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121.
Xin Wang Parick Y. Kwon Caleb Sturtevant Dave Kim Jeff Lantrip 《Journal of Manufacturing Processes》2013,15(1):127-135
This study aimed to investigate the wear of certain coated drills when drilling carbon fiber reinforced composites (CFRP). Three different drills were used in the drilling experiments: uncoated, diamond coated and AlTiN coated carbide (WC–Co) drills. The tool wear in CFRP machining was quite different from that in conventional metal machining. The primary wear type was a dulling or blunting of the cutting edge, which has been referred to as edge rounding wear or edge recession. In this paper, a hypothesis has been developed to explain the edge rounding wear in CFRP machining. Due to the fracture-based chip formation of CFRP, there is lack of the work material stagnation zone in front of the cutting edge, which normally prevents the edge wear in metal machining. Series of wear lead to rapid dulling of the cutting edge. The resistance to edge rounding wear on the coated as well as uncoated drills has been investigated. The diamond coating significantly reduces the edge rounding wear. However, AlTiN coated drills showed no visible improvement over the uncoated carbide drill, despite of their high hardness, thus not protecting the drill. The wear mechanisms of the uncoated carbide drill and coatings are discussed. It is believed that the 2-body and 3-body abrasive wear fail to explain the observed tool wear in CFRP drilling. However, the wear of the coatings and uncoated carbide substrate from tribo-meter tests correlated well with the tool wear in the CFRP drilling. Therefore, the tribo-meter test can be used to screen the prospective tool materials before carrying drilling experiment. 相似文献
122.
Antonella?De?DonnoEmail author Tiziana?Grassi Francesco?Bagordo Adele?Idolo Francesca?Serio Giovanni?Gabutti 《Food and environmental virology》2012,4(2):81-88
The purpose of this study was to demonstrate that shellfish can be used to detect enteric viruses in marine waters where they
are present at very low concentrations. Aqua-cultured mussels were placed in the sea just off the mouth of a drainage channel
affected by human and animal faecal contamination. Samples were taken from the channel, the sea and the mussels at intervals
over two 4-week periods. The samples were tested to verify the presence of both rotaviruses and E. coli. Rotaviruses were detected by Real Time-PCR, typed by multiplex PCR and subsequently sequenced. E. coli was enumerated in water matrices by a filtering method and in mussels by the MPN method. The presence of E. coli in the examined matrices demonstrates contamination of faecal origin throughout the studied environments. Rotaviruses were
recorded in channel waters, but not in sea water. In both experiments, rotaviruses were detected in mussels 21 and 28 days
after being placed in the sea water off the channel mouth. The use of mussels thus enabled the detection of rotaviruses in
waters where the high dilution rendered direct investigation impossible. This study indicates that mussels can be used in
marine virological surveillance programs. 相似文献
123.
Building regional priorities in forests for development and adaptation to climate change in the Congo Basin 总被引:1,自引:0,他引:1
Denis J. Sonwa Johnson N. Nkem Monica E. Idinoba Mekou Y. Bele Cyprain Jum 《Mitigation and Adaptation Strategies for Global Change》2012,17(4):441-450
Indentifying common priorities in shared natural resource systems constitutes an important platform for implementing adaptation
and a major step in sharing a common responsibility in addressing climate change. Predominated by discourses on REDD + (Reduced
Emissions from Deforestation and Forest Degradation and conservation, sustainable management of forests and enhancement of
forest carbon stocks in developing countries) with little emphasis on adaptation there is a risk of lack of policy measures
in addressing climate change in the Congo Basin. Forest products and ecosystem services provide security portfolios for the
predominantly rural communities, and play major roles in national development programmes in both revenue and employment opportunities.
