A multi-stage stochastic programming approach in master production scheduling

Master Production Schedules (MPS) are widely used in industry, especially within Enterprise Resource Planning (ERP) software. The classical approach for generating MPS assumes infinite capacity, fixed processing times, and a single scenario for demand forecasts. In this paper, we question these assumptions and consider a problem with finite capacity, controllable processing times, and several demand scenarios instead of just one. We use a multi-stage stochastic programming approach in order to come up with the maximum expected profit given the demand scenarios. Controllable processing times enlarge the solution space so that the limited capacity of production resources are utilized more effectively. We propose an effective formulation that enables an extensive computational study. Our computational results clearly indicate that instead of relying on relatively simple heuristic methods, multi-stage stochastic programming can be used effectively to solve MPS problems, and that controllability increases the performance of multi-stage solutions.     

Speciation of Iron in Soils and the Relation with Its Concentration in Fruits

An attempt was made to identify the iron species that is most responsible for plant-available Fe. Iron concentrations in fruit samples were determined by using flame atomic absorption spectrometry (FAAS). The soil samples related to these fruits were also analyzed for Fe by using various digestion and extraction reagents. The relation between the fruit-Fe and soil-extractable-Fe concentrations was examined to explain the Fe uptake of fruit from soil. The probable chemical forms of Fe in the soil were evaluated for the speciation of Fe.     

A new rational approximation technique based on transformational high dimensional model representation

In this work, a new rational approximation scheme, based on the recently developed Transformational High Dimensional Model Representation (THDMR) approximation method is developed. As an initial step to the construction of a rational approximation for multivariate functions via THDMR, this paper focuses on the general theoretical background of the method and gives explicit formulae for the computation of such approximants. The performance of the technique is shown by several examples both in univariate and bivariate cases.     

Health network mergers and hospital re-planning

This paper presents an integer programming formulation for the hospital re-planning problem which arises after hospital network mergers. The model finds the best re-allocation of resources among hospitals, the assignment of patients to hospitals and the service portfolio to minimize the system costs subject to quality and capacity constraints. An application in the Turkish hospital networks case is illustrated to show the implications of consolidation of health insurance funds on resource allocations and flow of patients in the system.     

Oil recovery performances of surfactant solutions by capillary imbibition

Critical parameters playing a role in oil recovery by capillary imbibition of surfactant solutions were studied. Experiments conducted on sandstone and carbonate samples using different oil and surfactant types were evaluated for surfactant selection. In this evaluation interfacial tension (IFT), surfactant type, solubility characteristics of surfactants, rock type, initial water (pre-wet rock), and surfactant concentration were considered. In addition to these, a new technique was adopted to facilitate the surfactant screening process. This technique is based on assigning inorganic and organic property values and plotting organic conception diagrams (OCD) for surfactants. OCD defines the property of a compound in terms of physical chemistry in such a way that the property that depends much on the van der Waals force is called "organic" and the one that depends much on electric affinity is called "inorganic." Correlations between the capillary imbibition recovery performance and the properties of surfactant and oil (organic value (OV), inorganic value (IV), and IFT of surfactant solutions, oil viscosity, and surfactant type) were obtained. These correlations are expected to be useful in selecting the proper surfactant for improved oil recovery as well as identifying the effects of surfactant properties on the capillary imbibition performance.     

p-Hertz excitation spectroscopy of an optical antenna, optical transmitter-receiver mechanism

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.     

Determination of beryllium in solid samples by flame atomic absorption spectrometry after preconcentration on activated carbon.

It is generally supposed that the preconcentration procedure is used for the determination of metal concentrations under the sensitivity of the measurement method. This study showed that preconcentration is also need for the beryllium (Be) concentration over the sensitivity of atomic absorption spectrometry. For this purpose, a simple and selective method for the determination of Be in solid samples is modified. The method is based on the preconcentration of the complexes of beryllium-acetylacetone plus morin, oxine, PAN and PAR on activated carbon at different pH values. The adsorbed beryllium was eluted with aqua regia and measured by flame atomic absorption spectrometry (FAAS). Recoveries of up to 85% were achieved. For removing chemical interferences and applying the method to Be determination in solid samples, the masking studies and reproducibility were examined. The detection limit was found to be 0.12 ng mL(-1). The relative sandard deviations (RSD) were found to be 8% for 60 mL of 10.0 ng mL(-1) using 10 replicate enrichment procedures. Beryllium concentrations in the studied solid samples were found in the range of 0.28 - 3.95 mg kg(-1).     

Variations in Toxic Metal Levels of Two Fish Species,Pomatomus saltatrix and Dicentrarchus labrax,and Risk Estimation for Children

The concentrations of five toxic metals were monthly determined in two fish species,obtained from fish markets in Turkey during 2010—2011.For the determinations,AAS and ICP-AES were used.The obtained lead concentrations for all studied Pomatomus saltatrix(mean 635μg·kg-1)and Dicentrarchus labrax(mean 463μg·kg-1)samples were found to be significantly higher than the maximum allowances concentration(MAC)of 300μg·kg-1.Mean chromium(324μg·kg-1)and Cu(940μg·kg-1)concentrations in Pomatomus saltatrix were higher than in Dicentrarchus labrax(268μg Cr·kg-1 and 600μg Cu·kg-1)while Ni in Pomatomus saltatrix(216μg·kg-1)was lower in Dicentrarchus labrax(291μg·kg-1).The estimated non-carcinogenic and carcinogenic health risks by the Target Hazard Quotient and target carcinogenic risk indicate that there are no sytemic effects,and the risk of developing cancer over a human lifetime is between 2~9in 1 000 000.     

Solvent‐Catalyzed Ring–Chain–Ring Tautomerization in Axially Chiral Compounds

The mechanism of ring–chain–ring tautomerization and the prominent effect of the solvent environment have been computationally investigated in an effort to explain the enantiomeric interconversion observed in 2‐oxazolidinone derivatives, heterocyclic analogues of biphenyl atropisomers, which were isolated as single stable enantiomers and have the potential to be used as axially chiral catalysts. This study has shed light on the identity of the intermediate species involved in the ring–chain–ring tautomerization process as well as the catalytic effect of polar protic solvents. These mechanistic details will prove very useful in predicting and understanding ring–chain tautomeric equilibria in similar heterocyclic systems and will further enable experimentalists to devise appropriate experimental conditions in which axially chiral catalysts remain stable as single enantiomers.     

Can Extensional Flow Rupture Macromolecules in an Electrospinning Process?

The fracture of high molecular weight poly(ethylene oxide) (PEO) chains under extensional stretching during the electrospinning of aqueous solutions was investigated by measuring solution viscosities and monitoring the change of molecular weight. The degree of macromolecular chain fractures in 1.0% polymer solutions increased with the increase in molecular weight. The strain rates for stretching and fracturing of macromolecules are critical for the degradation of polymers along with experimental elongational strain rates. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1051–1054