Showing papers by "Fraunhofer Society published in 2001"

Materials for fuel-cell technologies

Abstract: Fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel-cell technology can gain a significant share of the electrical power market, important issues have to be addressed. These issues include optimal choice of fuel, and the development of alternative materials in the fuel-cell stack. Present fuel-cell prototypes often use materials selected more than 25 years ago. Commercialization aspects, including cost and durability, have revealed inadequacies in some of these materials. Here we summarize recent progress in the search and development of innovative alternative materials.

Component-Based Product Line Engineering with UML

Abstract: Component-based development promises to revolutionize the way in which software is developed and maintained. However, contemporary component technologies, such as COM+/.NET, EJB/J2EE and CORBA, only support components in the final, implementation-oriented stages of development, leaving the earlier stages of analysis and design to be organized in largely traditional, non-component oriented ways. This book describes the KobrA method, which supports a model-driven, UML-based representation of components, and a product line approach to their development and evolution. This enables the benefits of component-based development to be realized throughout the software life-cycle, and allows the reusability of components to be significantly enhanced.

Characterization of Root Exudates at Different Growth Stages of Ten Rice (Oryza sativa L.) Cultivars

Abstract: Plant root exudates play important roles in the rhizosphere. We tested three media (nutrient solution, deionized water and CaSO4 solution) for three periods of time (2, 4 and 6 h) for collecting root exudates of soil-grown rice plants. Nutrient culture solution created complications in the analyses of exudates for total organic C (TOC) by the wet digestion method and of organic acids by HPLC due to the interference by its components. Deionized water excluded such interference in analytical analyses but affected the turgor of root cells; roots of four widely different rice cultivars excreted 20 to 60 % more TOC in deionized water than in 0.01 M CaSO4. Furthermore, the proportion of carbohydrates in TOC was also enhanced. Calcium sulfate solution maintained the osmotic environment for root cells and did not interfere in analytical procedures. Collection for 2 h avoided under-estimation of TOC and its components exuded by rice roots, which occurred during prolonged exposure. By placing plants in 0.01 M CaSO4 for 2 h, root exudates of soil-grown traditional, tall rice cultivars (Dular, B40 and Intan), high-yielding dwarf cultivars (IR72, IR52, IR64 and PSBRc 20), new plant type cultivars (IR65598 and IR65600) and a hybrid (Magat) were collected at seedling, panicle initiation, flowering and maturity and characterized for TOC and organic acids. The exudation rates were, in general, lowest at seedling stage, increased until flowering but decreased at maturity. Among organic acids, malic acid showed the highest concentration followed by tartaric, succinic, citric and lactic acids. With advancing plant growth, exudation of organic acids substituted exudation of sugars. Root and shoot biomass were positively correlated with carbon exudation suggesting that it is driven by plant biomass. As root exudates provide substrates for methanogenesis in rice fields, large variations in root exudation by cultivars and at different growth stages could greatly influence CH4 emissions. Therefore, the use of high-yielding cultivars with lowest root excretions, for example IR65598 and IR65600, would mediate low exudate-induced CH4 production. The screening of exciting rice cultivars and breeding of new cultivars with low exudation rates could offer an important option for mitigation of CH4 emission from rice agriculture to the atmosphere.

Overview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR)

Abstract: Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest) has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site, giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary. A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles was correlated with the product of the sulphuric acid production and the ammonia concentrations. No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2–10×10 7 vapour molecules cm −3 . The estimations for source rate give 7.5–11×10 4 cm −3 s −1 . These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (∼3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1–5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation DOI: 10.1034/j.1600-0889.2001.530402.x

Long‐term stability of dye‐sensitised solar cells

Abstract: Accelerated ageing tests on large numbers of nanocrystalline dye-sensitised solar cells (nc-DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye-sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd.

