Computational Study of the Structure and Thermodynamic Properties of Ammonium Chloride Clusters Using a Parallel J-Walking Approach

The thermodynamic and structural properties of (NH$_4$Cl)$_n$ clusters, n=3-10 are studied. Using the method of simulated annealing, the geometries of several isomers for each cluster size are examined. Jump-walking Monte Carlo simulations are then used to compute the constant-volume heat capacity for each cluster size over a wide temperature range. To carry out these simulations a new parallel algorithm is developed using the Parallel Virtual Machine (PVM) software package. Features of the cluster potential energy surfaces, such as energy differences among isomers and rotational barriers of the ammonium ions, are found to play important roles in determining the shape of the heat capacity curves.Comment: Journal of Chemical Physics, accepted for publicatio

Multivariable Repetitive-predictive Controllers using Frequency Decomposition

Repetitive control is a methodology for the tracking of a periodic reference signal. This paper develops a new approach to repetitive control systems design using receding horizon control with frequency decomposition of the reference signal. Moreover, design and implementation issues for this form of repetitive predictive control are investigated from the perspectives of controller complexity and the effects of measurement noise. The analysis is supported by a simulation study on a multi-input multi-output robot arm where the model has been constructed from measured frequency response data, and experimental results from application to an industrial AC motor

Quiet Clean Short-haul Experimental Engine (QCSEE) Under-The-Wing (UTW) composite nacelle subsystem test report

The element and subcomponent testing conducted to verify the under the wing composite nacelle design is reported. This composite nacelle consists of an inlet, outer cowl doors, inner cowl doors, and a variable fan nozzle. The element tests provided the mechanical properties used in the nacelle design. The subcomponent tests verified that the critical panel and joint areas of the nacelle had adequate structural integrity

The planetary nebula population in the halo of M87

We investigate the diffuse light in the outer regions of the nearby elliptical galaxy M87 in the Virgo cluster, using planetary nebulas (PNs) as tracers. The surveyed areas (0.43 squared degrees) cover M87 up to a radial distance of 150 kpc, in the ransition region between galaxy halo and intracluster light (ICL). All PNs are identified through the on-off band technique using automatic selection criteria based on the distribution of the detected sources in the colour-magnitude diagram and the properties of their point-spread function. We extract a catalogue of 688 objects down to m_5007=28.4, with an estimated residual contamination from foreground stars and background Lyalpha galaxies, which amounts to ~35% of the sample. This is one of the largest extragalactic PN samples in number of candidates, magnitude depth, and radial extent, which allows us to carry out an unprecedented photometric study of the PN population in the outer regions of M87. We find that the logarithmic density profile of the PN distribution is shallower than the surface brightness profile at large radii. This behaviour is consistent with the superposition of two components associated with the halo of M87 and with the ICL, which have different luminosity specific PN numbers, the ICL contributing three times more PNs per unit light. Because of the depth of this survey we are also able to study the shape of the PN luminosity function (PNLF) in the outer regions of M87. We find a slope for the PNLF that is steeper at fainter magnitudes than the standard analytical PNLF formula and adopt a generalised model that treats the slope as a free parameter. Comparing the PNLF of M87 and the M31 bulge, both normalised by the sampled luminosity, the M87 PNLF contains fewer bright PNs and has a steeper slope towards fainter magnitudes.Comment: 16 pages, 13 figures, 5 tables, accepted for publication in A&

Motif-based communities in complex networks

Community definitions usually focus on edges, inside and between the communities. However, the high density of edges within a community determines correlations between nodes going beyond nearest-neighbours, and which are indicated by the presence of motifs. We show how motifs can be used to define general classes of nodes, including communities, by extending the mathematical expression of Newman-Girvan modularity. We construct then a general framework and apply it to some synthetic and real networks

Conserving Water in Irrigated Agriculture: The Economics and Valuation of Water Rights

