On the dimension of contact loci and the identifiability of tensors

Let $X\subset \mathbb{P}^r$ be an integral and non-degenerate variety. Set $n:= \dim (X)$. We prove that if the $(k+n-1)$-secant variety of $X$ has (the expected) dimension $(k+n-1)(n+1)-1<r$ and $X$ is not uniruled by lines, then $X$ is not $k$-weakly defective and hence the $k$-secant variety satisfies identifiability, i.e. a general element of it is in the linear span of a unique $S\subset X$ with $\sharp (S) =k$. We apply this result to many Segre-Veronese varieties and to the identifiability of Gaussian mixtures $G_{1,d}$. If $X$ is the Segre embedding of a multiprojective space we prove identifiability for the $k$-secant variety (assuming that the $(k+n-1)$-secant variety has dimension $(k+n-1)(n+1)-1<r$, this is a known result in many cases), beating several bounds on the identifiability of tensors.Comment: 12 page

Model for an evaluation of electricity production and economical affordability of a wind turbine in Ireland

openThe aim of this thesis is to build a model to evaluate the electricity production and the economical affordability of a wind turbine, suitable for every site considered in which a database of wind speed is available. In particular this thesis analyses a site located in Cork County, Ireland. Starting from an analysis of the windiness of the site, using the two-parameter Weibull distribution, which is defined by his two parameters, both derived from six different numerical methods. The best method is evaluated calculating the errors on the measurement and for the number of samples available for this study, the empirical method turns out to be the best way to obtain the parameters. Having the wind distribution, in particular the velocity that carries the maximum energy, a selection of different wind turbine models can be done. In this thesis three different models are compared because the selected wind turbines have different power coefficient curves that suits differently the wind probability distribution, they have different range of wind in which they can operate and different value of the diameter. As a result, the Fuhrländer FL MD7 is the model that gives the most electricity production. To evaluate the economical affordability of the investment economic tools are used, which are the Discounted Pay Back Period, the Net Present Value (NPV) of the wind turbine at the end of life of the turbine and the Levelized Cost of Electricity (LCOE). In this thesis six different scenarios are evaluated in order to show how the variation of the electricity price, the investment costs and the Weighted Average Cost of Capital (WACC) affect the cash flow, and therefore the return of the investment. The first two scenarios are considered the base scenarios, in which the investment costs, operating and maintenance costs and the electricity price are the average obtained from the literature. The first one, which does not consider the WACC, shows a return of the investment of 7.3 and a NPV of 3053929.25 € while the second, as it can be expected, gives a return of the investment of 10.6 years, a NPV of 912187 € and a LCOE of 5.17 €cent/kWh. The second two scenarios vary on the electricity price. In the first one it is chosen a current price equal to 125 €/MWh which is an increase of more than 50% compared to the base scenario. The pay-back period is about 7.1 years, the NPV at the end of life is 1169486.85 € and the LCOE is the same as the base the case since the electricity price does not affect this parameter. The second scenario is a forecast of the electricity price to the 2030 and therefore also the investment costs are a forecast. The scenario considers an electricity price of 60 €/MWh and at the same time a reduction of the investment cost to 847 € per each kW of power of turbine installed. The pay-back period is about 12.4 years, the NPV at the end of life is 198246.20 €. A further study considers an electricity price of 60 €/MWh but without a decrease on the investment costs and sees a non-return of the investment in the lifetime of the wind turbine. The last two scenarios consider a variation of ± 10% on the WACC. In the scenario in which it decreases and equal to 5.4% the pay-back period is about 10.1 years, the NPV at the end of life is 1059697.03 and the LCOE is 5 €cent/kWh. In the scenario in which it decreases and equal to 6.6% the pay-back period is about 11.2 years, the NPV at the end of life is 774947.47 and the LCOE is 5.35 €cent/kWh.The aim of this thesis is to build a model to evaluate the electricity production and the economical affordability of a wind turbine, suitable for every site considered in which a database of wind speed is available. In particular this thesis analyses a site located in Cork County, Ireland. Starting from an analysis of the windiness of the site, using the two-parameter Weibull distribution, which is defined by his two parameters, both derived from six different numerical methods. The best method is evaluated calculating the errors on the measurement and for the number of samples available for this study, the empirical method turns out to be the best way to obtain the parameters. Having the wind distribution, in particular the velocity that carries the maximum energy, a selection of different wind turbine models can be done. In this thesis three different models are compared because the selected wind turbines have different power coefficient curves that suits differently the wind probability distribution, they have different range of wind in which they can operate and different value of the diameter. As a result, the Fuhrländer FL MD7 is the model that gives the most electricity production. To evaluate the economical affordability of the investment economic tools are used, which are the Discounted Pay Back Period, the Net Present Value (NPV) of the wind turbine at the end of life of the turbine and the Levelized Cost of Electricity (LCOE). In this thesis six different scenarios are evaluated in order to show how the variation of the electricity price, the investment costs and the Weighted Average Cost of Capital (WACC) affect the cash flow, and therefore the return of the investment. The first two scenarios are considered the base scenarios, in which the investment costs, operating and maintenance costs and the electricity price are the average obtained from the literature. The first one, which does not consider the WACC, shows a return of the investment of 7.3 and a NPV of 3053929.25 € while the second, as it can be expected, gives a return of the investment of 10.6 years, a NPV of 912187 € and a LCOE of 5.17 €cent/kWh. The second two scenarios vary on the electricity price. In the first one it is chosen a current price equal to 125 €/MWh which is an increase of more than 50% compared to the base scenario. The pay-back period is about 7.1 years, the NPV at the end of life is 1169486.85 € and the LCOE is the same as the base the case since the electricity price does not affect this parameter. The second scenario is a forecast of the electricity price to the 2030 and therefore also the investment costs are a forecast. The scenario considers an electricity price of 60 €/MWh and at the same time a reduction of the investment cost to 847 € per each kW of power of turbine installed. The pay-back period is about 12.4 years, the NPV at the end of life is 198246.20 €. A further study considers an electricity price of 60 €/MWh but without a decrease on the investment costs and sees a non-return of the investment in the lifetime of the wind turbine. The last two scenarios consider a variation of ± 10% on the WACC. In the scenario in which it decreases and equal to 5.4% the pay-back period is about 10.1 years, the NPV at the end of life is 1059697.03 and the LCOE is 5 €cent/kWh. In the scenario in which it decreases and equal to 6.6% the pay-back period is about 11.2 years, the NPV at the end of life is 774947.47 and the LCOE is 5.35 €cent/kWh

