Search

The primary objective of this study is to propose the use of nonlinear functions to find a feasible interior point in a region defined by the constraints of linear programming problems with the advantage of not having to use slack or surplus variables. The feasible region of linear programming problems is defined by convex sets named polyhedra that have the form Ax ≤ b and that can be bounded or unbounded. Finding an interior point (even extreme or frontier point) is not a trivial issue but is a necessary condition to initialize algorithms for solving a linear programming problem. To achieve this, unrestricted nonlinear penalty functions are applied and optimized. As a result, it is demonstrated that the optimal solution point corresponds to an interior point of the original polyhedron. It is concluded that the proposed algorithmic procedure possesses features that provide advantages for solving linear programming problems. [ABSTRACT FROM AUTHOR]

• A novel method was developed to use solid CO 2 for supercritical fluid extraction (SFE). • The method involves controlled expansion of solid CO 2 in a stirred hermetic vessel. • P-V-T curves were obtained to relate solid CO 2 loadings to final supercritical conditions. • Batch supercritical CO 2 extractions of cannabis threshing residues were carried out. • Extraction yields were similar to those obtained in commercial SFE equipment. The change in the existing regulations in different countries regarding cannabis crops management and trading has enabled the commercial exploitation of the plant parts and of their extracts, metabolites and derivatives. Industrially, key metabolites such as cannabinoids and terpenoids are commonly extracted from the flowers by using supercritical CO 2. However, supercritical units require an extremely high capital investment even at low production capacities becoming a main drawback for exploratory and de-risking research stages. In this direction, this works aims to assess a low-cost CO 2 supercritical extraction technique for exploratory experiments employing solid CO 2 (known as dry ice) within a high-pressure vessel. By heating the solid CO 2 within the vessel, supercritical conditions can be achieved enabling extraction and recovery of the extract by subsequent depressurization. P-V-T curves were experimentally obtained to determine the required dry ice loadings to achieve specific supercritical conditions. Evaluated ranges corresponded to temperatures in-between 291 and 365 K, specific molar volumes of 47–90 mL/mol and the corresponding pressures ranging between 54 and 300 bar. Subsequently, the developed technique was validated in the lab-scale for the supercritical extraction of cannabis sativa threshing residues at CO 2 loadings of 0.63–0.73 g/mL, temperatures between 313 and 343 K and the corresponding pressures of 91–176 bar. The proposed technique enabled extraction yields of 3.9–6 % wt. with respect to dry biomass, with cannabinoids contents in extracts of 191.86 mg/g for CBD and 28.48 mg/g for THC. Results were comparable with those obtained in commercial supercritical equipment. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Extraction of cannabis flowers and leaves with cryogenic ethanol was carried out. • A bench scale rotary tumbler extractor was use and compared with soxhlet extraction. • Extraction efficiency of ∼22% of cannabinoids and terpenes was verified. • Lower content of chlorophyll and other impurities observed at cryogenic conditions. • Extraction can be suitably done at −20 °C and 15:1 solvent:solid ratio. Extraction of natural products using safe, selective and green solvents is of major importance for their use as ingredients in foods, beverages, cosmetics and pharmaceutical products. In the particular case of cannabis, ethanol at ambient conditions has been found to be very effective in the extraction of cannabinoids, terpenoids, and other valuable metabolites; however, it also extracts chlorophyll, vegetable oils and waxes. Alternatively, the selectivity towards cannabinoids could be increased by operating at lower temperatures. In this regard, this work focused on the cryogenic extraction of leaves and flowers of Cannabis sativa L. with ethanol. Extractions were carried out in a rotary tumbler under batch operation at different temperatures (−80 °C to 20 °C) and solvent:solid ratios (4:1 to 25:1 mL/g). The content of cannabinoids in samples was measured via U-HPLC under isocratic elution using a mixture of a 0.1% wt. formic acid aqueous solution and pure acetonitrile, using a diode array detector at 280 nm, and with an external standard method. Terpenes were quantified by GC using headspace injection, FID detection, and using external standards for calibration. The yields with respect to dry biomass were in-between 0.43% and 4.22% wt. The corresponding cannabinoids content with respect to dry material ranged from 0.25% to 2.67% wt., and these mainly corresponded to cannabidiol and cannabinol. The content of terpenoids was in between 0.01 and 1% wt., and the major fraction corresponded to monoterpenes d-Limonene, β-Myrcene, α-Terpinene, Terpinolene, and p-Cymene. Cryogenic extracts were characterized by a translucent aspect with minor content of coloring compounds and other impurities. Preferred operating conditions corresponded to −20 °C and a solvent:solid ratio of 16:1 mL/g; under these conditions and with respect to dry biomass, the extraction yield was 3.47% wt., the cannabinoids content was 0.67% wt., and the CBD content was 0.59% wt. [ABSTRACT FROM AUTHOR]

