Makespan estimation and order acceptance in batch process industries when processing times are uncertain

Batch process industries are characterized by complex precedence relationships between operations, which renders the estimation of an acceptable workload very difficult. A detailed schedule based model can be used for this purpose, but for large problems this may require a prohibitive large amount of computation time. We propose a regression based model to estimate the makespan of a set of jobs. We extend earlier work based on deterministic processing times by considering Erlang-distributed processing times in our model. This regression-based model is used to support customer order acceptance. Three order acceptance policies are compared by means of simulation experiments: a scheduling policy, a workload policy and a regression policy. The results indicate that the performance of the regression policy can compete with the performance of the scheduling policy in situations with high variety in the job mix and high uncertainty in the processing times. Correspondence to: C.V. Ivanescu     

Allergy and depression: A neurochemical threshold model of the relation between the illnesses.

Empirical studies suggest a very high prevalence of atopic disorder in people with depression. Research indicates that individuals with allergy have cholinergic hyperresponsiveness and beta-adrenergic hyporesponsiveness in the autonomic nervous system. Evidence is reviewed that similar imbalances in CNS cholinergic–adrenergic activity play a causal role in depression behaviors. It is hypothesized that the allergic state or allergic reactions can accentuate cholinergic–adrenergic activity imbalances in the CNS of a small subgroup of people at risk for endogenous depression thereby producing depression symptomatology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of leaf-spring with aircushion trailer suspensions in the transport environment

Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies.     

β-Si3N4Whiskers Embedded in Oxynitride Glasses: Interfacial Microstructure

Interfacial microstructures in βP-Si₃N₄( w )-Si-Al-Y-O-N-glass systems were investigated by systematically varying the nitrogen content and the Al:Y ratio of the glass matrix. High-resolution and analytical transmission electron microscopy (HREM and AEM) studies revealed that the interfacial microstructure is a function of the glass composition. No interfacial phases were formed in glasses with low Al:Y ratios and in glasses with high Al:Y ratios and low nitrogen content, whereas epitaxial growth of an interfacial layer (100–200 μm thick) on the βP-Si₃N₄( w ) occurred in a glass matrix with high Al:Y ratio and high nitrogen content. The interfacial layer was identified to be a β'-SiAION phase. Interfaces containing the SiAION layer exhibited high debonding energy compared to Si₃N₄( w )–glass interfaces. HREM studies indicated that the lattice-mismatch strain in the SiAION layer was relieved by dislocation formation at the SiAION–Si₃N₄( w ) interface. The difference in interfacial debonding energy was, hence, attributed to the local atomic structure and bonding between the glass-β-Si₃N₄ and the glass–β'-SiAION phases. This observation was clear evidence of the strong influence of glass chemistry on the interfacial debonding behavior by altering the interfacial microstructure.     

The Air is Always Cleaner on the Other Side: Race,Space, and Ambient Air Toxics Exposures in California

Abstract: Environmental justice advocates have recently focused attention on cumulative exposure in minority neighborhoods due to multiple sources of pollution. This article uses U.S. EPA's National Air Toxics Assessment (NATA) for 1996 to examine environmental inequality in California, a state that has been a recent innovator in environmental justice policy. We first estimate potential lifetime cancer risks from mobile and stationary sources. We then consider the distribution of these risks using both simple comparisons and a multivariate model in which we control for income, land use, and other explanatory factors, as well as spatial correlation. We find large racial disparities in California's “riskscape” as well as inequalities by other factors and suggest several implications for environmental and land use policy.     

Development and simulation studies of an unsteady state biofilter model for the treatment of cyclic air emissions of an α‐pinene gas stream

This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, C_{g, max}/C_g, relative value of the half‐saturation constant in the Monod expression, K_s, and effective diffusivity of α‐pinene in the biofilm, D_e. Copyright © 2005 Society of Chemical Industry     

Ultrasound‐activated Knoevenagel condensation of malononitrile with carbonylic compounds catalysed by alkaline‐doped saponites

α,β‐Unsaturated nitriles have been synthesized by Knoevenagel condensation of a carbonylic compound with malononitrile, assisted by sonochemical irradiation. Two alkaline‐promoted clays (Li⁺‐ and Cs⁺‐exchanged saponites) have been employed as catalysts. The influence of the carbonylic compound (benzaldehyde or cyclohexanone) and the use of a solvent on the catalytic activity have been studied. Remarkable increase in the conversion values has been found when the reaction is activated by ultrasound, as compared with the thermal activation. In this green, solvent‐free procedure, α,β‐unsaturated nitriles have been produced in very high yields (97%) when the Cs⁺‐saponite is used as catalyst. Copyright © 2004 Society of Chemical Industry