A comparative study of many-objective evolutionary algorithms for the discovery of software architectures

During the design of complex systems, software architects have to deal with a tangle of abstract artefacts, measures and ideas to discover the most fitting underlying architecture. A common way to structure such complex systems is in terms of their interacting software components, whose composition and connections need to be properly adjusted. Along with the expected functionality, non-functional requirements are key at this stage to guide the many design alternatives to be evaluated by software architects. The appearance of Search Based Software Engineering (SBSE) brings an approach that supports the software engineer along the design process. Evolutionary algorithms can be applied to deal with the abstract and highly combinatorial optimisation problem of architecture discovery from a multiple objective perspective. The definition and resolution of many-objective optimisation problems is currently becoming an emerging challenge in SBSE, where the application of sophisticated techniques within the evolutionary computation field needs to be considered. In this paper, diverse non-functional requirements are selected to guide the evolutionary search, leading to the definition of several optimisation problems with up to 9 metrics concerning the architectural maintainability. An empirical study of the behaviour of 8 multi- and many-objective evolutionary algorithms is presented, where the quality and type of the returned solutions are analysed and discussed from the perspective of both the evolutionary performance and those aspects of interest to the expert. Results show how some many-objective evolutionary algorithms provide useful mechanisms to effectively explore design alternatives on highly dimensional objective spaces.     

Bicriteria Optimization Model for Locating Maritime Container Depots: Application to the Port of Valencia

Since the location of container depots has an impact on maritime logistics costs, the container depot location problem is usually treated as a cost minimization problem. But the location of the container depots also has a serious environmental impact, given the heavy traffic load inherent to these operations and the setting up and maintenance of the depots. In this paper a bicriteria optimization model for designing a network of depots in a hinterland is proposed and its application to the Port of Valencia, Spain is reported. The two objectives considered are (1) the total cost of the network and (2) the environmental impact of the container depots and the transport operations associated with them. An Analytic Hierarchy Process (AHP) has been used to determine the environmental impact of each depot, and the ε-constraint method to obtain the optimal Pareto set of the problem. The results clearly show that trade-offs are possible between both objective functions and that, for our case study, the proposed approach can obtain solutions that are more cost-effective and have lower environmental impacts than those currently existing.     

A Numerical Approximation‐Based Controller for Mobile Robots with Velocity Limitation

In this paper the problem of trajectory tracking considers that the values of the control actions do not exceed a maximum allowable value and the zero convergence of tracking errors is demonstrated. The control law is based on a linear algebra approach. First, the desired trajectories of some state variables are determined by analyzing the conditions for a system of linear equations to have an exact solution. Therefore, the control signals are obtained by solving the system of linear equations. The optimal controller parameters are selected through nonlinear programming so as to prevent the saturation of the control actions. Experimental results are presented and discussed, demonstrating the controller's good performance. Finally, the performance of the proposed controller is compared with a fuzzy controller, and all the results are validated through experimental laboratory tests.     

A decision support methodology for increasing public investment efficiency in Brazilian agrarian reform

The Brazilian Agrarian Reform Program has subsidized the settlement of over 425,000 destitute families on previously unproductive land in what has become a very effective vehicle for social inclusion and productivity growth for those settlers who reach the final stage of the process and receive definitive title to the land. Unfortunately, there is a large difference in efficiency and productivity between more and less successful settlements – fewer than 10% of relocated families have received title and over 25% of them have abandoned the property to which they were assigned. This paper presents a decision support methodology for increasing the efficiency of public investments in agrarian reform that includes a data envelopment analysis model and a mechanism for building consensus among the various constituencies of the agrarian reform process, who not infrequently have conflicting objectives. The OR model described herein uses principal component analysis and data envelopment analysis to identify the most important success factors for relocated families leading to an increase in the chance of both autonomous integration with the market economy and definitive entitlement by these displaced families as well as an increase in the predictability of future settlement success. The model was implemented successfully in Rio Grande do Sul, the southernmost state of Brazil, and was partially used in a pilot project for the countrywide agrarian reform accelerated consolidation program.     

Fermentation of enzymatic hydrolysates from olive stones by Pachysolen tannophilus

BACKGROUND: Olive stones were pretreated with liquid hot water (LHW or autohydrolysis) at maximum temperatures between 175 and 225 °C (severity factors, logR₀, between 2.73 and 4.39) to be subjected (both liquid and solid components) afterwards to enzymatic hydrolysis with cellulases from Trichoderma viride. Ethanol fermentation of hydrolysates was performed with the non‐traditional yeast Pachysolen tannophilus ATCC 32691. RESULTS: After the enzymatic step, yields of hemicellulose solubilization reached 100%, while the cellulose was only partially hydrolysed (23%, logR₀ = 4.39). The maximum yields in total reducing sugars and acetic acid, at the upper end of the severity range, was close to 0.25 and 0.04 g g^?1 dry stone, respectively. During the fermentation stage, the increase in R₀ reduced the maximum specific growth rate, biomass productivity, and overall biomass yield. The overall yields of ethanol and xylitol ranged, respectively, from 0.18 to 0.25 g g^?1 and from 0.01 to 0.13 g g^?1. CONCLUSIONS: The results demonstrate the possibility of producing ethanol from olive stones, making use of the cellulose and hemicellulose fraction of the waste. It was confirmed that the overall yield in xylitol strongly depended on severity factor, while the overall yield in ethanol remained practically constant for all the pretreatment conditions tested. Copyright © 2008 Society of Chemical Industry     

