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We present a variant of Barvinok’s algorithm for computing a short rational generating function for the integer points in a nonempty pointed polyhedron P:={x∈Rn:Ax≤b} given by rational inequalities. A main use of such a rational generating function is to count the number of integer points in P.
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Given a simplicial complex K with weights on its simplices and a chain on it, the Optimal Homologous Chain Problem (OHCP) is to find a chain with minimal weight that is homologous (over Z) to the given chain. The OHCP is NP-complete, but if the boundary matrix of K is totally unimodular (TU), it becomes solvable in polynomial time when modeled as a linear program (LP). We define a condition on the simplicial complex called non total-unimodularity neutralized, or NTU neutralized, which ensures that even when the boundary matrix is not TU, the OHCP LP must contain an integral optimal vertex for every input chain. This condition is a property of K, and is independent of the input chain and the weights on the simplices. This condition is strictly weaker than the boundary matrix being TU. More interestingly, the polytope of the OHCP LP may not be integral under this condition. Still, an integral optimal vertex exists for every right-hand side, i.e., for every input chain. Hence a much larger class of OHCP instances can be solved in polynomial time than previously considered possible. As a special case, we show that 2-complexes with trivial first homology group are guaranteed to be NTU neutralized.
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The multi-proxy data (pollen, diatoms, Cladocera, 14C) from the sediments of Lake Suchar Wielki representing the period ca. 11,600–9800 cal. BP have allowed the reconstruction of the influence of Preboreal cold oscillations on terrestrial and aquatic environments in NE Poland. The reconstructed changes in plant, cladoceran and diatom communities indicated an occurrence of four short-lasting negative climate events during the Preboreal period. The first three of them occurred in the early Preboreal (ca. 11,300–11,150, 11,100–11,000 and 10,900–10,850 cal. BP) and they were separated by short, warmer intervals. The obtained palynological data indicated that these events did not result in the transformations of the pine-birch forests strongly dominant in that period, but were only manifested by changes in the pollen production by the trees forming woodstands. In the lake during these coolings, cold-water Cladocera species developed, and the abundance of aquatic organisms decreased. Water level in the lake during two older early-Preboreal cold events increased significantly, and remained low during the last event. In the late Preboreal a fourth cooling took place. The cold peak was relatively short (ca. 10,300–10,200 cal. BP), but was preceded by a ca. 300-year-long period when conditions for plants were unfavourable. The drop in temperature was accompanied by a decrease in the humidity of the climate and a decrease in the water level in the lake. Again, the abundance of cold-water species increased. The acreage covered by pine decreased, and a temporary spreading of birch occurred. This last cold event in the Preboreal was followed by a relatively stable warm phase at the end of this chronozone. The recorded climate changes in NE Poland during the Preboreal correspond fairly well with those reported for other regions of Europe and the whole Northern Hemisphere.
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The study on runoff series variation is of great significance for the development and utilization of water resources in a river basin. In this paper, runoff series data from the Three Gorges reservoir and five upstream catchments observed from 1951 to 2013 are used to analyze the changes in the Three Gorges reservoir inflow series via the Mann–Kendall test. Based on the hydro-metrological data (i.e. precipitation, and temperature) and the human activities data (i.e. urbanization percentage, effective irrigation area, afforestation area, population, and gross domestic product (GDP)) during the same period, the back-propagation artificial neutral network (BP-ANN) model is applied to quantify the influence of the driving factors. The results show: (1) During the study period, there is a significant decrease in the Three Gorges reservoir inflow and the reduction rate is 0.73 mm per year; (2) Runoff from all of the five upstream catchments of the Three Gorges reservoir decrease. Specifically, the decreased trends in the runoff from the Mintuo River catchment and the Jialing River catchment are statistical significant; (3) Impacts of climate change and human activities on changes in the Three Gorges reservoir inflow series account for 36% and 64%, respectively. Among all the driving factors, the precipitation is the dominant influencing factor, accounting for the relative contribution of 25%. The temperature, urbanization percentage, effective irrigation area, population and GDP are the minor factors, accounting for the relative contributions of 11%, 17%, 15%, 15% and 14%, respectively. The afforestation area is the least effective factor with a relative contribution of 3%.
