive eruption of the Philippine volcano Pinatubo in mid-June 1991. Three years of lidar measurements show the depletion of the initial equatorial aerosol reservoir and the subsequent transport to the north. These lidar data are the basis for the calculation of the climatically relevant parameters aerosol optical depth, mass and surface area.

Journal ArticleDOI
TL;DR: The present paper attempts some new approaches to the presentation of bibliometric macro-level indicators by aiming at a compromise between the two extremes.
Abstract: The present paper attempts some new approaches to the presentation of bibliometric macro-level indicators. Whilst in former suties national indicators on the 5 major science fields, life science, physis, chemistry, engineering and mathematics and /or 128 subfieds, this study aims at a compromise between the two extremes. In that order the subfields have been grouped into 27 broader science areas

Journal Article
TL;DR: Exposure of AL to RSV appeared to stimulate their immunoregulatory functions, whereas the microbicidal activity of these cells seemed to be severely diminished.
Abstract: Alveolar macrophages (AL) are the first line of defense against inhaled pathogens and are exposed to virus during the course of a respiratory syncytial virus (RSV) infection. Interference of virus with alveolar macrophage functions may contribute to the risk of acquiring secondary bacterial infections during or after respiratory tract infections with RSV or other viral agents. We studied whether murine AL get infected with RSV and whether they support viral replication in vitro. In addition, the effects of RSV on microbicidal and on immunoregulatory functions were examined. Only a subpopulation of AL expressed viral F proteins after exposure of these cells to RSV. Infected AL released only small amounts of infectious virus into the supernatant. The extent of virus replication in AL seemed to be dependent in part on the amount of IFN induced by the virus, as has been demonstrated by infection of lung tissue macrophages and AL in vitro. In general, RSV infection of pulmonary macrophages appeared to be abortive. Nevertheless, release of reactive oxygen intermediates, phagocytosis, and killing of protozoa were reduced in RSV-infected AL in comparison to noninfected AL. In contrast, RSV stimulated secretion of TNF-alpha, IL-1, and IL-6 in an infectious-dose dependent manner. Along with the increased cytokine release, accessory functions of AL were increased after RSV exposure. Thus, exposure of AL to RSV appeared to stimulate their immunoregulatory functions, whereas the microbicidal activity of these cells seemed to be severely diminished.

Journal ArticleDOI
TL;DR: In this paper, the fluxes in the turbulent region of the atmospheric surface layer are parameterized by first-order closure principles, and the uptake processes by vegetation and the soil are described by a Deardorfl=type soil-vegetation-atmosphere transfer scheme.

Journal ArticleDOI
TL;DR: In this paper, the Fraunhofer Institute for Applied Materials Research (IFAM) developed a new process, named "multiphase jet solidification" (MJS), which is able to produce metallic or ceramic parts.
Abstract: Rapid prototyping (RP) systems were designed to reduce the time taken to develop new products, and, today, available RP systems work with different techniques using paper, polymers and waxes. In order to fulfil the demand for the direct production of metallic prototypes for functional application and testing, the Fraunhofer Institute for Applied Materials Research (IFAM) has developed a new process, named “multiphase jet solidification (MJS)”, which is able to produce metallic or ceramic parts. The MJS process uses low‐melting alloys or a powder‐binder mixture which is squeezed out through a computer‐controlled nozzle. Parts are manufactured layer by layer and the “green parts” are debinded and sintered to reach final density. Presents experiences of using this new technique, along with some results.

Journal ArticleDOI
01 Apr 1995
TL;DR: The issues behind a integrated authoring environment are examined, a prototype for information access, telecooperation and distributed authoring in a wide area network is introduced, and the ability to create and share annotations is introduced.
Abstract: Human cooperation and interaction is highly dependent on efficient means for communication. While the World-Wide Web provides powerful tools for information retrieval, it still lacks support for document authoring. Distributed authoring of documents requires not only the possibility to jointly view and edit a document, but also the ability to create and share annotations. This article examines the issues behind a integrated authoring environment, and introduces a prototype for information access, telecooperation and distributed authoring in a wide area network.

