GISPART (GIbraltar Strait PARticle Tracking model) is a three-dimensional particle-tracking code that simulates the dispersion
of radionuclides in the Strait of Gibraltar. It consists of a hydrodynamic module that is run off-line to determine tidal
constants and residuals in the domain. This information is stored in files that are read by the dispersion module to reconstruct
water movements. A Lagrangian approach is used, thus, a radionuclide release is simulated by a number of particles, whose
paths are computed individually. Radionuclide concentrations are obtained from the density of particles per water volume unit.
Some examples of the results are shown. Matlab GUIs (graphical user interfaces) allow an easy application of the model and
visualization of results.
The effect of hot-air roasting temperatures and time on colour (L*), moisture content (% d.b.), hardness (N), and fracturability (mm) attributes of two different type of peanuts (China and India origin) were investigated using response surface methodology (RSM). The central composite design (CCD) was used to investigate temperatures ranging from 130–170 °C (China) and 130–200 °C (India), while roasting time was from 20–80 min (China) and 15–50 min (India). The results revealed that temperature and time have significant effect on all the responses. Increase in roasting time and temperature caused a decrease in all the responses for both peanuts. A feasible experimental condition of peanut roasting obtained from the optimisation of simultaneous multiple attributes’ response for the China and India peanuts was 152 °C for 60 min and 158 °C for 45 min, respectively. The strongest linearrelationship was found between hardness and fracturability, while the weakest was between colour and fracturability for both peanuts.
The effect of various fertiliser treatments on the yield of maize hybrids was studied on the basis of 26 years of data obtained in a long-term bifactorial split-plot experiment set up in 1967. The seven treatments (NPK ratio 2:1:1) applied were as follows (rates per hectare): 1. Control (no fertiliser), 2. 100 kg NPK, 3. 200 kg NPK, 4. 300 kg NPK, 5. 400 kg NPK, 6. 600 kg NPK, 7. 800 kg NPK. The maize was grown with the conventional cultivation techniques in continuous cropping. The results of analyses carried out with three different methods (analysis of variance, cumulative yield analysis and regression analysis) all indicated that under the given conditions the yield of maize hybrids was highest at an NPK fertiliser rate of 200-400 kg ha
. The effect of fertilisation on the maize yield was significant in 21 of the 26 years. Combined analysis of variance for the years showed that the year effect (quantity of rainfall) had the greatest effect on the maize yield, but although the year effect had a fundamental effect on the yield level it did not influence the fertiliser response pattern. The fertiliser responses of the maize hybrids were described by fitting four types of functions (quadratic, square root, inverse exponential, linear-plateau) to the yield data. It was found that when selecting the best function a consideration of the regression deviations (measured yield - calculated yield) was just as important as the coefficient of determination (R
). In 12 of the 26 years the fitting of the quadratic function was not significant and overestimated the fertilisation optimum. The fertiliser response curve generally has a broad maximum which is far better described by the square root function than by the quadratic. If the fertiliser response pattern includes a depressive phase, a square root function should definitely be used in place of the quadratic function. If the maximum of the response surface forms a plateau (as opposed to a maximum point) a linear-plateau function or an inverse exponential function can be recommended. In the present work the linear-plateau function gave the best results.
Authors:Michael L. Hobbs, James T. Nakos, and Patrick D. Brady
decomposition model with comparison to data. Subsequent sections describe a responsemodel for MXB-71 including contributions due to gas conduction, condensed conduction, and diffuse radiation.
MXB-71 decomposition model
Functional response describes the rate at which a predator consumes prey. Handling time, duration that a predator spends on a captured prey for the consumption, is one of the parameters of many functional response models. Although models typically assume that handling time is static, most empirical studies that directly quantified the relationship between handling time and prey density show that handling time decreases with prey density. In this study, I compare a community model that employs density-dependent handling time and a model with static handling time for their responses to enrichment. The density-dependent handling time is derived by assuming that predators adjust handling time to maximize their fitness. I show that the model with adaptive handling time is more robust to enrichment than the model with static handling time at realistic parameter values. Although community response to enrichment is used as an illustrative example, density-dependent handling time is a common empirical observation and would have general implications to ecological dynamics.
The effect of prey stages of the two-spotted spider mite Tetranychus urticae on the functional response of the coccinellid predator Stethorus gilvifrons was studied at 25±1 °C, 65±10% rh, and 16:8 h (L:D photoperiod). The functional response of S. gilvifrons female, to increasing prey stage density from 10–100 preys per patch, was of the curvilinear shape depicting Roger’s type II response with the highest consumption rate of larval prey stage. Results of the maximum likelihood analyses confirmed this type. By plotting a type II functional response model and polynomial logistic regression model to the numbers and proportions of consumed stages of T. urticae, respectively, the resulting regression lines fitted the data well. However, a composite waving form that appeared to be a decelerating (type II) response at low to medium prey densities and an accelerating (type III) response at high prey densities. We assume that the small size of experimental arena or predator feeding behaviour at low and high prey densities may have induced the modified type II response. A sensitivity analysis of the functional response model shows the crucial effect of prey stages on predation rates by S. gilvifrons. Theoretically, based on the lowest handling time for S. gilvifrons on larval stage of T. urticae, the maximum numbers of mites that could consume by a single female of S. gilvifrons within 24 h period were 77.42 larvae. These results improve our understanding of the interaction among S. gilvifrons and T. urtica stages and provide insights into the control of T. urticae.
We used space-for-time substitution to obtain a directed successional sequence for subalpine meadow vegetation in the Swiss National Park. Since human impacts (e.g., domestic animal grazing) ceased in 1914, the successional processes documented are assumed to be autogenic in nature. The data consist of 59 permanent plots spanning almost 90 years, and include many spatial replications. An initial inspection of the individual time series revealed the existence of a variety of response patterns, which are described in the literature as representing different successional types. However, a closer inspection suggested that many of these series can be superimposed, as they are part of a much longer deterministic series. Linking the individual time series proved to be challenging. A heuristic approach produced results that differed depending on initial starting conditions. We therefore derived a deterministic algorithm to produce a unique solution. The resulting sequence largely confirmed the heuristic interpretation, suggesting a trend from early successional (post-grazing) grassland to pine invasion spanning about 400 years. This timespan is valid only for the climatic conditions near the treeline, and for plant species specific to the study site. Our results suggest that the various species temporal response models described in the literature may be artifactual, representing portions of underlying Gaussian responses. The data also indicate that species assemblages may persist for several decades with only minor fluctuations, only to change suddenly for no apparent reason.
Authors:Ruzica Loncaric, Zdenko Loncaric, and Krunoslav Zmaic
Cruzdemina, R., Morenoramos, o. H. and Chapman, P. L. (1996): Wheat yield responsemodels to nitrogen and phosphorus fertilizer for rotation experiments in the northwest Mexico. Cereal research Communications. 24(2): 239