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Nam Co (Heavenly Lake) not only responds sensitively to climate change, but also exerts significant influences on climate change. Previous studies revealed that the lake effects from the North American Great Lakes shown interaction with climate changes. However, the lakes effect of more than 1200 lakes with an area of 47,000 km2 on the Tibetan Plateau remains less studied. In this study, we analyzed the spatial distribution of precipitation in the Nam Co Basin during July–August and November–December to clarify the lake effect. We found that the lake cooling effect during July–August and lake heating effect during November–December resulted in the spatial differences of precipitation within the Nam Co Basin. These effects generally caused more precipitation in the south than in the north during July–August, and more precipitation in the east than in the west during November–December. Weakening Indian monsoon and climate warming led to an increased north–south precipitation difference in the Nam Co Basin. However, the precipitation differences between the west and east during November–December decreased with climate warming. The intensification of the westerly might be responsible for the particular phenomenon.
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Agricultural residues management is considered to be a vital strategy in order to accomplish resource conservation and to maintain the quality of the environment. In recent years, biofibers have attracted increasing interest due to their wide applications in food packaging and in the biomedical sciences. These eco-friendly polymers reduce rapidly and replace the usage of the petroleum-based synthetic polymers due to their safety, low production costs, and biodegradability. This paper reports an efficient method for the production of the cellulose acetate biofiber from flax fibers and cotton linters. The used process satisfied a yield of 81% and 54% for flax fibers and cotton linters respectively (based on the weight of the cellulosic residue used). The structure of the produced bioplastic was confirmed by X-ray diffraction, FT-IR and gel permeation chromatography. Moreover, this new biopolymer is biodegradable and is not affected by acid or salt treatment but is alkali labile. A comparison test showed that the produced cellulose acetate was affected by acids to a lesser extent than polypropylene and polystyrene. Therefore, this new cellulose acetate bioplastics can be applied in both the food industry and medicine.
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Nigeria realizes the devastating effects of HIV/AIDS on its people, health, economic, and social progress fairly recently. This paper analyses descriptively the HIV epidemiology in Nigeria based on the sentinel surveillance system in place. Recently, it is estimated that about 3, 229, 757 people live with HIV in Nigeria and about 220, 393 new HIV infections occurred in 2013 and 210,031 died from AIDS related cases. People practicing low-risk sex are the driving force of HIV epidemic in Nigeria while the high risk groups involving female sex workers, men who have sex with men and injecting drug users contribute substantially to new infections. In conclusion, HIV prevalence among adults in Nigeria is relatively low (3.2%), yet Nigeria is an enormous country where HIV infection remains an issue that demands a systematic and highly tailored intervention.
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One of the challenges in data analysis is to distinguish between different sources of variability manifested in data. In this paper, we consider the case of multiple sensors measuring the same physical phenomenon, such that the properties of the physical phenomenon are manifested as a hidden common source of variability (which we would like to extract), while each sensor has its own sensor-specific effects (hidden variables which we would like to suppress); the relations between the measurements and the hidden variables are unknown. We present a data-driven method based on alternating products of diffusion operators and show that it extracts the common source of variability. Moreover, we show that it extracts the common source of variability in a multi-sensor experiment as if it were a standard manifold learning algorithm used to analyze a simple single-sensor experiment, in which the common source of variability is the only source of variability.
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Despite the current financial crisis, accounting and finance programmes in UK have remained popular. Finance undergraduate teaching in accounting degrees is a significant component of the degree and relies heavily on Modern Finance Theory (MFT). Some of the developments in the finance curricula are critically examined. It is argued that current finance education should become more reflective and more heterodox in approach as the current curricula is biased towards techniques based on neoclassical theory. Suggestions are given for improvement of the curricula which will allow the narrow assumptions of neoclassical theory to be widened. These involve students taking into account not only the structures and patterns of finance but also the processes which are created by human experiences as part of their interactions as well as what helps to make these processes sustainable.
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This paper describes the optimization and comparison of conventional and microwave-assisted methods for efficient, cheap, one-pot, and straightforward synthesis of isocoumarins under mild reaction conditions. On this basis of this aim, synthesis of 3-acetyl isocoumarin from 2-formylbenzoic acid with mono-chloroacetone was chosen as a model reaction. Afterward, four different methods conventional (Method A), microwave open vessel (Method B), microwave sealed vessel (Method C), and microwave closed system (Method D) were used methodologically to determine best experimental conditions for each of these methods in this model reaction. The results revealed that developed Methods A, C and D could be used successfully under solvent-free conditions with good yields (84–87%) for the future efficient, one-pot synthesis of isocoumarins. This paper is also a first for characterizing 3-acetyl isocoumarin by using ATR, 1H NMR, 13C NMR and GC–MS.
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