Flood River Water Level Forecasting using Ensemble Machine Learning for Early Warning Systems

Flood forecasting is crucial for early warning system and disaster risk reduction. Yet the flood river water levels are difficult and challenging task that it cannot be easily captured with classical time-series approaches. This study proposed a novel intelligence system utilised various machine learning techniques as individual models, including radial basis function neural network (RBF-NN), adaptive neuro-fuzzy inference system (ANFIS), support vector machine (SVM), and long short-term memory network (LSTM) to establish intelligent committee machine learning flood forecasting (ICML-FF) framework. The combination of these individual models achieved through simple averaging method, and further optimised using weighted averaging by K-nearest neighbour (K-NN) and genetic algorithm (GA). The effectiveness of the proposed model was evaluated using real case study for Malaysia's Kelantan River. The results show that ANFIS outperforms as individual model, while ICML-FF-based model produced better accuracy and lowest error than any one of the individuals. In general, it is found that the proposed ICML-FF is capable of robust forecasting model for flood early warning systems

Changes in foliar nutrient content and resorption in Fraxinus excelsior L., Ulmus minor Mill. and Clematis vitalba L. after prevention of floods

This paper focuses on the impact of flood on tree mineral nutrition through measurement of resorption (i.e. transfer of nutrients from leaves to perennial organs). Nutrient (N, P, K, Mg, Ca) concentrations in leaves of three representative species, Fraxinus excelsior L., Ulmus minor Mill. and Clematis vitalba L. were measured before and after abscission on flooded and unflooded hardwood forests of the upper Rhine plain. The nutrient concentrations in the soils, which were measured in the top layer of the study sites, were higher in the flooded sites for P but slightly lower for N and K, and identical at both types of site for Ca and Mg. The summer foliage concentrations were higher for N and P in the flooded areas, and probably related to the flooding process, which contributes to regular nutrient inputs in the flooded forest, causes high fluctuations of water level and increases bioavailability of certain nutrients. Resorption occurred for all nutrients in the three species, and was higher for N, P and K (40-70 %) than for Ca and Mg (0-45 %), but not significantly different at the two sites. This paper stresses the variability of the test species response (nutrient content and resorption) to the soil and flood water nutrient sources, and tries to specify parameters which control resorption, i.e. soil fertility, tree species or flood stress. © 1999 Inra/Éditions scientifiques et médicales Elsevier SAS

Flood basalt eruptions, comet showers, and mass extinction events

A chronology of initiation dates of the major continental flood basalt episodes has been established from compilation of published K-Ar and Ar-Ar ages of basaltic flows and related basic intrusions. The dating is therefore independent of the biostratigraphic and paleomagnetic time scales, and the estimated errors of the inititation dates are approximately + or - 4 pct. There are 11 distinct episodes of continental flood basalts known during the past 250 Myr. The data show that flood basalt episodes are generally relatively brief geologic events, with intermittent eruptions during peak output periods lasting ony 2 to 3 Myr or less. Statistical analyses suggest that these episodes may have occurred quasi-periodically with a mean cycle time of 32 + or - 1 Myr. The initiation dates of the flood basalts are close to the estimated dates of marine mass extinctions and impact-crater clusters. Although a purely internal forcing might be argued for the flood basalt volcanism, quasi-periodic comet impacts may be the trigger for both the flood basalts and the extinctions. Impact cratering models suggest that large-body impactors lead to deep initial cratering, and therefore may cause mantle disturbances and initiate mantle plume activity. The flood basalt episodes commonly mark the initiation or jump of a mantle hotspot, and are often followed by continental rifting and separation. Evidence from dynamical studies of impacts, occurrences of craters and hotspots, and the geochemistry of boundary layers is synthesized to provide a possible model of impact-generated volcanism. Flood basalt eruptions may themselves have severe effects on climate, and possibly on life. Impacts might, as a result, have led to mass extinctions through direct atmospheric disturbances, and/or indirectly through prolonged flood basalt volcanism

The complexity of flood-filling games on graphs

We consider the complexity of problems related to the combinatorial game Free-Flood-It, in which players aim to make a coloured graph monochromatic with the minimum possible number of flooding operations. Although computing the minimum number of moves required to flood an arbitrary graph is known to be NP-hard, we demonstrate a polynomial time algorithm to compute the minimum number of moves required to link each pair of vertices. We apply this result to compute in polynomial time the minimum number of moves required to flood a path, and an additive approximation to this quantity for an arbitrary k x n board, coloured with a bounded number of colours, for any fixed k. On the other hand, we show that, for k>=3, determining the minimum number of moves required to flood a k x n board coloured with at least four colours remains NP-hard.Comment: More typos corrected

