Bayesian estimation of parameters in a regional hydrological model

International audienceThis study evaluates the applicability of the distributed, process-oriented Ecomag model for prediction of daily streamflow in ungauged basins. The Ecomag model is applied as a regional model to nine catchments in the NOPEX area, using Bayesian statistics to estimate the posterior distribution of the model parameters conditioned on the observed streamflow. The distribution is calculated by Markov Chain Monte Carlo (MCMC) analysis. The Bayesian method requires formulation of a likelihood function for the parameters and three alternative formulations are used. The first is a subjectively chosen objective function that describes the goodness of fit between the simulated and observed streamflow, as defined in the GLUE framework. The second and third formulations are more statistically correct likelihood models that describe the simulation errors. The full statistical likelihood model describes the simulation errors as an AR(1) process, whereas the simple model excludes the auto-regressive part. The statistical parameters depend on the catchments and the hydrological processes and the statistical and the hydrological parameters are estimated simultaneously. The results show that the simple likelihood model gives the most robust parameter estimates. The simulation error may be explained to a large extent by the catchment characteristics and climatic conditions, so it is possible to transfer knowledge about them to ungauged catchments. The statistical models for the simulation errors indicate that structural errors in the model are more important than parameter uncertainties. Keywords: regional hydrological model, model uncertainty, Bayesian analysis, Markov Chain Monte Carlo analysis</p

Infrared Thermography to Monitor Natural Ventilation during Storage of Potat

A thermographic imaging system is applied as a climate control component in a big potato box store. Traditional temperature sensors distributed in the boxes give product information, i.e. temperatures and relative air humidity values, only for local spots. A thermographic infrared imaging camera system however is able to record a general view over a comparably wide area of the store to detect local differences of surface temperatures in the storage. The project objective is to improve climate control by application of thermography in a free convective ventilated (FCV) box store for potatoes to reduce high temperature differences, which is a typical problem in such types of stores.It was proved that the FCV principle is working even for huge stores. For stores of that type no cooling or ventilation devices are applied to save energy and finally to protect the environment. Thus, these types of stores are only dependent on ‘natural’ ventilation with ambient (environment) air.Low temperature differences can be controlled by moving the top and bottom dampers, according to the temperature fluctuations, dependent on outside wind velocity, and can be determined by the thermography system. The visibility of the air movements i.e. directions of flow can be seen by temperature changes. This allows controlling of separate grouped numbers of dampers. Airflow direction and velocity of the outside air can therefore better be involved into control strategies. Anyway, the assumed efficiency of the ‘air-throw ventilation strategy’ (‘cellar-effect’) to cool the whole store by simply opening the top dampers only, could not be verified

Cohousing for older people: Housing innovation in the Netherlands and Denmark

Objective: The aim of this paper is to elucidate cohousing for older people. Method: The research is based on a literature review and interviews (in English) with residents of seven schemes in the Netherlands and Denmark, a social housing organisation and several researchers in the field (in 1995 and 2002). Results and Conclusions: Cohousing for older people is now well established in its countries of origin - Denmark and the Netherlands - as a way for older people to live in their own house or unit, with a self-chosen group of other older people as neighbours, with shared space and facilities they collectively determine or control. As more such housing is built and occupied it has become easier to choose and assess this option. It remains to be seen how widespread its appeal will be, but cohousing for older people is now a valued housing niche

Respiration-Induced Intraorgan Deformation of the Liver: Implications for Treatment Planning in Patients Treated With Fiducial Tracking.

Stereotactic body radiation therapy is a well-tolerated modality for the treatment of primary and metastatic liver lesions, and fiducials are often used as surrogates for tumor tracking during treatment. We evaluated respiratory-induced liver deformation by measuring the rigidity of the fiducial configuration during the breathing cycle. Seventeen patients, with 18 distinct treatment courses, were treated with stereotactic body radiosurgery using multiple fiducials. Liver deformation was empirically quantified by measuring the intrafiducial distances at different phases of respiration. Data points were collected at the 0%, 50%, and 100% inspiration points, and the distance between each pair of fiducials was measured at the 3 phases. The rigid body error was calculated as the maximum difference in the intrafiducial distances. Liver disease was calculated with Child-Pugh score using laboratory values within 3 months of initiation of treatment. A peripheral fiducial was defined as within 1.5 cm of the liver edge, and all other fiducials were classified as central. For 5 patients with only peripheral fiducials, the fiducial configuration had more deformation (average maximum rigid body error 7.11 mm, range: 1.89-11.35 mm) when compared to patients with both central and peripheral and central fiducials only (average maximum rigid body error 3.36 mm, range: 0.5-9.09 mm, P = .037). The largest rigid body errors (11.3 and 10.6 mm) were in 2 patients with Child-Pugh class A liver disease and multiple peripheral fiducials. The liver experiences internal deformation, and the fiducial configuration should not be assumed to act as a static structure. We observed greater deformation at the periphery than at the center of the liver. In our small data set, we were not able to identify cirrhosis, which is associated with greater rigidity of the liver, as predictive for deformation. Treatment planning based only on fiducial localization must take potential intraorgan deformation into account