Tax systems and tax reforms in south and East Asia: Overview of the tax systems and main policy tax issues

The paper discusses the main aspects of taxation in South and East Asia. Particolar attention is given to the main issues which emerge from the tax systems of China, India, Japan, Malysia, South Korea and ThailandTax Systems Tax Reforms South East Asia

Tax Systems and Tax Reforms in South and East Asia: Overview of Tax Systems and main policy issues

South and East Asia are a particularly fast developing world economic areas, and are becoming increasingly more economically integrated. These countries, however, are not homogenous, and are lacking in any supra - national Authority. The total fiscal pressure of South and East Asian countries looks somewhat low when compared to that of countries with a similar per-capita income, pertaining to other economic world areas. However, a smooth Wagner law is confirmed by the data so that fiscal pressure is destined somewhat to increase as growth continues. With regards to similar experiences of developing and transition countries, indirect taxes prevail over direct ones. Low tax wedges on labor improve efficiency, by inducing both the supply and demand of labor. The heavy burden on consumption lessens equity and increases welfare losses. Any further uniform analysis of South and East Asian countries’ tax policy issues would be however quite fruitless. It is far better to consider tax policies issues which rise inside the whole area separately to those more specific to each cluster made up by similar countries. Intra-regional economic integration poses severe challenges to the tax structure in the Asian area. Three tax policy issues seem most problematic: the building of intra-countries’ agreements on reducing trade tariffs; the sequential revenue consequences of reduction in foreign trade taxes; the increasing tax competition for FDI. Intra-countries clusters’ tax policy issues differ from each other. In Japan and in S. Korea different choices have been made regarding the comprehensiveness of the PIT’s basis, whose burden as a consequence ends up being more fairly distributed in S. Korea. The two countries are facing the common problem of an ageing population and consequentially, social contributions, and eventually VAT are being raised. Malaysia’s direct taxes look higher than Thailand’s, but this is only because of the taxation of oil companies. Thailand has adopted VAT, while Malaysia has not changed its traditional sales tax. Both the countries are engaged in the recovery of revenue by improving tax administration. Both in China and in India income tax is small and poorly redistributing. Also, India has just moved from a schedular to a comprehensive tax basis. VAT is well established in China, while it is just arriving in India, as a consequence of a long waited but challenging reform, especially regarding the tax relationships among levels of government. Taxing power is now more centralized in China, but this needs to be corrected in order to avoid a lack of accountability on the part of the provinces.Tax Systems; Tax Reforms; South and East Asia

Bounds on the tensor rank

We give a sufficient criterion for a lower bound of the cactus rank of a tensor. Then we refine that criterion in order to be able to give an explicit sufficient condition for a non-redundant decomposition of a tensor to be minimal and unique.Comment: 14 page

Respiratory muscle training with normocapnic hyperpnea improves ventilatory pattern and thoracoabdominal coordination, and reduces oxygen desaturation during endurance exercise testing in COPD patients

