66,671 research outputs found

    Resource availability at Taurus-Littrow

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    Early lunar technologies will probably use a common lunar material as ore. They will be robust to minor fluctuations in feedstock composition and will not require appreciable feedstock beneficiation such as rock grinding or mineral concentration. Technologies using unprocessed soil and indifferent to its composition will have the advantage. Nevertheless, the size and grade of the ore body must be confirmed for even the most indiscriminate process. Simple uses such as heaping unprocessed lunar soil for thermal insulation or radiation shielding onto a habitat require that we know the depth of the regolith, the size distributions of its soils, the locations of large boulders, and the ease of excavation. Costs of detailed site surveys trade against restrictions on site selection and conservative engineering design to accommodate unknown conditions of a poorly explored site. Given the above considerations, we consider briefly some abundant lunar materials, their proposed uses, and technologies for their preparation, with particular attention to the Taurus-Littrow site

    A network resource availability model for IEEE802.11a/b-based WLAN carrying different service types

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    The electronic version of this article is the complete one and can be found online at: http://jwcn.eurasipjournals.com/content/2011/1/103. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Operators of integrated wireless systems need to have knowledge of the resource availability in their different access networks to perform efficient admission control and maintain good quality of experience to users. Network availability depends on the access technology and the service types. Resource availability in a WLAN is complex to gather when UDP and TCP services co-exist. Previous study on IEEE802.11a/b derived the achievable throughput under the assumption of inelastic and uniformly distributed traffic. Further study investigated TCP connections and derived a model to calculate the effective transmission rate of packets under the assumption of saturated traffic flows. The assumptions are too stringent; therefore, we developed a model for evaluating WLAN resource availability that tries to narrow the gap to more realistic scenarios. It provides an indication of WLAN resource availability for admitting UDP/TCP requests. This article presents the assumptions, the mathematical formulations, and the effectiveness of our model

    Assessment of Feed Resource Availability and Quality in Kedida Gamela District, Southern Ethiopia

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    Availability of major livestock feed resources, their chemical composition and balance between available feed resources and requirements of existing tropical livestock units (TLU) in Kedida Gamela district (Southern Ethiopia) were assessed. A survey was conducted on 100 sample households (HH) and data collected using group discussions, structured questionnaire and personal observations. Furthermore, chemical composition and in vitro dry matter (DM) digestibility (IVDMD) of major feed resources identified (natural pasture and crop residues) were also determined. A total of 28,675 tonnes of DM were produced annually for a total of 40,080 TLU which satisfies only 31.4% of their maintenance requirement. Maize stover and wheat straw contain lowest ash and from agro-industrial by-products noug cake and wheat bran the highest ash content. The highest (p0.05) between the agro-industrial by-products. The highest acid detergent lignin content for roughage feed was recorded from maize stover to natural pasture and the highest from agro-industrial by-products was recorded from wheat bran to noug cake. Differences in IVDMD for major feed resources were not significant (P>0.05). The differences in nutrient composition and IVDMD of the feed resources in midland and highland followed similar trend, although there were slight differences in nutrient content and IVDMD of similar feedstuffs from the two altitudinal zones. In conclusion, the main feed resource is crop residues which are of low quality with high fiber content, low digestibility which may result in reduced livestock productivity and disease resistance. Chopping followed by soaking or ammonaition or urea treatment could be suggested to improve quality of the roughages

    Double Relative Deprivation: Combining the Personal and Political

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    Double relative deprivation, which has been virtually ignored in research on relative deprivation, was expected to predict women\u27s collective action over and above egoistic and collective deprivation. The role of socio-political resources in perceiving deprivation and participation in action was also investigated. Female students (N=164) completed a questionnaire designed to assess their perceptions of egoistic, collective, double relative deprivation (defined as the interaction between egoistic and collective deprivation), resource availability and participation in collective action. Hierarchical regression analyses indicated that double relative deprivation predicted collective action over and above egoistic and collective relative deprivation, and that resource availability also uniquely predicted action. Implications for expanding conceptual and operational definitions of these constructs are discussed

    Environmental differences between sites control the diet and nutrition of the carnivorous plant Drosera rotundifolia