Thus, raising the profile of forests in the policy arena especially in the twin roles of addressing climate change in mitigation
and adaptation and achieving resilient development is crucial. Within the framework of the Congo Basin Forests and Climate
Change Adaptation project (COFCCA) project, science policy dialogue was conducted to identify and prioritize forest based
sectors vulnerable to climate change but important to household livelihoods and national development. The goal of the prioritization
process was for the development of intervention in forest as measures for climate change adaptation in Central Africa. Participants
constituted a wide range of stakeholders (government, Non Governmental Organizations, research institutions, universities,
community leaders, private sectors etc.) as representatives from three countries directly involved in the project: Cameroon,
Central African Republic and Democratic Republic of Congo. Building on national priorities, four forest related sectors were
identified as common priorities at the regional level for focus on climate change adaptation. These sectors included: (1)
energy with emphasis on fuel wood and Charcoal; (2) Water principally quality, quantity, accessibility, etc.; (3) Food with emphasis on Non Timber Forest Products, and (4) Health linked to healthcare products (medicinal plants). Using these prioritized sectors, the project focused on addressing the impacts of climate change on local communities and the development of adaptation strategies in the three pilot countries
of the Congo Basin region. The four sectors constitute the key for development in the region and equally considered as priority sectors in the poverty
reduction papers. Focused research on these sectors can help to inject the role of forests in national and local development
and their potentials contributions to climate change adaptation in national and public discourses. Mainstreaming forest for
climate change adaptation into national development planning is the key to improve policy coherence and effectiveness in forest
management in the region. 相似文献
124.
Simon?BrinerEmail author Michael?Hartmann Robert?Finger Bernard?Lehmann 《Mitigation and Adaptation Strategies for Global Change》2012,17(4):337-355
We assessed the economic suitability of 4 greenhouse gas (GHG) mitigation options and one GHG offset option for an improvement
of the GHG balance of a representative Swiss suckler cow farm housing 35 Livestock units and cultivating 25 ha grassland.
GHG emissions per kilogram meat in the economic optimum differ between the production systems and range from 18 to 21.9 kg
CO2-eq./kg meat. Only GHG offset by agroforestry systems showed the potential to significantly reduce these emissions. Depending
on the production system agroforestry systems could reduce net GHG emissions by 66% to 7.3 kg CO2-eq./kg meat in the most intensive system and by 100% in the most extensive system. In this calculation a carbon sequestration
rate of 8 t CO2/ha/year was assumed. The potential of a combination of the addition of lipids to the diet, a cover of the slurry tank and
the application of nitrification inhibitors only had the potential to reduce GHG emissions by 12% thereby marginal abatement
costs are increasing much faster than for agroforestry systems. A reduction of the GHG emissions to 7.5 kg CO2-eq./kg meat—possible with agroforestry only—raised costs between 0.03 CHF/kg meat and 0.38 CHF/kg meat depending on the production
system and the state of the system before the reduction. If GHG emissions were reduced maximally average costs ranged between
0.37 CHF/kg meat, if agroforestry had the potential to reduce net GHG emissions to 0 kg CO2-eq., to 1.17 CHF/kg meat if also other options had to be applied. 相似文献
125.
Population dynamics and regulation in the cave salamander <Emphasis Type="Italic">Speleomantes strinatii</Emphasis> 总被引:1,自引:0,他引:1
Salvidio S 《Die Naturwissenschaften》2007,94(5):396-400
Time series analysis has been used to evaluate the mechanisms regulating population dynamics of mammals and insects, but has
been rarely applied to amphibian populations. In this study, the influence of endogenous (density-dependent) and exogenous
(density-independent) factors regulating population dynamics of the terrestrial plethodontid salamander Speleomantes strinatii was analysed by means of time series and multiple regression analyses. During the period 1993–2005, S. strinatii population abundance, estimated by a standardised temporary removal method, displayed relatively low fluctuations, and the
autocorrelation function (ACF) analysis showed that the time series had a noncyclic structure. The partial rate correlation
function (PRCF) indicated that a strong first-order negative feedback dominated the endogenous dynamics. Stepwise multiple
regression analysis showed that the only climatic factor influencing population growth rate was the minimum winter temperature.
Thus, at least during the study period, endogenous, density-dependent negative feedback was the main factor affecting the
growth rate of the salamander population, whereas stochastic environmental variables, such as temperature and rainfall, seemed
to play a minor role in regulation. These results stress the importance of considering both exogenous and endogenous factors
when analysing amphibian long-term population dynamics. 相似文献
126.
