Determination of optimal part delivery dates in a stochastic assembly line

We consider the problem of determining the optimal part delivery dates of a low volume, small lot assembly line which manufactures large and costly products. Parts are assembled at each stage to a subassembly. The arrival time of an assembly part from a vendor is assumed to be a normally distributed random variable. A dynamic programming algorithm is developed to minimize work-in-process inventory of parts and subassemblies. It is implemented on the single job problem. Its further extensions to the multi-job case and to incorporate the cost of setting delivery dates are also discussed.     

A reduced polynomial chaos expansion method for the stochastic finite element analysis

The stochastic finite element analysis of elliptic type partial differential equations is considered. A reduced method of the spectral stochastic finite element method using polynomial chaos is proposed. The method is based on the spectral decomposition of the deterministic system matrix. The reduction is achieved by retaining only the dominant eigenvalues and eigenvectors. The response of the reduced system is expanded as a series of Hermite polynomials, and a Galerkin error minimization approach is applied to obtain the deterministic coefficients of the expansion. The moments and probability density function of the solution are obtained by a process similar to the classical spectral stochastic finite element method. The method is illustrated using three carefully selected numerical examples, namely, bending of a stochastic beam, flow through porous media with stochastic permeability and transverse bending of a plate with stochastic properties. The results obtained from the proposed method are compared with classical polynomial chaos and direct Monte Carlo simulation results.     

INDICATORS OF FINANCIAL CONDITION IN PRE‐ AND POST‐MERGER LOUISVILLE

Proponents of metropolitan consolidation identify a range of benefits that may be realized through merger, including improved financial health. There is little agreement as to the actual outcomes across localities that have consolidated, even when limiting the scope to the four major urban mergers, including the merger of Louisville, Kentucky with Jefferson County in 2003, which is under consideration here. One likely reason for conflicting results is the limitation of reflexive analysis as a means of assessing financial impact. In the private sector, analysts would use financial ratio analysis to determine whether the new merged entity was financially healthier after merger. Though a political merger differs from a private sector merger, financial ratio analysis can still be used for pre‐ and post‐ analysis of merger effects on financial health. Further, when enough time has passed since merger, quasi‐experimental designs like interrupted time series can test the hypothesis that merger had no significant financial impact on the entity at all.     

Influence of dielectric constant of polymerization medium on processability and ammonia gas sensing properties of polyaniline

Polyaniline (PANI) was synthesized by the oxidation of aniline hydrochloride in the presence of ammonium persulphate and hydrochloric acid. The polymerization reaction was carried out in several batches in different solvent media by changing the volume ratio of N,N -dimethyl formamide (DMF) and water as binary solvent mixture. The dielectric constant of the polymerization medium for each batch reaction was determined by measuring the capacitance with change in frequency. The UV spectra of the synthesized polyaniline solutions helped us to optimize the ratio of the binary solvent to get sufficient polymer growth and processability. Thin film of processable polyaniline was then deposited on glass slides coated with polyvinyl alcohol (PVA) crosslinked with maleic anhydride (MA). FTIR and XRD studies of the coated film were also done. AFM studies further helped in the morphological study of the film deposited. Finally, conductivity and ammonia gas-sensing property of the polyaniline film were also studied.     

An investigation in InGaO<Subscript>3</Subscript>(ZnO)<Subscript>m</Subscript> pellets as cause of variability in thin film transistor characteristics

Indium–gallium–zinc oxide (IGZO) is a novel amorphous oxide semiconductor, which recently has received much attention for thin film transistors (TFTs) in flat panel displays. Published literature reports significant variations in the properties of thin films and TFTs prepared from IGZO even though the reported process conditions are similar. We demonstrate that these differences could arise from the method for preparation of targets from which the films are made. Accordingly, we also propose simple and appropriate conditions, specifically using much lower sintering temperatures and thus avoiding use of sealed Pt tubes for preparation of IGZO targets in composition range, InGaO₃(ZnO) _m , with 1 ≤ m ≤ 5. These target materials are suitable in physical vapour deposition processes such as pulsed laser deposition and sputtering. In developing the process for sintering, the phase analysis of the target pellets was carried out using X-ray diffraction (XRD). The chemical compositions of the phases are also confirmed with inductively coupled plasma optical emission spectrometry (ICP-OES) and energy dispersive X-ray (EDX) techniques. We also demonstrate successful deposition of amorphous IGZO thin films by pulse laser deposition using the targets prepared by the proposed sintering process. Finally, we demonstrate that unmonitored method of making pellets for films deposition is a cause of variability associated in published literature on IGZO TFTs.     

