3,267,643 research outputs found
Low cost propulsion systems for the developing world
Space has often been referred to as the final frontier. It is the curiosity of what lies beyond our planet that drives us to turn to the skies. This quest for knowledge and the chance of travelling to the heavens has compelled people to devote their lives to space science, innovation and analysis of our ever-expanding universe. Today the most significant impact of rocketry comes in the form of manned spaceflight. Vehicles like the Space Shuttle and Soyuz began the trend of greater commercialization of manned rocketry, enabling widespread access to space. Whilst the curiosity of what lies beyond may have propelled the development of the space tourism industry, its current operational cost is estimated as 28 million per passenger per flight. Although the vision of providing low cost space travel still exists, its application is hindered by the costs associated with current space vehicles and mission operations. Furthermore, if we are to better understand our universe and are keen on commercializing space, we would require the space tourism industry to operate in a similar fashion to the aviation industry. As most current launch vehicles rely on chemical propulsion, the level of uncertainty in the market drives their fuel costs. In order to reduce the cost per flight, we must effectively increase the load factor per flight and operate multiple flights, enabling a greater number of paying passengers. In order to provide widespread access to space there needs to be a greater emphasis on the research and development of low cost Reusable Launch Vehicles (RLV) which predominantly rely on alternative fuel technologies, thereby reducing the overall cost per flight. Although progress would be slow, we would still be able to witness a boom in space tourism. This paper proposes the use of magnetic levitation and propulsion (Maglev) within a vacuum chamber as a viable low-cost propulsion technology. It aims to prove that such a system is capable of providing adequate thrust to future space vehicles. As Maglev systems allow for horizontal take-off and landing, such a launch system could be used in conjunction with current airports worldwide. Although the inception and creation of such a system may seem expensive, the long-term fiscal costs are relatively lower than current day systems. This is primarily because such a system relies on electrical power, whose supply and generation costs are much lower than that of chemical propellants. Also, the maintenance costs associated with the Maglev track are minimal, as during take-off there is no physical contact between the track and the launch vehicle. Similar to the aviation industry, the success of future space exploration programs and space tourism relies on international cooperation and alliances. This not only ensures that no one country dominates access to space, but also nurtures healthy competition by providing a level playing field. By implementing the afore mentioned system in politically stable developing nations, we ensure employment, innovation and motivation, all achieved through an international alliance. This system would not only ensure a faster urban development within these countries, but would also bring the vision of space science and exploration to a larger global audience. This paper discusses the overall cost analysis for a vacuum operated Maglev system, the various options available for the generation of power required by such a system and how the systemâs long term costs can be aligned with the aviation industry
Radar altimetry systems cost analysis
This report discusses the application and cost of two types of altimeter systems (spaceborne (satellite and shuttle) and airborne) to twelve user requirements. The overall design of the systems defined to meet these requirements is predicated on an unconstrained altimetry technology; that is, any level of altimeter or supporting equipment performance is possible
On the cost-complexity of multi-context systems
Multi-context systems provide a powerful framework for modelling
information-aggregation systems featuring heterogeneous reasoning components.
Their execution can, however, incur non-negligible cost. Here, we focus on
cost-complexity of such systems. To that end, we introduce cost-aware
multi-context systems, an extension of non-monotonic multi-context systems
framework taking into account costs incurred by execution of semantic operators
of the individual contexts. We formulate the notion of cost-complexity for
consistency and reasoning problems in MCSs. Subsequently, we provide a series
of results related to gradually more and more constrained classes of MCSs and
finally introduce an incremental cost-reducing algorithm solving the reasoning
problem for definite MCSs
Evaluating cost taxonomies for information systems management
The consideration of costs, benefits and risks underpin many Information System (IS) evaluation decisions. Yet, vendors
and project-champions alike tend to identify and focus much of their effort on the benefits achievable from the
adoption of new technology, as it is often not in the interest of key stakeholders to spend too much time considering
the wider cost and risk implications of enterprise-wide technology adoptions. In identifying a void in the literature, the
authors of the paper present a critical analysis of IS-cost taxonomies. In doing so, the authors establish that such cost
taxonomies tend to be esoteric and difficult to operationalize, as they lack specifics in detail. Therefore, in developing a
deeper understanding of IS-related costs, the authors position the need to identify, control and reduce IS-related costs
within the information systems evaluation domain, through culminating and then synthesizing the literature into a
frame of reference that supports the evaluation of information systems through a deeper understanding of IS-cost taxonomies.
The paper then concludes by emphasizing that the total costs associated with IS-adoption can only be determined
after having considered the multi-faceted dimensions of information system investments
Long-Term Average Cost in Featured Transition Systems
A software product line is a family of software products that share a common
set of mandatory features and whose individual products are differentiated by
their variable (optional or alternative) features. Family-based analysis of
software product lines takes as input a single model of a complete product line
and analyzes all its products at the same time. As the number of products in a
software product line may be large, this is generally preferable to analyzing
each product on its own. Family-based analysis, however, requires that standard
algorithms be adapted to accomodate variability.
In this paper we adapt the standard algorithm for computing limit average
cost of a weighted transition system to software product lines. Limit average
is a useful and popular measure for the long-term average behavior of a quality
attribute such as performance or energy consumption, but has hitherto not been
available for family-based analysis of software product lines. Our algorithm
operates on weighted featured transition systems, at a symbolic level, and
computes limit average cost for all products in a software product line at the
same time. We have implemented the algorithm and evaluated it on several
examples
A framework for documenting and analyzing life-cycle costs using a simple network based representation
The introduction of high reliability systems combined with
new ways of operating complex systems, particularly in
aircraft design and operation has received much attention in
recent years. Some systems are now being introduced into
service, however, justifying such systems on a financial basis is difficult and may act to limit the rate of introduction on new products.
Conventional life cycle costing based on a hierarchical cost
breakdown structure is poor at recording and analysing the
cost implications of introducing new technologies that have
effects that span more than one phase in the life cycle. There is a risk that too much emphasis is put on âfaithâ that a candidate technology will reduce cost because the cost analysis methods lack descriptive and analytical power.
We describe an approach to representing the costs associated
with introducing new technologies and evaluating their total
cost. Our aim was to facilitate the comparison of different
technological choices in new product development, with a
particular interest in how the perceived benefits of enhanced reliability systems can be shown in a way that is inclusive, objective and easy to understand
Systems biology of energetic and atomic costs in the yeast transcriptome, proteome, and metabolome
Proteins vary in their cost to the cell and natural selection may favour the use of proteins that are cheaper to produce. We develop a novel approach to estimate the amino acid biosynthetic cost based on genome-scale metabolic models, and directly investigate the effects of biosynthetic cost on transcriptomic, proteomic and metabolomic data in _Saccharomyces cerevisiae_. We find that our systems approach to formulating biosynthetic cost produces a novel measure that explains similar levels of variation in gene expression compared with previously reported cost measures. Regardless of the measure used, the cost of amino acid synthesis is weakly associated with transcript and protein levels, independent of codon usage bias. In contrast, energetic costs explain a large proportion of variation in levels of free amino acids. In the economy of the yeast cell, there appears to be no single currency to compute the cost of amino acid synthesis, and thus a systems approach is necessary to uncover the full effects of amino acid biosynthetic cost in complex biological systems that vary with cellular and environmental conditions
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