A juvenile lizard specimen with well-preserved skin impressions from the Upper Jurassic/Lower Cretaceous of Daohugou, Inner Mongolia, China 总被引:1,自引:0,他引:1
Lizards are now relatively well known from the Yixian Formation of northeastern China. In this study, we describe a juvenile
lizard from a fossil horizon at Daohugou, Inner Mongolia. These beds predate the Yixian Formation, and are probably Late Jurassic
or earliest Cretaceous in age. The new specimen thus documents the first lizard material from the Daohugou locality and is
the earliest lizard skeleton from China. Comparisons with developmental stages of modern lizards suggest the Daohugou lizard
is a hatchling. Although tiny, the specimen is notable in preserving exquisite skin impressions showing the variation in scalation
across the body, the shape and position of the cloacal outlet, and details of the manus and pes. These are the earliest recorded
lepidosaurian skin traces. In its general proportions and the possession of paired frontals, the small Daohugou lizard resembles
both the Yixian taxon Yabeinosaurus tenuis and the questionable Jeholacerta formosa, but it differs from the latter in scalation and, based on other characters, may be distinct from both. 相似文献
127.
Törnvall FV Holmqvist K Davidsson J Svensson MY Håland Y Ohrn H 《Traffic injury prevention》2007,8(2):205-215
OBJECTIVE: Since the shoulders are rarely seriously injured in frontal or oblique collisions, they have been given low priority in the development of frontal impact crash test dummies. The shoulder complex geometry and its kinematics are of vital importance for the overall dummy kinematics. The shoulder complex also influences the risk of the safety belt slipping off the shoulder in oblique forward collisions. The first aim of this study was to develop a new 50th percentile male THOR shoulder design, while the second was to compare the new shoulder, mounted on a THOR NT dummy, with volunteer, THOR NT, and Hybrid III range of motion and stiffness data. The third aim was to test the repeatability of the new shoulder during dynamic testing and to see how the design behaves with respect to belt slippage in a 45 degrees far-side collision. METHODS: The new 50th percentile THOR shoulder design was developed with the aid of a shell model of the seated University of Michigan Transportation Research Institute (UMTRI) 50th percentile male with coordinates for joints and bony landmarks (Schneider et al., 1983). The new shoulder design has human-like bony landmarks for the acromion and coracoid processes. The clavicle curvature and length are also made similar to that of a male human, as is the range of motion in the anterior-posterior, superior-inferior, and medial-lateral directions. The new shoulder design was manufactured and tested under the same conditions that T?rnvall et al. (2005b) used to compare the shoulder range of motion for the volunteers, Hybrid III, and THOR Alpha. The new design was also tested in two dynamic test configurations: the first was a 0 degrees full-frontal test and the second was a 45 degrees far-side test. The dummy tests were conducted with an R-16 seat with a three-point belt, the Delta V was 27.0+/-0.5 km/h and the maximum peak acceleration was approximately 14.6+/-0.5 g for each test. RESULTS: A new shoulder design with geometry close to that of humans was developed to be retrofitted to the THOR NT dummy. The results showed that the range of motion for the new shoulder complex during static loading was larger by at least a factor of three, for the maximum load (200 N/arm), than that of either the Hybrid III or the THOR NT; this means it was more similar to the volunteers' range of motion. It was observed that the THOR NT with the new shoulder did not slide out of the shoulder belt during a far-side collision. The performance of the new shoulder was reasonably repeatable and stable during both the static tests and the sled tests. CONCLUSION: A new shoulder for the THOR NT has been designed and developed, and data from static range of motion tests and sled tests indicate that the new shoulder complex has the potential to function in a more human-like manner on the THOR dummy. 相似文献
128.
Vullo R 《Die Naturwissenschaften》2011,98(6):545-549
Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body
fossil associations attesting to this predator–prey relationship have never been described so far. Here, I report a unique
finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these
two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery
clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented
here provides new insights into the Mesozoic marine ecosystem food webs. 相似文献
129.
