Two approaches for solving the buffer allocation problem in unreliable production lines

This paper presents an integrated approach to solve the buffer allocation problem in unreliable production lines so as to maximize the throughput rate of the line with minimum total buffer size. The proposed integrated approach has two control loops; the inner loop and the outer loop. While the inner loop control includes an adaptive tabu search algorithm proposed by Demir et al. [8], binary search and tabu search are proposed for the outer loop. These nested loops aim at minimizing the total buffer size to achieve the desired throughput level. To improve the efficiency of the proposed tabu search, alternative neighborhood generation mechanisms are developed. The performances of the proposed algorithms are evaluated by extensive computational experimentation, and the results are reported.     

Synthesis and characterization of waterborne and phosphorus-containing flame retardant polyurethane coatings

Phosphorus-containing flame retardant water-dispersed polyurethane coatings were produced by incorporating different amounts of a phosphorus compound onto the polyurethane main chain. The novel phosphorus containing compound (phosphorus phenyl dihydroxy) was synthesized in three steps using benzaldehyde, pentaerythritol, phenyl phosphonic dichloride, and acetic acid. The addition of phosphorus phenyl dihydroxy to the main chain of polyurethane, in which NCO/OH ratio was kept constant at 1.5 and the amount of dimethylolpropionic acid (DMPA) at 3.5 wt%, increased the hardness and abrasion resistance, but only slightly decreased the gloss values of the polyurethane paints. All the samples showed superior impact resistance and flexibility. Moreover, increasing the phosphorus content increased the char yield, and the maximum fire retardancy was reached at 1.5% P content with a limiting oxygen index (LOI) value of 29. Kimya B?lümü, 06531 Ankara, Turkey.     

Energy and exergy analysis of Salihli geothermal district heating system in Manisa,Turkey

This study deals with an energy and exergy analysis of Salihli geothermal district heating system (SGDHS) in Manisa, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. Energy and exergy losses throughout the SGDHS are quantified and illustrated in the flow diagram. The exergy losses in the system, particularly due to the fluid flow, take place in the pumps and the heat exchanger, as well as the exergy losses of the thermal water (e.g. geothermal fluid) and the natural direct discharge of the system. As a result, the total exergy losses account for 2.22, 17.88 and 20.44%, respectively, of the total exergy input to the entire SGDHS. The overall energy and exergy efficiencies of the SGDHS components are also studied to evaluate their individual performances and determined to be 55.5 and 59.4%, respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Age-dependent deficits in spatial memory are related to impaired hippocampal kindling.

21 3-mo-old and 25 26-mo-old Fischer 334 rats were tested in an 8-arm maze in a behavioral assessment of spatial memory (SM) before undergoing hippocampal kindling (HK) to examine alterations in neuronal plasticity as a function of aging. Results indicate a positive relation between maze performance and speed of HK and that SM was poorer and HK slower in 26-mo-olds than in 3-mo-olds. Age-related deficits in SM and HK may reflect decreased efficacy of synaptic transmission in a common neuroanatomical substrate. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H₂SO₄, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φ_saved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φ_saved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W^?1 upon 455 nm illumination at a light intensity of 63.5 µW cm^?2 and applied potential of ?0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H₂SO₄ for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O₂‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.     

Comparing the Effects of Nb,Pb, Y,and La Replacement on the Structural,Electrical, and Magnetic Characteristics of Bi-Based Superconductors

