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Search Results: 1 - 10 of 7940 matches for " Ahmad Chaddad "
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Low-Noise Front-End Receiver Dedicated to Biomedical Devices: NIRS Acquisition System  [PDF]
Ahmad Chaddad
Circuits and Systems (CS) , 2014, DOI: 10.4236/cs.2014.58021
Abstract: This paper concerns the design and the implementation of a fully integrated front-end intended to Near-Infrared Spectroscopy System (NIRS) acquisition system. A low-noise transimpedance amplification (TIA) circuit followed by adjustable cut-off frequency and a low-pass filter (LPF) was implemented in order to decrease noise circuit of NIRS detectors. For TIA, a single ended common source, common gate input stage based on a cascode structure is used to get a higher gain-bandwidth closed-loop transimpedance amplifier. To enhance the circuit noise performance, a single feedback transistor technique is used, compared to passive feedback, to achieved high quality data from NIRS acquisition channel. The proposed LPF combines two control methods to adjust the low cut-off frequency. Simulation results show a TIA gain of 104.2 dBΩ, ?3dB bandwidth of 19 MHz and an equivalent input noise current spectral density of 446 fA/√Hz. LPF filter exhibits a relatively constant noise 201nV/√HzQUOTE√Hz from 0 Hz to 700 KHz and linearity performance over its entire tuning range. The proposed front-end of NIRS preamplifier is implemented using 0.18 μm CMOS technology.
Brain Function Diagnosis Enhanced Using Denoised fNIRS Raw Signals  [PDF]
Ahmad Chaddad
Journal of Biomedical Science and Engineering (JBiSE) , 2014, DOI: 10.4236/jbise.2014.74025
Abstract: Nowadays, brain function evaluation using Functional Near Infrared Spectroscopy (fNIRS) is one of the most potential non-invasive monitoring techniques. This paper concerns usefulness of the NIRS signals denoising using the Hemodynamic Evoked Response (HomER) as graphical user interface displays the NIRS data, fast independent component analysis (FASTICA) method to reduce data dimension and the combined Wavelet & PCA method for enhancing NIRS signals. NIRS signals include many types of noise, spread across a broad spectrum of frequencies, such as: low frequency noise from respiratory interference, 0.1 - 0.3 Hz, Mayer wave, about 0.1 Hz, cardiac interference, 0.8 - 2.0 Hz, and other artifacts from head and facial motions. Meanwhile, electronic components generate high frequency noise. Multi-resolution wavelet and PCA was applied successfully to enhance the NIRS signals. It consists of adaptively modifying the wavelet coefficients based on the degree of noise contamination of the processed NIRS signal. This is done subsequently to the signal pre-processing by reducing data dimension using the FASTICA method. We demonstrate, using signal-to-noise ratio and correlation indicators, that the technique used is superior to the wavelet and moving average filter and outperforms the proposed denoising NIRS signal.
Carcinoma cell identification via optical microscopy and shape feature analysis  [PDF]
Ahmad Chaddad, Camel Tanougast, Andrew Golato, Abbas Dandache
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.611128
Abstract: Optical microscopy is commonly used for cancer cell detection. Focusing on carcinoma cell identification via optical microscopy, a proof-of-concept study was performed at Laboratory of Design, Optimization and Modeling (LCOMS) to determine the grade of cancer cells. This paper focuses on three types of abnormal cells; namely, Benign Hyperplasia (BH), Intraepithelial Neoplasia (IN), which is a precursor state for cancer, and Carcinoma (Ca), which corresponds to abnormal tissue proliferation cancer. These types of cells were used to assess the efficiency of using shape features to identify carcinoma cells. A comparative study based on performance indicator concludes that three features, Area, Xor-Convex, and Solidity, were found to be effective in identifying the Carcinoma grade of cancer cells.
