844 research outputs found
The Big-M method with the numerical infinite M
No full textLinear programming is a very well known and deeply applied field of optimization theory. One of its most famous and used algorithms is the so called Simplex algorithm, independently proposed by Kantorovič and Dantzig, between the end of the 30s and the end of the 40s. Even if extremely powerful, the Simplex algorithm suffers of one initialization issue: its starting point must be a feasible basic solution of the problem to solve. To overcome it, two approaches may be used: the two-phases method and the Big-M method, both presenting positive and negative aspects. In this work we aim to propose a non-Archimedean and non-parametric variant of the Big-M method, able to overcome the drawbacks of its classical counterpart (mainly, the difficulty in setting the right value for the constant M). We realized such extension by means of the novel computational methodology proposed by Sergeyev, known as Grossone Methodology. We have validated the new algorithm by testing it on three linear programming problems
Le città dei libri: ambienti di copia e immaginari poetici nello spazio adriatico dei secoli XIV-XV
No full textIl contributo mette a fuoco il concetto di spazio adriatico come cornice
culturale inclusiva, capace di accogliere e rielaborare con originalità
le principali istanze dell’Umanesimo. Esso prende in esame alcuni casi
rappresentativi di città quali luogo di produzione e di collezione di manoscritti;
e di città quali punto di riferimento per elaborazioni letterarie
in versi, che nella loro tensione lirica tengono unito questo perimetro,
attraverso il viaggio immaginario dei testi che lo percorrono. Ne emerge
un reticolato di relazioni che, insieme al dato geografico, permette di evidenziare
realtà territoriali determinanti nei processi intellettuali alla base
della civiltà moderna.The paper focuses on the concept of the Adriatic space as an inclusive
cultural framework, capable of receiving and reworking with originality
the main instances of the Humanism. It examines some representative
cases of cities as places of production and collection of manuscripts; and
of cities as points of reference for literary elaborations in verse, which in
their lyrical tension hold this perimeter together through the imaginary
journey of the texts that pass through it. What emerges is a network of
relationships that, together with the geographical datum, allows us to
highlight territorial realities that were decisive in the intellectual processes
at the foundation of modern civilisation
Un codice del Bessarione alla base della princeps di Atanasio nella versione di Ognibene da Lonigo
No full textManagerial discretion and optimal financing policies with cash flow uncertainty
No full textBuilding on the work of Stulz (1990), this paper analyzes the impact of managerial discretion on optimal leverage within an agency cost model of corporate financing. Under the assumption that stockholders do not know with certainty the mean of the cash flow distribution, we argue that leverage fails to control for the amount of cash the manager can misappropriate in personal projects. We develop a model of a firm’s value maximization problem that predicts that as expected earnings uncertainty increases the firm will decrease its optimal level of borrowing. In a second part, we test this proposition on a panel of non–financial UK firms, by investigating the determinants of firms’ performance and allowing for endogeneity of capital structure decisions. The estimates confirm that earnings uncertainty, as measured by the volatility in monthly consensus forecasts of individual companies’ earnings per share, negatively affects corporate leverage. Furthermore, new empirical support is found to the agency cost view that corporate performance is positively correlated with leverage when poorly managed firms are selected.
Intravenous clomipramine decreases excitability of human motor cortex: a study with paired magnetic stimulation
No full textSeveral recent reports suggest the possibility of monitoring pharmacological effects on brain excitability through transcranial magnetic stimulation (TMS). In these studies, paired magnetic stimulation has been used in normal subjects and on patients who were taking different antiepileptic drugs. The aim of our study was to investigate motor area excitability on depressed patients after intravenous administration of a single dose of clomipramine, a tricyclic antidepressant. Motor cortex excitability was studied by single and paired transcranial magnetic stimulation (TMS) before and after 4, 8 and 24 h from intravenous administration of 25 mg of clomipramine. Cortical excitability was measured using different TMS parameters: motor threshold (MT), motor evoked potential (MEP) amplitude, duration of cortical silent period (CSP), intracortical inhibition (ICI) and intracortical facilitation (ICF). Spinal excitability and peripheral nerve conduction was measured by F response and M wave. A temporary but significant increase of motor threshold and intracortical inhibition and a decrease of intracortical facilitation were observed 4 h following drug administration. MEP amplitude, cortical silent period, F response and M wave were not significantly affected by drug injection. Our findings suggest that a single intravenous dose of clomipramine can exert a significant but transitory suppression of motor cortex excitability in depressed patients. TMS represents a useful research tool in assessing the effects of motor cortical excitability of neuropsychiatric drugs used in psychiatric disease
Long-term levodopa admnistration in chronic stroke patients. A clinical and neurophysiologic single-blind placebo-controlled cross-over pilot study.
No full textOptimization of laser beam welding of stainless steels in overlap joint configuration
No full textThis paper presents experimental design approach to process parameter optimization for laser welding of martensitic AISI416 and AISI440FSe stainless steels in a constrained overlap configuration. To determine the optimal laser-welding parameters, a set of mathematical models were developed relating welding parameters to each of the selected weld characteristics. Both the statistical and the experimental validations for the models were confirmed. The weld quality criterion considered determining optimal parameters was the maximization of weld penetration depth and resistance length. Laser power and welding speed in the range of 855-930W and 4.50-4.65 m/min respectively with a fiber diameter of 300μm were identified as the optimal set of process parameters. However, reducing the laser power in the range 800-840W and increasing the welding speed in the range 4.75-5.37 m/min caused stronger and better welds
A double blind placebo RCT to investigate the effects of serotonergic modulation on brain excitability and motor recovery in stroke patients.
No full textMotor excitability is increased in both hemispheres in stroke patients during motor recovery. Pharmacologically controlled changes of cortical excitability might be beneficial for synaptic plasticity and therefore facilitate functional recovery after a brain lesion. In particular, it has been suggested that antidepressant drugs can modulate motor excitability. Several recent reports suggest the possibility of monitoring pharmacological effects on brain excitability through transcranial magnetic stimulation (TMS). The aim of this study was to investigate motor area excitability in patients with stroke after oral administration of citalopram. We conducted a prospective randomised placebo controlled study. Twenty patients with unilateral stroke were included in the study: ten patients treated by antidepressive drug and ten patients with placebo. A selective serotonergic drug (citalopram) or a placebo was administered using a mean dosage of 10 mg/day in combination with physiotherapy. Motor cortex excitability was studied by single and paired transcranial magnetic stimulation. TMS recording was tested before (T1) and 1 month after (T2) beginning drug treatment. Patients treated by the serotonergic drug, compared to patients that received a placebo, showed a significant improvement in neurological status as measured by NIHSS and a decrease of motor excitability over the unaffected hemisphere, while no differences were observed over the affected hemisphere. Our findings suggest that treatment with serotonergic drugs can bring about a significant decrease of the motor cortex excitability in stroke patients with effects on both the affected and unaffected hemispheres associated with a better motor recovery
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