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    Background and aims: Carnivorous plants are sensitive to small changes in resource availability, but few previous studies have examined how differences in nutrient and prey availability affect investment in and the benefit of carnivory. We studied the impact of site-level differences in resource availability on ecophysiological traits of carnivory for Drosera rotundifolia L. Methods: We measured prey availability, investment in carnivory (leaf stickiness), prey capture and diet of plants growing in two bogs with differences in N deposition and plant available N: Cors Fochno (0.62 g m−2 yr.−1, 353 μg l−1), Whixall Moss (1.37 g m−2 yr.−1, 1505 μg l−1). The total N amount per plant and the contributions of prey/root N to the plants’ N budget were calculated using a single isotope natural abundance method. Results: Plants at Whixall Moss invested less in carnivory, were less likely to capture prey, and were less reliant on prey-derived N (25.5% compared with 49.4%). Actual prey capture did not differ between sites. Diet composition differed – Cors Fochno plants captured 62% greater proportions of Diptera. Conclusions: Our results show site-level differences in plant diet and nutrition consistent with differences in resource availability. Similarity in actual prey capture may be explained by differences in leaf stickiness and prey abundance

    Grasses and the resource availability hypothesis: the importance of silica-based defences

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    The resource availability hypothesis (RAH) predicts that allocation of resources to anti-herbivore defences differs between species according to their growth rate. We tested this hypothesis by assessing the growth and defence investment strategies of 18 grass species and comparing them against vole feeding preferences. In addition, we assessed the effectiveness of silica, the primary defence in many grasses, in influencing vole feeding behaviour. Across species, we found that there was a strong negative relationship between the overall investment in defence and growth rate, thus supporting predictions of the RAH. However, no such relationship was found when assessing the various individual anti-herbivore defences, suggesting that different grass species show significant variation in their relative investment in strategies such as phenolic concentration, silica concentration and leaf toughness. Silica was the most influential defensive factor in determining vole feeding preference. Experimentally induced increases in leaf silica concentration deterred vole feeding in three of the five species tested, and altered feeding preference ranks between species. The strong positive relationship between silica concentration and leaf abrasiveness, when assessed both within and between species, suggests that increased abrasiveness is the mechanism by which silica deters feeding. Although grasses are often considered to be tolerant of herbivore damage rather then defended against it, they do follow predictions of defence allocation strategy based on their growth rates, and this affects the feeding behaviour of generalist grass-feeding herbivores

    Model and Integrate Medical Resource Available Times and Relationships in Verifiably Correct Executable Medical Best Practice Guideline Models (Extended Version)

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    Improving patient care safety is an ultimate objective for medical cyber-physical systems. A recent study shows that the patients' death rate is significantly reduced by computerizing medical best practice guidelines. Recent data also show that some morbidity and mortality in emergency care are directly caused by delayed or interrupted treatment due to lack of medical resources. However, medical guidelines usually do not provide guidance on medical resource demands and how to manage potential unexpected delays in resource availability. If medical resources are temporarily unavailable, safety properties in existing executable medical guideline models may fail which may cause increased risk to patients under care. The paper presents a separately model and jointly verify (SMJV) architecture to separately model medical resource available times and relationships and jointly verify safety properties of existing medical best practice guideline models with resource models being integrated in. The SMJV architecture allows medical staff to effectively manage medical resource demands and unexpected resource availability delays during emergency care. The separated modeling approach also allows different domain professionals to make independent model modifications, facilitates the management of frequent resource availability changes, and enables resource statechart reuse in multiple medical guideline models. A simplified stroke scenario is used as a case study to investigate the effectiveness and validity of the SMJV architecture. The case study indicates that the SMJV architecture is able to identify unsafe properties caused by unexpected resource delays.Comment: full version, 12 page

    Lithium and the Foreseeable Future

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    This paper aims to clarify the uncertainties regarding worldwide lithium resource availability in the years to come. Previous studies made on the subject are presented with some ambiguity and this work intends to fill the gaps. The information and data presented throughout this script with respect to global lithium resources and reserves are mostly based on data released by the United States Geological Survey (USGS). Lithium resource availability in the future is a point of paramount significance primarily for the automotive, portable electronics, and the power generation industry. Since, a change of supply would ultimately affect the price of lithium, which would then affect the industries mentioned. Theoretical scenarios and predictions about future lithium supply and demand are presented at the latter part of this paper intended to give the reader a better understanding of the actual size of the total global lithium resources
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