Advances in Learning Bayesian Networks of Bounded Treewidth

This work presents novel algorithms for learning Bayesian network structures with bounded treewidth. Both exact and approximate methods are developed. The exact method combines mixed-integer linear programming formulations for structure learning and treewidth computation. The approximate method consists in uniformly sampling $k$-trees (maximal graphs of treewidth $k$), and subsequently selecting, exactly or approximately, the best structure whose moral graph is a subgraph of that $k$-tree. Some properties of these methods are discussed and proven. The approaches are empirically compared to each other and to a state-of-the-art method for learning bounded treewidth structures on a collection of public data sets with up to 100 variables. The experiments show that our exact algorithm outperforms the state of the art, and that the approximate approach is fairly accurate.Comment: 23 pages, 2 figures, 3 table

Solving Limited Memory Influence Diagrams

We present a new algorithm for exactly solving decision making problems represented as influence diagrams. We do not require the usual assumptions of no forgetting and regularity; this allows us to solve problems with simultaneous decisions and limited information. The algorithm is empirically shown to outperform a state-of-the-art algorithm on randomly generated problems of up to 150 variables and $10^{64}$ solutions. We show that the problem is NP-hard even if the underlying graph structure of the problem has small treewidth and the variables take on a bounded number of states, but that a fully polynomial time approximation scheme exists for these cases. Moreover, we show that the bound on the number of states is a necessary condition for any efficient approximation scheme.Comment: 43 pages, 8 figure

Study of Ceramic Membrane from Naturally Occurring-Kaolin Clays for Microfiltration Applications

The focus of this work is to assess the quality of porous membranes prepared from naturally occurring kaolin clays and to evaluate the performance of tubular ceramic membranes treating integrated raw effluents from seafood industry. This material has been chosen due to its natural abundance, its non-toxicity, low cost and its valuable properties. The preparation and characterization of porous tubular ceramic membranes, using kaolin powder with and without corn starch as poreforming agent, were reported. SEM photographs indicated that the membrane surface was homogeneous. The effects of material compositions, additives and the relatively lower sintering temperature, ranging from 1100° to 1250°C, on porosity, average pore size, pore-size distribution and mechanical strength of membranes have been investigated. A correlation between microstructure and mechanical properties of membranes has been discussed. The performance of the novel ceramic membranes thus obtained was determined by evaluating both the water permeability and rejection. The obtained membrane was used to treat cuttlefish effluents generated from the conditioning seawater product industry which consumes a great amount of water. Cross-flow microfiltration was performed then, in order to reduce the turbidity and chemical oxygen demand (COD).

Optimization of peptide production by enzymatic hydrolysis of tuna dark muscle by-product using commercial proteases

A protein hydrolysate was prepared from proteins of tuna dark muscle by-product. The hydrolysis conditions (time, temperature, pH and enzyme concentration) using Alcalase and Neutrase were optimized by response surface methodology (RSM). The regression coefficient close to 1.0, observed during experimental and validation runs, indicated the validity of the model. The hydrolysate produced under the optimum conditions determined by RSM using Alcalase, had a low rate of peptide fraction of molecular weight of 1-4 kDa. Meanwhile, the results obtained by hydrolysis under optimal conditions determined by a complementary study (temperature 55°C, time 60 min, 1% enzyme concentration and pH 8.5) show that the hydrolysate produced had a high rate of the peptide fraction of molecular weight of 1-4 kDa. The amino acid composition of the protein hydrolysate prepared proved to have the potential for application as an ingredient in balanced fish diets and as a source of nitrogen in microbial growth media.Keywords: Alcalase, neutrase, tuna dark muscle, RSM, optimization, protein hydrolysate, peptides, degree of hydrolysisAfrican Journal of Biotechnology Vol. 12(13), pp. 1533-154

Use of nanofiltration membrane technology for ceramic industry wastewater treatment

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+ , Mg2+, Cl- , and SO4 2- . In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater qualit

Fabrication, Characterization and Permeation Studies of Ionically Cross-linked Chitosan/Kaolin Composite Membranes

This paper presents the successful preparation of porous membranes based on chitosan with enhanced mechanical, thermal and chemical properties applicable in water treatment field. Herein, chitosan/kaolin composite membranes with a cross-linking agent and a porogen were prepared using the solvent casting method. The characterization of the as-fabricated membranes indicated that the combined effect of kaolin as reinforcing agent, polyethylene glycol as pore former and citric acid as cross-linker in a chitosan matrix showed a significant influence on the membrane properties. The results indicated that the incorporation of a hydrophilic porogenic reagent into the collodion in addition to providing a porous morphology makes it possible to obtain a more hydrophilic membrane, and thus induces an increase in the pure water permeability. The cross-linked membranes exhibited an improved water resistance, better thermal and mechanical properties as compared to neat chitosan films. The cross-linked membranes had a mean pore size of 50 nm falling in the range of ultrafiltration. Their functional properties were determined in terms of pure water filtration and molecular weight cut-off tests

Integrating question answering and text-to-SQL in Portuguese

Deep learning transformers have drastically improved systems that automatically answer questions in natural language. However, different questions demand different answering techniques; here we propose, build and validate an architecture that integrates different modules to answer two distinct kinds of queries. Our architecture takes a free-form natural language text and classifies it to send it either to a Neural Question Answering Reasoner or a Natural Language parser to SQL. We implemented a complete system for the Portuguese language, using some of the main tools available for the language and translating training and testing datasets. Experiments show that our system selects the appropriate answering method with high accuracy (over 99\%), thus validating a modular question answering strategy.Comment: Published at International Conference on the Computational Processing of Portuguese (PROPOR 2022

Polymeric membranes for treatment of produced water on offshore plateform

Introduction Phase separation using non-solvent coagulation of a polymer solution is the most widespread industrial process to manufacture membranes. Large solvent quantity is then use that it complicates the overall process and may lead to environmental and health problems. Knowing that polymer concentration is usually in the range 15-20 % and coagulation and washing baths require to be often renewed, large amounts of aqueous solutions must be treated. For instance 10 m2 of ultrafiltration membrane need about 1 to 1.5 kg of solvent. Our objective in this proposal is to develop a novel process for membrane mass production in agreement with the principles of green chemistry. The main technical and economic output of using water instead organic solvents should consist in a simplification of the manufacturing process by lowering wastes and recycling. Environmental outputs will be a safer process, more economic on atoms, limiting the wastes and applicable to renewable naturally-occurring polymers. Please click Additional Files below to see the full abstract