The results of experiments on twin-roll casting of aluminum–steel clad strips are presented. For the first time this energy-saving production technology for a clad material of this metals combination was implemented. Besides the experimental equipment and processing details, the results of metallographic, electron microprobe and transmission electron microscopy analysis of the aluminum–steel interface are shown. The pack rolling and deep-drawing tests of the twin-roll cast clad strips were performed to check their applicability for a further processing using plastic deformation. In addition adhesive strength of the bond was tested. The performed analysis have shown the formation of a continuous, thin and uniform layer of intermetallic phases on the materials interface of approx. 3 μm thickness having an adhesive strength over 70 MPa. 相似文献
Air exchange between the large nests of Atta vollenweideri leaf-cutting ants and the environment strongly relies on a passive, wind-induced ventilation mechanism. Air moves through nest tunnels and airflow direction depends on the location of the tunnel openings on the nest mound. We hypothesized that ants might use the direction of airflow along nest tunnels as orientation cue in the context of climate control, as digging workers might prefer to broaden or to close tunnels with inflowing or outflowing air in order to regulate nest ventilation. To investigate anemotactic orientation in Atta vollenweideri, we first tested the ants’ ability to perceive air movements by confronting single workers with airflow stimuli in the range 0 to 20 cm/s. Workers responded to airflow velocities ≥ 2 cm/s, and the number of ants reacting to the stimulus increased with increasing airflow speed. Second, we asked whether digging workers use airflow direction as an orientation cue. Workers were exposed to either inflow or outflow of air while digging in the nest and could subsequently choose between two digging sites providing either inflow or outflow of air, respectively. Workers significantly chose the side with the same airflow direction they experienced before. When no airflow was present during initial digging, workers showed no preference for airflow directions. Workers developed preferences for airflow direction only after previous exposure to a given airflow direction. We suggest that experience-modified anemotaxis might help leaf-cutting ants spatially organize their digging activity inside the nest during tasks related to climate control. 相似文献
We analyze how the threat of a potential future regime shift affects optimal management. We use a simple general growth model to analyze four cases that involve combinations of stock collapse versus changes in system dynamics, and exogenous versus endogenous probabilities of regime shift. Prior work in economics has focused on stock collapse with endogenous probabilities and reaches ambiguous conclusions on whether the potential for regime shift will increase or decrease intensity of resource use and level of resource stock. We show that all other cases yield unambiguous results. In particular, with endogenous probability of regime shift that affects system dynamics the potential for regime shift causes optimal management to become precautionary in the sense of maintaining higher resource stock levels. 相似文献
Sea turtles migrate between feeding and nesting areas that are often geographically separated by hundreds or thousands of kilometers. Observations of their aggregations at sea and at nesting beaches have led to the hypothesis that sea turtles migrate in socially structured groups. While this migratory strategy is common to many marine vertebrates, socially facilitated behavior is not well documented in testudines. In 1990 and 1991, we attached satellite transmitters to olive ridleys (Lepidochelys olivacea Eschscholtz) found ovipositing together during a mass nesting at Nancite Beach, Costa Rica, to determine whether they migrate independently or in groups after they leave the nesting beach. Results showed that the turtles were not spatially associated during the internesting period, were capable of re-establishing themselves as a group during a subsequent nesting emergence, and were not spatially associated during their postnesting migrations to oceanic feeding areas. We suggested that what appear to be socially structured groups of L. olivacea are in fact individual turtles simultaneously using the same habitat. 相似文献
The advent of automated vehicles is already taking place and will significantly disrupt the motor insurance industry. The shift from the human driver to the system as the driver cannot be reflected in the current insurance risk assessment. This call for an amendment of the insurance underwriting was discussed with German experts from both the primary insurance and reinsurance sector with their professional background on motor insurance. Based on the findings, we propose an alternative method to underwrite automated vehicles of level 4 & 5 using an enhanced telematics approach which considers new risk categories such as systems used and the transformed role of the driver as the general user of the automated vehicle.
Although numerous bodies were deposited in Western European bogs in the past centuries, few were found and underwent archeological
analysis. No studies comparing skeletal structure and mineralization of bog bodies from different ages have been performed
to this day. Therefore, the aim of this study was to analyze and compare skeletal features and specifics of the human remains
of three bog bodies from the Iron and Middle Ages found in Northern European peat bogs. Demineralization due to the acidic
environment in peat bogs was comparably pronounced in all three bodies. Still, the macroscopic state of skeletal preservation
was excellent. In addition to contact radiography, we used peripheral quantitative computed tomography to measure cortical
bone mineral density. The conservation of skeletal three-dimensional microstructural elements was assessed by high-resolution
microcomputed tomography analysis. These techniques revealed severe differences in bone mineral density and enabled us to
determine handedness in all three bodies. Additionally, unique skeletal features like intravital bone lesions, immobilization
osteoporosis, and Harris lines were found. A deformity of the left femoral head was observed which had the typical appearance
of an advanced stage of Legg–Calve–Perthes disease. This study gives detailed insight into the skeletal microstructure and
microarchitecture of 800- to 2,700-year-old bog bodies. Skeletal analysis enables us to draw conclusions not only concerning
changes in the acidic environment of the bog, but also serves as a diagnostic tool to unravel life circumstances and diseases
suffered by humans in the Iron and Middle Ages. 相似文献
Extensive degradation of Indonesian peatlands by deforestation, drainage and recurrent fires causes release of huge amounts
of peat soil carbon to the atmosphere. Construction of drainage canals is associated with conversion to other land uses, especially
plantations of oil palm and pulpwood trees, and with widespread illegal logging to facilitate timber transport. A lowering
of the groundwater level leads to an increase in oxidation and subsidence of peat. Therefore, the groundwater level is the
main control on carbon dioxide emissions from peatlands. Restoring the peatland hydrology is the only way to prevent peat
oxidation and mitigate CO2 emissions. In this study we present a strategy for improved planning of rewetting measures by dam constructions. The study
area is a vast peatland with limited accessibility in Central Kalimantan, Indonesia. Field inventory and remote sensing data
are used to generate a detailed 3D model of the peat dome and a hydrological model predicts the rise in groundwater levels
once dams have been constructed. Successful rewetting of a 590 km2 large area of drained peat swamp forest could result in
mitigated emissions of 1.4–1.6 Mt CO2 yearly. This equates to 6% of the carbon dioxide emissions by civil aviation in the European Union in 2006 and can be achieved
with relatively small efforts and at low costs. The proposed methodology allows a detailed planning of hydrological restoration
of peatlands with interesting impacts on carbon trading for the voluntary carbon market. 相似文献
What kinds of PV project configurations do lenders prefer to finance? Recent developments in the field of renewable energy project finance have reinforced the need for investigation, as fundraising has become more challenging and project evaluation by banks more demanding. To contribute to the limited research in this field, we focus on photovoltaic projects and report from an Adaptive Choice-Based Conjoint experiment with German experts in project finance. We find a bias which we call “debt for brands”. Simulations reveal that debt investors prefer projects with premium brand technology (modules, inverters) to low-cost technology. Although we assumed that lenders prefer projects with the highest Debt Service Cover Ratio (DSCR), they favor projects with lower DSCR, as long as those projects include premium brand technology. We find that, if premium brands were engaged, lenders would also choose projects with higher risk. Our findings have implications for renewable energy project finance in practice and research. 相似文献