Universidade Federal do Cearà / Este estudo pretende apresentar o perfil do empreendedor e quantificar os fatores determinantes da mortalidade das micro e pequenas empresas (MPEs), cuja taxa mÃdia anual brasileira à acima de 50%. AlÃm desse foco a pesquisa procura resgatar o histÃrico das aÃÃes empreendedoras e das polÃticas de incentivo ao empreendedorismo de pequeno porte, no Brasil e em outros paÃses. Uma vez que esse segmento à de real importÃncia para o paÃs, haja vista contribuir sobremaneira para geraÃÃo de emprego e renda com participaÃÃo de 20% no PIB nacional, e consequentemente na reduÃÃo da desigualdade social, um trabalho que se propÃe a analisar as causas da elevada taxa de mortalidade se identifica como relevante. Para atingir o objetivo foi desenvolvida uma pesquisa de campo, atravÃs de uma amostra representativa junto aos sÃcios principais ou proprietÃrios de empresas ativas e extintas constituÃdas no perÃodo de 2001 a 2005 na cidade de Picos/PI. Foram coletadas informaÃÃes sobre as caracterÃsticas das empresas como tambÃm sobre os perfis dos sÃcios e, uma vez tabulados foram confrontados com os dados consolidados de uma pesquisa do SEBRAE/2005 para a cidade de SÃo Paulo, as quais mostraram conformidade, exceto quanto a variÃvel nÃvel de escolaridade. AtravÃs de um modelo de escolha binÃria foram construÃdos vÃrios cenÃrios de previsÃo, variando de situaÃÃes extremamente otimistas Ãs pessimistas quanto Ãs caracterÃsticas das empresas e perfis dos sÃcios, de onde foram estimadas probabilidades para uma empresa representativa vir a ser extinta. A justeza do modelo se deu de forma estatisticamente satisfatÃria, vez que as previsÃes dos cenÃrios pessimistas e otimistas revelaram probabilidades de 99% e 1%, respectivamente, para ocorrÃncia de insucesso de uma empresa implantada.

This thesis explores forecasting for intermittent demand requirements. Intermittent demand occurs at random, with some time periods showing no demand. In addition, demand, when it occurs, may not be for a single unit or a constant size. Consequently, intermittent demand creates significant problems in the supply and manufacturing environment as far as forecasting and inventory control are concerned. A certain confusion is shared amongst academics and practitioners about how intermittent demand (or indeed any other demand pattern that cannot be reasonably represented by the normal distribution) is defined. As such, we first construct a framework that aims at facilitating the conceptual categorisation of what is termed, for the purposes of this research, “non-normal” demand patterns. Croston (1972) proposed a method according to which intermittent demand estimates can be built from constituent elements, namely the demand size and inter-demand interval. The method has been claimed to provide unbiased estimates and it is regarded as the “standard” approach to dealing with intermittence. In this thesis we show that Croston’s method is biased. The bias is quantified and two new estimation procedures are developed based on Croston’s concept of considering both demand sizes and inter-demand intervals. Consequently the issue of variability of the intermittent demand estimates is explored and finally Mean Square Error (MSE) expressions are derived for all the methods discussed in the thesis. The issue of categorisation of the demand patterns has not received sufficient academic attention thus far, even though, from the practitioner’s standpoint it is appealing to switch from one estimator to the other according to the characteristics of the demand series under concern. Algebraic comparisons of MSE expressions result in universally applicable (and theoretically coherent) categorisation rules, based on which, “non-normal” demand patterns can be defined and estimators be selected. All theoretical findings are checked via simulation on theoretically generated demand data. The data is generated upon the same assumptions considered in the theoretical part of the thesis. Finally, results are generated using a large sample of empirical data. Appropriate accuracy measures are selected to assess the forecasting accuracy performance of the estimation procedures discussed in the thesis. Moreover, it is recognised that improvements in forecasting accuracy are of little practical value unless they are translated to an increased customer service level and/or reduced inventory cost. In consequence, an inventory control system is specified and the inventory control performance of the estimators is also assessed on the real data. The system is of the periodic order-up-to-level nature. The empirical results confirm the practical validity and utility of all our theoretical claims and demonstrate the benefits gained when Croston’s method is replaced by an estimator developed during this research, the Approximation method.

