An economic production quantity model with random defective rate,rework process and backorders for a single stage production system

This paper revisits the economic production quantity (EPQ) model with rework process at a single-stage manufacturing system with planned backorders. It is well known that any imperfect production system of real life has random defective rates. In this direction, this paper extends an inventory model to allow random defective rates. Basically, three different inventory models are developed for three different distribution density functions such as uniform, triangular, and beta. The analytical derivation provides closed-form solution for each inventory model. We have made comparison tables of optimal results among the distribution functions. Some numerical examples and sensitivity analysis are given to illustrate the inventory models.     

Evaluating scenario-based SPL requirements approaches: the case for modularity,stability and expressiveness

Software product lines (SPL) provide support for productivity gains through systematic reuse. Among the various quality attributes supporting these goals, modularity, stability and expressiveness of feature specifications, their composition and configuration knowledge emerge as strategic values in modern software development paradigms. This paper presents a metric-based evaluation aiming at assessing how well the chosen qualities are supported by scenario-based SPL requirements approaches. The selected approaches for this study span from type of notation (textual or graphical based), style to support variability (annotation or composition based), and specification expressiveness. They are compared using the metrics developed in a set of releases from an exemplar case study. Our major findings indicate that composition-based approaches have greater potential to support modularity and stability, and that quantification mechanisms simplify and increase expressiveness of configuration knowledge and composition specifications.     

Effect of sodium bicarbonate on the properties of metronidazole floating matrix tablets

The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO₂ bubbles, and the matrix volume expansion produced after addition of SB.     

Residual-free bubbles for the Helmholtz equation

The Galerkin method enriched with residual-free bubbles is considered for approximating the solution of the Helmholtz equation. Two-dimensional tests demonstrate the improvement over the standard Galerkin method and the Galerkin-least-squares method using piecewise bilinear interpolations. © 1997 John Wiley & Sons, Ltd.     

Distribution of volatile organic compounds in Sicilian groundwaters analysed by head space-solid phase micro extraction coupled with gas chromatography mass spectrometry (SPME/GC/MS)

This work presents the results of an assessment of the existence and concentration of 13 volatile organic compounds (VOCs) in groundwaters from 14 hydrological basins in Sicily (25,710km(2)). On the basis of hydrological, hydrogeochemical and geological studies, 324 sampling points were selected. All groundwater sampled were collected twice, from October to December 2004 and from February to May 2005, and were analysed to determine the concentration and spatial distribution of the VOCs in the aquifers. The need to analyze a large number of samples in a short space of time so as to obtain quantitative analyses in trace concentration levels spurred us to create a new analytical method, both simple and sensitive, based on HS-SPME/GC/MS. The concentrations of VOCs measured in industrial and intensive agricultural unconfined aquifers were greater than those found in other aquifers. Tetrachloroethylene, chloroform, trichloroethylene and 1,2-dichloropropane were the most frequently detected VOCs. However, they exceeded the guideline values proposed by the EU in only three aquifers located near to industrial and intense agricultural areas.     

Methyl Ethyl Ketone Production through an Intensified Process

Methyl ethyl ketone (MEK) is widely used in the industry and is mainly produced from petroleum. Some works have projected MEK as a possible fuel since its performance in spark engines has overcome the performance of gasoline in certain indexes. Two intensified alternatives to produce MEK are introduced here, consisting of a reactive distillation column, an extractive distillation column, and three conventional distillation columns. The direct alternative resulted as the most promising when it was evaluated based on energy consumption, greenhouse gas emissions, and an environmental index. The obtained energy consumption for MEK production was 11.62 MJ kg_MEK⁻¹ for the entire process. Moreover, those intensified alternatives showed better performance indexes in comparison with a conventional process.     

The effect of advance payment with discount facility on supply decisions of deteriorating products whose demand is both price and stock dependent

Generally, in the business world, it is observed that suppliers give different kinds of benefits to retailers due to advance payment. One of the popular benefits is instant cash discount due to advance payment. If a retailer pays off his total purchase cost before receiving the products, then he receives a certain percentage of cash discount instantly. However, if the retailer pays off a certain fraction of the total purchasing cost, then price discount is given only at the time of receiving the products while paying the remaining amount of the total purchasing cost. Using this concept, this paper formulates, under both cases of advance payment (full or partial), an inventory model for deteriorating products where shortages are allowed and demand function is considered as price and stock dependent. The closed‐form solutions for each case are presented and two numerical examples are solved. In addition, a sensitivity analysis is also performed to show the effects of advance payment with discount facility.     

Hydroponics with wastewater: a review of trends and opportunities

Hydroponics is a method of crop production that has been successfully used for the growth of vegetables and flowers. It uses a nutrient solution and generally controlled environmental conditions which makes it more energy intensive, yet more productive than conventional agriculture. Hydroponic systems can be used as a treatment process for partially treated wastewater or reclaimed water (RW) before its release to the environment, as plants have the ability to uptake nutrients, toxic metals and emerging contaminants. The present review has the aim to look into the advantages of hydroponics and evaluate the success of using RW as a nutrient solution. It was found that many examples exist of successful experiments; however, full‐scale examples are still limited. With the recent interest in vertical farming and the production of legal cannabis, interest in hydroponics has increased and the use of RW as a nutrient solution may finally be economically viable.     

Synthesis of ZSM‐5 from diatomite: a case of zeolite synthesis from a natural material

A highly crystalline ZSM‐5 product was obtained from diatomite, a natural raw material, both with and without the presence of diethanolamine. The synthesis process took 40 h, and was carried out under hydrothermal conditions, at autogenic pressure, and at a temperature of 180 °C. The resulting crystals were identified as ZSM‐5 by X‐ray diffraction and characterized by scanning electron microscopy, infrared spectroscopy, thermal gravimetry and differential thermal analysis. Copyright © 2004 Society of Chemical Industry