The objective of this study was to compare the effects of repeated field applications of three urban compost amendments and one farmyard manure amendment over a 9-year period on aggregate stability in a silty loam soil initially characterized by low clay and initial organic matter contents and poor aggregate stability. Three different aggregate stability tests with increasing disruptive intensities (fast wetting > mechanical breakdown > slow wetting tests) and different disaggregation mechanisms, were used. All of the amendments, which were applied at approximately 4 Mg C ha−1 every other year, increased the organic carbon content and improved the stability of the aggregates against the disruptive action of water, as determined by each of the stability tests. However, the year-to-year variations in the aggregate stability that related to factors other than the organic inputs were greater than the cumulative increase in aggregate stability relative to the control. The positive effects of the tested amendments on aggregate stability were linked to their contribution to soil organic C contents (r = 0.54 for the fast wetting test and r = 0.41-0.42 for the mechanical breakdown and slow wetting tests; p < 0.05). The addition of urban composts had a larger positive effect on aggregate stability than farmyard manure at the majority of sampling dates. The addition of biodegradable immature compost, such as municipal solid waste (MSW), improved the aggregate stability through an enhanced resistance to slaking. The addition of mature composts, such as the co-compost of sewage sludge and green wastes (GWS) or biowaste compost (BW), improved the aggregate stability by increasing interparticular cohesion. The MSW compost was the most efficient in improving aggregate stability during the first 6 years of the experiment (average improvements of +22%, +5% and +28% in the fast wetting, mechanical breakdown and slow wetting tests, respectively, compared to the control treatment); this result was likely due to the larger labile organic pool of the MSW compost that was highly effective at stimulating soil microbial activity. After the first 6 years, the two other composts, GWS and BW, became more efficient (average improvements of +25%, +61% and +33% in the fast wetting, mechanical breakdown and slow wetting tests, respectively, compared to the control treatment), which was probably linked to the greater increase in soil organic C contents. Therefore, the application of urban compost to silty soil that is susceptible to water erosion was effective at improving aggregate stability and thus could be used to enhance the resistance of soil to water erosion. 相似文献
130.
Some emerging technologies are expected to be pivotal for solving many of the environmental challenges faced today, especially those related to energy. However, many of these technologies may incur significant environmental impacts over their life cycle, while having environmental benefits during their use. This paper presents results of a Life Cycle Assessment (LCA) of a proposed type of nanophotovoltaic, quantum dot photovoltaic (QDPV) module. The LCA is confined to the stages of raw materials acquisition, manufacturing, and use. The impacts of QDPV are compared with other types of PV modules and energy sources - both renewable and nonrenewable. To provide a comprehensive comparative assessment, QDPV modules were compared with mature as well as emerging PV types for which data are available. Comparative assessment with other types of energy sources includes coal, oil, lignite, natural gas, diesel, nuclear, wind, and hydropower.QDPV modules may have the potential to overcome two current barriers of solar technology: low efficiencies and high manufacturing costs. If higher efficiencies are realized, QDPV modules could pave the way to large scale implementation of solar energy, helping nations move toward greater energy independence. On the other hand, candidate materials as quantum dots for solar cell applications are mostly compound semiconductors such as cadmium selenide, cadmium telluride, and lead sulfide which may be toxic and for which renewable options are limited. Toxic effects of these materials may be exacerbated by their nanoscale features.The LCA was carried out using the software SimaPro, and the Ecoinvent Life Cycle Inventory (LCI) database supplemented with available literature and patent information. Our results indicate that while QDPV modules have shorter Energy PayBack Time (EPBT), lower Global Warming Potential (GWP), SOx and NOx emissions than other types of PV modules, they have higher heavy metal emissions, underscoring the need for investigation of emerging technologies, especially nano-based ones, from a life cycle perspective. QDPV modules are better in all impact categories assessed than carbon-based energy sources but they have longer EPBT than wind and hydropower and higher GWP. 相似文献