Financial Integration: A New Methodology and an Illustration

This paper develops a simple new methodology to test for asset integration and applies it within and between American stock markets. Our technique is tightly based on a general intertemporal asset-pricing model, and relies on estimating and comparing expected risk-free rates across assets. Expected risk-free rates are allowed to vary freely over time, constrained only by the fact that they are equal across (risk-adjusted) assets. Assets are allowed to have general risk characteristics, and are constrained only by a factor model of covariances over short time periods. The technique is undemanding in terms of both data and estimation. We find that expected risk-free rates vary dramatically over time, unlike short interest rates. Further, the S&P 500 market seems to be well integrated, and the NASDAQ is generally (but not always) integrated. However, the NASDAQ is poorly integrated with the S&P 500.

Estimation of minority carrier diffusion lengths in InP/GaAs solar cells

Minority carrier diffusion length is one of the most important parameters affecting the solar cell performance. An attempt is made to estimate the minority carrier diffusion lengths is the emitter and base of InP/GaAs heteroepitaxial solar cells. The PC-1D computer model was used to simulate the experimental cell results measured at NASA Lewis under AMO (air mass zero) spectrum at 25 C. A 16 nm hole diffusion length in the emitter and a 0.42 micron electron diffusion length in the base gave very good agreement with the I-V curve. The effect of varying minority carrier diffusion lengths on cell short current, open circuit voltage, and efficiency was studied. It is also observed that the front surface recombination velocity has very little influence on the cell performance. The poor output of heteroepitaxial cells is caused primarily by the large number of dislocations generated at the interfaces that propagate through the bulk indium phosphide layers. Cell efficiency as a function of dislocation density was calculated and the effect of improved emitter bulk properties on cell efficiency is presented. It is found that cells with over 16 percent efficiencies should be possible, provided the dislocation density is below 10(exp 6)/sq cm

Effect of emitter parameter variation on the performance of heteroepitaxial indium phosphide solar cells

Metallorganic chemical-vapor-deposited heteroepitaxial indium phosphide (InP) solar cell experimental results were simulated by using a PC-1D computer model. The effect of emitter parameter variation on the performance of n(+)/p/p(+) heteroepitaxial InP/GaAs solar cell was presented. The thinner and lighter doped emitters were observed to offer higher cell efficiencies. The influence of emitter thickness and minority carrier diffusion length on the cell efficiency with respect to dislocation density was studied. Heteroepitaxial cells with efficiencies similar to present day homojunction InP efficiencies (greater than 16 percent AMO) were shown to be attainable if a dislocation density lower than 10(exp 6)/sq cm could be achieved. A realistic optimized design study yielded InP solar cells of over 22 percent AMO efficiency at 25 C

Fixes: Of The Forward Discount Puzzle

Regressions of ex post changes in floating exchange rates on appropriate interest differentials typically imply that the high- interest rate currency tends to appreciate, the `forward discount puzzle.' Using data from the European Monetary System, we find that a large part of the forward discount puzzle vanishes for regimes of fixed exchange rates. That is, deviations from uncovered interest parity appear to vary in a way which is dependent upon the exchange rate regime. By using the many EMS realignments, we are also able to quantify the `peso problem.'

Monolithic and mechanical multijunction space solar cells

High-efficiency, lightweight, radiation-resistant solar cells are essential to meet the large power requirements of future space missions. Single-junction cells are limited in efficiency. Higher cell efficiencies could be realized by developing multijunction, multibandgap solar cells. Monolithic and mechanically stacked tandem solar cells surpassing single-junction cell efficiencies have been fabricated. This article surveys the current status of monolithic and mechanically stacked multibandgap space solar cells, and outlines problems yet to be resolved. The monolithic and mechanically stacked cells each have their own problems related to size, processing, current and voltage matching, weight, and other factors. More information is needed on the effect of temperature and radiation on the cell performance. Proper reference cells and full-spectrum range simulators are also needed to measure efficiencies correctly. Cost issues are not addressed, since the two approaches are still in the developmental stage

Uncovered Interest Parity in Crisis

This paper tests for uncovered interest parity (UIP) using daily data for 23 developing and developed countries during the crisis-strewn 1990s. We find that UIP works better on average in the 1990s than in previous eras in the sense that the slope coefficient from a regression of exchange rate changes on interest differentials yields a positive coefficient (which is sometimes insignificantly different from unity). UIP works systematically worse for fixed and flexible exchange rate countries than for crisis countries, but we find no significant differences between rich and poor countries. Copyright 2002, International Monetary Fund