An efficient optimal algorithm for the quantity discount problem in material requirement planning

An optimal algorithm based on branch-and-bound approach is presented in this paper to determine lot sizes for a single item in material requirement planning environments with deterministic time-phased demand and constant ordering cost with zero lead time, where all-units discounts are available from vendors and backlog is not permitted. On the basis of the proven properties of optimal order policy, a tree-search procedure is presented to construct the sequence of optimal orders. Some useful fathom rules have been proven, which make the algorithm very efficient. To compare the performance of this algorithm with the other existing optimal algorithms, an experimental design with various environments has been developed. Experimental results show that the performance of our optimal algorithm is much better than the performance of other existing optimal algorithms. Considering computational time as the performance measure, this algorithm is considered the best among the existing optimal algorithms for real problems with large dimensions (i.e. large number of periods and discount levels).     

The Effects of SiO2/Al2O3 and H2O/Al2O3 Molar Ratios on SAPO-34 Catalyst in the Methanol to Olefin Process

Silicon - Informed through synthesis and characterization of NH 3 TPD, BET techniques, the current study investigated the right contribution of silicon and water content on a 9 sample SAPO-34...     

Effect of amino acids as capping agent on the size and morphology of pure TmVO<Subscript>4</Subscript> nanoparticles and their photocatalyst properties

In this paper, thulium vanadate (TmVO₄) nanoparticles were synthesized via a simple precipitation method based on the reaction between thulium nitrate hexahydrate and ammonium metavanadate in water. Besides, three capping agent such as alanine, valine, and glycine were used to investigate their effects on the morphology and particle size of thulium vanadate nanoparticles. According to the vibrating sample magnetometer, thulium vanadate nanoparticles indicated a paramagnetic behavior at room temperature. In addition, the photocatalyst activity of as-prepared thulium vanadate nanoparticles was evaluated by degradation of methyl orange under ultraviolet light irradiation. The structural, morphological, and optical properties of as-obtained products were characterized by techniques such as XRD, SEM, EDX, and UV–Vis spectroscopy.     

Development and physico-mechanical characterization of carrageenan and poloxamer-based lyophilized matrix as a potential buccal drug delivery system

Context and objectives: The buccal mucosa presents a unique surface for non-invasive drug delivery and also avoids first-pass metabolism. The objective of this study was the formulation development of polymeric mucoadhesive lyophilized wafers as a matrix for potential buccal drug delivery.

Materials and methods: Differential scanning calorimetry (DSC) was used to develop an optimum freeze-cycle, incorporating an annealing step. The wafers were prepared by lyophilization of gels containing three polymers, κ-carrageenan (CAR 911), poloxamer (P407) and polyethylene glycol 600 (PEG 600). The formulations were characterized using texture analysis (for mechanical and mucoadhesion properties), hydration studies, thermogravimetric analysis (TGA), DSC, X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM).

Results and discussion: DSC showed the eutectic temperature (12.8?°C) of the system where the liquid solution and pure solids both existed at a fixed pressure which helped determine the freeze-annealing cycle at 55?°C for 7?h. Mechanical resistance to compression, hydration and mucoadhesion studies showed that optimized wafers were obtained from aqueous gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600. TGA showed residual water of approximately 1% and SEM showed a porous polymeric network that made ease of hydration possible.

Conclusions: Lyophilized wafers by freeze-drying gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600 with optimum physico-mechanical properties has been achieved.     

Preparation of nickel ferrite nanoparticles via a new route and study of their photocatalytic properties

Pure nickel ferrite (NiFe₂O₄) were prepared via sol-gel route in presence of different amino acids as a capping agent. The effect of different amino acids such as leucine, asparagine, and cysteine on the size, and morphology of NiFe₂O₄ nanoparticles were investigated. The magnetic properties of the samples were investigated using VSM analyze. We found that the NiFe₂O₄ nanoparticles synthesized at temperature of 800 °C exhibit a ferromagnetic behavior with a saturation magnetization of 34 emu/g and a coercivity of 100 Oe. Furthermore, the photocatalytic properties of as synthesized NiFe₂O₄ were evaluated by degradation of methyl orange as water contaminant. XRD, SEM, EDS, and UV–Vis spectroscopy were employed to characterize structural, morphological, and optical properties of NiFe₂O₄ nanoparticles.     

Production and characterization of polypropylene fiber upon addition of selective peroxide during melt spinning and comparison with conventional polypropylene fibers

In the present work, effect of selective peroxide on reactor grade polypropylene (PP) (known as V30S) during melt spinning process on the physical and thermal properties of as‐spun resultant multifilament yarn was studied. Attempts have also been made to compare this yarn sample with other fiber samples produced from reactor and controlled rheology grades polypropylene. The results show that the multifilament yarn spun from V30S/Peroxide sample shows higher birefringence and tensile strength and also lower modulus, elongation at break, and shrinkage compared with that of spun from pure V30S granule. Density and thermal behavior studies show low variations compared with original sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of modified catalyst and stabilization of CuO/NH4‐ZSM‐5 for conversion of methanol to gasoline

In this article, the catalytic conversion of methanol to gasoline range hydrocarbons has been studied over CuO/ NH₄‐ZSM‐5(3,5,7,9%) catalysts prepared via sono‐chemistry methods. In order to improve, copper oxide can be used as a booster on NH₄‐ZSM‐5 this catalyst property. Accordingly, the conversion process of Methanol to Gasoline (MTG) was conducted under a pressure of 1 atm and temperature of 400°C by a fixed‐bed reactor on copper oxide catalysts which were prepared based on synthetic NH₄‐ZSM‐5. The synthetic catalyst was investigated by such analyses as BET, XRD, FT‐IR, and SEM. Formation of copper oxide phase and proper distribution of copper oxide were proven on the basic level of using XRD analysis. BET analysis showed the reduction in catalyst level and SEM images depicted the proper distribution of particles. The present investigation is to study the effect of CuO loading on NH4‐ZSM‐5 support for conversion of methanol to gasoline range hydrocarbons. A series of CuO/ NH4‐ZSM‐5 catalysts were prepared, characterized, and experimented for their performance on methanol conversion and hydrocarbon yield.     

New dispatching rules to minimize rejection and tardiness costs in a dynamic flexible flow shop

This paper studies a flexible flow shop system considering dynamic arrival of jobs and the ability of acceptance and rejection of new jobs. The problem objective is to determine a schedule that minimizes sum of the tardiness and rejection costs of jobs. A 0–1 mixed integer model of the problem is formulated. Since this problem class is NP-hard, four dispatching rules have been developed to solve the problem approximately. Moreover, a discrete event simulation model of the flexible flow shop system is developed for the purpose of experimentation. Four dispatching rules from the literature and four new dispatching rules proposed in this paper are incorporated in the simulation model. Simulation experiments have been conducted under various experimental conditions characterized by factors such as shop utilization level, due date tightness and number of stages in flexible flow shop. The results indicate that proposed dispatching rules provide better performance under problem assumptions.