693 research outputs found
Modelo de simulação para projecto e avaliação de sistemas de rega localizada
O modelo iterativo AVALOC, em linguagem VISUAL BASIC 4.0, foi desenvolvido para o dimensionamento e a análise de funcionamento de sistemas de rega localizada (ou microrrega). O modelo apoia-se numa base de dados contendo informação relativa aos emissores e aos tubos disponĂveis no comĂ©rcio, e aos sectores de rega a que Ă© aplicado o programa. A base de dados permite com relativa facilidade a introdução, a consulta e a correcção dos dados e, desta forma, reduzir o tempo de utilização do programa. No modo de dimensionamento em projecto, o programa permite seleccionar os emissores que melhor respondam aos objectivos do projecto, bem como escolher e dimensionar as condutas que constituem a rede de rega. Os cálculos sĂŁo realizados segundo criterios de exclusĂŁo, i.e. obrigando a que sejam satisfeitos determinados critĂ©rios de desempenho fixados pelo utilizador, nomeadamente referentes Ă variação de carga e Ă uniformidade de emissĂŁo, visando assegurar que a distribuição de caudais no sector seja adequadamente uniforme. No modo de análise de desempenho, a simulação hidráulica visa calcular os parâmetros de funcionamento caracterĂsticos do sistema, tais como o par carga - caudal de cada saĂda, o tempo de funcionamento, a percentagem de solo humedecido e indicadores de desempenho da rega, nomeadamente o coeficiente de uniformidade de Christiansen e a uniformidade de emissĂŁo. O modelo Ă© apresentado utilizando um caso de projecto de um sector de rega em olival
Synthesis of Dehydrodipeptide and N-ethyl-dehydrodipeptide Derivatives with an α-Aminoisobutyric Acid Residue
Several dipeptides with an N-benzyloxycarbonyl or an N-(tert-butyloxycarbonyl) α-aminoisobutyric acid residue and a β-hydroxyamino acid methyl ester were subjected to dehydration to form dehydrodipeptide derivatives. N-Ethylation of these dipeptides using triethyloxonium tetrafluoroborate with potassium tert-butoxide as auxiliary base led to complex mixtures that failed to render pure products. However, when the 4-nitrophenylsulfonyl protecting group was substituted for the benzyloxycarbonyl or tert-butyloxycarbonyl groups and N,N-diisopropylethylamine was substituted for potassium tert-butoxide, the dehydrodipeptide derivatives were selectively N-alkylated at the amino terminal nitrogen in fair to high yields. Alternatively, N-ethylation can be carried out prior to dehydration. Thus, through a combination of dehydration and N-ethylation procedures, it was possible to obtain dipeptides with α-aminoisobutyric acid and dehydroamino acid residues, which are N-alkylated at the amino terminal nitrogen.Foundation for Science and Technology (FCT) – Portugal and Fundo Europeu de Desenvolvimento Regional (FEDER) for financial support to Chemistry Centre of University of Minho. The NMR spectrometer Bruker Avance II+ 400 is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Re-equipment; contract REDE/1517/RMN/2005, with funds from POCI 2010, FEDER and FCT.info:eu-repo/semantics/publishedVersio
Analysis and improvement of internal logistic flows at an industrial company
Undertaken at Preh Portugal, Ltd., the main objective of this study project resided in defining the system of supply to a new assembly line, the Ford B479. Supply to the assembly lines is a crucial activity in internal logistics since the entire production system relies on the supply of materials required for the line. It is, therefore, extremely important to study solutions which will facilitate these activities, thus enhancing productivity and guaranteeing the on-time availability of products, in suitable quantities and at the best cost.
The initial phase consisted of studying the type of supply system used by the company for the remaining lines, as well as gaining a detailed understanding of the entire assembly line production process. One was then able to create a database to include all of this information. Once all the required information had been gathered, one proceeded to define the supermarket for the Ford B479 line, and calculated the number of positions required. With the purpose of building a more effective and efficient supermarket, one analyzed the possibility of building the supermarket next to line instead of resorting to the existing solution where the shelves for all lines are in the same location. When the site for the supermarket was defined, one proceeded with its construction and determined the supply system of both the supermarket as well as the line sides. Due to the proposed changes, one was able to reduce the distance covered by raw materials by 55% as well as to decrease handling.info:eu-repo/semantics/publishedVersio
Communities of practice as a tool to support the GCIO function
A Community of Practice (CoP) allows practitioners of a clearly defined domain to share knowledge, experience,and best practices. It provides a social context for practitioners,often distributed across multiple organizations,and emerged over the last few decades as a fundamental mechanism for knowledge sharing, management,and generation within organizations. Best practices, innovations,and solutions to shared problems first emerge within CoPs. These are, and must be perceived as, an investmentin organizations’ future and competitiveness.Establishing a CoP is a straightforward process, the most challenging factor being the recruitment of members to attain critical mass. The challenge is to maintain the CoP active, with members contributing with high quality, innovative content. Increasing a CoP’smedium / long-termsurvival probabilities requires careful planning to avoid incurringinsome well-known pitfalls.This paper proposes and discusses a set of nine guidelines for establishing and maintaining a community of practice within the context of Electronic Governance (EGOV) and Government Chief Information Officers (GCIO). This research was motivated by the initiative of the government of a developing country. Results are based on a review of the relevant literature, together with the detailed analysis of interviews to members or coordinators of large communities of practice. This analysis was further validated against the opinions of public servantsdirectly involved on EGOV-GCIO-related functions during two focus groups meetingsSmartEGOV: Harnessing
EGOV for Smart Governance (Foundations, Methods, Tools)
NORTE-01-0145-FEDER-000037, supported by Norte Portugal
Regional Operational Programme (NORTE 2020), under the
PORTUGAL 2020 Partnership Agreement, through the European
Regional Development Fund (EFDR
Synthesis of N-alkyl-C α, α-dimethylglycine derivatives
The application of trialkyloxonium tetrafluoroborates for N-alkylation of the nonnatural amino acid Cα, α-dimethylglycine is described. Several methyl esters of dimethylglycine protected with different amine protecting groups were subject to N-ethylation or N-methylation with triethyloxonium tetrafluoroborate or trimethyloxonium tetrafluoroborate, respectively. The corresponding N-akyl-Cα, α-dimethylglycine derivatives were obtained in good to high yields. Removal of the methyl ester rendered amino acid derivatives ready for application in peptide synthesis.Foundation for Science and Technology (FCT) – Portugal and Fundo Europeu de Desenvolvimento Regional (FEDER) for financial support to Chemistry Centre of University of Minho. The NMR spectrometer Bruker Avance II+ 400 is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Re-equipment; contract REDE/1517/RMN/2005, with funds from POCI 2010, FEDER and FCT.info:eu-repo/semantics/publishedVersio
Setting Irrigation Thresholds for Building a Platform Aimed at the Improved Management of Citrus Orchards in Coastal Syria.