Biocomposites based on poly-3-hydroxybutyrate/polycaprolactone/cannabis sativa indica-Russia white sawdust 70/30/(0 and 30) parts by weight were prepared. Mixing was carried out on a conventional laboratory two roll mill. Sheets of biocomposites were manufactured by compression molding. Specimens of each compound were buried in soil for four months. At the end of the period, the specimens were taken out of the soil and subjected to infrared spectroscopy, X-ray diffraction, electron scanning microscopy, tensile tests and mass loss. The biocomposites that were buried in the soil presented changes in the chemical and crystalline structure, decrease in mechanical properties, loss of mass and surface deterioration with respect to the control samples. The results of this study provide relevant information about the initial biodegradation of biocomposites manufactured with sawdust obtained from the stem of legal marijuana crops (for medical application). This paper is intended to promote the manufacture of 100% biodegradable polymeric compounds. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a procedure to create escape vectors specifically developed to perform an orthogonal projection from an Ax≤b type polyhedron's edge to its interior. The proposed procedure can be implemented in interior-point methods for solving linear programming problems since in these methods various strategies are used to avoid reaching the borders of the polyhedron. A projection procedure was developed to the polyhedron's interior starting from three scenarios and it was used on a context case demonstrating its applicability. The results show that the projection carried out in the iteration in which the escape is done not only allows abandoning from a suboptimal solution but it also kept the same objective function value. Therefore, it can be concluded that interior-point methods do not need to avoid the frontier or to adjust values, as it occurs in other applications. [ABSTRACT FROM AUTHOR]

This paper presents a study done to find an interior point in the feasible region of linear programming problems is an aspect that should be solved in the initial stage of the implementation of the interior point algorithms used to optimize them. Consequently, it is proposed a methodology that starts with a formulation that does not require adding surplus or slack variables. It only includes an additional variable to generate a polyhedron in a new expanded space and with simple projections finds an interior point in the same polyhedron. It is demonstrated that the optimal solution of the extended linear programming problem allows obtaining a feasible point of the original problem or concluding that it has no feasible solutions. [ABSTRACT FROM AUTHOR]

An experimental study was performed to measure the resistance to adhesive peel strength of two sheets of similar composition bonded with adhesive. The sheets were made from polyethylene with 32% Telinne monspessulana flour and 5.2% maleated polyethylene. Two types of eco-friendly adhesives were used: aqueous dispersion polyurethane and hot melt ethylene vinyl acetate base. The substrates or surfaces to be bonded from each sheet previously were subjected to mechanical abrasion. Subsequently the surface was treated with vinyl tri (2 -methoxyethoxy) silane, acrylic and diisocyanate primers. The resistance to the separation of both substrates also named as adhesive force of the joint, was determined with the test 180° T-peel adhesión. Chemical treatments increased the peeling strength in the bonded joints with polyurethane water-based, however higher values were obtained by joining the substrates with hot melt adhesive without chemical treatment. The addition of maleate in the wood plastic composite did not improve the efficiency of chemical treatments. [ABSTRACT FROM AUTHOR]

The effect of the addition of maleated polyethylene to compounds of ethylene vinyl acetate with Telinne Monspessulana flour previously mercerized was investigated. Two factors were analyzed: (ii) concentration of maleated polyethylene with five levels 2; 4; 6; 8; 10 parts per hundred polymer; and (ii) concentration of flour with two levels 25 and 40 parts per hundred of polymer. The effect of maleated polyethylene on compatibility between ethylene vinyl acetate and flour was evaluated by tensile testing of compounds. Analysis indicates that the coupling agent improved the compatibility between Telinne Monspessulana flour and ethylene vinyl acetate, effect that was observed by the values of tensile strength and Young's modulus. Based on these results, maleated polyethylene is a good alternative as a coupling agent in ethylene vinyl acetate and natural fibers compounds. [ABSTRACT FROM AUTHOR]

In this paper we present a new algorithm for finding the convex hull C(P) for P sets of n points in R2. This problem has been widely studied in computational geometry and has important applications in engineering and other fields of knowledge. The proposed algorithm is based on a directional search of supporting hyperplanes and a variant which includes separating hyperplanes to reduce the number of evaluated points, ignoring the interior ones. The application of the proposed algorithm is illustrated using an example. The complexity of the algorithm obtained is O(max (nvo; nvo)), vo ≤ v ≤ n y vo ≤ v ≤ n, where v is the number of vertices of the convex hull. [ABSTRACT FROM AUTHOR]

The objective of this paper is to establish what are the critical factors for the spatial design of distribution centers, specially inmotic storage ships. To do so, the principles of the adjusted general methodology (MGA) were used along with the implementation of experimental design (DOE) in the context of a faucet production company in Bogotá, Colombia. The MGA methodology lays its foundations in the application to industrial real estate projects, in a supply network scheme. Furthermore, DOE is used as a way of obtaining an optimal alternative which satisfies the expectations of the company and its clients from an economic and statistical point of view. The results show that the storage capacity of the centralized distribution center is the most significant factor in the design stage, being an essential factor for rationalizing investment in working capital and for maximizing the benefits of the company. [ABSTRACT FROM AUTHOR]