Vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme

This paper presents a joint economic lot size (JELS) model for coordinated inventory replenishment decisions under the vendor-managed inventory (VMI) with consignment stock (CS) agreement and an emission-trading scheme. The paper assumes a single product that flows along a two-level supply chain system, with a single vendor and a single buyer. The total cost of the system is the performance measure, which is the sum of the vendor’s and the buyer’s total costs. The total cost includes the set-up and order costs, inventory holding costs, greenhouse gases (GHG) emissions tax and penalty costs. A mathematical model is proposed to determine: (1) the vendor’s production lot size quantity; (2) the number of shipments sent by the vendor to the buyer in a cycle; and (3) the production rate that minimises the total cost of the supply chain. Some numerical examples are carried out, as well as comparisons with the traditional JELS model for a classic two-level supply chain. Results show that the performance of the system is better when it is operated under a VMI with CS agreement, which is capable of reducing the traditional inventory holding costs and, for some values of given parameters, the GHG emissions tax and penalty costs.     

A consignment stock coordination scheme for the production,remanufacturing and waste disposal problem

This paper extends the model of a production, remanufacturing and waste disposal system by adding a buyer (retailer) to the vendor’s system to form a two-level forward/reverse supply chain. The vendor and the buyer are assumed to operate according to a consignment stock policy. A mathematical model is developed for the cases when the production and remanufacturing batches are of different and equal sizes. The model also accounts for transportation, inspection and sorting costs. Numerical examples are provided and results are discussed. The results show that the collection rate of used items and the repairable rate have a significant impact on the total cost of the system and the batch sizes. It was suggested that it may not be possible to operate a system like the one described in the paper at its maximum environmental edge without receiving some incentives or tax brackets. Another possibility is for the system to undergo a continuous improvement process to reduce its operational costs, which may require additional investment.     

Effects of sodium and calcium sulphates on volume stability and strength of lime-stabilized kaolinite

Lime treatment of sulphate-bearing clay soils has been shown to adversely affect their properties. In the current work, the effects of soaking untreated and lime-stabilized kaolinite samples in water and sodium and calcium sulphate on swelling and unconfined compressive strength are investigated and compared. Specimens were treated with 1, 3, or 5% lime and cured at 35 °C for 1, 7, or 28 days, followed by soaking in water or 10,000 ppm sodium or calcium sulphate solutions. The results show that soaking lime-treated kaolinite samples in sodium and calcium sulphate solutions promotes swelling, which is greatly influenced by the length of the curing period. Swelling is the result of the formation of ettringite with high affinity for water absorption, which results in a reduction in unconfined compressive strength. Ettringite forms in environments with high pH and active sulphates as small crystals which destroy the structure of stabilized soils due to expansion, particularly at the early stages of formation, given its high affinity for water absorption. SEM micrographs show ettringite crystals growing on and between clay particles.

     

Use of axial dispersion and plug flow models for determination of axial mixing and mass transfer coefficient in an l‐shaped pulsed packed extraction column

In this study, the volumetric overall mass transfer and phases axial mixing coefficients have been investigated in a pilot plant of an L‐shaped pulsed packed extraction column by using two liquid systems of toluene/acetone/water and n‐butyl/acetone/water. The mass transfer performance has been evaluated using two methods of axial dispersion and a plug flow model. The effect of the operational variables and physical properties, including the dispersed and continuous phases flow rates, pulsation intensity, and interfacial tension, on mass transfer and phases axial mixing coefficients have been considered. It has been found that the pulsation intensity and the continuous phase flow rate seriously affect the mass transfer coefficient, however, the dispersed phase flow rate has a weaker effect. Also, the axial mixing of a phase is strongly affected by the pulsation intensity and the flow rate of the phase itself and it is not affected by the second phase flow rate. Finally, new correlations are proposed to accurately predict the mass transfer and axial mixing coefficients.     

Natural gas usage as a heat source for integrated SMR and thermochemical hydrogen production technologies

This paper investigates various usages of natural gas (NG) as an energy source for different hydrogen production technologies. A comparison is made between the different methods of hydrogen production, based on the total amount of natural gas needed to produce a specific quantity of hydrogen, carbon dioxide emissions per mole of hydrogen produced, water requirements per mole of hydrogen produced, and a cost sensitivity analysis that takes into account the fuel cost, carbon dioxide capture cost and a carbon tax. The methods examined are the copper–chlorine (Cu–Cl) thermochemical cycle, steam methane reforming (SMR) and a modified sulfur–iodine (S–I) thermochemical cycle. Also, an integrated Cu–Cl/SMR plant is examined to show the unique advantages of modifying existing SMR plants with new hydrogen production technology. The analysis shows that the thermochemical Cu–Cl cycle out-performs the other conventional methods with respect to fuel requirements, carbon dioxide emissions and total cost of production.     