Este estudo trata das proteínas relacionadas ao desenvolvimento e à formação da parede celular vegetal de cana-de-açúcar, com o objetivo de auxiliar no desenvolvimento de novas tecnologias para a produção de etanol celulósico a partir do bagaço de cana. Com isso, as proteínas de parede celular de entrenós e folhas de plantas com 4 meses de idade em dois estádios de desenvolvimento, juvenil e maduro, foram identificadas. Para extração foi utilizado o método não destrutivo por infiltração a vácuo utilizando dois sais, 0,2 M de CaCl2 e 2 M de LiCl seguido de centrifugação. As amostras complexas foram digeridas, fracionadas, sequenciadas por LC-MSE . Os peptídeos foram processados utilizando o ProteinLynx 2.5 e comparados com a base de dados de ESTs traduzidos de cana e sorgo. A anotação das proteínas foi realizada com base no programa PFAM e dividas em classes funcionais. Apenas as proteínas que apareceram em pelo menos duas das três repetições biológicas foram utilizadas na análise principal. Para prever a localização subcelular das proteínas selecionadas utilizaram-se os softwares: SignalP, TargetP, Predotar e TMHMM. Apenas aquelas proteínas que foram preditas para serem secretadas por dois ou mais programas foram consideradas como proteínas de parede celular (PPC). Ao todo, 543 proteínas foram consideradas como PPC: 205 em entrenós jovens, 143 em entrenós maduros, 124 em folhas jovens e 71 em folhas maduras. Dentre essas proteínas, 365 foram consideradas diferentes, e caracterizadas em dez classes funcionais. A análise estatística compreendeu a análise de PCA e PLS-DA, havendo diferença estatística entre os tratamentos analisados. Neste trabalho, foram encontradas 66 glicosil-hidrolases e 39 peroxidases, sendo 14 e 11 exclusivas de tecidos juvenis, respectivamente. Essas proteínas são conhecidas por terem funções relacionadas à quebra e ao remodelamento dos polissacarídeos da parede celular vegetal, e, portanto, foram indicadas neste estudo como alvo de pesquisas futuras que utilizem as próprias enzimas da planta para otimização da produção do etanol celulósico.Individualmente, este estudo foi o que mais identificou PPCs dentre a literatura existente, além de ter sido pioneiro na utilização da análise quantitativa para PPC. / This study provides information about the proteins of the cell wall of sugarcane at diferente stages of development and formation. The aim of this study is to assist in the development of new technologies for the production of cellulosic ethanol from sugarcane bagasse. Cell wall proteins from 4-month-old internodes and leaves of sugarcane in two developmental stages, juvenile and mature, have been identified. Protein extraction was performed with a non-destructive method by using vacuum infiltration with two salts, 0.2 M CaCl2 and 2 M LiCl, followed by centrifugation. Complex samples were digested, fractionated and sequenced by LC-MSE. Peptides were processed by ProteinLynx 2.5 and compared to the translated sugarcane and sorghum ESTs database. The annotation of the proteins was performed using PFAM and the functional classification was according the one used in other related studies. Only the proteins that appeared in at least two of the three biological replicates were used in the main analysis. In order to predict the subcellular localization of these proteins, SignalP, TargetP, TMHMM and Predotar softwares were used. Only those proteins that were predicted to be secreted by two or more programs were considered as cell wall proteins (PPS). Altogether, 543 proteins were classified as PPC: 205 inimmature internodes, 143 in mature internodes, 124 in young leaves and 71 in matured leaves. Among these proteins, 365 were considered different, and divided into ten functional classes. Statistical analysis was made with PCA and PLSDA, confirming that there were statistical differences among the treatments. In this work, 66 glycoside hydrolases and 39 peroxidases c identified, being 14 and 11 unique to young tissues, respectively. These proteins have their function related to plant cell wall polysaccharides breakdown and remodeling, and, therewith, the glycoside hydrolases and peroxidases found in this study were indicated to be the target of future research using the plant\'s own enzymes to optimize the cellulosic ethanol production. Individually, this study was the one that most identified PPC among the existing literature, and is a pioneer in the use of quantitative analysis for PPCs.

