Showing papers by "Fraunhofer Society published in 1996"

How reuse influences productivity in object-oriented systems

Abstract: Although reuse is assumed to be especially valuable in building high quality software as well as in Object Oriented (OO) development, limited empirical evidence connects reuse with productivity and quality gains. The author's eight system study begins to define such benefits in an OO framework, most notably in terms of reduce defect density and rework as well as in increased productivity.

Practical Guidelines for Measurement-based Process Improvement

Abstract: Despite significant progress in the last 15 years, implementing a successful measurement program for software development is still a challenging undertaking. Most problems are not of theoretical but of methodological or practical nature. In this article, we present lessons learned from experiences with goal-oriented measurement. We structure them into practical guidelines for efficient and useful software measurement aimed at process improvement in industry. Issues related to setting measurement goals, defining explicit measurement models, and implementing data collection procedures are addressed from a practical perspective. In addition, guidelines for using measurement in the context of process improvement are provided.

Three-dimensional cell model analyses of void growth in ductile materials

Abstract: Three-dimensional micromechanical models were developed to study the damage by void growth in ductile materials. Special emphasis is given to the influence of the spatial arrangement of the voids. Therefore, periodical void arrays of cubic primitive, body centered cubic and hexagonal structure are investigated by analyzing representative unit cells. The isotropic behaviour of the matrix material is modelled using either v. Mises plasticity or the modified Gurson-Tvergaard constitutive law. The cell models are analyzed by the large strain finite element method under monotonic loading while keeping the stress triaxiality constant. The obtained mesoscopic deformation response and the void growth of the unit cells show a high dependence on the value of triaxiality. The spatial arrangement has only a weak influence on the deformation behaviour, whereas the type and onset of the plastic collapse behaviour are strongly affected. The parameters of the Gurson-Tvergaard model can be calibrated to the cell model results even for large porosity, emphasizing its usefulness and justifying its broad applicability.

Millimeter-wave performance of chip interconnections using wire bonding and flip chip

Abstract: The performances of two different interconnection techniques for coplanar MMICs, wire bonding and flip chip, are investigated at millimeter-wave frequencies. By developing an accurate model for the interconnections, which is validated with experimental data up to 120 GHz, the limitations with respect to frequency and interconnection distance of either technique are pointed out, yielding useful data for the design of hybrid MMW-subsystems.

Transmittance of a cloud is wavelength‐dependent in the UV‐range

Abstract: Spectral irradiance measured at two stations at different altitudes (the Zugspitze-summit at 2964 m a.s.l. and the Fraunhofer-Institute for Atmospheric Environmental Research at 730 m a.s.l., 8 km apart in horizontal direction) was used to examine the spectral attenuation of the UV-irradiance by a homogeneous cloud-layer at an altitude of about 1200 m. Calculating the ratio of the global spectral irradiance beneath a homogenous cloud-cover (22 October, 1995) to the global spectral irradiance on a cloudless day (24 October, 1995) both measured at the valley station, delivered the spectral transmittance of the cloud. By means of data measured on the Zugspitze on the same two days possible differences in the atmospheric conditions above 2964 m were eliminated and thus the influence of the cloud on the UV-irradiance at Garmisch-Partenkirchen was separated. The transmittance of the cloud-layer was found to be wavelength-dependent, ranging from 45% in the UVA to 60% in the UVB. Therefore it can be assumed that clouds are not generally “grey” (i.e. that the attenuation is dependent on wavelength).

Characterization of murine lung interstitial macrophages in comparison with alveolar macrophages in vitro.

Abstract: The present study was performed to characterize the immunologic potential of interstitial macrophages (INT) in comparison with alveolar macrophages (AL). The data showed that AL, compared with INT, have a more efficient phagocytic potential. In addition, they have a strong microbicidal activity and secrete large amounts of reactive oxygen radicals, nitric oxides, TNF, and IFN on appropriate stimulation. They also exert strong tumoricidal and parasiticidal activities. In contrast, INT are more efficient in releasing immunoregulatory cytokines such as IL-1 and IL-6. As determined by Ab staining, INT express more MHC class II molecules and are more effective in functioning as accessory cells for mitogen-stimulated lymphocyte proliferation compared with AL. Thus, AL appear to be particularly effective as nonspecific first line defense cells against infectious agents, whereas INT are equipped to cooperate with interstitial lymphocytes in inducing a specific immune reaction.

Damping properties of aluminium foams

Abstract: The mechanical damping properties of aluminium foams were measured. An experimental apparatus for measuring the loss factor avoiding parasitic damping is described. The difficulties, originating from random spatial density variations, are discussed. A procedure to overcome the problems is proposed and tested. The measured loss factors show that aluminium foams have a damping capacity which is enhanced in comparison with most massive cast aluminium alloys and increases with increasing porosity level.

