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Search Results: 1 - 10 of 461795 matches for " A Azimzadeh "
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Weakly chained matrices and impulse control
Parsiad Azimzadeh,Peter A. Forsyth
Quantitative Finance , 2015,
Abstract: This work is motivated by numerical solutions to Hamilton-Jacobi-Bellman quasi-variational inequalities (HJBQVIs) associated with combined stochastic and impulse control problems. In particular, we consider (i) direct control, (ii) penalized, and (iii) explicit control schemes applied to the HJBQVI problem. Scheme (i) takes the form of a Bellman problem involving an operator which is not necessarily contractive. We consider the well-posedness of the Bellman problem and give sufficient conditions for convergence of the corresponding policy iteration. To do so, we use weakly chained diagonally dominant matrices, which give a graph-theoretic characterization of weakly diagonally dominant M-matrices. We compare schemes (i)--(iii) under the following examples: (a) optimal control of the exchange rate, (b) optimal consumption with fixed and proportional transaction costs, and (c) pricing guaranteed minimum withdrawal benefits in variable annuities. Perhaps controversially, we find that one should abstain from using scheme (i).
The existence of optimal bang-bang controls for GMxB contracts
Parsiad Azimzadeh,Peter A. Forsyth
Quantitative Finance , 2015, DOI: 10.1137/140953885
Abstract: A large collection of financial contracts offering guaranteed minimum benefits are often posed as control problems, in which at any point in the solution domain, a control is able to take any one of an uncountable number of values from the admissible set. Often, such contracts specify that the holder exert control at a finite number of deterministic times. The existence of an optimal bang-bang control, an optimal control taking on only a finite subset of values from the admissible set, is a common assumption in the literature. In this case, the numerical complexity of searching for an optimal control is considerably reduced. However, no rigorous treatment as to when an optimal bang-bang control exists is present in the literature. We provide the reader with a bang-bang principle from which the existence of such a control can be established for contracts satisfying some simple conditions. The bang-bang principle relies on the convexity and monotonicity of the solution and is developed using basic results in convex analysis and parabolic partial differential equations. We show that a guaranteed lifelong withdrawal benefit (GLWB) contract admits an optimal bang-bang control. In particular, we find that the holder of a GLWB can maximize a writer's losses by only ever performing nonwithdrawal, withdrawal at exactly the contract rate, or full surrender. We demonstrate that the related guaranteed minimum withdrawal benefit contract is not convexity preserving, and hence does not satisfy the bang-bang principle other than in certain degenerate cases.
Restarted Adomian decomposition method for solving Duffing-van der Pol equation
A. R. Vahidi,Z. Azimzadeh,S. Mohammadifar
Applied Mathematical Sciences , 2012,
Abstract:
Efficacy of Microwave and Infrared Radiation in the Treatment of the Skin Lesions Caused by Leishmania major in an Animal Model
SE Eskandari,A Azimzadeh,M Bahar,Z Safai Naraghi
Iranian Journal of Public Health , 2012,
Abstract: Background: Cutaneous leishmaniasis caused by L. major is an important public health problem in endemic areas. The aim of this study was to explore the therapeutic effect of microwave and or infrared radiation in the treatment of lesion induced in BALB/c mice by L. major inoculation.Methods: The footpad lesion was induced in BALB/c mice by inoculation of L. major promastigotes subcutaneously. The lesion was treated with 600 watts power, 2.450 GHz frequency and/or infrared device with 150 watts and a wave length of 890 nanometres. The size of the lesion was recorded by footpad swelling measurement every 10 days. Results: The lesion growth was significantly hampered in treated mice compared with the untreated control group (P<0.05). Infrared radiation was more effective than microwave in inhibiting ulcer enlargement.Conclusion: Infrared radiation and microwave significantly hampered L. major lesion growth in BALB/c mice. This therapeutic effect was more in infrared radiation treated mice than microwave treated mice.
A Comparison Between Adomian’s Decomposition Method and the Homotopy Perturbation Method for Solving Nonlinear Differential Equations
E. Babolian,A.R. Vahidi,Z. Azimzadeh
Journal of Applied Sciences , 2012,
Abstract: In this study, we have compared the performance of the Adomian Decomposition Method (ADM) and the Homotopy Perturbation Method (HPM) for solving nonlinear differential equations. By comparative theoretical analysis of these methods, we show that the ADM is equivalent to the HPM with a specific convex homotopy for nonlinear differential equations.
The Indigenous Cuminum Cyminum L. of Yazd Province: Chemical Assessment and Evaluation of its Antioxidant Effects
F Haghiroalsadat,A Vahidi,M Sabour,M Azimzadeh
Journal of Shahid Sadoughi University of Medical Sciences , 2011,
Abstract: Introduction: Iran is one of the greatest and the most divergent resources of medicinal plants. Cuminum cyminum is one of the important and valuable medicinal plants of our country with such medical effects as anti-seizure, anti- epilepsy, stomach-strengthening, diuretic, anti-flatulence and maldigestion. The aim of this research is to assess the chemical components and antioxidant effects of the seed essence of this plant. Methods: The seed essence from southwest mountains of Behabad, Yazd was extracted by Clevenger apparatus, then segregation and recognition of components was performed by Gas Chromatography(GC) and Gas Chromatography-Mass Spectrometry(GC-MS) methods. The DPPH test was used for estimating antioxidant effects and Follin-Ciocalteu method was used for estimating the quantity of phenol compounds. This study was an applied research. Results: Components identification revealed that propanal (26.19%), 1-phenyl-1-butanol (16.49%), γ-Terpinene (13.04%) and benzene methanol (25.4%) had the highest percentage in the essence. The antioxidant test showed a high antioxidant effect with IC50 of 1.49 μg/mg and a high phenolic component percentage of about 162.62 mg/g. Conclusion: The propanal, the main component of seed essence, has a wide range of applications in industries and pharmacy. The result of this research showed a much higher antioxidant activity for native Cuminum Cyminum of Yazd province comparing the previous similar studies about this plant in other areas.
