2,029 research outputs found
On the dimension of contact loci and the identifiability of tensors
Let be an integral and non-degenerate variety. Set
. We prove that if the -secant variety of has (the
expected) dimension and is not uniruled by lines, then
is not -weakly defective and hence the -secant variety satisfies
identifiability, i.e. a general element of it is in the linear span of a unique
with . We apply this result to many Segre-Veronese
varieties and to the identifiability of Gaussian mixtures . If is
the Segre embedding of a multiprojective space we prove identifiability for the
-secant variety (assuming that the -secant variety has dimension
, 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<0.01); exercise endurance time (+150 seconds, P=0.04), 6-minute walk test (+30 meters, P=0.03), and QoL (-8, P<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<0.01, P=0.02, and P<0.01, respectively; one-way ANOVA). The improvement in tidal volume and oxygen saturation after NH were significantly related (R2=0.65, P<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 -function for symplectic and outer billiards
We compute explicitly the higher order terms of the formal Taylor expansion
of Mather's -function for symplectic and outer billiards in a
strictly-convex planar domain . In particular, we specify the third terms of
the asymptotic expansions of the distance (in the sense of the symmetric
difference metric) between and its best approximating inscribed or
circumscribed polygons with at most vertices. We use tools from affine
differential geometry.Comment: 17 pages, 3 figure
A Simple Contrast Matching Rule for OSEM Reconstructed PET Images with Different Time of Flight Resolution
Background: Time-of-Flight (TOF) is a leading technological development of Positron Emission Tomography (PET) scanners. It reduces noise at the Maximum-Likelihood solution, depending on the coincidence–timing–resolution (CTR). However, in clinical applications, it is still not clear how to best exploit TOF information, as early stopped reconstructions are generally used. Methods: A contrast-recovery (CR) matching rule for systems with different CTRs and non-TOF systems is theoretically derived and validated using (1) digital simulations of objects with different contrasts and background diameters, (2) realistic phantoms of different sizes acquired on two scanners with different CTRs. Results: With TOF, the CR matching rule prescribes modifying the iterations number by the CTRs ratio. Without TOF, the number of iterations depends on the background dimension. CR matching was confirmed by simulated and experimental data. With TOF, image noise followed the square root of the CTR when the rule was applied on simulated data, while a significant reduction was obtained on phantom data. Without TOF, preserving the CR on larger objects significantly increased the noise. Conclusions: TOF makes PET reconstructions less dependent on background dimensions, thus, improving the quantification robustness. Better CTRs allows performing fewer updates, thus, maintaining accuracy while minimizing noise
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