Rela??es contratuais de crédito agrícola e o papel dos agentes financeiros privados: teoria e evidências dos EUA
Chaddad, Fabio R;Lazzarini, Sérgio G;
Revista de Economia e Sociologia Rural , 2003, DOI: 10.1590/S0103-20032003000300002
Abstract: este trabalho analisa a quest?o do financiamento da produ??o agrícola sob uma ótica sistêmica, considerando o papel dos agentes privados no fornecimento de crédito rural. desenvolve-se a idéia de que o volume e o custo de recursos financeiros disponibilizados para a produ??o agrícola s?o afetados por "fric??es" em diversas transa??es sequenciais interligando emprestadores e tomadores de crédito. o objetivo do trabalho é analisar as vantagens comparativas dos diversos agentes que atuam no mercado de crédito, enfocando o potencial de cada agente em reduzir as tais fric??es. esta análise comparativa baseia-se na leitura do funcionamento do mercado de crédito agrícola dos estados unidos e pode ser aplicada nara o desenvolvimento de novos arranjos contratuais no mercado brasileiro.
Desulphurization of Transportation Fuels by Per-Formic Acid Oxidant Using MoOx Loaded on ZSM-5 Catalyst  [PDF]
Waqas Ahmad, Imtiaz Ahmad
Journal of Power and Energy Engineering (JPEE) , 2017, DOI: 10.4236/jpee.2017.512011
Desulphurization of model and real oil samples was investigated using performic acid as oxidant assisted by air as co-oxidant. The catalysts used were Mo-oxide supported on ZSM-5 zeolite, which was synthesized in the laboratory and characterized by FT-IR, XRD, SEM and SSA analysis. In case of model oil, the optimum condition determined for complete oxidation of all the model compounds including thiophene, DBT and 4,6-DMDBT were; 60?C, 60 min, ambient pressure and air flow rate of 100 mL/min. The oxidation reactivity decreased from 4,6-DMDBT to DBT and thiophene, which was found to follow pseudo first order kinetics. The real oil sample used in the study included untreated naphtha (NP), light gas oil (LGO), heavy gas oil (HGO) and Athabasca bitumen (Bit.). In case of NP and LGO the sulfur removal of above 78% was attained whereas in case of HGO and Bit. samples about 60% of desulfurization was achieved.
Decis?es financeiras em cooperativas: fontes de ineficiência e possíveis solu??es
Lazzarini, Sérgio Giovanetti;Bialoskorski Neto, Sigismundo;Chaddad, Fabio R.;
Gest?o & Produ??o , 1999, DOI: 10.1590/S0104-530X1999000300010
Abstract: this paper discusses the impact of certain organizational characteristics on financial decisions of cooperatives. a theoretical analysis is presented, including the discussion of some important variables to study capital structure and investment decisions in cooperatives, such as the nature of equity, cost of capital, organizational incentives, and specificity of assets. the main challenge is the design and implementing an organizational structure to attract equity capital, thereby reducing constraints to debt financing. furthermore, the design of a proper incentive structure is needed to avoid the selection of projects with negative net present value - a typical problem in cooperatives due to the underestimation of the marginal cost of equity capital. this is a conceptual study suggesting some relevant topics for further theoretical and empirical research.
A craniotomia pterional: descri??o passo a passo
Chaddad Neto, Feres;Ribas, Guilherme Carvalhal;Oliveira, Evandro de;
Arquivos de Neuro-Psiquiatria , 2007, DOI: 10.1590/S0004-282X2007000100021
Abstract: this article intends to describe in a didactical and practical manner the frontotemporosphenoidal craniotomy, that is usually known as pterional craniotomy and that constitute the cranial approach mostly utilized in the modern neurosurgery. this is then basically a descriptive text, divided according to the main stages involved in this procedure, and that describes with details how the authors currently perform this craniotomy.