Numerical prediction of optimum hollowness and material of hollow rollers under combined loading

Fatigue life investigations have been made for cylindrical hollow rollers in pure rolling contact. In addition to normal loading, the rollers have been subjected to tangential loading of 1/3rd the normal load value. Sufficient coefficient of friction has been used to ensure no slipping occurs. Two main models were built with different hollowness percentages to investigate the hollowness percentage that gives the longest fatigue life. The first model consists of two cylindrical rollers of same size, while the second model consists of two rollers of different sizes. Two cases have been studied, when both rollers are hollow and when only one roller is hollow. The stress distribution in the roller body and the resulting deformation has been investigated using the finite element package, ABAQUS. Then the Ioannides–Harris (IH) theory was used to predict the fatigue life of the hollow rollers in pure rolling contact. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. It has been found that the optimum hollowness percentage with the longest fatigue life ranges is around 50%. Many factors affect the optimum hollowness percentage, like the kind of the material used for the cylindrical roller, whether the rollers in contact are of the same size or different size and whether the hollow roller is in contact with another hollow roller or in contact with solid roller.     

Effect of Structural Parameters on Drop Size Distribution in Pulsed Packed Columns

The effect of packing type on drop size distribution in pulsed packed columns was investigated by means of different columns and three packing types with three liquid systems including n‐butyl acetate, toluene, and kerosene with water. These liquid systems cover a wide range of interfacial tensions. Also the influence of operating variables in terms of pulse intensity and volumetric flow rates of dispersed and continuous phases was examined. Pulse intensity, interfacial tension, and packing shape were found as the main important factors for drop size distribution while volumetric flow rates had no significant effect. Correlations are presented to predict drop distribution and mean drop size in pulsed packed columns.     

Iron storage indices and risk of bacterial infections in hemodialysis patients

Background: Infection is the second leading cause of death among hemodialysis (HD) patients. Because iron overload may be a risk factor for bacterial infection, concerns about excessive use of intravenous (IV) iron have arisen. In this retrospective analysis, we explored the relationship between target iron storage indices, as outlined in the Dialysis Outcomes Quality Initiative (DOQI) guidelines, and the incidence of bacterial infections. Methods: We reviewed the charts of 87 HD patients who received their first course of IV iron at our dialysis unit between 1997 and 2001. Transferrin saturation (TSAT) rate, ferritin level, and other clinical/laboratory measures were recorded at baseline. Patients were followed for up to 2 years for the outcomes of bacteremia and bacterial pneumonia and censored at death, end‐of‐study observation, or kidney transplantation. Cox proportional hazards regression was used to evaluate the relationship of bacterial infections to iron storage indices. Results: Thirty‐two patients had at least one episode of bacterial infections. In multivariate analyses, after adjusting for sex and venous catheter use, iron‐replete state (ferritin > 100 ng/mL and TSAT > 20%) was associated with a threefold higher risk of bacterial infections (95% CI 1.3–6.6; p = 0.01). Although diabetes mellitus and lower serum albumin had a nonsignificant trend toward an increased risk of bacterial infections, no such relationship was seen with the first 3‐month cumulative IV iron dose. Conclusions: This study suggests an increased risk for bacterial infections at modest levels of iron stores (ferritin > 100 ng/mL and TSAT > 20%) among HD patients initiating IV iron. Large prospective studies are needed to confirm these relationships.     

Bedload Transport in Gravel-Bed Streams with Unimodal Sediment

Bedload transport in many gravel-bed streams becomes highly complicated because of the nonuniformity of the grain size and the vertical stratification of channel bed material. A new relation for computing bedload transport rates in gravel-bed streams is proposed here. In an effort to account for the variation of the makeup of the surface material within a wide range of Shields stresses, the relation employs a two-parameter approach, one related to the material in the pavement and the other to that in the subpavement layers. The mode is used to represent the grain sizes of each layer. Available bedload transport data from gravel-bed streams with unimodal sediment are used to test the accuracy of the relation. A comparison with other bedload transport relations is also considered.     

Relations between feeding and sleep patterns in the rat.

A concomitant analysis of sleep and feeding patterns in 11 male Wistar rats was carried out over 8 days, using continuous EEG recording. The proportion of slow-wave sleep and paradoxical sleep within an intermeal interval was constant and varied only in relation to the time of the day. During the dark period only, there were significant correlations between meal size and amount of time spent in both stages of sleep in the following intermeal interval. These correlations were even stronger between meal size and sleep duration in the intermeal interval that followed the next meal. Circadian variations in satiety ratios (i.e., units of subsequent intermeal interval and sleep per units of food ingested) and in deprivation ratios (i.e., units of feeding per units of prior intermeal interval and sleep) suggest that division of 24-hr data into 3 8-hr periods rather than 2 12-hr periods reveals distinct correlations between meal size and pre- and postmeal sleep and might reflect more accurately the underlying metabolic events. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)