The log-normal distribution is a popular model in many areas, especially in biostatistics and survival analysis where the data tend to be right skewed. In our research, a total of ten different estimators of log-normal means are compared theoretically. Simulations are done using different values of parameters and sample size. As a result of comparison, ``A degree of freedom adjusted" maximum likelihood estimator and Bayesian estimator under quadratic loss are the best when using the mean square error (MSE) as a criterion. The ten estimators are applied to a real dataset, an environmental study from Naval Construction Battalion Center (NCBC), Super Fund Site in Rhode Island.

Full scale lateral load testing was performed on four 12.75x0.375 pipe piles spaced at 3.9, 2.9, 2.8, and 1.7 pile diameters behind an MSE wall which was constructed for this research to determine appropriate reduction factors for lateral pile resistance based on pile spacing behind the back face of the wall. The load induced on eight soil reinforcements located at various transverse distances from the pile and at different depths was monitored to determine the relationship between lateral load on the pile and load induced in the reinforcement. Each pile was loaded towards the wall in 0.25 in. increments to a total deflection of 3.0 in. Additionally, wall panel displacement was also monitored to determine if it remained in acceptable bounds. The results of the research indicate that pile resistance tends to decrease as spacing decreases. P-multipliers for the 3.9, 2.9, 2.8, 1.7D tests were found to be 1.0, 1.0, 1.0, and 0.5, respectively using back-analysis with the computer model LPILE. However, these multipliers are higher than expected based on previous testing and research. Piles spaced further than 3.8D can be assumed to have no interaction with the wall. The resistance of piles spaced closer to the wall than 3.8D can be modeled in LPILE using a p-multiplier less than 1.0. The reinforced backfill can be modeled in LPILE using the API Sand (1982) method with a friction angle of 31º and a modulus of approximately 60 pci when a surcharge of 600 psf is applied. If no surcharge is applied, a friction angle of 39º and modulus of 260 pci is more appropriate. Maximum wall panel displacement was highest for the 2.8D test and was 0.35 in. at 3.0 in. of pile head displacement. For all the other tests, the maximum wall displacement at 3.0 in. of pile head displacement was similar and was approximately 0.15 inches. Induced load in the soil reinforcement increases with depth to the 2nd or 3rd layer of reinforcement after which it decreases. Induced load in the reinforcement increases as pile spacing decreases. Induced load in the reinforcement decreases rapidly with increased transverse distance from the pile. Induced load in the reinforcement can be estimated using a regression equation which considers the influence of pile load, pile spacing behind the wall, reinforcement depth or vertical stress, and transverse spacing of the reinforcement.

Pile foundations for bridges must often resist lateral loads produced by earthquakes and thermal expansion and contraction of the superstructure. Right-of-way constraints near bridge abutments are leading to an increased use of mechanically stabilized earth (MSE) walls below the abutment. Previous research has shown that lateral pile resistance can be greatly reduced when piles are placed close to MSE walls but design codes do not address this issue. A full-scale MSE wall was constructed and 24 lateral load tests were conducted on pipe, square and H piles spaced at distances of about 2 to 5 pile diameters from the back face of the wall. The MSE wall was constructed using welded-wire grid and ribbed strip inextensible reinforcements. This paper focuses on four lateral load tests conducted on steel pipe piles located behind a 20-ft section of MSE wall reinforced with welded-wire grids. Results showed that measured lateral resistance decreases significantly when pipe piles are located closer than about 4 pile diameters from the wall. LPILE software was used to back-calculate P-multipliers that account for the reduced lateral resistance of the pile as a function of normalized spacing from the wall. P-multipliers for this study were 0.95, 0.68, and 0.3 for piles spaced 4.3, 3.4 and 1.8 pile diameters from the wall, respectively. Based on results from this study and previous data, lateral pile resistance is relatively unaffected (p-multiplier = 1.0) for piles spaced more than approximately 3.9 pile diameters (3.9D) from the MSE wall. For piles spaced closer than 3.9D, the p-multiplier decreased linearly as distance to the wall decreased. P-multipliers were not affected by differences in reinforcement length to height (L/H) ratio or reinforcing type. Lateral pile loads induce tensile forces in the soil reinforcement such that, as pile load increases the maximum induced tensile force increases. Results also indicate that maximum tensile forces typically occurred in the soil reinforcement near the pile location. Past research results were combined with data from this study and a statistical regression analysis was performed using all data associated with welded-wire grid reinforcements. A regression equations was developed to predict the peak induced tensile force in welded-wire grids based on independent variables including lateral pile load, normalized pile distance (S/D), transverse distance (T/D), L/H ratio, and vertical stress. The equation has an R2 value of 0.79, meaning it accounts for approximately 79% of variation for all welded-wire grid reinforcements tested to date.