Implementing product line variabilities

Abstract: Software product lines have numerous members. Thus, a product line infrastructure must cover various systems. This is the significant difference to usual software systems and the reason for additional requirements on the various assets present during software product line engineering. It is imperative that they support the description of the product line as a whole, as well as its instantiation for the derivation of individual products.Literature has already addressed how to create and instantiate generic product line assets, such as domain models and architectures to generate instance specific ones [1, 2, 3], yet little attention has been given on how to actually deal with this genericity at the code level.This paper addresses the issue of handling product line variability at the code level. To this end various implementation approaches are examined with respect to their use in a product line context.

Content-based Identification of Audio Material Using MPEG-7 Low Level Description.

Abstract: Along with investigating similarity metrics between audio material, the topic of robust matching of pairs of audio content has gained wide interest recently. In particular, if this matching process is carried out using a compact representation of the audio content ("audio fingerprint"), it is possible to identify unknown audio material by means of matching it to a database with the fingerprints of registered works. This paper presents a system for reliable, fast and robust identification of audio material which can be run on the resources provided by today's standard computing platforms. The system is based on a general pattern recognition paradigm and exploits low level signal features standardized within the MPEG-7 framework, thus enabling interoperability on a world-wide scale. Compared to similar systems, particular attention is given to issues of robustness with respect to common signal distortions, i.e. recognition performance for processed/modified audio signals. The system's current performance figures are benchmarked for a range of real-world signal distortions, including low bitrate coding and transmission over an acoustic channel. A number of interesting applications are discussed.

A controlled experiment for evaluating quality guidelines on the maintainability of object-oriented designs

Abstract: The paper presents a controlled experiment, focusing on the impact of applying quality design principles such as the ones provided by P. Coad and E. Yourdon (1991) on the maintainability of object oriented designs. Results, which repeat the findings of a previous study, strongly suggest that such design principles have a beneficial effect on the maintainability of object oriented designs. It is argued that object oriented designs are sensitive to poor design practices because the cognitive complexity introduced becomes increasingly unmanageable. However, as our ability to generalize these results is limited, they should be considered as preliminary, i.e., it is very likely that they can only be generalized to programmers with little object oriented training and programming experience. Such programmers can, however, be commonly found on maintenance projects. As well as additional research, external replications of this study are required to confirm the results and achieve confidence in these findings.

High density interconnects and flexible hybrid assemblies for active biomedical implants

Abstract: Advanced microtechnologies offer new opportunities for the development of active implants that go beyond the design of pacemakers and cochlea implants. Examples of future implants include neural and muscular stimulators, implantable drug delivery systems, intracorporal monitoring devices and body fluid control systems. The active microimplants demand a high degree of device miniaturization without compromising on design flexibility and biocompatibility requirements. With the need for integrating various microcomponents for a complex retina stimulator device, we have developed a novel technique for microassembly and high-density interconnects employing flexible, ultra-thin polymer based substrates. Pads for interconnections, conductive lines, and microelectrodes were embedded into the polyimide substrate as thin films. Photolithography and sputtering has been employed to pattern the microstructures. The novel "MicroFlex interconnection (MFI)" technology was developed to achieve chip size package (CSP) dimensions without the requirement of using bumped flip chips (FC). The MFI is based on a rivet like approach that yields an electrical and mechanical contact between the pads on the flexible polyimide substrate and the bare chips or electronic components. Center to center bond pad distances smaller than 100 /spl mu/m were accomplished. The ultra thin substrates and the MFI technology was proven to be biocompatible. Electrical and mechanical tests confirmed that interconnects and assembly of bare chips are reliable and durable. Based on our experience with the retina stimulator implant, we defined design rules regarding the flexible substrate, the bond pads, and the embedded conductive tracks. It is concluded that the MFI opens new venues for a novel generation of active implants with advanced sensing, actuation, and signal processing properties.

Complement factors C3a and C5a are increased in bronchoalveolar lavage fluid after segmental allergen provocation in subjects with asthma.