Weblog Search Engine Based on Quality Criteria
F. Azimzadeh,,A. R. Ramli,,B. M. Ali, H. Ibrahim,B. M. Ali
International Journal on Computer Science and Engineering , 2011,
Abstract: Nowadays, increasing amount of human knowledge is placed in computerized repositories such as the World Wide Web. This gives rise to the problem of how to locate specific pieces of information in these often quite unstructured repositories. Search engines is the best solved. Some studied show that, almost half of the traffic to the blog server comes from search engines. The more outgoing and informal social nature of the blogosphere opens the opportunity for exploiting more socially-oriented features. The nature of blogs, which are usually characterized by their personal and informal nature, dynamically and constructed on the new relational links required new quality measurement for blog search engine. Link analysis algorithms that exploit the Web graph may not work well in the blogosphere in general. (Gon alves et al 2010) indicated that most of the popular blogs in the dataset (70%) have a PageRank value equal -1, being thus almost invisible to the search engine. We expected that incorporated the special blogs quality criteria would be more desirably retrieved by search engines.
Comparison of Fecal Calprotectin Levels in Iranian general population and army personnel
Pedram Azimzadeh,Shahrokh Iravani
Journal of Paramedical Sciences , 2012,
Abstract: Fecal Calprotectin is released in colon by activated neutrophils. Investigation of diagnostic application of determination of fecal Calprotectin levels is considered by many researchers to compare between different colorectal diseases like Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Diseases (IBD). Due to the effect of nutrition habits on the inflammatory processes of bowel, the main goal of this study was to evaluate the level of fecal Calprotectin in healthy subjects in Iranian army personnel that have specific and the same nutrition habits, in comparison with non-military population and also make this test an in-house method in Army laboratories. In this study a prospective and sample collection method used available samples (Convenience sampling). We collected stool samples from 108 subjects from Army personnel and 108 samples from non-military Iranian population with corresponding data collection form. Determination of Calprotectin levels was done by specific third generation quantitative ELISA method and statistics were done using SPSS software. The results showed that mean Calprotectin level in two included groups were 26.1 micrograms per gram in Army personnel group and 25.4 micrograms per gram in non-military control subjects. Fecal Calprotectin level in two studied groups wasn’t significantly different. Despite the little increase in Calprotectin levels in Army personnel group compared with control group this difference wasn’t statistically significant (P>0.05). We can conclude that the nutrition habits of army personnel could cause effects on inflammatory processes in digestive system. Determination of fecal Calprotectin levels as a cost effective and non invasive test could be used by military physicians for early diagnosis of inflammation in personnel by routine tests subjects.
Fast Engset computation
Parsiad Azimzadeh,Tommy Carpenter
Mathematics , 2015,
Abstract: The blocking probability of a finite-source bufferless queue is a fixed point of the Engset formula, for which we prove existence and uniqueness. Numerically, the literature suggests a fixed point iteration. We show that such an iteration can fail to converge and is dominated by a simple Newton's method, for which we prove a global convergence result. The analysis yields a new Tur\'an-type inequality involving hypergeometric functions, which is of independent interest.
Prone Position: Does It Help with Acute Respiratory Distress Syndrome (ARDS) Requiring Extracorporeal Membrane Oxygenation (ECMO)?  [PDF]
Nava Azimzadeh, Michael Baram, Nicholas C. Cavarocchi, Hitoshi Hirose
Open Journal of Respiratory Diseases (OJRD) , 2017, DOI: 10.4236/ojrd.2017.71003
Abstract: Introduction: Lung protective ventilation therapy with low tidal volume-high PEEP is the standard treatment for the patients with acute respiratory distress syndrome (ARDS). Oscillators are occasionally used for salvage ventilation in cases where poor compliance restricts the use of traditional ventilation with ARDS. In addition to ventilator therapy, prone positioning has been used to improve oxygenation. We presented a challenging case of ARDS, which failed medical management extracorporeal membrane oxygenation (ECMO) support and oscillatory ventilation. Prone positioning was initiated which improved oxygenation, respiratory compliance and posterior atelectasis. Case presentation: A 41-year-old morbid obese female developed ARDS due to influenza pneumonia. The patient remained hypoxic despite optimum medical and ventilator management and required veno-venous extracorporeal membrane oxygenation (VV ECMO). CT scan of the chest showed ARDS with posterior consolidation. Despite ARDSnet ventilation support, antiviral therapy and ECMO support, there was no clinical improvement. High frequency oscillatory ventilation was initiated on ECMO day #13, which resulted in no respiratory improvement over the next 5 days. On ECMO day #18, the patient was placed on a Rotaprone? bed Therapy, utilizing a proning strategy of 16 hours a day. The clinical improvements observed were resolving of the consolidation on CXR, improvements in ventilatory parameters and decreased oxygen requirements. The patient was successfully weaned off ECMO on POD#25 (8 days post prone bed). Conclusions: Prone position improved oxygen saturation and pulmonary compliance in severe ARDS requiring ECMO and it might facilitate early weaning.
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