Very-fast transmission line pulsing of integrated structures and the charged device model

Abstract: Transmission line pulsing (TLP) is well-established for the IV-characterization of ESD-protection elements. There still is a significant gap between the performance of present TLP-systems and the demands of the Charged Device Model (CDM). A very-fast, narrow-pulse (>3.5 ns), high-current TLP (VF-TLP) is designed to reduce this gap. It is feasible to study the pulsed breakdown of gate oxides and to determine at least the quasi-static IV-characteristics of input structures. Gate oxide breakdown is monitored within the first 6 ns of stress. Correlation with nn-CDM tests is achieved in terms of the failure signature. However, the failure thresholds of VF-TLP and nn-CDM do not correlate.

Bistable microvalve with pneumatically coupled membranes

Abstract: The paper reports on a novel bistable electrostatic actuator with pneumatic coupling. Two buckled Si/SiO/sub 2/ membranes span over connected air filled cavities with enclosed driving electrodes. The membranes operate in counteraction. If one electrode is pulled down electrostatically, the other is pushed up pneumatically, and vice versa. The actuator module is designed to achieve a deflection of /spl plusmn/10 /spl mu/m and will be integrated in a microvalve for liquids. With first completed actuator modules the electrostatic/pneumatic driving principle could be demonstrated. Grey-tone lithography has been developed to fabricate curved driving electrodes on the cavity bottom. It is calculated that compared to flat electrodes the driving voltage then can be reduced up to a factor of five. The curved cavity bottom also improves the pneumatic coupling since the enclosed air volume is minimized.

Fluxes and pools of methane in wetland rice soils with varying organic inputs

Abstract: Measurements of methane emission rates and concentrations in the soil were made during four growing seasons at the International Rice Research Institute in the Philippines, on plots receiving different levels of organic input. Fluxes were measured using the automated closed chambers system (total emission) and small chambers installed between plants (water surface flux). Concentrations of methane in the soil were measured by collecting soil cores including the gas phase (soil-entrapped methane) and by sampling soil solution in situ (dissolved methane). There was much variability between seasons, but total fluxes from plots receiving high organic inputs (16-24 g CH4 m(-2)) always exceeded those from the low input plots (3-9 g CH4 m(-2)). The fraction of the total emission emerging from the surface water (presumably dominated by ebullition) was greater during the first part of the season, and greater from the high organic input plots (35-62%) than from the low input plots (15-23%). Concentrations of dissolved and entrapped methane in the low organic input plots increased gradually throughout the season; in the high input plots there was an early-season peak which was also seen in emissions. On both treatments, periods of high methane concentrations in the soil coincided with high rates of water surface flux whereas low concentrations of methane were generally associated with low flux rates.

Spillover effects and the science base of innovations reconsidered: an empirical approach

Abstract: When quantifying spillover effects among technologies and between science and technology one faces the problem that clear-cut measurement procedures are difficult to define and to validate. The well-known approach by indexing certain outputs (patent documents) grasps only parts of the complex and feedback innovation-oriented processes. However, recently, new promising lines of research for understanding technological externalities have been embarked upon. New measurements of the science-technology-innovation interface are presented from three different aspects. First, the overall properties of technological spillover and, second, of science involvement in innovations are presented on a world-wide scale. The third main section of the results provides a panoramic view of scientific involvement in technology in terms of a country comparison. The contribution attempts to add quantitative evidence for an evolutionary understanding of the externalities between public science, latent public technology and private innovation.

The application of a predictive migration model for evaluating the compliance of plastic materials with European food regulations

Abstract: A model for estimating the migration of organic substances from plastic materials into foodstuffs has been previously developed. The use of this model allows a shift away from expensive and time consuming migration analysis in foods to much simpler and more economic compositional analysis in the material. Starting with toxicologically-based specific migration values, like the over 400 specific migration limit values for organic substances listed in the European Union's Synoptic Document No. 7, the corresponding allowable maximum quantity limits of these substances in the plastic were calculated. The amount of migration that can occur depends on many different factors such as the natures of the plastic, substance and food, contact time and temperature conditions, material thickness and number of uses. These factors can result in a variety of situations which must be taken into account in the estimation of migration. The handling of the migration estimation model is demonstrated for several practical migration scenarios using a series of case studies.

Foresight in Science and Technology

Abstract: Where are science and technology heading in the decades ahead? All leading industrial nations have been looking for plausible answers to this question. Government agencies and industry - particularly in Japan and the US - have been carrying out technological studies in recent years to gather facts and arguments for their research planning. This article gives a brief introduction of some of the methodologies for foresight in science and technology used in Germany. As Germany recently has started to work in this field on federal and state level, an overview of the recent German experiences in technology foresight will be provided, focusing on two methodologies including a German Delphi inquiry which is modeled like the Japanese Delphi inquiries and the relevance tree approach. The concluding chapter briefly discusses how these government activities may be and are now effectively used for different purposes.