Book ChapterDOI
TL;DR: In this paper, the capabilities of the GURSON model in predicting J R -curves for different specimen geometries under static and dynamic loading with one set of material parameters.
Abstract: Compared with conventional fracture mechanics concepts, constitutive equations which account for local damage of the material have the advantage that the corresponding material parameters for ductile fracture can be transferred between different specimen geometries. They will hence be able to describe the physical effect of constraint on the tearing resistance in a natural way. The paper shows the capabilities of the GURSON model in predicting J R -curves for different specimen geometries under static and dynamic loading with one set of material parameters. It is shown how these parameters can be determined from the numerical simulation of simple tensile tests. Problems and open questions are discussed and perspectives for future applications are given.

Book ChapterDOI
12 Jun 1995
TL;DR: An improved version of the MIP algorithm that requires roughly 2%–10% of the computational effort of the brute-force, straight-forward version and conserves the image quality and requires no pre-processing is presented.
Abstract: We present an improved version of the MIP algorithm that requires roughly 2%–10% of the computational effort of the brute-force, straight-forward version. The algorithm conserves the image quality and requires no pre-processing. We propose four different quality levels: a fast line-traversing nearest neighbour algorithm for previewing, two efficient approximation algorithms that are sufficient for most applications, and an analytical method for images of highest quality. Additionally we present an improved cache memory access scheme. The employed ’sub-cube’ volume data representation provides an additional speed up of at least 50% compared to the classical linear memory access. This is of particular interest for (but not restricted to) parallel volume rendering on shared memory multiprocessor systems.

Journal ArticleDOI
TL;DR: Aerosol size distributions derived from balloon-borne particle counter data from Laramie, WY, were used to calculate ratios of extinction, mass, and surface area to lidar backscatter at the widely used lidar wavelength of 532 nm as mentioned in this paper.
Abstract: Aerosol size distributions derived from balloon-borne particle counter data from Laramie, WY, are used to calculate ratios of extinction, mass, and surface area to lidar backscatter at the widely used lidar wavelength of 532 nm. The results cover the range of the stratospheric aerosol layer from the tropopause to 30 km. These ratios may be used to infer particle extinction, mass, and surface area from midlatitude lidar backscatter data for the period late 1979 to 1993. This period includes the major volcanic eruptions of El Chichon and Pinatubo. The wavelength dependence of aerosol backscatter in the visible was calculated for the period 1991 to 1993 to allow conversions of the results to other lidar wavelengths. The wavelength dependence is similar to estimates from southern hemisphere midlatitude measurements indicating that these conversions may also be applied to southern hemisphere midlatitude lidar measurements.

Proceedings ArticleDOI
16 May 1995
TL;DR: In this article, the difference between flip chip and wire bond technology is demonstrated, and the influence of a metallic lid on a coplanar waveguide structure is examined, where the flip chip version has a lower insertion loss of the flip-chip interconnections and the higher flexibility of mounting the MMICs directly on the back structure of the planar patch antenna, leading to reduced losses of the feedline.
Abstract: In this paper the difference between flip chip and wire bond technology is demonstrated. Test assemblies with coplanar waveguides have been attached in flip chip and wire bond technology and measured up to 75 GHz. Further, the influence of a metallic lid on a coplanar waveguide structure is examined. To compare flip chip and wire bond interconnections, 51 GHz frontends with GaAs devices in coplanar waveguide technology have been realized. In one frontend the low noise amplifier (LNA) is connected to a planar patch antenna by wire bonding and in a second one by flip chip attachment. RF evaluations show the clear advantage of the flip chip version due to the lower insertion loss of the flip chip interconnections and the higher flexibility of mounting the MMICs directly on the back structure of the planar patch antenna, leading to reduced losses of the feedline. >

Journal ArticleDOI
TL;DR: The RSPFC as mentioned in this paper is a battery-like hydrogen/oxygen system which offers the possibility of splitting water by electrolysis, storing the gases hydrogen and oxygen and regenerating electricity by the fuel cell process.

Journal ArticleDOI
H. Shen1, H. Shen2, Z. Li2, B. Günther1, A.V. Korznikov, R.Z. Valiev 
TL;DR: In this article, composites of Ag-Cu powder compacts of identical composition have been prepared by three different methods: a) compaction of AgCu alloy nanopowder prepared by inert gas condensation of a prealloy (IGC), b) mechanical alloying (MA) of elemental Ag+Cu powder, c) severe plastic deformation (SPD) of a course grained ingot material as well as of a compact of IGC and MA powder.