88 research outputs found

    Methods of Step-Size Distribution Optimization Used in S-SSFM Simulations of WDM Systems, Journal of Telecommunications and Information Technology, 2009, nr 1

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    Brief review of methods used for simulation of signal propagation in wavelength division multiplexed (WDM)links is presented. We propose two novel methods of stepsize distribution optimization used to improve symmetrized split step Fourier method (S-SSFM) numerical efficiency: presimulated local error S-SSFM (PsLE S-SSFM) and modified logarithmic (ML S-SSFM). The PsLE S-SSFM contains two stages: in the initial stage step-size distribution optimization is carried out by combining local error method and presimulation with signal spectrum averaging; in the second stage conventional SSFM is used by applying optimal step-size distribution obtained in the initial stage. The ML S-SSFMis generalization of logarithmic method proposed to suppress spurious FWM tones, in which a slope of logarithmic step-size distribution is optimized. Overall time savings exceed 50%, depending of a simulated system scenario

    The best currency for an independent Scotland would be Norway’s krone

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    British Tata Steel Collapse What Happened?

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    Any firm, large or small, must generate profit. The only difference between them is that the former can sustain the losses forlonger. However, is a 2 billion pounds loss in five years enough to quit? For Tata Steel, it was and we cannot blame it forthis. The reasons for such decision listed by the firm were, among others, huge surplus of steel in the world market andhigh costs of its production in the UK.This is not the first British producer, which closed its steel mills. In September 2015, Sahaviriya Steel Industries UK, 100percent owned by Thailand’s largest steel producer, Sahaviriya Steel Industries PLC, stopped its production in North EastEngland Recar plant citing poor trading conditions and a drop in world steel prices. This left only 450 workers out of 2150just to keep the plant up until better times. Tata also tried to survive by cutting its labour. Since the middle of 2015, itdismissed 3000 workers...

    25(OH)D Concentration in Neonates, Infants, and Toddlers From Poland—Evaluation of Trends During Years 1981–2011

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    Introduction: The numerous evidence showing spectrum of vitamin D effects on human health resulted in both updates of vitamin D supplementation guidelines for general population and concerns on potential risk of hypercalcaemia. The aim of this study was to analyse trends in serum 25-hydroxyvitamin D concentration (25(OH)D) change over the 30 years of operation of a single pediatric diagnostic unit.Materials and methods: Calcium-phosphate metabolism markers and 25(OH)D concentrations were analyzed in a group that consisted of newborns and infants commissioned for diagnostics due to suspected calcium-phosphate metabolic disturbances (n = 3,163; mean age 8.0 ± 3.0 months).Results: 25(OH)D < 10 ng/ml was noted in 4.5% of patients (n = 163), 10–20 ng/ml in 14.7% (n = 465), 20–30 ng/ml in 23.9% (n = 756) and 30–50 ng/ml in 35.9% (n = 1,136). The mean 25(OH)D concentration in analyzed group was 37.5 ± 24.5 ng/ml. In patients with 25(OH)D concentration < 10 ng/ml a normal calcaemia (2.25–2.65 mmol/l) was noted in 83.4% cases (n = 136). Eighty one patients had 25(OH)D concentrations above 100 ng/ml with co-existing calcaemia in range of 2.6–4.38 mmol/l (mean Ca = 2.69 mmol/l). Hypocalcaemia (Ca < 2.25 mmol/l) was observed in 0.54%, (n = 17). 13.8% patients revealed calcium levels >2.65 mmol/l (n = 435). In general, the mean calcium-phosphate markers values were within the reference range for age. The highest mean 25(OH)D concentration of 51.8 ng/ml ± 38.8 was noted in years 1981–1999 (n = 305). The lowest mean 25(OH)D value was observed in years 2010–2011 (29.0 ng/ml ± 13.6; n = 412). The trend of decreasing 25(OH)D concentration during analyzed time period was significant (r = −0.29, p < 0.0001).Conclusions: Eighty percentage of children aged 0–36 months had 25(OH)D concentration >20 ng/ml, however, during 3 decades a mean 25(OH)D concentrations trended significantly to decrease. A direct relationship between low 25(OH)D concentration and hypocalcaemia was not observed nor between high 25(OH)D concentration and hypercalcemia
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