Electrochemical and optical properties of a new donor–acceptor type conjugated polymer derived from 3,4–didodecyloxythiophene

In this communication, we report the synthesis and characterization of a new donor–acceptor type conjugated polymer carrying alternate 3,4-didodecyloxythiophene and (1,3,4-oxadiazol-yl)pyridine moieties and evaluation of its optical and electrochemical properties. The polymer was synthesized through precursor polyhydrazide route. It has well defined structure, stability and it shows good solubility in common organic solvents. Optical and electrochemical properties were studied by UV-visible, fluorescence spectroscopy and cyclic voltammetric studies, respectively. It displays bluish-green fluorescence both in solution and in film state. Cyclic voltammetric studies showed that the polymer P1 possesses a HOMO energy level of −6·01 and LUMO energy level of −3·34 eV. The preliminary studies clearly reveal that the new polymer can have potential application in the fabrication of light emitting diodes. The studies on its device application are in progress.     

CHANGES IN THE PROFILE OF ORGANIC ACIDS IN PLAIN SET AND STIRRED YOGURTS DURING MANUFACTURE AND REFRIGERATED STORAGE1

The organic acids profile in fermented dairy foods is an indicator of the metabolic activity of added bacterial cultures. These acids act as natural preservatives and contribute to the characteristic sensory properties. This study was done to determine the effect of encapsulation on the metabolic activity of probiotic supplements, i.e. bifidobacteria, in plain yogurts. Metabolically active bifidobacteria may increase the concentration of certain organic acids, mainly acetic and propionic acids, which might lead to decreased acceptability of the product. Changes in the profiles of organic acids were determined in plain set and stirred‐type yogurts containing the starter culture and microencapsulated and nonencapsulated probiotic strains of either Bifidobacterium longumB6 or B. longum ATCC15708. Ion‐exchange high‐performance liquid chromatography was used for the separation and quantification of the organic acids. Concentrations of acetic and lactic acid increased during storage, while those of citric and uric acid remained stable. No particular pattern was observed for propionic or butyric acid, while pyruvic acid initially decreased and then increased during storage.     

Development of a knowledge-based system for dynamic scheduling

In this paper we develop an interactive, real time, knowledge-based approach for dynamic scheduling. Blackboard concept has been utilized to organize and maintain the dynamic data base. The major knowledge representation schemes used in the system include frame structures, relational tables, and production rules. The system design is highly modular in nature thereby providing the ease for further development and enhancement. Based on this system, a design philosophy of an AI/OR integrated approach is also presented.     

Poly(aniline-co-m-aminobenzoic acid) deposited on poly(vinyl alcohol): Synthesis and characterization

In this work, we have deposited poly(aniline-co-m-aminobenzoic acid) on poly(vinyl alcohol) (PVA) by in situ polymerization. The polymerization was effected within maleic acid (MA) cross-linked PVA hydrogel. The copolymer was obtained by oxidative polymerization of aniline hydrochloride and m-aminobenzoic acid using ammonium persulfate as an oxidant. Instead of conventional solution polymerization, here synthesis was carried out on APS soaked MA cross-linked PVA (MA–PVA) film where the polymer was in situ deposited in its conducting form. The composite film was characterized by Fourier transform infra red (FT–IR) and ultraviolet visible (UV–VIS) spectroscopy and electrical measurements. Surface morphology of the composite films was studied by field emission scanning electron microscopy (FESEM). The variation of conductivity of the films was studied.