Abstract: Allergic asthma is thought to be the result of an inappropriate specific immune response against common environmental antigens. However, studies of animal asthma models have also linked the innate immune system, in particular complement factors C3a and C5, to murine airway hyperresponsiveness. Because the possible role of these anaphylatoxins in patients with asthma is not understood, we tested the hypothesis that C3a and C5a will increase in the bronchoalveolar lavage (BAL) fluid of patients with asthma after segmental allergen provocation. In a group of 15 subjects with mild asthma we found a significant upregulation of C3a and C5a 24 h after allergen challenge compared with baseline values (p < 0.01). In a control group of healthy volunteers the concentrations remained basically unchanged. Furthermore, we found a strong correlation between both anaphylatoxins and the number of eosinophils (p < 0.01) and, to a lesser degree, with the number of neutrophils (p < 0.05) in BAL fluid. These data suggest a contribution of anaphylatoxins C3a and C5a to the pathogenesis in asthma. However, the pathogenic role of these substances in relation to asthma remains to be elucidated, for example, by using anaphylatoxin receptor blockers as a possible new therapeutic principle.

Replicated Case Studies for Investigating Quality Factorsin Object-Oriented Designs

Abstract: This paper aims at empirically exploring the relationships between most of the existing design coupling, cohesion, and inheritance measures for object-oriented (OO) systems, and the fault-proneness of OO system classes. The underlying goal of this study is to better understand the relationship between existing design measurement in OO systems and the quality of the software developed. in addition, we aim at assessing whether such relationships, once modeled, can be used to effectively drive and focus inspections or testing. The study described here is a replication of an analogous study conducted in a university environment with systems developed by students. In order to draw more general conclusions and to (dis)confirm the results obtained there, we now replicated the study using data collected on an industrial system developed by professionals. Results show that many of our findings are consistent across systems, despite the very disparate nature of the systems under study. Some of the strong dimensions captured by the measures in each data set are visible in both the university and industrial case study. For example, the frequency of method invocations appears to be the main driving factor of fault-proneness in all systems. However, there are also differences across studies, which illustrate the fact that, although many principles and techniques can be reused, quality does not follow universal laws and quality models must be developed locally, wherever needed.

First isolation of an isoprene synthase gene from poplar and successful expression of the gene in Escherichia coli

Abstract: For the first time, the complete functional gene for isoprene synthase has been isolated from poplar (Populus alba × Populus tremula). The gene was quite similar to known limonene and other monoterpene synthases, but was found to specifically catalyze the formation of isoprene from the precursor dimethylallyl diphosphate with only a marginal activity for the formation of the monoterpene limonene from geranyl diphosphate as compared with limonene synthases. Omitting the part of the gene that putatively encoded the signal peptide necessary for transport into the chloroplast led to an enhanced rate of isoprene formation by the recombinant protein.

A programmable intraocular CMOS pressure sensor system implant

Abstract: We present a programmable intraocular pressure sensor system implant integrated on a single CMOS chip. It contains an on-chip micromechanical pressure sensor array, a temperature sensor, readout and calibration electronics, a /spl mu/C-based digital control unit, and an RF transponder. The transponder enables wireless data transmission and wireless power reception, thus making batteryless operation feasible. The chip has been fabricated in a 1.2-/spl mu/m n-well CMOS process complemented by additional processing steps.

Using public domain metrics to estimate software development effort

Abstract: The authors investigate the accuracy of cost estimates when applying most commonly used modeling techniques to a large-scale industrial data set which is professionally maintained by the International Software Standards Benchmarking Group (ISBSG). The modeling techniques applied are ordinary least squares regression (OLS), analogy based estimation, stepwise ANOVA, CART, and robust regression. The questions addresses in the study are related to important issues. The first is the appropriate selection of a technique in a given context. The second is the assessment of the feasibility of using multi-organizational data compared to the benefits from company-specific data collection. We compare company-specific models with models based on multi-company data. This is done by using the estimates derived for one company that contributed to the ISBSG data set and estimates from using carefully matched data from the rest of the ISBSG data. When using the ISBSG data set to derive estimates for the company, generally poor results were obtained. Robust regression and OLS performed most accurately. When using the company's own data as the basis for estimation, OLS, a CART-variant, and analogy performed best. In contrast to previous studies, the estimation accuracy when using the company's data is significantly higher than when using the rest of the ISBSG data set. Thus, from these results, the company that contributed to the ISBSG data set, would be better off when using its own data for cost estimation.

