Exploring knowledge benchmarking using time-series directional distance functions and bibliometrics

For strategic reasons, benchmarking best practices from efficient competitors is not usual in many data envelopment analysis (DEA) applications. Even for industries composed of multiple branches, providing information about efficient practices for their peers can jeopardize results for those branches if they compete for market, resources or recognition by the central administration. In this work, a time-series adaptation for the DEA directional model is proposed as an alternative for coping with this problem. The methodological approach has three stages for this benchmarking to occur: Data, Information and Knowledge Extraction. In the first stage, we compare the same unit in different moments to identify efficient periods instead of efficient competitors. As a result, successful performance strategies are investigated using the bibliometric coupling of employees' relevant statements in the second and third stages. The application in a branch of the Brazilian Federal Savings Bank allowed an internal benchmarking of efficient periods when specific performance incentives, innovative processes, competitive strategies, and human resource changes were adopted for improving the unit's performance.     

Differential Sintering and Self-Stress Effects on YSZ Ionic Conductivity

Thermomechanical stress simulations are combined with experimental tests to assess the effects of rigid inclusions on the sintering of 8 mol% yttria-stabilized zirconia (8YSZ) green compacts and the phenomena of restricted and differential sintering on microstructure development and electrical properties are investigated. Rigid inclusions of sintered ceramic particles with different shapes (spherical and jagged) and compositions (alumina, 3YSZ, and 8YSZ) are added in different volume fractions (1, 5, and 15 vol%) to 8YSZ commercial powders, which are formed by isostatic pressing and sintered by conventional method. Restricted and differential sintering effects are observed in the development of the microstructure varying in function of volume fraction, shape, structural composition, and thermomechanical properties of the inclusions, resulting in different combinations of tensile and compressive strain states in the matrix, and varying electrical behaviors. The addition of 1 vol% of 8YSZ irregular rigid inclusions leads to an increase of 36% in total electrical conductivity and a 33% increase in power density under solid oxide fuel cells operation conditions compared to samples without inclusions.     

A decision support system for fraud detection in public procurement

Over the past few years, investigators in Brazil have been uncovering numerous corruption and money laundering schemes at all levels of government and in the country's largest corporations. It is estimated that between 2% and 5% of the global GDP is lost annually because of such practices, not only directly impacting public services and private sector development but also strengthening organized crime. However, most law enforcement agencies do not have the capability to carry out systematic corruption risk assessment leveraging on the availability of data related to public procurement. The currently prevailing approach employed by Brazilian law enforcement agencies to detect companies involved in potential cases of fraud consists in receiving circumstantial evidence or complaints from whistleblowers. As a result, a large number of companies involved in fraud remain undetected and unprosecuted. The decision support system (DSS) described in this work addresses these existing limitations by providing a tool for systematic analysis of public procurement. It allows the law enforcement agencies to establish priorities concerning the companies to be investigated. This DSS incorporates data mining algorithms for quantifying dozens of corruption risk patterns for all public contractors inside a specific jurisdiction, leading to improvements in the quality of public spending and to the identification of more cases of fraud. These algorithms combine operations research tools such as graph theory, clusterization, and regression analysis with advanced data science methods to allow the identification of the main risk patterns, such as collusion between bidders, conflicts of interest (e.g., a politician who owns a company contracted by the same government body where he or she was elected), and companies owned by a potentially straw person used for disguising its real owner (e.g., beneficiaries of cash conditional transfer programs). The DSS has already led to a detailed analysis of large public procurement datasets, which add up to more than 50 billion dollars. Moreover, the DSS provided strategic inputs to investigations conducted by federal and state agencies.     

Hydrolytic resistance of K2O–PbO–SiO2 glasses in aqueous and high-humidity environments

Some historical glasses (lead-wood ash glasses, lead-crystal glasses…) are silicate glasses with high content of lead and potassium. This work presents the evaluation of the chemical stability of high-lead glasses in a high relative humidity atmosphere and as result of aqueous immersion. In both situations, the alteration mechanism begins with the lixiviation of alkali metal and lead ions, followed by the hydrolytic attack of the silica glass network. According to the results, the glasses with a higher content of lead show the fastest degradation due to their higher hygroscopicity. Environmental CO₂ can be dissolved in the adsorbed water and favor the formation of intermediate degradation compounds.     

