A quantity discount approach to supply chain coordination

Quantity discounts provide a practical foundation for inventory coordination in supply chains. However, typical supply chain participants may encounter difficulties in implementing the coordination policy simply because (1) specified lot size adjustments may deviate from the economic lot sizes and (2) the buying firm may face amplified overstocking risks related to increased order quantities. The main objective of this study is to develop a quantity discount model that resolves the practical challenges associated with implementing quantity discount policies for supply chain coordination between a supplier and a buyer. The proposed Buyer’s Risk Adjustment (B-RA) model allows the supplier to offer discounts that capitalize on the original economic lot sizes and share the buyer’s risk of temporary overstocking under uncertain demand. The analytical results suggest that the proposed B-RA discount approach is a feasible alternative for supply chain coordination under uncertain demand conditions.     

HZE beam transport in multilayered materials

A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multiple-layered materials. The code is established to operate on the Langley nuclear fragmentation model used in space engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurement. Comparison with 56Fe ion with Pb-Al and Pb-(CH2)x targets shows reasonable agreement.     

The interstitial atom of the nitrogenase FeMo-cofactor: ENDOR and ESEEM show it is not an exchangeable nitrogen

A recent high-resolution X-ray crystallographic study (1.16 A) of the Azotobacter vinelandii nitrogenase MoFe protein revealed a previously undetected electron density associated with the active site FeMo-cofactor. The density is located inside the cluster at the center of the "trigonal prism" of six irons and is assigned to a species "X". The identity of species X was not resolved, although the electron density is consistent with a single N, O, or C atom. One proposal is that X is an N atom that derives from and exchanges with N from N2 during catalysis. In the present study, we have examined this possibility by employing 14N and 15N isotopes of N2 along with ENDOR and ESEEM spectroscopies. The WT MoFe protein and alpha-359Arg-->Lys and alpha-381Phe-->Leu variants were allowed to turn over in the presence of 14N2 or 15N2, and then were examined as resting enzymes by ENDOR and ESEEM at X- and Q-bands to look for all 14N and 15N signals coupled to the electron spin of the FeMo-cofactor and to determine if any exchanged during turnover. We have found five peaks in Q-band pulsed ENDOR spectra that appear to arise not only from previously reported N1/N2, which give rise to the ESEEM, but also from one or two additional coupled nitrogens. None of the ENDOR and ESEEM signals vanish or are altered by catalytic turnover with 15N2, and no new 15N signal is detected, leading to the conclusion that if species X is a nitrogen atom, it does not exchange during dinitrogen reduction.     

Manufacturing planning and control: The evolution of MRP and JIT integration

Material Requirements Planning (MRP) and Just-in-Time (JIT) system are directed toward planning and controlling the important characteristics of material flow: how much of what materials flow and when. Since the material flow is at the heart of the manufacturing firm, MRP and JHT are the powerful management tools that could determine the success or failure of an entire manufacturing system. One of the strongest debates in manufacturing has been centered on the performance comparison and compatibility of JIT production system to the existing MRP. The primary intent of this research is to provide an overview of the manufacturing planning and control environment associated with MRP and JIT. Classifying the existing MRP/JIT comparison and integration literature, two different perspectives on MRP/JIT are discussed, and future research area is proposed based on the taxonomy.     

PHASE BEHAVIOR OF DILUTE SODIUM DODECYL SULFATE-HEXANOL-BRINE SYSTEMS

ABSTRACT

Dilute aqueous “solutions” of anionic surfactants injected during enhanced oil recovery processes usually contain liquid crystalline material. Phase behavior has been studied in a model system containing sodium chloride brine with surfactant, alcohol, and salt contents maintained below 6, 10, and 3 weight percent respectively. Pseudoternary phase diagrams at constant salinities are used to represent the results. Some interpretation of the results is given in terms of micellar shape transformations produced by changes in the relative hydrophilic and hydrophobic properties of surfactant-alcohol mixtures.