The Virtual Showcase

Abstract: We introduce a new projection-based AR display system-the Virtual Showcase. The Virtual Showcase has the same form factor as a real showcase, making it compatible with traditional museum displays. Real scientific and cultural artifacts are placed inside the Virtual Showcase allowing their 3D graphical augmentation. Inside the Virtual Showcase, virtual representations and real artifacts share the same space providing new ways of merging and exploring real and virtual content. Solely virtual exhibits may also be displayed. The virtual part of the showcase can react in various ways to a visitor, which provides the possibility for intuitive interaction with the displayed content.

Chemical composition of aerosol during particle formation events in boreal forest

Abstract: Size-segregated chemical aerosol analysis of a total 5 integrated samples has been performed for the atmospheric aerosol during events of new particle formation. The experiments were conducted during the BIOFOR 3 measurement campaign at a boreal forest site in southern Finland in spring 1999. Aerosol samples collected by a cascade low-pressure impactor were taken selectively to distinguish particle formation event aerosol from non-event aerosol. The division into “event” and “non-event” cases was done “in situ” at field, based on the on-line submicron number size distribution. The results on the chemical ionic composition of the particles show only small differences between the event and non-event sample sets. The event samples show lower concentrations of total sulfate and ammonium as well as light dicarboxylic acids such as oxalate, malonate and succinate. In the event samples, nucleation mode particle MSA (methanesulphonic acid) was found to be present exceeding the concentrations found in the non-event samples, but at larger particle sizes the sample sets contained rather similar concentrations of MSA. The most significant difference between the event and non-event sets was found for dimethylammonium, ionic component of dimethylamine ((CH 3 ) 2 NH), which seems to be present in the particle phase during the particle formation periods and/or during the subsequent particle growth. The absolute event sample dimethylamine concentrations were more than 30-fold greater than the non-event concentrations in the accumulation mode size range. On the other hand, the non-event back-up filter stage for sub-30 nm particles contained more dimethylamine than the event samples. This fractionation is probably a condensation artifact of the impactor sampling. A simple mass balance estimate is performed to evaluate the quality and consistency of the results for the overall mass concentration. DOI: 10.1034/j.1600-0889.2001.530405.x

A resonantly excited 2D-micro-scanning-mirror with large deflection

Abstract: We present a novel resonantly excited 2D-micro-scanning-mirror which makes use of an electrostatic driving principle. To achieve large deflection angles, the driving electrodes are located in the chip plane. With that, small electrode gaps can be used without restricting the deflection angle geometrically. The mirror plate, with an area up to 1.5 mm×1.5 mm, is suspended by a gimbal mounting and can, therefore, be deflected along two axes. The base material for the fabrication of the device is a SOI-wafer with a top layer thickness of 30 μm. A special isolation technique which is based on open and filled isolation trenches is suitable to seperate the electrical potentials on the fixed and movable parts. In particular, the filled trenches allow to excite the two oscillations independently. The influence of the surrounding gas on the coupling of the oscillations is examined. No significant influence is observed. The investigations of the mechanical performance show that the devices have a shock resistivity of about 3.4×10 3 × g . Results of long run tests with a duration of 7×10 9 periods at a torsional angel of ±10° show that the change of the eigenfrequency is smaller than 0.01%. The performance of the novel 2D-micro-scanning-mirror is demonstrated by the generation of various Lissajous patterns by the reflected laser beam. Frequency ratios of 1:1 up to 13:1 are obtained with the presented devices.