The effective management of water resources in Alberta is crucial to sustainable agriculture, industrial development, and environmental management. The historical water allocation mechanism, administrative apportionment, has been viewed in recent years as ineffective and cumbersome. Accordingly, the revision of the Water Act in 1996, included an attempt to improve the efficiency of water allocation. By making the transfer of water rights possible, the revised Act provides many new options for water use and flexibility. The implications of transferable water rights in Alberta water policy must be carefully considered in order to determine the viability and suitability of such a system in the provincial context. This project examines some of the economic aspects of transferable water rights and the potential for effective water allocation by way of transfers in an Alberta setting. As a major part of this project, a hedonic price model, focusing on land values in southern Alberta, was constructed based on similar models, which have been used elsewhere to value water rights or agricultural products. The hedonic approach to market analysis uses the relationship between the price of land and the attributes of the land, such as water availability, soil quality and location, to explain differences in land prices. In this process, the hedonic model is used to estimate the implicit marginal price or value of each land attribute -- in our case, the marginal value of irrigation water. This value will provide us with an indirect estimate of the value of water rights in the region studied. An advantage of the technique is that it estimates the value that farmers express for irrigation water in the market place for land. Such values, then, give us an indication of the anticipated prices, which might prevail for water rights in southern Alberta. The focus of the study was an area of southern Alberta encompassing the counties of Wheatland, Newell, Cypress, Forty Mile, Taber, Warner, Lethbridge and Vulcan and the irrigation districts of Western, Eastern, St.Mary's, Taber, Lethbridge Northern, and portions of Raymond. Information was collected on the physical and economic characteristics of 230 land parcels, which were sold in this region in 1993 and early 1994. A crude comparison of the value of irrigated agricultural land and non-irrigated agricultural land in the sample reveals that irrigated land was worth, on average, $325 more per acre than non-irrigated land. In the ensuing analysis, it was estimated that the value of a parcel of land was determined largely by the buildings on it, the number of acres in the parcel, the proximity of the parcel to a major city (in this case Calgary or Lethbridge), and by the availability of irrigation water. In the hedonic model, the coefficient values of the variables included represent the marginal impact of each of these characteristics on land prices holding all other things constant. For example, the value of water rights represents the average difference between land values of farms that have access to irrigation and farms that do not. This study estimated that every dollar of improvements to farm buildings translates to a one cent increase in the per acre price of the land parcel, where the addition of one extra acre of land to a land parcel lowers the price per acre by$5.17 per acre. Land prices were seen to increase with the proximity of the parcel to large cities. Similarly, the results of the preferred model indicate that the implicit value of having access to irrigation water in southern Alberta is approximately $190 per acre, or, using the conventional estimate that irrigating one acre of land requires 1.5 acre feet of water, this translates to$126 per acre foot of irrigation water. Accordingly, it is revealed that the existence of water rights adds approximately 35% to the value of non-irrigated land. Since this value represents the implicit amount farmers are willing to pay for access to water, it could also be construed as an indirect measure of the value of water rights. From these results, it is reasonable to conclude that water rights do have a measurable impact on land values. Accordingly, proper incentives may be needed to ensure that water is used efficiently and not incorrectly treated as a relatively free or cheap good. One possible method of policy reform to achieve such a system would be the institution of a system of transferable water rights, permitting water to be traded, or effectively sold, at its market price or scarcity value. Further work was done to determine the potential effects of transferable water rights on the Eastern Irrigation District in southern Alberta. Farm budget information was used to gather information and create twelve representative farm types whose financial performance was analysed using linear programming with increasing water quantity constraints. The resulting productive water values were then used to imply potential reallocations of water among farm types and cropping systems. Analysis of the data gathered revealed that all representative farms faced downward sloping demand functions for water. The overall value of water for a 1% reduction ranged from $8 to$250 per acre foot, with the lowest value belonging to largely pasture operations and the highest value attributed to specialty crop producers. This large range in water values for the region indicates that there is sufficient heterogeneity within the EID to accommodate a transferable rights system. Further analysis of the data reveals that the implementation of a transfer system would result in water being transferred to specialty crop producers and the acreage devoted to specialty crops would increase. Small irrigated pasture operations and cereal crop producers would be the first to give up their water allocations under a transfer system. The analysis indicates that there is considerable potential for economic gains from water trade within this district, the main constraint being the market limitations to expanded specialty crop production. Using these two major studies and other sources, this report concludes with a brief evaluation of the economic advantages, disadvantages and other issues involved in instituting a system of transferable water rights in Alberta. Experience elsewhere, primarily in Australia and the western United States, strongly suggests that transferable water rights, despite some drawbacks and problems of implementation, can be a very worthwhile water policy tool. Now that such tradable water rights are permissible under the revised Water Resources Act of 1996, it is recommended that a pilot project involving transferable water rights be instituted in a water short basin or sub-basin in southern Alberta once a water management plan for that basin is completed.Resource /Energy Economics and Policy,

