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ULA
Mérida, Venezuela

Doutres O.,GAUS | Atalla N.,GAUS | Osman H.,ULA
INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control | Year: 2014

Porousmaterials are widely used for improving sound absorption and sound transmission loss of vibrating structures. However, their efficiency is limited to medium and high frequencies. A common solution for improving their low frequency behavior while keeping an acceptable thickness is to embed resonant structures such as Helmholtz resonators. This work investigates the absorption and transmission acoustic performances of a cellular porous material with large resonatorinclusions. The homogenization theory cannot be appliedto cellular material made of suchlargeperiodic unit-cell (e.g., cubeof side L≈100 mm). A low frequency modelof a larger esonant unit-cell based on the Parallel Transfer Matrix Methodis proposedin this work.Theproposed model is validated by comparison with impedance tube measurements and finite element calculations. At the Helmholtzresonance frequency; (i) the transmission loss is greatly improved and (ii) the sound absorption of the host material isdecreasedif it is made of a highly sound absorbing material. Source


Quintero K.,Thales Alenia | Quintero K.,INSA Lyon | Niel E.,INSA Lyon | Aguilar J.,ULA | Pietrac L.,INSA Lyon
Engineering Letters | Year: 2014

The following work proposes a (max,+) optimization model for scheduling operations on an oil seaport considering flexible maintenance activities on valves. The work is based on previous results for the same case study, where fixed maintenance was studied in the framework of scheduling oil transfer operations through a pipeline network. The case study is a Venezuelan seaport for oil export and real operational constraints and goals are modeled. Results corroborate the drawbacks that arise when considering fixed maintenance in the system. Moreover, the adjustments made to obtain a model considering maintenance relaxation are straightforward and intuitive. Some linear representations of the problem are also explored through prioritization of certain tasks. Source


Quintero K.,Thales Alenia | Niel E.,INSA Lyon | Aguilar J.,ULA | Pietrac L.,INSA Lyon
Lecture Notes in Engineering and Computer Science | Year: 2013

The aim of this work is to propose a (max, +) optimization model for scheduling transfer operations on a flow network within a given maintenance framework. The case study involves the scheduling of oil batch transfer operations in coordination with valve maintenance activities in an oil-exporting seaport. The optimum schedule is determined through an intuitive, and synthetized mathematical model based on (max,+) algebra with the objective of minimizing financial penalties. Real operational constraints and goals in the seaport are modeled with data from an oil seaport in Venezuela. Results show the optimum schedule obtained from a concise and relatively simple optimization model which is the main contribution of this work. Source


Rojas-Runjaic B.,University of Zulia | Perdomo D.A.,University of Los Andes, Venezuela | Garcia D.E.,ULA | Gonzalez-Estopinan M.,ULA | And 3 more authors.
Zootecnia Tropical | Year: 2011

An experiment was carried out in order to evaluate the carcass yields and filleting of the tilapia (Oreochromis niloticus strain: Chitralada) with weights among 250-400g (range: 250-300, 300-350 and 350-400g), cultivated under intensive conditions in Trujillo state, Venezuela; using a completely randomized design with 60 measured animals. The morphometric measured parameters were: total length (LT), standard length (LS), head length (LC), head height (AC), body thickness (EH), body longitude (LH) and body height (AH); the variables related with the weight (in g) were: weigh fresh (PF), carcass weight (Pc), body weight (Pt), weight of the clean trunk (TSe), fillet weigh (PFi) and component of residuals; the parameters relating with yields were evaluated to: carcass yield (%RC), fillet yield according to fresh weight (% RPF) and yield of the fillet according to the carcass (%RFPc). The morphometric parameters showed significant differences (P<0,05), exception of EH and AH. No differences (P>0,05) in the variables related with weight of gills and fins were observed. No differences regarding the yield according to the variables of corporal yield were observed (P>0,05). The hight morphometric and weight values were observed in animals with 350-400g of live weight. However, the hight size presented marginal influence in yield results. Source


The current study was carried out with the purpose of evaluating two alternative diets in the feeding of Colossoma macropomum alevins using earthworm flour (Eisenia foetida), soybean (Glycine max) and beans (Phaseolus vulgaris) as the protein source and as fishmeal substitute and was compared with a control diet. The diets were formulated with a crude protein with a theoretical 32% protein. The body composition of C. macropomum fed the different diets showed that protein was between 47,3% and 48,6% and the lipid content was found between 21,2% and 24,3% not showing significant differences between diets (p>0,05). According to the results obtained there is a reason to think that a total substitution of fishmeal by earthworm meal, soybean and beans would be successful in feeding C. macropomum alevins. Source

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