The memetic self-organizing map approach to the vehicle routing problem

The paper presents an extension of the self- organizing map (SOM) by embedding it into an evolutionary algorithm to solve the Vehicle Routing Problem (VRP). We call it the memetic SOM. The approach is based on the standard SOM algorithm used as a main operator in a population based search. This operator is combined with other derived operators specifically dedicated for greedy insertion moves, a fitness evaluation and a selection operator. The main operators have a similar structure based on the closest point findings and local moves performed in the plane. They can be interpreted as performing parallels and massive insertions, simulating the behavior of agents which interact continuously, having localized and limited abilities. This self-organizing process is intended to allow adaptation to noisy data as well as to confer robustness according to demand fluctuation. Selection is intended to guide the population based search toward useful solution compromises. We show that the approach performs better, with respect to solution quality and/or computation time, than other neural network applications to the VRP presented in the literature. As well, it substantially reduces the gap to classical Operations Research heuristics, specifically on the large VRP instances with time duration constraint.     

Improvement in stability of poly(3-hexylthiophene-2,5-diyl)/[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction solar cell by using UV light irradiation

A study of organic solar cells based on photoactive blends of the conjugated regioregular-poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with different UV-light treatments is presented. As expected, air exposure of an unencapsulated P3HT:PCBM solar cell is observed to result in rapid degradation of device efficiency. In order to ease this degradation, we found that exposing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to UV light may reduce the degradation and preserve good performance. Samples with PEDOT:PSS exposed to UV light show better long-run stability than the pristine cells. The active layer exposed to UV light shows the poorest performance and degrades rapidly. From the initial value, the efficiency decreased by 56% and 35% for pristine cells and cells with PEDOT:PSS exposed to UV light, respectively. It has been found that device half-life was 650 and 400 h for the samples with and without UV treatment, respectively. The trend in device performance was explained by observed changes in work function of the PEDOT:PSS layer and decreased absorption intensity of P3HT:PCBM.     

Indium zinc oxide ohmic contact to poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) induced by UV light

In this research, we investigated the I–V characteristics of ITO/PEDOT:PSS/InZnO devices for two sets of samples. The first set is composed of PEDOT:PSS as-prepared, while the second set is composed of PEDOT:PSS irradiated by UV light source. We found that UV irradiation improves the electrical conductivity of the fabricated devices and yields to ohmic contact. Based on the UPS measurements, it was found that UV irradiation leads to an increase in the work function and the enhancement of electrical conductivity of PEDOT:PSS films. XPS and AFM measurements indicate that conformational changes of the PEDOT:PSS films are responsible for this behavior. We also studied the effect of storage on the electrical properties of our devices. No significant changes of electrical characteristics have been found after storing the devices for a period of 30 days.     

Photosensitive terpolymer for all-wet-etching process: Material characterization and device fabrication

A photosensitive terpolymeric composition suitable for practical waveguide devices is provided. The terpolymer was produced from pentafluorostyrene, perfluoro-n-octyl acrylate, and glycidyl methacrylate. We present a fabrication process where the device structure utilizes the same class of material for the core and cladding layers and it was fabricated without a plasma etching process. Based on the developed material and process; a 16-channel arrayed waveguide grating with good performance has been realized. During temperature cycling, a slight thickness hysteresis and refractive index hysteresis was observed above the glass transition temperature and is ascribed to the fact that the terpolymer material may not completely recover its elasticity in the heating/cooling cycle.