Application of network flow models for the cash management of an agribusiness company

In this study, we apply network flow models with gains and losses to deal with the cash flow management problem of a typical Brazilian company which produces frozen concentrated orange juice. The aim is to maximize the cash return of the financial resources at the end of a multi-period and finite planning horizon. Two real-life situations are analyzed: in the first, the network flow model in Golden, Liberatore, and Lieberman (1979) is used to support operational cash flow decisions and in the second, the model is extended to cope with tactical planning of loan payments. The corresponding linear programming models representing these situations were solved using a solver tool available in well-known spreadsheet software, which is of wide applicability for analytical work in business. The numerical results obtained show that the models are flexible and effective to support the decisions involved, being able to generate solutions as good as or better than the ones of the treasury of the citrus company.     

Microstructural and electrical properties of sintered tungsten trioxide

Tungsten trioxide sintered wafers were prepared from WO₃ powder obtained when ammonium paratungstate is decomposed in air at moderate temperature. Two wafer series of five samples were sintered under the same conditions in the temperature range 600–1000 °C. One of these wafers series was submitted to a subsequent annealing at 700 °C under a hydrogen atmosphere. All samples were characterized at room temperature by X-ray diffraction and electrical measurements. X-ray spectra show that WO₃ ceramic presents a mixture of the triclinic and monoclinic phases before the reduction process. After the reduction process, WO₂ and four hydrogen tungsten bronze phases are present in wafers. Capacitance measurements showed that the samples submitted only to the sintering process changed the dielectric constant with the frequency according to the Debye model. The reduced WO₃ shows a semiconductor behavior, as determined by electrical resistivity measurements.     

Constitutive models for cohesive zones in mixed-mode fracture of plain concrete

Discrete mixed-mode fracture (modes I and II) of plain concrete is investigated using a coupled and an uncoupled cohesive zone constitutive model in a finite element context. Fracture surfaces are confined to inter-element boundaries that are not necessarily coincident with the actual fracture surfaces. For this reason, traction components on the cohesive zone do not correspond to actual values either. In this work is demonstrated that only the coupled model is able to cope with these spurious traction components, that must decrease with crack opening. It is shown also that, in this regard, the key variable is the plastic potential adopted in the integration of tractions. Three mixed-mode fracture examples were tested in this work: a three-point single-edge notched beam, double-edge notched plates under variable lateral and normal deformation and four-point double-edge notched beams. A good fitting with experiments was obtained only for the coupled model. Mode II parameters can change in a large range without noticeable change in results, at least in the tested examples.     

Characterization of Alzheimer paired helical filaments by electron microscopy

We show how electron microscopy can be used to answer several critical issues in neurodegenerative disorders that course with the formation of aberrant filamentous structures. Thus, electron microscopy is a useful technique to study in vitro assembly of pathogenic proteins, to map the regions involved in filament formation, as well as to detect by immunoelectron microscopy which proteins bind to the filaments. Furthermore, electron microscopy is the main technique used to discover if an animal model develops fibrillar pathology and if those filaments are similar to those found in human patients. This review focuses on Alzheimer's disease and related tauopathies, although similar studies have been done with other neurodegenerative disorders as, for example, Huntington's disease.     

On the correct measurement of relative heavy charged particles to gamma thermoluminescent efficiencies

In order to better understand the most important experimental aspects for performing correct measurements of relative thermoluminescent (TL) efficiencies, an investigation has been carried out to quantify the effect of using different experimental procedures in the evaluation of 3 MeV proton-to-gamma relative efficiency (etap,gamma) of LiF:Mg,Ti. Variations in batch, presentation, annealing and reader have been studied. When the same protocol is used to measure proton and gamma TL response, efficiency values obtained range from 0.36 to 0.59 for peak 5 and from 0.44 to 0.79 for the total signal. The use of different annealings and different batches leads to 20% and 10% differences in etap,gamma respectively. Large differences (40%) are found between efficiency values measured with TLD-100 chips and those obtained using TLD-100 microcubes. When 'mixed' procedures are used to measure the proton and the gamma response, differences in etap,gamma may increase even more. The main conclusion of this work is to stress the importance of measuring an entire series of experiments in the same laboratory with a carefully defined protocol and using dosemeters from the same batch to obtain heavy charged particle TL response and gamma TL response with identical annealing and readout procedures.     

Underground transmission in the United States

The means for providing underground transmission of large quantities of electric power at a reduction in present-day cost by at least an order of magnitude ranks among the high imperatives of today's research efforts. Demand for the expansion of ``undergrounding' is soundly based upon such factors as the rapid growth of cities, the doubling of power requirements with every passing decade, and esthetic objections to the appearance of overhead lines. Unfortunately, at the present time, such expansion is possible only at excessive cost. The authors present the problem as it exists within the United States, and offer solutions that are commensurate with the state of the art.     

Elections in Anonymous Networks

We address the problem of electing a leader in an anonymous, asynchronous network of arbitrary topology. Our algorithms are considerably simpler than known algorithms and have equal or improved communication complexity.