Sporulation in Saccharomyces cerevisiae includes the processes of meiosis and spore formation. The genes involved in this developmental process are tightly regulated at the level of transcription to ensure that genes are expressed at the correct time and level. The co-ordinated expression of middle sporulation genes is mediated by a key timing promoter element called the middle sporulation element (MSE). While this element sets the timing of gene expression to middle sporulation, in some cases, the level of expression is mediated by cis-acting auxiliary promoter elements. This study has addressed the role that auxiliary transcription factors play in fine-tuning of timing and level of expression of the MSE-regulated middle sporulation genes SPS18 and SPS19 and the mid-late sporulation genes DIT1 and DIT2. The MSE*SPS18/19 was shown previously to set the timing of expression of SPS18 and SPS19 to middle sporulation. In order to achieve the full level of meiotic activation, a novel bipartite auxiliary promoter element called the MAE (MSE-associated element) was required (Dalton, 2004). This study has revealed that proteins bind to specific regions of the MAE motif during sporulation in vitro and has attempted to isolate the proteins by affinity chromatography and identify them by mass spectrometry. The timing of expression of DIT1 and DIT2 during sporulation was of particular interest since two MSE-like elements had been identified in the promoter of the these genes (Hepworth et al., 1995). If these MSEs were functional, it was thought that auxiliary elements may delay expression of these genes until mid-late sporulation. This study has shown that the MSE*NRE confers a normal middle sporulation pattern of expression on a reporter gene. The DRE (DIT repressor element) previously identified by Bogengruber et al. (1998) was further characterised as an element that alters the level of expression conferred by an MSE without altering the timing. Several proteins were shown to bind to specific regions of the DIT promoter surrounding the DRE motif in vitro, with a different set of proteins binding during vegetative growth and sporulation. Attempts to isolate and identify these proteins by affinity chromatography and mass spectrometry are discussed.

In wireless communications, channel estimation is necessary for coherent symbol detection. This thesis considers a network which consists of two transceivers communicating with the help of a relay applying the amplify-and-forward (AF) relaying scheme. The training based channel estimation technique is applied to the proposed network where the numbers of the training sequence transmitted by the two transceivers, are different. All three terminals are equipped with a single antenna for signal transmission and reception. Communication between the transceivers is carried out in two phases. In the first phase, each transceiver sends a transmission block of data embedded with known training symbols to the relay. In the second phase, the relay retransmits an amplified version of the received signal to both transceivers. Estimates of the channel coefficients are obtained using the Maximum Likelihood (ML) estimator. The performance analysis of the derived estimates are carried out in terms of the mean squared error (MSE) and we determine conditions required to increase the estimation accuracy. / UOIT

In simulation, time averages are important for estimating equilibrium parameters. In particular, we would like to have the variance, bias and mean-square error for time averages. First, we will discuss various factors and their effect on the bias, the variance and the mean-square error. We will use the Markovian Event System to model various systems, including M/M/1 queues, M/E_k/1 queues, M/M/c queues, sequential queues, inventory systems and queueing networks. We use a numerical method for the computation of the variance, the bias and the mean-square error of the time average. The effectiveness of the method is tested by experimenting with models of various stochastic systems. The contribution of this thesis is to use numerical and graphical interpretations to study the general characteristics of the measures. The important characteristics included in our study are decomposability and periodicity.

In simulation, time averages are important for estimating equilibrium parameters. In particular, we would like to have the variance, bias and mean-square error for time averages. First, we will discuss various factors and their effect on the bias, the variance and the mean-square error. We will use the Markovian Event System to model various systems, including M/M/1 queues, M/E_k/1 queues, M/M/c queues, sequential queues, inventory systems and queueing networks. We use a numerical method for the computation of the variance, the bias and the mean-square error of the time average. The effectiveness of the method is tested by experimenting with models of various stochastic systems. The contribution of this thesis is to use numerical and graphical interpretations to study the general characteristics of the measures. The important characteristics included in our study are decomposability and periodicity.