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Several Scenarios (several + scenario)
Selected AbstractsModelling natural conditions and impacts of consumptive water use and sedimentation of Lake Abaya and Lake Chamo, EthiopiaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2006Seleshi Bekele Awulachew Abstract There is few available information regarding the water resource systems of Abaya Lake and Chamo Lake, which are found in the Southern Rift Valley Region of Ethiopia. This paper describes modelling of the water balance components of these lakes, as well as the impacts of water uses, and sediment transport and deposition in the lakes. The various parameters and data needed for the water balance model are derived on the basis of various surveys, analysis of data and modelling efforts. The watershed characteristics are derived using geographical information system, whereas the morphometry of the lakes is investigated by undertaking bathymetry surveys. The hydrometeorological components of this lake system also were investigated through the development of relevant database and information systems, by identifying regional relationships, and by a rainfall-run-off model. These information systems have subsequently been integrated to model the water balance of the two lakes, and simulating the in-lake water levels. Several scenarios reflecting the natural conditions, water consumptive development possibilities, and sedimentation impacts have been investigated in this study. Based on the model simulation results, and on the computation of the life expectancies of the two lakes, it was found that sediment inflow and deposition significantly threaten their existence. [source] Reverse Auctions with Multiple Reinforcement Learning Agents,DECISION SCIENCES, Issue 1 2008Subhajyoti Bandyopadhyay ABSTRACT Reverse auctions in business-to-business (B2B) exchanges provide numerous benefits to participants. Arguably the most notable benefit is that of lowered prices driven by increased competition in such auctions. The competition between sellers in reverse auctions has been analyzed using a game-theoretic framework and equilibria have been established for several scenarios. One finding of note is that, in a setting in which sellers can meet total demand with the highest-bidding seller being able to sell only a fraction of the total capacity, the sellers resort to a mixed-strategy equilibrium. Although price randomization in industrial bidding is an accepted norm, one might argue that in reality managers do not utilize advanced game theory calculations in placing bids. More likely, managers adopt simple learning strategies. In this situation, it remains an open question as to whether the bid prices converge to the theoretical equilibrium over time. To address this question, we model reverse-auction bidding behavior by artificial agents as both two-player and n -player games in a simulation environment. The agents begin the game with a minimal understanding of the environment but over time analyze wins and losses for use in determining future bids. To test for convergence, the agents explore the price space and exploit prices where profits are higher, given varying cost and capacity scenarios. In the two-player case, the agents do indeed converge toward the theoretical equilibrium. The n -player case provides results that reinforce our understanding of the theoretical equilibria. These results are promising enough to further consider the use of artificial learning mechanisms in reverse auctions and other electronic market transactions, especially as more sophisticated mechanisms are developed to tackle real-life complexities. We also develop the analytical results when one agent does not behave strategically while the other agent does and show that our simulations for this environment also result in convergence toward the theoretical equilibrium. Because the nature of the best response in the new setting is very different (pure strategy as opposed to mixed), it indicates the robustness of the devised algorithm. The use of artificial agents can also overcome the limitations in rationality demonstrated by human managers. The results thus have interesting implications for designing artificial agents in automating bid responses for large numbers of bids where human intervention might not always be possible. [source] VegTrack: A structured vegetation restoration activity databaseECOLOGICAL MANAGEMENT & RESTORATION, Issue 2 2009Andre Zerger Summary, Information about on-ground vegetation restoration activities (e.g. fencing and revegetation) is critical if natural resource management (NRM) groups are to monitor progress towards restoration targets, assess the efficacy of their interventions and adaptively learn from different actions. However, in Australia, there are few practical guidelines for recording data, making it difficult to consistently compare actions between sites and through time. Records of primary information are particularly important given the ongoing national investment in vegetation restoration activities. With the aid of six-case study areas in different landscapes, robust guidelines and tools were developed and incorporated into VegTrack, a methodology, which allows groups to develop their own vegetation restoration activity database. VegTrack differentiates spatial data from attribute data storing each in different databases (a GIS and a relational database management system respectively). We describe the process which enables NRM groups to develop their own database, and