Damping-limited modulation bandwidths up to 40 GHz in undoped short-cavity In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers

Abstract: We demonstrate record direct modulation bandwidths from MBE-grown In/sub 035/Ga/sub 065/As-GaAs multiple-quantum-well lasers with undoped active regions and with the upper and lower cladding layers grown at different growth temperatures Short-cavity ridge waveguide lasers achieve CW direct modulation bandwidths up to 40 GHz for 6/spl times/130 /spl mu/m/sup 2/ devices at a bias current of 155 mA, which is the damping limit for this structure We further demonstrate large-signal digital modulation up to 20 Gb/s (limited by the measurement setup) and linewidth enhancement factors of 14 at the lasing wavelength at threshold of /spl sim/11 /spl mu/m for these devices

Repeatable software engineering experiments for comparing defect-detection techniques

Abstract: Techniques for detecting defects in source code are fundamental to the success of any software development approach. A software development organization therefore needs to understand the utility of techniques such as reading or testing in its own environment. Controlled experiments have proven to be an effective means for evaluating software engineering techniques and gaining the necessary understanding about their utility. This paper presents a characterization scheme for controlled experiments that evaluate defect-detection techniques. The characterization scheme permits the comparison of results from similar experiments and establishes a context for cross-experiment analysis of those results. The characterization scheme is used to structure a detailed survey of four experiments that compared reading and testing techniques for detecting defects in source code. We encourage educators, researchers, and practitioners to use the characterization scheme in order to develop and conduct further instances of this class of experiments. By repeating this experiment we expect the software engineering community will gain quantitative insights about the utility of defect-detection techniques in different environments.

A novel thick film conductive type CO2 sensor

Abstract: A low-cost CO2 sensor in thick film technology has been developed using BaTiO3 and various semiconducting oxides. The sensing principle of this new CO2 sensor is based on changes in conductance of the metal oxides in the presence of carbon dioxide. In this report, effects of preparation parameters and effects of various additives on the sensitivity of the CO2 sensor are described, and measurements of the sensor resistance as a function of CO2 concentration are presented. The sensor is applicable over a wide range of CO2 concentrations. Humidity changes have only minor effects on the sensor response.

Effects of Grain Size and Humidity on Fretting Wear in Fine-Grained Alumina, Al2O3/TiC, and Zirconia

Abstract: Friction and wear of sintered alumina with grain sizes between 0.4 and 3 {micro}m were measured in comparison with Al{sub 2}O{sub 3}/TiC composites and with tetragonal ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effect reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al{sub 2}O{sub 3}/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 {micro}m.

Voltammetric multichannel measurements using silicon fabricated microelectrode arrays

Abstract: A modular voltammetric multichannel detection system has been developed for use in flow analysis. Two different types of multichannel potentiostats, an adjustable and a ground-fixed potentiostat, are realized. Both types work with up to sixteen independent working electrodes at one chip electrode array and are controlled through a personal computer and a microcontroller. Simultaneous difference pulse and cyclic voltammetric procedures are realized. Platinum thin-film array electrodes have been arranged on silicon wafers as pairs of interdigitated microband electrodes (interdigitated array electrodes; IDA) with an interelectrode gap in the submicrometer range. Furthermore the multichannel electrodes in a flow system were used to characterize the highly sensitive flow profiles and flow rate measurements using redox mediators. A brief description of applying the multichannel device for ‘window’ stripping of heavy metals is given.

Contact stability issues in position based impedance control: theory and experiments

Abstract: The contact stability has been considered based on simplified linearized models of robot and environment. It is shown that the most crucial parameter for contact stability is the target damping ratio. When a high compliance is required the stability boundary conditions require significantly overdamped impedance behavior to ensure a stable contact with a stiff environment. These conditions for a SISO system are defined in the analytic form. Obtained minimal damping ratio values are significantly lower than those previously proposed in the literature.

Investigation of cathode spots and plasma formation of vacuum arcs by high speed microscopy and spectroscopy

Abstract: Though the vacuum arc cathode spot has been under investigation for more than a century, its structure and operation is still discussed controversially. Experimentally measured parameters and descriptions of the visible structures given by different authors far from provide a uniform picture. In the present paper, the wide range of findings, parameter values and phenomenological descriptions are explained as different semblances of a complex structured object. The random behavior of all arc spot related parameters, mostly stated as a factor complicating their accessibility, gives the key to a better understanding of its nature. It is shown that the arc spot is mainly characterized by the statistical self-similarity of its structure. Recognizing fractal structures as one of the main features of the arc spot, its comparable appearance on different spatial scales is understandable. Scale dependent values of structure dimensions and time constants are inevitable consequences of this "fractal picture".