A Spatial Quantile Regression Hedonic Model of Agricultural Land Prices

Abstract Land price studies typically employ hedonic analysis to identify the impact of land characteristics on price. Owing to the spatial fixity of land, however, the question of possible spatial dependence in agricultural land prices arises. The presence of spatial dependence in agricultural land prices can have serious consequences for the hedonic model analysis. Ignoring spatial autocorrelation can lead to biased estimates in land price hedonic models. We propose using a flexible quantile regression-based estimation of the spatial lag hedonic model allowing for varying effects of the characteristics and, more importantly, varying degrees of spatial autocorrelation. In applying this approach to a sample of agricultural land sales in Northern Ireland we find that the market effectively consists of two relatively separate segments. The larger of these two segments conforms to the conventional hedonic model with no spatial lag dependence, while the smaller, much thinner market segment exhibits considerable spatial lag dependence. Un mod�le h�donique � r�gression quantile spatiale des prix des terrains agricoles R�sum� Les �tudes sur le prix des terrains font g�n�ralement usage d'une analyse h�donique pour identifier l'impact des caract�ristiques des terrains sur le prix. Toutefois, du fait de la fixit� spatiale des terrains, la question d'une �ventuelle d�pendance spatiale sur la valeur des terrains agricoles se pose. L'existence d'une d�pendance spatiale dans le prix des terrains agricoles peut avoir des cons�quences importantes sur l'analyse du mod�le h�donique. En ignorant cette corr�lation s�rielle, on s'expose au risque d'�valuations biais�es des mod�les h�doniques du prix des terrains. Nous proposons l'emploi d'une estimation � base de r�gression flexible du mod�le h�donique � d�calage spatial, tenant compte de diff�rents effets des caract�ristiques, et surtout de diff�rents degr�s de corr�lations s�rielles spatiales. En appliquant ce principe � un �chantillon de ventes de terrains agricoles en Irlande du Nord, nous d�couvrons que le march� se compose de deux segments relativement distincts. Le plus important de ces deux segments est conforme au mod�le h�donique traditionnel, sans d�pendance du d�calage spatial, tandis que le deuxi�me segment du march�, plus petit et beaucoup plus �troit, pr�sente une d�pendance consid�rable du d�calage spatial. Un modelo hed�nico de regresi�n cuantil espacial de los precios del terreno agr�cola Resumen T�picamente, los estudios del precio de la tierra emplean un an�lisis hed�nico para identificar el impacto de las caracter�sticas de la tierra sobre el precio. No obstante, debido a la fijeza espacial de la tierra, surge la cuesti�n de una posible dependencia espacial en los precios del terreno agr�cola. La presencia de dependencia espacial en los precios del terreno agr�cola puede tener consecuencias graves para el modelo de an�lisis hed�nico. Ignorar la autocorrelaci�n espacial puede conducir a estimados parciales en los modelos hed�nicos del precio de la tierra. Proponemos el uso de una valoraci�n basada en una regresi�n cuantil flexible del modelo hed�nico del lapso espacial que tenga en cuenta los diversos efectos de las caracter�sticas y, particularmente, los diversos grados de autocorrelaci�n espacial. Al aplicar este planteamiento a una muestra de ventas de terreno agr�cola en Irlanda del Norte, descubrimos que el mercado consiste efectivamente de dos segmento relativamente separados. El m�s grande de estos dos segmentos se ajusta al modelo hed�nico convencional sin dependencia del lapso espacial, mientras que el segmento m�s peque�o, y mucho m�s fino, muestra una dependencia considerable del lapso espacial.Spatial lag, quantile regression, hedonic model, C13, C14, C21, Q24,

The impact of a school-based water supply and treatment, hygiene, and sanitation programme on pupil diarrhoea: a cluster-randomized trial.

The impact of improved water, sanitation, and hygiene (WASH) access on mitigating illness is well documented, although impact of school-based WASH on school-aged children has not been rigorously explored. We conducted a cluster-randomized trial in Nyanza Province, Kenya to assess the impact of a school-based WASH intervention on diarrhoeal disease in primary-school pupils. Two study populations were used: schools with a nearby dry season water source and those without. Pupils attending 'water-available' schools that received hygiene promotion and water treatment (HP&WT) and sanitation improvements showed no difference in period prevalence or duration of illness compared to pupils attending control schools. Those pupils in schools that received only the HP&WT showed similar results. Pupils in 'water-scarce' schools that received a water-supply improvement, HP&WT and sanitation showed a reduction in diarrhoea incidence and days of illness. Our study revealed mixed results on the impact of improvements to school WASH improvements on pupil diarrhoea

Module identification in bipartite and directed networks

Modularity is one of the most prominent properties of real-world complex networks. Here, we address the issue of module identification in two important classes of networks: bipartite networks and directed unipartite networks. Nodes in bipartite networks are divided into two non-overlapping sets, and the links must have one end node from each set. Directed unipartite networks only have one type of nodes, but links have an origin and an end. We show that directed unipartite networks can be conviniently represented as bipartite networks for module identification purposes. We report a novel approach especially suited for module detection in bipartite networks, and define a set of random networks that enable us to validate the new approach

Schemes for Parallel Quantum Computation Without Local Control of Qubits

Typical quantum computing schemes require transformations (gates) to be targeted at specific elements (qubits). In many physical systems, direct targeting is difficult to achieve; an alternative is to encode local gates into globally applied transformations. Here we demonstrate the minimum physical requirements for such an approach: a one-dimensional array composed of two alternating 'types' of two-state system. Each system need be sensitive only to the net state of its nearest neighbors, i.e. the number in state 1 minus the number in state 2. Additionally, we show that all such arrays can perform quite general parallel operations. A broad range of physical systems and interactions are suitable: we highlight two potential implementations.Comment: 12 pages + 3 figures. Several small corrections mad