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Modelos alternativos em filas M/G/1
(Universidade Federal de São Carlos, 2015-11-26) Prado, Silvia Maria; Louzada Neto, Francisco; https://lattes.cnpq.br/0994050156415890; https://lattes.cnpq.br/1860827349387828
The main aim of this work is to develop alternative queuing models to M/ G/l, in which arrivals follow a Poisson process, the total number of customers on the system and the total number of service channels are unknown. Our interest is just to observe the service channel that will offer the maximum or minimum service time. Wherefore, the service distributions are obtained from the composition of the Conwav-Maxwell-Poisson distribution truncated at zero, used to model the number of service channels, with the general distribution to the maximum and minimum service time. Thus, we obtain new distributions for service time, which are called Maximum-Conwav-Maxwell-Poisson-general, denoted by MAXCOMPG distribution, and Minimum-Conwav-Maxwell-Poisson-general, denoted by MINCOMPG distribution, consequently, we obtain the queue models M/MAXCOMPG/1 and M/MINCOMPG/ 1, respectively. As general distributions, we use the distributions exponential, Weibull and Birnbaum Saunders, To illustrate the proposed queue models, a simulation study is done and also real data are used.
Avaliação do grau de conhecimento e de aplicação das práticas do Quick Response Manufacturing : estudo comparativo transnacional
(Universidade Federal de São Carlos, 2015-11-26) Marchesini, Antonio Gilberto; Godinho Filho, Moacir; https://lattes.cnpq.br/6136685270563354; https://lattes.cnpq.br/8580028974493724
In recent decades, the lead time reduction has become crucial to ensure the competition of enterprises. To address this, plus the abandonment of the tradit ional mindset based on efficiency and cost, to a mentality based on the reduction of lead time, companies began to incorporate in production management, principles and practices related, outstandingly, to the Quick Response Manufacturing (QRM) and the Lean Manufacturing (LM). In this context, this work aims, according to companies located in Brazil, Europe, and in the USA: (I) Verify if the degree of knowledge of the exclusive principles of QRM approach is equal to the degree of knowledge regarding common concepts to LM and QRM, (II) Verify if the degree of knowledge of the exclusive principles of QRM is greater due to factors such as training, dissemination, and awareness, (III) Check if the mindset based on economies of scale and cost reduction is still the main obstacle in the degree of knowledge of the companies surveyed, (IV) Verify if the concepts / elements / exclusive practices QRM less adopted by companies are those related to the change of economies of scale and cost-based mindset, still fairly entrenched in enterprises, (V) Verify if there is a significant difference between the degree of implementation of QRM practices due to the region studied, and (VI) Check whether the use of concepts / elements / practices of LM favors the adoption of QRM. For this, it was carried out an exploratory survey with an intentional sample of companies in these regions who wish to reduce the lead time. Data were analyzed using descriptive statistics and non-parametric tests. Concerning to the knowledge of the companies surveyed about the QRM, it was concluded that the level of knowledge about the exclusive practices of QRM is lower than in relation to the common practice at LM and QRM. The companies’ knowledge degree about the exclusive principles of QRM is possibly greater due to training, dissemination, and awareness and such factors are present more at the region of US. The mindset based on economies of scale and cost reduction is possibly the main barrier in the degree of knowledge in the companies surveyed. Concerning to the application of the QRM practices by companies surveyed, it was concluded that the extent of implementation of practices regarding the key concept "power of time" is lower than the other key concepts; there was not observed any statistically significant differences in the degree of implementation of QRM practices due to the region; the LM practices helps and contribute to the effort of implementation of QRM in companies that seek to reduce the lead time and; the concepts, elements and practices of QRM less adopted by companies are those related to the abandonment of the mindset based on economies of scale and cost reduction.
Uso de técnicas espectroanalíticas na avaliação de amostras de placas de circuito impresso de lixo eletrônico
(Universidade Federal de São Carlos, 2015-11-26) Santos, Jozemir Miranda dos; Pereira Filho, Edenir Rodrigues; https://lattes.cnpq.br/3394181280355442; https://lattes.cnpq.br/3701702963740025
The increase in the consumer electronics equipment, especially, the cell has aroused the academia and society in general interest. Such equipment when obsolete became part of the so-called junk mail. Among the components of this type of waste, are the printed circuit boards (PCB’s). The concentration of toxic elements such as Cd, Cr and Pb these PCB has proved high. Because of this situation becomes important to develop analytical methodologies for evaluation of these dangerous elements in PCB. Among the analytical techniques available, the most used in the determination of these elements has been the ICP OES. The evaluation of samples PCB by ICP OES performed in this study revealed that in addition to the regulated elements by RoHS (Cd, Cr and Pb), are present in high quantities, the elements Ba (2% w/w) and As (400 mg/kg). The Cu element was the one with the highest levels of concentration in some samples amounted to 35% (m/m). The use of a multivariate analysis such as PCA, showed some correlation between certain elements of the PCB. This is observed for the elements Ba and Ni, and also to the As, Cr and Fe. Alternatively to the use of techniques that require a pretreatment of the samples comes LIBS. The obtained emission spectra provided important information about the composition of these PCB’s. An analysis of the spectra reveals the presence of emission lines of elements such as Ba, Cd, Pb, Ni, Cu, Fe, Sb, among others. The elements that provide the most intense emission lines were Cu and Ba. Based on the obtained reference concentration by ICP OES and the values of the area and intensity of the spectra obtained, the construction of multivariate calibration models has been proposed. Employing MLR was possible to build the multivariate calibration models for elements of interest. However, due to lack of verified correction, among the area parameters, maximum intensity and reference concentrations, the proposed models are considered viable. However, the use of LIBS for characterization purposes samples for the presence of an element, shown to be feasible from a qualitative point of view.