A vehicle routing problem solved by using a hybrid genetic algorithm

The main purpose of this study is to find out the best solution of the vehicle routing problem simultaneously considering heterogeneous vehicles, double trips, and multiple depots by using a hybrid genetic algorithm. This study suggested a mathematical programming model with a new numerical formula which presents the amount of delivery and sub-tour elimination. This model gives an optimal solution by using OPL-STUDIO(ILOG CPLEX). This study also suggests a hybrid genetic algorithm (HGA) which considers the improvement of generation for an initial solution, three different heuristic processes, and a float mutation rate for escaping from the local solution in order to find the best solution. The suggested HGA is also compared with the results of a general genetic algorithm and existing problems suggested by Eilon and Fisher. We found better solutions rather than the existing genetic algorithms.     

Piezoresistive effects of copper-filled polydimethylsiloxane composites near critical pressure

Piezoresistive properties of polydimethylsiloxane (PDMS) filled with copper particles in volume fraction above the electrical percolation threshold (25.3–50.7 vol%) were investigated. Piezoresistive behavior of the PDMS-copper composites under compressive pressure showed not only a change in resistance by approximately six orders of magnitude (∼1.5 MPa), but also a change in the critical pressure due to variations in the hardness of the composites. Resistivity relaxation was observed near the critical pressure and was explained through a stress relaxation and percolation mechanism. The mean tunneling distance was calculated by using a theoretical equation for percolation under compression. When the gauge factors of the composites were plotted versus strain, a universal curve was obtained regardless of the copper contents. Finally, the PDMS-copper composite demonstrated good repeatability, showing only small differences in the relative resistance after five successive tests.     

Effects of moisture on properties of epoxy molding compounds

In this article the effects of moisture on a novel epoxy molding compound, including the mechanical properties, temperature transition, and thermal degradation behavior, are studied. The experimental results reveal that the absorbed water acts predominantly as a crazing agent, continuously decreasing the mechanical strength with the time in water. The glass-transition temperature decreases at the early stage and is finally equilibrated. The thermal degradation behavior of the materials is not greatly influenced by the hydrothermal age. The decomposition of samples in oxygen is composed of two independent steps: the thermal degradation and oxidation at high temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2253–2259, 2001     

Nanostructural and optical features of nc-Si:H films prepared by nickel-induced crystallization

A 30-nm-thick Ni layer was deposited on top of the nc-Si:H (hydrogenated nanocrystalline Si) films by rf-magnetron sputter, and then heat-treatments were carried out at temperatures of 350–500^∘C. Si nanocrystallites were formed in the Ni/nc-Si:H bilayer films during the post-deposition heat-treatments. The intensity of the photoluminescence spectra of the post-deposition heat-treated films gradually increased at wavelengths of ∼420 as well as ∼580 nm with raising the annealing temperature from 350 to 500^∘C. It is highly likely that the increase of the photoluminescence intensity is caused by the increase in the total volume of the nanocrystallites in the films. It was found that the nickel-induced crystallization processing enhanced the formation of Si cystallites with the size of ∼2 and ∼5 nm in the films.     

Biofilter in water and wastewater treatment

Biofilter is one of the most important separation processes that can be employed to remove organic pollutants from air, water, and wastewater. Even though, it has been used over a century, it is still difficult to explain theoretically all the biological processes occurring in a biofilter. In this paper, the fundamental of biological processes involved in the biofilter is critically reviewed together with the mathematical modeling approach. The important operating and design parameters are discussed in detail with the typical values used for different applications. The most important parameter which governs this process is the biomass attached to the medium. The relative merits of different methods adopted in the measurement of the biomass are discussed. The laboratory-and full-scale applications of the biofilter in water and wastewater treatment are also presented. Their performances in terms of specific pollutant removal are highlighted.     

Prediction of Long-Term Treatment Response to Selective Serotonin Reuptake Inhibitors (SSRIs) Using Scalp and Source Loudness Dependence of Auditory Evoked Potentials (LDAEP) Analysis in Patients with Major Depressive Disorder

Background: Animal and clinical studies have demonstrated that the loudness dependence of auditory evoked potentials (LDAEP) is inversely related to central serotonergic activity, with a high LDAEP reflecting weak serotonergic neurotransmission and vice versa, though the findings in humans have been less consistent. In addition, a high pretreatment LDAEP appears to predict a favorable response to antidepressant treatments that augment the actions of serotonin. The aim of this study was to test whether the baseline LDAEP is correlated with response to long-term maintenance treatment in patients with major depressive disorder (MDD). Methods: Scalp N1, P2 and N1/P2 LDAEP and standardized low resolution brain electromagnetic tomography-localized N1, P2, and N1/P2 LDAEP were evaluated in 41 MDD patients before and after they received antidepressant treatment (escitalopram (n = 32, 10.0 ± 4.0 mg/day), sertraline (n = 7, 78.6 ± 26.7 mg/day), and paroxetine controlled-release formulation (n = 2, 18.8 ± 8.8 mg/day)) for more than 12 weeks. A treatment response was defined as a reduction in the Beck Depression Inventory (BDI) score of >50% between baseline and follow-up. Results: The responders had higher baseline scalp P2 and N1/P2 LDAEP than nonresponders (p = 0.017; p = 0.036). In addition, changes in total BDI score between baseline and follow-up were larger in subjects with a high baseline N1/P2 LDAEP than those with a low baseline N1/P2 LDAEP (p = 0.009). There were significantly more responders in the high-LDAEP group than in the low-LDAEP group (p = 0.041). Conclusions: The findings of this study reveal that a high baseline LDAEP is associated with a clinical response to long-term antidepressant treatment.     

Nonsmooth feedback stabilizer for strict-feedback nonlinear systems that may not be linearizable at the origin

We present a continuous feedback stabilizer for nonlinear systems in the strict-feedback form, whose chained integrator part has the power of positive odd rational numbers. Since the power is not restricted to be larger than or equal to one, the linearization of the system at the origin may fail. Nevertheless, we show that the closed loop system is globally asymptotically stable (GAS) with the proposed continuous (but, possibly not differentiable) feedback. We formulate a condition that enables our design by characterizing the powers of the given system. The condition also shows that our result is an extension of Qian and Lin [Non-lipschitz continuous stabilizers for nonlinear systems with uncontrollable unstable linearization, Systems Control Lett. 42 (2001) 185–200] where the power of odd positive integers has been considered. New result on the global finite time stabilization problem is also presented.     

Multi-digit maximum voluntary torque production on a circular object

Individual digit-tip forces and moments during torque production on a mechanically fixed circular object were studied. During the experiments, subjects positioned each digit on a 6-dimensional force/moment sensor attached to a circular handle and produced a maximum voluntary torque on the handle. The torque direction and the orientation of the torque axis were varied. From this study, it is concluded that: (1) the maximum torque in the closing (clockwise) direction was larger than in the opening (counter clockwise) direction; (2) the thumb and little finger had the largest and the smallest share of both total normal force and total moment, respectively; (3) the sharing of total moment between individual digits was not affected by the orientation of the torque axis or by the torque direction, while the sharing of total normal force between the individual digit varied with torque direction; (4) the normal force safety margins were largest and smallest in the thumb and little finger, respectively.