Morphology optimization for achieving air stable and high performance organic field effect transistors

To develop an all organic active matrix light emitting display required for large area thin display, electronic paper and electronic paints, Si-based thin film transistor has to be replaced with organic thin film transistor (OTFT). The most important issues in OTFT are the low charge carrier mobility and poor stability under ambient conditions, which critically depend on how organic thin films are grown on different substrates. Here we show that both these issues are correlated and can be overcome by certain surface morphology which can only be achieved through anisotropic growth. Careful control of different growth parameters can lead to unprecedented control on thin film morphology which has been shown to be engineered reversibly and reproducibly. High temperature and low evaporation rate increase the diffusive mobility of molecules, which are responsible for the stacking of molecules to higher length scales. By carefully choosing a temperature and evaporation rate, elongated rod-like grains were grown for achieving high performance and stable thin film transistors.     

Three stage trade credit policy in a three-layer supply chain–a production-inventory model

The main purpose of this paper is to investigate the optimal replenishment lot size of supplier and optimal production rate of manufacturer under three levels of trade credit policy for supplier–manufacturer–retailer supply chain. The supplier provides a fixed credit period to settle the accounts to the manufacturer, while the manufacturer gives a fixed credit period to settle the account to the retailer and the retailer, in turn, also offers a credit period to each of its customers to settle the accounts. We assume that the supplier supplies the raw material to the manufacturer and sends back the defective raw materials to the outside supplier after completion of inspection at one lot with a sales price. The system always produces good items in the model. Also, we consider the idle times of supplier and manufacturer. Finally, numerical examples are provided to illustrate the behaviour and application of the model with graphical simulation.     

A multi-echelon production–inventory system with supply disruption

The article investigates an integrated multi-layer supply chain model consisting of supplier, manufacturer and retailer while supply disruption, machine breakdown, safety stock, maintenance breakdown occur simultaneously. At beginning of the production, manufacturer keeps some raw materials in stock received from second supplier at high price, as safety stock due to supply disruption of first supplier. Corrective maintenance is done immediately to restore its normal stage when machine breakdown occurs. Stock out situations at manufacturer and retailer are considered due to disruption of production for machine breakdown. The integrated expected costs of the chain in centralized (collaborating) and decentralized (Stakelberg approach) system are compared. A numerical example and its sensitivity analysis are provided to test feasibility of the model.     

Synthesis of carbon nano-fibers on p-Si having improved temperature sensing capability

Synthesis of an innovative material for temperature sensor based on carbon nano-fibers (CNFs) on p-Si substrates has been demonstrated. The CNF films were characterized by SEM, Raman and FTIR studies. First order Raman spectra indicated a G band at ～1597 cm^?1 corresponding to the E_2g tangential stretching mode of an ordered graphitic structure with sp² hybridization and a D band located ～1350 cm^?1 originated from disordered carbon. Gold fingers were deposited on the p-Si/CNF surface for resistance measurement. Temperature sensing properties were also investigated critically. Resistance changes with temperature (ΔR/R) in p-Si/CNF films are found to be significantly large 30–60% Very stable, reproducible and improved temperature sensing properties would make this material superior to commonly available temperature sensors.     

Project network-oriented materials management policy for complex projects: a Fuzzy Set Theoretic approach

This work devises a materials management policy integrated with project network characteristics of complex projects. It proposes a relative quantitative measure, overall criticality (OC), for prioritisation of items based on penalty incurred due to their non-availability. In complex projects, practicing managers find it difficult to measure OC of items because of the subjective factors and intractable nature of penalties involved. However, using their experience, they can linguistically identify the antecedents and relate them to consequent OC. This work adopts Fuzzy Set Theory to capture managerial tacit knowledge which provides them enough flexibility to provide information in real form. Computed OC values can be used for items prioritisation and as shortage cost coefficient in inventory models. The revised materials management policy was applied to a shipbuilding project. OC values were analysed to justify the importance of incorporating project network characteristics and potential cost savings were calculated.     

Electron paramagnetic resonance and Mössbauer spectroscopy of transition metal ion doped mullite

Appreciable difference in the properties of undoped and oxide-doped mullite are observed. The oxidation state of cation, its concentration and the position of the mullite lattice occupied by it appear to be the responsible factors. Mullite has, therefore, been doped with four transition metal ions, Mn, Fe, Cr and Ti. With the help of EPR and Mössbauer spectroscopy (supplimented by X-ray diffractometry) the oxidation states of these ions and the mullite lattice sites where they enter has been investigated. It was observed that Mn ion was present in Mn²⁺ and Mn³⁺ states, the former remained as clusters and the latter occupied the octahedral sites in the mullite lattice. Only Fe³⁺ ion was detected and conclusive evidence was obtained for the entry of Fe³⁺ in the octahedral lattice position of mullite from the analysis of Mössbauer spectra with the help of a specially written computer programme. The Cr ion entered the mullite structure only in the Cr³⁺ state. The change in lattice parameters of Cr doped mullite were measured by the XRD technique. The results showed that the expansion of b-axis was more than that of the a-axis which supported the presence of Cr³⁺ ion in the octahedral site of mullite lattice. The absence of signal in the EPR spectra of Ti doped mullite suggested the presence of only Ti⁴⁺ (3d⁰) ion. Very low electrical resistivity of Ti doped mullite and close similarity between mullite and Al₂TiO₅ structures stood as evidence for incorporation of Ti⁴⁺ ion in the octahedral site of mullite lattice by replacing Al³⁺ ion.     

Microstructure and growth of ZnTe films

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.     

Lightpath Re-optimization in mesh optical networks

Intelligent mesh optical networks deployed today offer unparalleled capacity, flexibility, availability, and, inevitably, new challenges to master all these qualities in the most efficient and practical manner. More specifically, demands are routed according to the state of the network available at the moment. As the network and the traffic evolve, the lightpaths of the existing demands becomes sub-optimal. In this paper we study two algorithms to re-optimize lightpaths in resilient mesh optical networks. One is a complete re-optimization algorithm that re-routes both primary and backup paths, and the second is a partial re-optimization algorithm that re-routes the backup paths only. We show that on average, these algorithms allow bandwidth savings of 3% to 5% of the total capacity in scenarios where the backup path only is re-routed, and substantially larger bandwidth savings when both the working and backup paths are re-routed. We also prove that trying all possible demand permutations with an online algorithm does not guarantee optimality, and in certain cases does not achieve it, while for the same scenario optimality is achieved through re-optimization. This observation motivates the needs for a re-optimization approach that does not just simply look at different sequences, and we propose and experiment with such an approach. Re-optimization has actually been performed in a nationwide live optical mesh network and the resulting savings are reported in this paper, validating reality and the usefulness of re-optimization in real networks.     

Growth and microstructure of Cd1−xZnxS films

The growth and microstructure of Cd_1–x Zn _x S films were studied by depositing the films on to freshly cleaved NaCl, KCl, and LiF substrates at various x values (0相似文献