On Hausdorff dimension of the set of closed orbits for a cylindrical transformation

We deal with Besicovitch's problem of existence of discrete orbits for transitive cylindrical transformations $T_\varphi:(x,t)\mapsto(x+\alpha,t+\varphi(x))$ where $Tx=x+\alpha$ is an irrational rotation on the circle \T and \varphi:\T\to\R is continuous, i.e.\ we try to estimate how big can be the set D(\alpha,\varphi):=\{x\in\T:|\varphi^{(n)}(x)|\to+\infty\text{as}|n|\to+\infty\}. We show that for almost every $\alpha$ there exists $\varphi$ such that the Hausdorff dimension of $D(\alpha,\varphi)$ is at least $1/2$. We also provide a Diophantine condition on $\alpha$ that guarantees the existence of $\varphi$ such that the dimension of $D(\alpha,\varphi)$ is positive. Finally, for some multidimensional rotations $T$ on \T^d, $d\geq3$, we construct smooth $\varphi$ so that the Hausdorff dimension of $D(\alpha,\varphi)$ is positive.Comment: 32 pages, 1 figur

High-performance computing enables simulations to transform education

This paper presents the case that education in the 21st Century can only measure up to national needs if technologies developed in the simulation community, further enhanced by the power of high performance computing, are harnessed to supplant traditional didactic instruction. The authors cite their professional experiences in simulation, high performance computing and pedagogical studies to support their thesis that this implementation is not only required, it is feasible, supportable and affordable. Surveying and reporting on work in computer-aided education, this paper will discuss the pedagogical imperatives for group learning, risk management and “hero teacher” surrogates, all being optimally delivered with entity level simulations of varying types. Further, experience and research is adduced to support the thesis that effective implementation of this level of simulation is enabled only by, and is largely dependent upon, high performance computing, especially by the ready utility and acceptable costs of Linux clusters

Crop conceptual model for predicting productivity of bread wheat in semi-arid Kenya

&nbsp;P. K. Kimurto1, K. Gottschalk2, M. G. Kinyua3, J. B. O. Ogola4, B. K. Towett 1(1. Department of Crops, Horticulture &amp; Soil Sciences, Egerton University, P.O. Box 536, Njoro, Kenya;2. Leibniz-Institut f&uuml;r Agrartechnik Potsdam-Bornim e.V. ATB, Max-Eyth-Allee 100, 14469 Potsdam, Germany;3. Department of Plant Breeding and Biotechnology, Moi University, P.O. Box 39000, Eldoret, Kenya;4. Department of Plant Production, University of Venda, a, Private bag X5050, South Africa)&nbsp;Abstract: Carrying out field trial-research in dryland areas is usually expensive and costly for most national breeding programmes; hence development of simple crop simulation models for predicting crop performance in actual semi-arid and arid lands (ASALS) would reduce the number of field evaluation trials. &nbsp;This is especially critical in developing countries like Kenya where dry areas is approximately 83% of total land area and annual rainfall in these area is low, unreliable and highly erratic, causing frequent crop failures, food insecurity and famine. &nbsp;This paper used data generated from the rain shelter by measurement of evapotranspiration together with weather variables in Katumani to predict wheat yields in that site. &nbsp;Maximum yield of the wheat genotype considered for genotype Chozi under ideal conditions was 5 t/ha. &nbsp;Total above-ground biomass was obtained and grain yield was to be predicted by the model. &nbsp;Transpiration was estimated from the relationship between total dry matter production and normalised TE (7.8 Pa). &nbsp;The results presented are based on the assumption that all agronomic conditions were optimal and drought stress was the major limiting factor. &nbsp;Predicted grain yield obtained from the conceptual model compares very well with realised yields from actual field experiments with variances of 14% &ndash; 43% depending on watering regime. &nbsp;This study showed that it is possible to develop simple conceptual model to predict productivity in wheat in semi-arid areas of Kenya to supplement complicated and more sophisticated models like CERES-maize and ECHAM models earlier used in Kenya. &nbsp;The presence of uncontrolled factors in the simulation not accounted for in the estimation and could have contributed to decrease in observed yield need to be included in the model, hence modulation of the equations by introducing these factors may be necessary to reduce variances; thus need to be quantified. &nbsp;To improve the accuracy of prediction and increase wheat production in these areas measures that conserve water and/or make more water available to the crop such as prevention or minimisation of run-off, and rain water harvesting for supplemental irrigation are necessary.Keywords: wheat, conceptual model, drought, evapotranspiration, yield response&nbsp;Citation: Kimurto P. K., K. Gottschalk, M. G. Kinyua, J. B. O. Ogola, and B. K. Towett. &nbsp;Crop conceptual model for predicting productivity of bread wheat in semi-arid Kenya. &nbsp;Agric Eng Int: CIGR Journal, 2010, 12(3): 25-37.&nbsp