Citrus is one of the most valuable crops in Syria, with the largest production areas being in
the coastal provinces of Tartus and Latakia, where this study was performed. A companion paper
reported on the basal crop coefficients derived from the field water balance and on the performance
assessment of various irrigation methods used in a citrus orchard located in the same region. That
study evidenced the need for the improved management of irrigation water, mainly reducing water
applications and increasing productivity, thus leading to the current research. The main objectives
consisted of (i) providing a set of reliable basal (Kcb) and average (Kc) crop coefficients to be used
in practice in the citrus orchards of the Syrian coastal area, while accounting for the diversity of
characteristics observed; (ii) to estimate the seasonal consumptive use of typical orchards under
different climate-demand and deficit-irrigation scenarios; and (iii) to assess possible water savings
and related yield reductions. The previously calibrated water balance model SIMDualKc was used
for these purposes. The computed Kcb values for the mid-season and average demand for water
ranged from 0.52, when the plant density was low, to 0.84, when plant density was very high. The
corresponding Kc values, which further reflected the impact of drip irrigation on controlling soil
evaporation, were 0.72 and 0.97, respectively. Overall, the consumptive use of water was estimated to
range from 867 to 1573 mm. The assessed water-saving scenarios consisted of adopting increased
management-allowed depletion (MAD) thresholds relative to the p depletion fraction for no stress:
MAD = 1.05, 1.10, 1.20, and 1.30 p. For trees under a very high climatic demand, water savings ranged
from 12 to 34%, but the yield losses induced by the water deficits ranged from 8 to 48%. Although
the selection of optimal strategies should be based upon economic terms, these may only be used
when the Syrian economy recovers from civil war and the current crisis. The present results show the
feasibility of adopting such MAD thresholds for building an irrigation management platform. The
data provided by the current study are valuable because they can be efficiently used to support of the
irrigation management of Syrian citrus production systems.info:eu-repo/semantics/publishedVersio
Layout and process optimisation: using computer-aided design (CAD) and simulation through an integrated systems design tool
The design of production and logistic systems is a process of managing both technical and organisational variants in order to identify the best solution for a given system. This paper discusses design issues of production systems that are applied to an internal logistic system in the automotive industry. As far as the production systems design (PSD) is concerned, three basic classes of software tools usually pertain: computer-aided design (CAD), process simulation, and information systems. However, these software tools have been used with low levels of integration. Vik et al. (2010b, 2010c) proposed integrating these software resources in production systems and developed an advanced tool called integrated design of systems (IDS). The proposed IDS tool involves a wide set of functions for the most common tasks of PSD, from conceptualisation to implementation, including systems analysis (P-Q, cluster, and material flow analysis), automatic generation of simulation models, generation of alternatives for the layout of facilities and factories, material flows display, transportation system design, and iterative buffer size specification. The IDS approach takes advantage of simulation, CAD systems, and their integration. This paper will demonstrate the concept and functionalities of the proposed tool in a real industrial case study.Fundação para a Ciência e Tecnologi
Comparison of SIMIO and ARENA simulation tools
The purpose of this paper is to establish a comparison between Simio and Arena, helping a vast community of simulation practitioners to gain access to advanced modelling capabilities to address complex problems. Several aspects were compared, such as: concept of simulation models, animation development, modelling philosophies, Simio libraries and Arena templates, concept of entities, interface of the tools and Simio objects versus Arena blocks. The comparison was consolidated through the analysis of two case studies where the authors aimed to emphasize the way each simulation tool addresses some important issues related to model construction. The several compared aspects indicate the many advantages of using the more recent tool. Thus, this object-oriented tool appears to have all the conditions to trigger a widespread paradigm shift in the way practitioners build models.This work has been supported by FCT – Fundação para a Ciência e
Tecnologia in the scope of the project: PEst-OE/EEI/UI0319/2014
Modeling and simulating a textile production system
This paper presents a study for a production scheduling
problem in a textile company, specifically in the weaving
preparation area. Basically, the processing orders can be
considered as sequential working steps trough three
operations (charging - weaving - discharging), and the goal
is to minimize time variation and to avoid delays. The
machine utilization should be as higher as possible due to
short delivering deadlines. The production unit has got 4 of
these weaving machines functioning at the same time.
Four dispatching rules were tested in order to find the best
solution. The optimization procedure highlighted some
interesting issues that are discussed in this paper
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