Background: Few data are available about the effects of respiratory muscle training with normocapnic hyperpnea (NH) in COPD. The aim is to evaluate the effects of 4 weeks of NH (Spirotiger®) on ventilatory pattern, exercise capacity, and quality of life (QoL) in COPD patients. Methods: Twenty-six COPD patients (three females), ages 49-82 years, were included in this study. Spirometry and maximal inspiratory pressure, St George Respiratory Questionnaire, 6-minute walk test, and symptom-limited endurance exercise test (endurance test to the limit of tolerance [tLim]) at 75%-80% of peak work rate up to a Borg Score of 8-9/10 were performed before and after NH. Patients were equipped with ambulatory inductive plethysmography (LifeShirt®) to evaluate ventilatory pattern and thoracoabdominal coordination (phase angle [PhA]) during tLim. After four supervised sessions, subjects trained at home for 4 weeks 10 minutes twice a day at 50% of maximal voluntary ventilation. The workload was adjusted during the training period to maintain a Borg Score of 5-6/10. Results: Twenty subjects completed the study. After NH, maximal inspiratory pressure significantly increased (81.5±31.6 vs 91.8±30.6 cmH2O, P&lt;0.01); exercise endurance time (+150 seconds, P=0.04), 6-minute walk test (+30 meters, P=0.03), and QoL (-8, P&lt;0.01) all increased. During tLim, the ventilatory pattern changed significantly (lower ventilation, lower respiratory rate, higher tidal volume); oxygen desaturation, PhA, and dyspnea Borg Score were lower for the same work intensity (P&lt;0.01, P=0.02, and P&lt;0.01, respectively; one-way ANOVA). The improvement in tidal volume and oxygen saturation after NH were significantly related (R2=0.65, P&lt;0.01). Conclusion: As expected, NH improves inspiratory muscle performance, exercise capacity, and QoL. New results are significant change in ventilatory pattern, which improves oxygen saturation, and an improvement in thoracoabdominal coordination (lower PhA). These two facts could explain the reduced dyspnea during the endurance test. All these results together may play a role in improving exercise capacity after NH training

Renal sodium retention in pre-ascitic cirrhosis: the more we know about the puzzle, the more it becomes intricate.

Ascites develops in 5–10% of patients with compensated cirrhosis per year and carries an ominous prognosis [1] . The appropriate management and possible prevention of this complication obvi- ously depends on an in-depth knowledge of ascites pathophysiol- ogy, which remains somewhat elusive despite many studies that have addressed the topic over decades. There is no doubt that post-sinusoidal portal hypertension is the main ''local" pathoge- netic factor, and renal sodium retention is the main ''systemic" event leading to a positive fluid balance and, ultimately, ascites formation. However, uncertainties surround both the efferent (that is the factors/systems promoting renal sodium retention) and afferent (that is the factors that activate efferent mecha- nisms) factors associated with renal sodium handling abnormal- ities [2] . Sodium balance has been demonstrated to become positive before ascites formation both in animal models of cirrho- sis and humans [3–6] . Study of the early mechanisms leading to ascites would help unveil its pathophysiology in a stage of the disease where further complications involving systemic hemody- namics and renal function may act as confounding factors. In this issue of the Journal of Hepatology, Sansoè and co-workers pres- ent a fine study on an efferent mechanism potentially leading to renal sodium retention in pre-ascitic cirrhosi

Radio recombination lines from obscured quasars with the SKA

We explore the possibility of detecting hydrogen radio recombination lines from 0 < z < 10 quasars. We compute the expected Hnalpha flux densities as a function of absolute magnitude and redshift by considering (i) the range of observed AGN spectral indices from UV to X-ray bands, (ii) secondary ionizations from X-ray photons, and (iii) stimulated emission due to nonthermal radiation. All these effects are important to determine the line fluxes. We find that the combination of slopes: alpha_X,hard = -1.11, alpha_X,soft = -0.7, alpha_EUV = -1.3, alpha_UV = -1.7, maximizes the expected flux, f_Hnalpha = 10 microJy for z = 7 quasars with M_AB = -27 in the n = 50 lines; allowed SED variations produce variations by a factor of 3 around this value. Secondaries boost the line intensity by a factor of 2 to 4, while stimulated emission in high-z quasars with M_AB = -26 provides an extra boost to RRL flux observed at nu = 1 GHz if recombinations arise in HII regions with T_e = 10^3-5 K, n_e = 10^3-5 cm^-3. We compute the sensitivity required for a 5sigma detection of Hnalpha lines using the SKA, finding that the SKA-MID could detect sources with M_AB < -27 (M_AB < -26) at z < 8 (z < 3) in less than 100 hrs of observing time. These observations could open new paths to searches for obscured SMBH progenitors, complementing X-ray, optical/IR and sub-mm surveys.Comment: 11 pages, 9 figures; to be published in Monthly Notices of the Royal Astronomical Society Main Journa

Higher order terms of Mather's β\beta-function for symplectic and outer billiards

We compute explicitly the higher order terms of the formal Taylor expansion of Mather's $\beta$-function for symplectic and outer billiards in a strictly-convex planar domain $C$. In particular, we specify the third terms of the asymptotic expansions of the distance (in the sense of the symmetric difference metric) between $C$ and its best approximating inscribed or circumscribed polygons with at most $n$ vertices. We use tools from affine differential geometry.Comment: 17 pages, 3 figure