Reburning and burnout simulations of natural gas for heavy oil combustion

Reburning and burnout simulations were carried out through PLUG code of CHEMKIN-III using a reduced mechanism, in order to determine preliminary experimental parameters for achieving maximum NO_x reduction to implement the reburning technology for heavy oil combustion in pilot scale equipments in Brazil. Gas compositions at the entrance of the reburning zone were estimated by the AComb program. Simulations were performed for eight conditions in the usual range of operational parameters for natural gas reburning. The maximum NO reduction (ca. 50%) was reached with 10 and 17.5% of power via natural gas and 1.5 and 3.0% O₂ excess, respectively, at 1273 K. The model predicts 250 ppm of NO, 50 ppm of CO and air mass flows in the range of about 50-130 kg/h for burnout.     

Effect of Niobium Oxide on the Structure and Properties of Melt‐Derived Bioactive Glasses

The effects of adding Nb₂O₅ on the physical properties and glass structure of two glass series derived from the 45S5 Bioglass^® have been studied. The multinuclear ²⁹Si, ³¹P, and ²³Na solid‐state MAS NMR spectra of the glasses, Raman spectroscopy and the determination of some physical properties have generated insight into the structure of the glasses. The ²⁹Si MAS NMR spectra suggest that Nb⁵⁺ ions create cross‐links between several oxygen sites, breaking Si–O–Si bonds to form a range of polyhedra [Nb(OM)_6?y(OSi)_y], where 1 ≤ y ≤ 5 and M = Na, Ca, or P. The Raman spectra show that the Nb–O–P bonds would occur in the terminal sites. Adding Nb₂O₅ significantly increases the density and the stability against devitrification, as indicated by ΔT(T_x ? T_g). Bioglass particle dispersions prepared by incorporating up to 1.3 mol% Nb₂O₅ by replacing P₂O₅ or up to 1.0 mol% Nb₂O₅ by replacing SiO₂ in 45S5 Bioglass^® using deionized water or solutions buffered with HEPES showed a significant increase in the pH during the early steps of the reaction, compared using the rate and magnitude during the earliest stages of BG45S5 dissolution.     

Hessian and Concavity of Mutual Information, Differential Entropy, and Entropy Power in Linear Vector Gaussian Channels

Within the framework of linear vector Gaussian channels with arbitrary signaling, the Jacobian of the minimum mean square error and Fisher information matrices with respect to arbitrary parameters of the system are calculated in this paper. Capitalizing on prior research where the minimum mean square error and Fisher information matrices were linked to information-theoretic quantities through differentiation, the Hessian of the mutual information and the entropy are derived. These expressions are then used to assess the concavity properties of mutual information and entropy under different channel conditions and also to derive a multivariate version of an entropy power inequality due to Costa.     

A PD path-tracking controller plus inner velocity loops for a wheeled mobile robot

In this paper, we present a controller to solve the path-tracking task in a wheeled mobile robot. We show that a linear PD controller, driven by the tracking error, can be used to generate the desired profiles to be tracked by the motor velocities by means of two linear inner proportional-integral loops. We formally prove that an ultimate bound exists which can be rendered small by a suitable selection of the controller gains. This is the first time that such a result is presented in the literature when considering, simultaneously, both the kinematic and the dynamic models of the wheeled mobile robot.     

The traveling tournament problem with predefined venues

Sports scheduling is a very attractive application area not only because of the interesting mathematical structures of the problems, but also due to their importance in practice and to the big business that sports have become. In this paper, we introduce the Traveling Tournament Problem with Predefined Venues, which consists in scheduling a compact single round robin tournament with a predefined venue assignment for each game (i.e., the venue where each game takes place is known beforehand) while the total distance traveled by the teams is minimized. Three integer programming formulations are proposed and compared. We also propose some simple enumeration strategies to generate feasible solutions to real-size instances in a reasonable amount of time. We show that two original enumeration strategies outperform an improvement heuristic embedded within a commercial solver. Comparative numerical results are presented.     

Designing data warehouses with OO conceptual models

The authors propose an approach that provides a theoretical foundation for the use of object-oriented databases and object-relational databases in data warehouse, multidimensional database, and online analytical processing applications. This approach introduces a set of minimal constraints and extensions to the Unified Modeling Language for representing multidimensional modeling properties for these applications. Multidimensional modeling offers two benefits. First, the model closely parallels how data analyzers think and, therefore, helps users understand data. Second, multidimensional modeling helps predict what final users want to do, thereby facilitating performance improvements. The authors are using their approach to create an automatic implementation of a multidimensional model. They plan to integrate commercial online-analytical-processing tool facilities within their GOLD model case tool as well, a task that involves data warehouse prototyping and sample data generation issues