An efficient heuristic for scheduling batches of parts in a flexible flow system

Flexible manufacturing systems (FMSs) are a class of automated systems that can be used to improve productivity in batch manufacturing. Four stages of decision making have been defined for an FMS—the design, planning, scheduling, and control stages. This research focuses on the planning stage, and specifically in the area of scheduling batches of parts through the system.The literature to date on the FMS planning stage has mostly focused on the machine grouping, tool loading, and parttype selection problems. Our research carries the literature a step further by addressing the problem of scheduling batches of parts. Due to the use of serial-access material-handling systems in many FMSs, the batch-scheduling problem is modeled for a flexible flow system (FFS). This model explicitly accounts for setup times between batches that are dependent on their processing sequence.A heuristic procedure is developed for this batch-scheduling problem—the Maximum Savings (MS) heuristic. The MS heuristic is based upon the savings in time associated with a particular sequence and selecting the one with the maximum savings. It uses a two-phase method, with the savings being calculated in phase I, while a branch-and-bound procedure is employed to seek the best heuristic solution in phase II. Extensive computational results are provided for a wide variety of problems. The results show that the MS heuristic provides good-quality solutions.     

Preliminary model of the Ribeira Grande geothermal field (Azores Islands)

On the basis of a geological - volcanological - geophysical survey, integrated with petrological and geochronological data, a structural model, including a shallow magmatic body, was defined for the Ribeira Grande area, Sao Miguel island (Azores). Two series of production tests were carried out in the Pico Vermelho 1 and Ribeira Grande 1 wells, which led to a preliminary definition of the deep fluid circulation. The data obtained from these studies were used to reconstruct a preliminary model of the Ribeira Grande geothermal field.     

Formation of cube texture in nickel-palladium alloys for epitaxial substrates for deposition of high-temperature superconductors

The texture, structure, and magnetic and mechanical properties of thin ribbons of nickel-palladium alloys have been studied. It has been demonstrated that in Ni₉₄Pd₆ and Ni_92.5Pd₅W_2.5 alloys, a sharp cube texture can be formed that is stable up to rather high annealing temperatures. Segregation of palladium atoms to surface layers of ribbons has been found, which gives additional advantages for using these ribbons as substrates for epitaxial deposition of high-temperature superconductors.     

Emergy account for biomass resource exploitation by agriculture in China

On the basis of Odum's ecological economic measure of emergy as embodied solar energy, a system account of biomass resource exploitation by agriculture in China 2004 is developed in this paper, which supplements a former study on corresponding long-term historical trends during 1978 to 2000 (Chen et al., 2006. Emergy-based analysis of the Chinese agriculture. Agriculture, Ecosystems and Environment 115, 161–173). The aggregate fluxes and indicators for biomass resource exploitation in China 2004 are calculated and illustrated when compared with those for 2000 to elucidate the latest status of the Chinese agriculture as the exploitation sector for biomass resource. Data sources and algorithm are presented in detail as basic references for related analysis involving the ecological economy of biomass exploitation in agriculture.     

A Review of Dynamic Fracture Studies in Functionally Graded Materials

Abstract:  This article presents a review of dynamic fracture studies on functionally graded materials. A brief literature review on the fracture mechanics of graded materials is presented first. This is followed by a discussion on the higher-order asymptotic analysis of the transient elastic field surrounding the tip of a dynamically growing crack in a functionally graded material. A comprehensive experimental study of dynamic crack growth in model functionally graded material using the optical method of reflection photoelasticity and high-speed photography is then presented. The results are analysed to establish a generalised relationship between the crack velocity and the dynamic mode-I stress intensity factor (SIF). This relationship is found to be unique and is distinctly different from that previously established for the matrix material (polyester). Finally, an innovative experimental procedure is used to demonstrate the necessity of employing a fully transient stress-field representation in the analysis of optical data for an accurate prediction of the dynamic SIF history.     

Solution synthesis of crystallized AMO4 (A=Ba, Sr, Ca; M=W, Mo) film at room temperature

A well-crystallized AMO₄ (A=Ba, Ca, Sr; M=W, Mo) films have been prepared at room temperature through a simple solution reaction in respective alkaline solution at higher pH ranging from 12–14. Adopting the corrosion principle for oxidation of metal substrate, these double oxide films were carried out in presence of chemical driving force without any special apparatus or devices. Hydrogen peroxide was used to enhance the dissolution rate of metal substrates. The driving force for the film formation and growth were high concentration of A²⁺, MO₄²⁻ ions with high pH conditions. Average grain sizes of 8–10 μm with bipyramidal shaped particle were grown to the thickness of about 10–14 μm after 3–6 hours treatment. The crystallization of AMO₄ was characterized by three-dimensional nucleation. This work demonstrates the possibility of fabrication of functional ceramic films directly from the aqueous solution in a single step by solution reactions.     

Impedance spectroscopy of ultrafine-grain SnO2 ceramics with a variable grain size

The impedance spectra of nanocrystalline SnO₂ ceramics with an average grain size d ranging from 3 to 43 nm were investigated in the frequency range 1–10⁶ Hz at temperatures from 25 to 300°C in a dry oxygen atmosphere. Analysis of the experimental data by the graphoanalytical method made it possible to separate the contributions of grain bulk and grain boundaries to the conductivity. It is shown that the samples investigated can be arbitrarily divided into two groups with respect to the character of their conductivity. For the samples with an average grain size d < 25 nm, the charge transfer processes are almost completely determined by the grain boundaries. In samples with a larger grain size, the contribution of grain bulk to the conductivity is comparable with that of grain boundaries.     

A pattern recognition-based approach for phylogenetic network construction with constrained recombination

The tree representation of evolutionary relationship oversimplifies the view of the process of evolution as it cannot take into account the events such as horizontal gene transfer, hybridization, homoplasy and genetic recombination. Several algorithms exist for constructing phylogenetic networks which result from events such as horizontal gene transfer, hybridization and homoplasy. Very little work has been published on the algorithmic detail of phylogenetic networks with constrained recombination. The problem of minimizing the number of recombinations in a phylogenetic network, constructed using binary DNA sequences, is NP-hard. In this paper, we propose a pattern recognition-based O(n²) time approach for constructing the phylogenetic network, where n is the number of nodes or sequences in the input data. The network is constructed with the restriction that no two cycles in the network share a common node.     

Improvement of the wavelength switching behavior of semiconductor tunable lasers through optical feedback from a periodic reference filter based on a novel prism-based implementation of a Fox-Smith resonator

We show that the wavelength switching behavior of semiconductor tunable lasers can be improved through optical feedback from a stable reference filter. The filter is based on a novel prism-based implementation of a Fox-Smith resonator and has a response consisting of periodically spaced peaks, both in reflection and transmission. The improvement of the wavelength switching behavior stems from the suppression of the thermally induced wavelength drift associated with the switching of the tuning currents.     

Octave-tunable miniature RF resonators

The development and testing of a miniaturized, high-Q, broadly tunable resonator is described. An exemplary device, with a center frequency that is continuously tunable from 1.2 to 2.6GHz, was tested in detail. Experimental results demonstrated a resonator Q of up to 380, and typical insertion loss of -1.9dB for a 25MHz 3-dB bandwidth. These resonators have been used to stabilize a broadly-tunable oscillator with phase noise of -132dBc/Hz at 100-kHz offset, with a center frequency tunable from 1.2-2.6GHz, and a tuning speed of 1GHz/ms.