provide a Microsoft Access 2003 version of VegTrack to allow NRM groups to commence activity recording. To demonstrate the utility of the VegTrack method in different situations and to encourage consistency across study areas, we describe the application of the guidelines for several scenarios including riparian revegetation, corridors disrupted by roads and infill plantings. [source] Spaces of Encounter: Public Bureaucracy and the Making of Client IdentitiesETHOS, Issue 3 2010Lauren J. Silver I emphasize the material deficits, spatial barriers, and bureaucratic procedures that restrict the storylines clients and officials use to make sense of one another. This article is drawn from a two-year ethnographic study with African American young mothers (ages 16,20) under the custody of the child welfare system. I focus here on the experiences of one young mother and explore several scenarios in her struggle to obtain public housing. I argue that service deficits can be explained not by the commonly articulated narratives of client "shortcomings" but, rather, by the nature of the organizational and material conditions guiding exchanges between public service gatekeepers and young mothers. I suggest that this work advances narrative approaches to psychological anthropology by attending to the roles of social and material boundaries in framing the stories people can tell each other. [identity, adolescent mothers, public bureaucracy, service negotiation, narrative] [source] An iris recognition approach through structural pattern analysis methodsEXPERT SYSTEMS, Issue 1 2010Hugo Proença Abstract: Continuous efforts have been made to improve the robustness of iris coding methods since Daugman's pioneering work on iris recognition was published. Iris recognition is at present used in several scenarios (airport check-in, refugee control etc.) with very satisfactory results. However, in order to achieve acceptable error rates several imaging constraints are enforced, which reduce the fluidity of the iris recognition systems. The majority of the published iris recognition methods follow a statistical pattern recognition paradigm and encode the iris texture information through phase, zero-crossing or texture-analysis based methods. In this paper we propose a method that follows the structural (syntactic) pattern recognition paradigm. In addition to the intrinsic advantages of this type of approach (intuitive description and human perception of the system functioning), our experiments show that the proposed method behaves comparably to the statistical approach that constitutes the basis of nearly all deployed systems. [source] Colonization by barnacles on fossil Clypeaster: an exceptional example of larval settlementLETHAIA, Issue 4 2008ANA G. SANTOS The presence of c. 1450 individuals of the balanid barnacle Balanus crenatus Bruguière encrusting the test of a clypeasteroid sea urchin from the Late Miocene of the Guadalquivir Basin (southwestern Spain) allows proposing a settlement pattern linked to the growth of the encrusting organism. The possible influence of dip angle was controlled by dividing the test into four concentric zones ranging from lowest margin to apex (0,15°, 15,30°, 30,50° and 0°). Contour diagrams were prepared to identify areas of highest barnacle density as well as size categories distribution in relationship to the pitch of the sea urchin test. The orientation of balanid tests was recorded and plotted on rose diagrams from 0° to 180°. Four size categories of barnacles were distinguished: (1) < 1 mm, (2) 1,2 mm, (3) 2,3 mm and (4) 3,4 mm; these correspond to a growth sequence ranging from post-larval forms to juveniles. Two areas of maximum settlement density are situated on the posterior margin of the test, on aboral as well as oral surfaces. The aboral surface shows the maximum number of barnacles. Two groups of individuals are defined on the basis of their location, that is, those encrusting the posterior medium part of the urchin, and those located on the anterior half. The results suggest that larval settlement was initially controlled by the availability of free space and afterwards by an intensification effect. Orientation and dip of the test may have played a secondary role in the settlement of the larvae. Substrate colonization seems to have been closely related to the biostratinomic history of the sea urchin test and although several scenarios are possible, our data are congruent with a synchronous settlement of both surfaces (aboral and oral) by one spat or several. [source] Ly, excess in high-redshift radio galaxies: a signature of star formation,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007M. Villar-Martín ABSTRACT About 54 per cent of radio galaxies at z, 3 and 8 per cent of radio galaxies at 2 ,z < 3 show unusually strong Ly, emission, compared with the general population of high-redshift (z, 2) radio galaxies. These Ly,-excess objects (LAEs) show Ly,/He ii values consistent with or above standard photoionization model predictions. We reject with confidence several scenarios to explain the unusual strength of Ly, in these objects: shocks, low nebular metallicities, high gas densities and absorption/scattering effects. We show that the most successful explanation is the presence of a young stellar population which provides the extra supply of ionizing photons required to explain the Ly, excess in at least the most extreme LAEs (probably in all of them). This interpretation is strongly supported by the tentative trend found by other authors for z, 3 radio