CO2 sequestration in coals and enhanced coalbed methane recovery: New numerical approach

Mixed gases injection into a large coal sample for CO₂ sequestration in coals and enhanced coalbed methane recovery was investigated using a new numerical approach. A dynamic multi-component transport (DMCT) model was applied to simulate ternary gas (CH₄-CO₂-N₂) diffusion and flow behaviors for better understanding and prediction of gas injection enhanced coalbed methane (ECBM) recovery processes. Several cases were designed to analyze the effects of injection gas composition and pressure on gas displacement dynamics in a large coal sample. The calculated results suggest that mixed gas injections have similar profiles of methane recovery as pure N₂ injection, and mixtures of N₂ and CO₂ reduce the ultimate methane recovery compared to pure CO₂. The breakthrough time of pure CO₂ injection is longer than mixed gas injections. Injection gas composition has significant effect on produced gas composition.     

New tuning conditions for a class of nonlinear PID global regulators of robot manipulators

Several nonlinear proportional-integral-derivative (PID) controllers for robot manipulators that ensure global asymptotic stability have been proposed in the literature. However, the tuning criteria obtained are expressed in terms of conditions so restrictive that they have avoided, until now, carrying out experimental tests with such controllers. Tuning criteria of some PID controllers for robot manipulators with conditions more relaxed than those presented previously in the literature have been proposed in two recent works by the authors. This was achieved by setting the tuning conditions individually for each joint instead of general conditions for the whole robot. In this paper we extend these results to a class of nonlinear PID global regulators for robot manipulators. The obtained tuning criteria are given in terms of conditions so relaxed that they have allowed to carry out, for the first time, experimental essays with these controllers. Such experiments are presented in this paper using a two-degrees-of-freedom robot manipulator.     

RELATIONSHIP BETWEEN A SOLAR DRYING MODEL OF RED PEPPER AND THE KINETICS OF PURE WATER EVAPORATION (II)

ABSTRACT

In part one, a simple drying model of red pepper related to water evaporation was developed. In this second part the drying model is applied by means of related experiments.

Both laboratory and open air drying experiments were carried out to validate the model and simulation results are presented.     

A simple analytical model for burr type prediction in drilling of ductile materials

This paper proposes a new analytical model to predict the type of burr at drilling exit. The model is based on the theory of slip-planes and is specially developed to predict burr type formation in drilling of ductile materials. First the analytical model is set up, based on mechanical and geometrical considerations. Then it has been validated through experimental drilling tests on aeronautical aluminum by predicting burr type and thickness. The experimental results show that the model is suitable in the drilling of ductile materials and its validity domain has been established.     

Hybridization of poly(rI) with poly(rC) adsorbed to the carbon nanotube surface

Hybridization of homopolynucleotide poly(rC) adsorbed to the carbon nanotube surface with poly(rI) free in solution has been studied by absorption spectroscopy and molecular dynamics method. It was found that hybridization on the nanotube surface has a slow kinetics, the behavior of which differs essentially from fast hybridization of free polymers. The duplex obtained is characterized with the reduced thermostability and a lower hyperchromic coefficient than it was observed when the duplex was formed in the absence of the nanotube. These features point to the imperfectness in the structure of the duplex hybridized on the nanotube surface. Computer simulation showed that the strong interaction of nitrogen bases with the nanotube surface weakens significantly hybridization of two complementary oligomers, as the surface prevents the necessary conformational mobility of the polymer to be hybridized.     

The chemical structure of the amorphous phase of propylene–ethylene random copolymers in relation to their stress–strain properties

A better understanding of structure-property relations is necessary to design novel materials. In this study, we investigate the morphology and chemical structure of five commercial grades of propylene-based polymers in relation to the change in yield- stress as a function of strain-rate. Substantial emphasis has been laid on understanding the chain microstructure in the relation to chain dynamics in the amorphous phase. Heterogeneous Ziegler–Natta catalysis was used to prepare the samples with differing ratios of propylene and ethylene units. Various analytical techniques such as WAXS, SAXS, solution- and solid-state NMR were employed to characterize their structure. The results indicate a reduction in crystallinity, melting temperature, long-period and crystal thickness with increasing ethylene content. Solid-state NMR data reveal the presence of four components in these samples, which is an extension of the traditional three phase model found in most semi-crystalline polymers. The additional fourth phase is attributed to a rubber-like component that is primarily composed of chain segments rich in ethylene units and shows an increase in chain dynamics with increasing ethylene content in the samples. Mechanical experiments show that yield stress decreases with increase in the amount ethylene which can be correlated to the observed increase in chain dynamics in the amorphous phase.     

Application of bootstrap method in conservative estimation of reliability with limited samples

Accurate estimation of reliability of a system is a challenging task when only limited samples are available. This paper presents the use of the bootstrap method to safely estimate the reliability with the objective of obtaining a conservative but not overly conservative estimate. The performance of the bootstrap method is compared with alternative conservative estimation methods, based on biasing the distribution of system response. The relationship between accuracy and conservativeness of the estimates is explored for normal and lognormal distributions. In particular, detailed results are presented for the case when the goal has a 95% likelihood to be conservative. The bootstrap approach is found to be more accurate for this level of conservativeness. We explore the influence of sample size and target probability of failure on the quality of estimates, and show that for a given level of conservativeness, small sample sizes and low probabilities of failure can lead to a high likelihood of large overestimation. However, this likelihood can be reduced by increasing the sample size. Finally, the conservative approach is applied to the reliability-based optimization of a composite panel under thermal loading.     

RELATIONSHIP BETWEEN A SOLAR DRYING MODEL OF RED PEPPER AND THE KINETICS OF PURE WATER EVAPORATION (I)

ABSTRACT

Drying of red pepper under solar radiation was investigated, and a simple model related to water evaporation was developed. Drying experiments at constant laboratory conditions were undertaken where solar radiation was simulated by a 1000 W lamp.

In this first part of the work, water evaporation under radiation is studied and laboratory experiments are presented with two objectives: to verify Penman's model of evaporation under radiation, and to validate the laboratory experiments. Modifying Penman's model of evaporation by introducing two drying conductances as a function of water content, allows the development of a drying model under Eolar radiation.

In the second part of this paper, the model is validated by applying it to red pepper open air solar drying experiments.     

Poly(2-oxazoline)s as materials for biomedical applications

The conjunction of polymers and medicine enables the development of new materials that display novel features, opening new ways to administrate drugs, design implants and biosensors, to deliver pharmaceuticals impacting cancer treatment, regenerative medicine or gene therapy. Poly(2-oxazoline)s (POx) constitute a polymer class with exceptional properties for their use in a plethora of different biomedical applications and are proposed as a versatile platform for the development of new medicine. Herein, a global vision of POx as a platform for novel biomaterials is offered, by highlighting the recent advances and breakthroughs in this fascinating field.     

The PIC implementation in LuNA system of fragmented programming

The main features of the LuNA system of fragmented programming, aimed at parallel implementation of the large-scale numerical models on the mesh, are considered. The complex application of the Particle-In-Cell method to a large-scale 3D dust-cloud model, developed in LuNA, demonstrates its advantages for providing such dynamic properties of application programs as portability, dynamic load balancing and tunability to all the available resources.