In this study, the effects of Pb, Nb, La, and Y replacements were investigated on Bi-based superconducting materials. In preparing the samples, we used a method called solid-state reaction method. The patterns of the X-ray diffraction of all samples indicated presence of Bi-2212 and Bi-2223 phases. The results obtained from XRD revealed that with increase of the melting point of substation elements, the Bi-2223 phase decreased while the Bi-2212 phase and impurity phases of samples grew. From the electrical resistivity measurements using the four-probe method, it was found that sample A with Pb and sample B with La replacements had the maximum and minimum critical temperatures of 111.4 and 81.6 K, respectively. Based on hysteresis loop (M–H) measurement using Bean’s model, estimation of critical current density (J_c) showed that sample A with Pb and sample B with La substitution had the maximum and minimum values respectively. These results may be due to the melting point of these elements with values of 888, 1512, 2315, and 2425 ^°C for PbO, Nb₂O₅, La₂O₃, and Y₂O₃, respectively. These elements were replaced by Bi₂O₃ with a melting point of 817 ^° C. Further, the samples were prepared at the temperature of 845 ^°C. It seems at this temperature, these elements not only dissolve within the main matrix and participate in the formation of the Bi-2212 phase during the sintering process but they also participate in the development of the variety of the impurity phases as confirmed by XRD results.     

Compatibilization of Poly(2,6-dimethyl-l,4-phenylene oxide) and Poly(2,6-dichloro-l,4-phenylene oxide) with Sulfonated Polystyrene and its Na and Zn-neutralized Ionomers

Compatibility of acidic (H), Na, and Zn neutralized sulfonated polystyrene ionomer blends with Poly(2,6-dimethyl- 1,4-phenylene oxide) (PPO) and Poly(2,6-dichloro- 1,4-phenylene oxide) (PDCIPO) was investigated by Dilute Solution Viscometry (DSV) and Differential Scanning Calorimetry (DSC). The intrinsic viscosities of the blends, are measured in suitable solvents. The degree of compatibility of the blends is characterized by Δb parameter. According to the results, PPO is completely miscible, except for Na-neutralized 1.7 mol% sulfonated polystyrene (Na1.7SPS) which is completely immiscible with PPO and PDClPO. PDClPO is completely miscible with Zn-neutralized sulfonated polystyrene (Zn4.8SPS) and partially miscible with acid sulfonated polystyrene (4.8SPS). Received: 12 August 2001/Revised version: 21 January 2002/Accepted: 11 March 2003 Correspondence to Leyla Aras     

COD fractionation of tannery wastewaters--particle size distribution, biodegradability and modeling

This study aims to establish the scientific link between particle size distribution (PSD) and biodegradability of different COD fractions of tannery wastewater, by means of sequential filtration/ultrafiltration, respirometric analysis and model evaluation. PSD profiles were determined in physical segregation experiments, using eight membrane discs, each with different pore sizes between 2 and 1600 nm. Biodegradability-related COD fractionation was determined at each size interval by model simulation and calibration of the corresponding oxygen uptake rate (OUR) profiles. Activated Sludge Model No. 3 (ASM3), modified for direct growth on hydrolysis products, was adopted for evaluation. PSD analyses defined a COD fingerprint with two significant portions at the two ends of size distribution, with 60% of the total COD at the particulate range, 25% at the soluble range and the remaining 15% well distributed among the colloidal range. Comparative evaluation of the sequence of OUR profiles yielded values of applicable model coefficients. It also enabled the assessment of size distribution for each major COD fraction, as an original tool for better interpretation of specific biodegradation characteristics of the selected tannery wastewater. Results also revealed a very slowly biodegradable/residual particulate COD component with a significant inhibitory effect. Model-based evaluation of the OUR profiles enabled quantifying the impact of inhibition in terms of changes in rate coefficients for growth, hydrolysis of soluble COD and endogenous decay.     

Exploring urban students’ constructions about school, work, race, and ethnicity.

This qualitative study is an exploration of 32 urban high school students’ narratives about the connection between school, work, and societal expectations of their future success related to their racial and ethnic background. The sample varied along 2 contextual dimensions: participation in a psychoeducational intervention (Tools for Tomorrow) and developmental status (i.e., half the sample were 9th-grade students and the other half were 12th-grade students). Using consensual qualitative research, the narratives revealed 3 major domains: future orientation; students’ perceptions of society’s expectations based on race and ethnicity; and students’ perception of the role of their race and ethnicity in future success. Results reveal that the majority of students endorse a connection between school and work, believe that society holds low expectations for them based on their racial and ethnic background, and cannot predict their future success based on their background. (PsycINFO Database Record (c) 2010 APA, all rights reserved)