Características morfológicas do lobo da ínsula em pacientes portadores de epilepsia do lobo temporal medial
Chaddad Neto Feres,Oliveira Evandro de,Paschoal Eric,Cendes Fernando
Arquivos de Neuro-Psiquiatria , 2006,
Abstract: A esclerose medial temporal (EMT) é caracterizada pela esclerose hipocampal e diferentes graus de acometimento das estruturas vizinhas como amígdala, giro parahipocampal e córtex entorrinal. O estudo avaliou 40 indivíduos com EMT e 40 do grupo controle. Os casos foram avaliados por um método para as medidas da ínsula (E-Film) e outro método para o cálculo do volume (Neuroline). N o houve diferen a estatística de altera o de volume e das medidas do lobo da ínsula nos pacientes portadores de EMT. O estudo n o demonstrou altera o morfológica da ínsula quando comparado os dois grupos.
Conduits of Innovation or Imitation? Assessing the Effect of Alliances on the Persistence of Profits in U.S. Firms
Sergio G. Lazzarini,Luiz A. L. Brito,Fabio R. Chaddad
BAR. Brazilian Administration Review , 2013,
Abstract: This paper examines if a firm’s alliances affect the persistence of its financial performance. The literature suggests two conflicting views concerning this effect. In particular, access to resources and innovation and the risk of imitation from alliances can have different impacts on performance. In our empirical analysis, based on a panel of 509 firms covering the years 1992 to 2002, return on assets was regressed on the number of alliances and other control variables using hierarchical linear modeling. Results support the positive view of alliances as mechanisms to sustain competitive advantage and escape from competitive disadvantage through access to external, valuable resources held by other firms. Alliances also help firms to constantly innovate and buffer themselves from external shocks that erode existing advantages. Our results, however, may be specific to the period and the institutional context under consideration and we do not distinguish between types, purposes and “strength” of alliances. We contribute to the debate about profit persistence by examining one particular factorthat has been neglected in the literature: the extent to which firms engage in alliances with other actors. From a managerial perspective, our study shows that alliances can be used as an effective tool to support superior performance or avoid lock-in into inferior performance.
Políticas para a inova o no Brasil: efeitos sobre os setores de energia elétrica e de bens de informática Policies for innovation in Brazil: effects on the electric power sector and IT goods sector
Henrique M. Barros,Danny P. Claro,Fabio R. Chaddad
Revista de Administra??o Pública , 2009, DOI: 10.1590/s0034-76122009000600011
Abstract: Este artigo examina como políticas públicas afetam o comportamento das empresas com rela o à inova o. Através do método de pesquisa de estudos de caso, o trabalho identifica como as empresas, em dois setores industriais no Brasil, têm respondido aos esfor os governamentais para estimular sua capacita o tecnológica. S o comparadas empresas do setor de energia elétrica do Brasil e do setor de informática do polo industrial de Manaus. De forma geral, os resultados indicam que as políticas de inova o têm contribuído para aumentar o interesse das empresas por inova o. No entanto, esse interesse tem se mostrado maior por parte das empresas cujo controle de capital é estatal e/ou estrangeiro, do que pelas empresas de controle de capital privado nacional. Isso é particularmente relevante, pois as empresas de capital privado nacional atuam em mercados pouco regulamentados, em que o nível de competi o é crescente. O limitado interesse dessas empresas por inova o refor a a ideia de que políticas de inova o n o podem englobar apenas a es voltadas para o lado da oferta, nem podem ser dissociadas de políticas voltadas para o fortalecimento do ambiente institucional. This article examines how public policies to foster innovation affect companies' behavior. Based on the case study research method, the article identifies how firms operating in the Brazilian electric power and IT sectors of the Manaus industrial district have responded to public efforts to stimulate technological innovation in both sectors. In general, the results suggest that these policies have increased private interest for innovation. However, this interest is greater among state controlled and multinational corporations than among domestic private companies. This finding is particularly relevant because domestic companies operate in deregulated markets with increasing competitive pressures. The limited interest of domestic companies for innovation suggests that innovation policies should not be limited to supply side factors and cannot be dissociated from policies aimed at strengthening the institutional environment.
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