Biological nutrient removal in a sequencing batch reactor using ethanol as carbon source

BACKGROUND: When organic matter is limiting for biological nutrient removal (BNR) from wastewater, external organic carbon can be added to a wastewater treatment plant (WWTP). This increases the overall treatment cost, so the choice of substrate is critical. The effect of using ethanol as the carbon source for BNR is investigated. RESULTS: The results clearly showed that using ethanol as a carbon source is a promising strategy for removing nutrients from wastewater. Effluent concentrations of 3.0 mg total nitrogen (TN) L^?1 (96% N removal efficiency) and 0.05 mg phosphate (P‐PO₄) L^?1 (99.9% P removal efficiency) were obtained. Furthermore, tests performed in order to identify the carbon source used by polyphosphate‐accumulating organisms (PAOs) showed that the phosphorus release/carbon uptake ratio using ethanol (0.41 mmol P mmol^?1 C) was slightly lower than that with acetate (0.50 mmol P mmol^?1 C) but close to that with propionate (0.42 mmol P mmol^?1 C). CONCLUSION: Therefore, taking into account the results presented for ethanol‐acclimatised biomass and the fact that the cost of ethanol is lower than that of acetate or propionate, ethanol can be considered as an alternative carbon source if one is needed in a WWTP. Copyright © 2007 Society of Chemical Industry     

Occurrence of Salmonella spp. in persimmon fruit (Diospyrus kaki) and growth of Salmonella enteritidis on the peel and in the pulp of this fruit

The occurrence of Salmonella spp. on persimmon (Diospyrus kaki) surface of ‘Fuyu’ and ‘Rama Forte’ was evaluated during a 5-month-period (from April to August) of two season periods (years 2005 and 2006). The fruits were collected in wholesale (CEAGESP) and street markets in Sao Paulo and Campinas City, Brazil. A total of 582 fruits were analyzed using the BAX^® system, which is based on the Polymerase Chain Reaction (PCR). The ability of this pathogen to grow on the peel and pulp of the two persimmon varieties was also verified at different incubation periods at temperatures of 10, 20 and 30 °C. The growth parameters were obtained by modeling the experimental data using the Gompertz function. The presence of Salmonella spp. was evidenced in 5 of the 582 analyzed fruits (0.9% incidence). The growth studies showed that Salmonella enteritidis can grow on the peel as well as in the pulp of the two persimmon varieties studied incubated at 10, 20 and 30 °C and that low temperatures can reduce the generation rate but do not inhibit its growth.     

Electrically Programmed Doping Gradients Optimize the Thermoelectric Power Factor of a Conjugated Polymer

Functionally graded materials (FGMs) are widely explored in the context of inorganic thermoelectrics, but not yet in organic thermoelectrics. Here, the impact of doping gradients on the thermoelectric properties of a chemically doped conjugated polymer is studied. The in-plane drift of counterions in moderate electric fields is used to create lateral doping gradients in films composed of a polythiophene with oligoether side chains, doped with 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F₄TCNQ). Raman microscopy reveals that a bias voltage of as little as 5 V across a 50 µm wide channel is sufficient to trigger counterion drift, resulting in doping gradients. The effective electrical conductivity of the graded channel decreases with bias voltage, while an overall increase in Seebeck coefficient is observed, yielding an up to eight-fold enhancement in power factor. Kinetic Monte Carlo simulations of graded films explain the increase in power factor in terms of a roll-off of the Seebeck coefficient at high electrical conductivities in combination with a mobility decay due to increased Coulomb scattering at high dopant concentrations. Therefore, the FGM concept is found to be a way to improve the thermoelectric performance of not yet optimally doped organic semiconductors, which may ease the screening of new materials as well as the fabrication of devices.     

Study of molecular structure and vibrational spectra of poly (β,-l-malic acid) [PMLA] using DFT approach

Poly (β-L-malic acid) (PMLA) is a biodegradable polymer and it has various important applications in the biomedical field. In the present work the structural and spectral characteristics of PMLA have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) using oligomeric approach employing B3LYP with complete relaxation in the potential energy surface using 6-311++G (d, p) basis set. Based on results, we have discussed the correlation between the vibrational modes and the structure of the PMLA. A complete analysis of the experimental infrared and Raman spectra has been reported on the basis of wavenumber of the vibrational bands and potential energy distribution. The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The calculated infrared and the Raman spectra of the polymer based on DFT calculations show reasonable agreement with the experimental results.