galaxies to show lower ultraviolet rest-frame polarization levels, or the dramatic increase in the detection rate at submm wavelengths of z > 2.5 radio galaxies. The enhanced star formation activity in LAEs could be a consequence of a recent merger which has triggered both the star formation and the active galactic nucleus/radio activities. The measurement of unusually high Ly, ratios in the extended gas of some high-redshift radio galaxies suggests that star formation activity occurs in spatial scales of tens of kpc. We argue that, although the fraction of LAEs may be incompletely determined, both at 2 ,z < 3 and at z, 3, the much larger fraction of LAEs found at z, 3 is a genuine redshift evolution and not due to selection effects. Therefore, our results suggest that the radio galaxy phenomenon is more often associated with a massive starburst at z > 3 than at z < 3. [source] The nature of high-redshift galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001Rachel S. Somerville Using semi-analytic models of galaxy formation set within the cold dark matter (CDM) merging hierarchy, we investigate several scenarios for the nature of the high-redshift ) Lyman-break galaxies (LBGs). We consider a ,collisional starburst' model in which bursts of star formation are triggered by galaxy,galaxy mergers, and find that a significant fraction of LBGs are predicted to be starbursts. This model reproduces the observed comoving number density of bright LBGs as a function of redshift and the observed luminosity function at and with a reasonable amount of dust extinction. Model galaxies at have star formation rates, half-light radii, colours and internal velocity dispersions that are in good agreement with the data. Global quantities such as the star formation rate density and cold gas and metal content of the Universe as a function of redshift also agree well. Two ,quiescent' models without starbursts are also investigated. In one, the star formation efficiency in galaxies remains constant with redshift, while in the other, it scales inversely with disc dynamical time, and thus increases rapidly with redshift. The first quiescent model is strongly ruled out, as it does not produce enough high-redshift galaxies once realistic dust extinction is accounted for. The second quiescent model fits marginally, but underproduces cold gas and very bright galaxies at high redshift. A general conclusion is that star formation at high redshift must be more efficient than locally. The collisional starburst model appears to accomplish this naturally without violating other observational constraints. [source] Augmenting real data with synthetic data: an application in assessing Radio-Isotope identification algorithms,QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 8 2009T. Burr Abstract The performance of Radio-Isotope IDentification (RIID) algorithms using gamma spectroscopy is increasingly becoming important. For example, sensors at locations that screen for illicit nuclear material rely on isotope identification to resolve innocent nuisance alarms arising from naturally occurring radioactive material. Recent data collections for RIID testing consist of repeat measurements for each of several scenarios to test RIID algorithms. Efficient allocation of measurement resources requires an appropriate number of repeats for each scenario. To help allocate measurement resources in such data collections for RIID algorithm testing, we consider using only a few real repeats per scenario. In order to reduce uncertainty in the estimated RIID algorithm performance for each scenario, the potential merit of augmenting these real repeats with realistic synthetic repeats is also considered. Our results suggest that for the scenarios and algorithms considered, approximately 10 real repeats augmented with simulated repeats will result in an estimate having comparable uncertainty to the estimate based on using 60 real repeats. Published in 2009 by John Wiley & Sons, Ltd. [source] Statistical properties and performance of pairwise relatedness estimators using turbot (Scophthalmus maximus L.) family dataAQUACULTURE RESEARCH, Issue 4 2010Ania Pino-Querido Abstract The statistical properties and performance of four estimators of pairwise relatedness were evaluated in several scenarios using the microsatellite genotype data from a set of large known full-sibships of turbot. All estimators showed a significant negative bias for the four kinships commonly used in these studies (unrelated: UR, half-sibs, full-sibs and parent,offspring), when allele frequencies of the reference population were estimated from the individuals analysed. When these frequencies were obtained from the base population from which all families proceeded, the bias was mostly corrected. The Wang (W) and Li (L) estimators were the least sensitive to this factor, while the Lynch and Ritland (L&R estimator) was the highest one. The error (mean around 0.130) was very similar in all scenarios for W, L and Queller and Goodnight (QG) estimators, while L&R was the highest error-prone estimator. Parent,offspring kinship resulted in the lowest error, when using W, L and QG estimators, while UR resulted in the lowest error with the L&R estimator. Globally, W was the best-performing estimator, although L&R could perform better in specific sampling scenarios. In summary, pairwise estimators represent useful tools for kinship classification in aquaculture broodstock management by applying appropriate thresholds depending on the goals of the analysis. [source] | |||||||||||||