A flexible framework for evaluating user and item fairness in recommender systems

User Modeling and User-Adapted Interaction - One common characteristic of research works focused on fairness evaluation (in machine learning) is that they call for some form of parity (equality)...     

Quantum Monte Carlo Study of Entanglement in Quantum Spin Systems

We perform an extensive quantum Monte Carlo investigation of entanglement properties in quantum spin systems close to or at a quantum critical point. Making use of the Stochastic Series Expansion method, we can systematically estimate the bipartite entanglement of the ground-state wavefunction in a large class of anisotropic spin models on unfrustrated lattices and in a uniform magnetic field. The behavior of the entanglement estimators as a function of the field shows remarkable universal features independent of the lattice dimensionality, marking both the occurrence of a field-induced quantum phase transition and of an exactly factorized state.PACS numbers: 03.67.Mn, 75.10.Jm, 73.43.Nq, 05.30.-d     

Oligopolymer,diglyceride and oxidized triglyceride contents as measures of olive oil quality

The objective of this study was to test the qualities of olive oils of different commercial grades by quantifying oligopolymer compounds by high-performance size-exclusion chromatography (HPSEC). The method required no sample manipulation and was accurate and rapid. The mean level of oligopolymers in refined olive oils was 0.70% and was more than twice as high in refined olive pomace oils. Conversely, edible virgin olive oils had no oligopolymer compounds. HPSEC analyses of polar compounds by silica gel column chromatography also allowed determination of oxidized triglycerides and partial glycerides, which help define levels of oxidative degradation and hydrolysis. Research supported by National Research Council of Italy, Special Project RAISA, Sub-project 4, Paper No. 321.     

A learn‐and‐construct framework for general mixed‐integer programming problems

In this paper, we propose a new framework for finding an initial feasible solution from a mixed‐integer programming (MIP) model. We call it learn‐and‐construct since it first exploits the structure of the model and its linear relaxation solution and then uses this knowledge to try to produce a feasible solution. In the learning phase, we use an unsupervised learning algorithm to cluster entities originating the MIP model. Such clusters are then used to decompose the original MIP in a number of easier sub‐MIPs that are solved by using a black box solver. Computational results on three well‐known problems show that our procedure is characterized by a success rate larger than both the feasibility pump heuristic and a state‐of‐the‐art MIP solver. Furthermore, our approach is more scalable and uses less computing time on average.     

Unveiling the Potentialities Provided by New Technologies: A Process to Pursue Technology Epiphanies in the Smartphone App Industry

When new technologies approach the market, companies usually look for ways to improve existing applications or simply to replace previous technologies. The management literature identifies several strategies for gaining value from technological discontinuities, including improving performance, becoming the cost leader and being the first‐mover, and scholars have identified several managerial practices and processes to leverage these various strategies. Recent literature suggests that there might be something more, namely, discovering new meanings, enabled by the technological discontinuity: a technology epiphany. No research has yet tried to understand what companies could do to actually develop such innovations. This paper aims to identify a process companies could adopt to pursue a technology epiphany strategy. Employing a case study approach, we investigate the navigation apps industry, both turn‐by‐turn and marine, to understand how companies manage the technology discontinuity embedded in smartphones. Comparing several players in the two industries, we first demonstrate that the rise of a new market leader is not related to a traditional strategy but to a technology epiphany. Finally, we propose a five‐step process to pursue a technology epiphany strategy.     

Improving responsiveness of time‐sensitive applications by exploiting dynamic task dependencies

In this paper, a mechanism is presented for reducing priority inversion in multiprogrammed computing systems. Contrary to well‐known approaches from the literature, this paper tackles cases where the dependency relationships among tasks cannot be known in advance to the operating system. The presented mechanism allows tasks to explicitly declare aforementioned relationships, enabling the operating system scheduler to take advantage of such information and trigger priority inheritance, resulting in reduced priority inversion. We present the prototype implementation of the concept within the Linux kernel in the form of modifications to the standard Portable Operating System Interface (POSIX) condition variable code, along with an extensive evaluation, including a quantitative assessment of the benefits for applications making use of the technique and comprehensive overhead measurements. In addition, we present an associated technique for the theoretical schedulability analysis of a system using the new mechanism, which is useful to determine whether all tasks can meet their deadlines or not, in the specific scenario of tasks interacting only through remote procedure calls and under partitioned scheduling.     

Balancing bike sharing systems with constraint programming

Bike sharing systems need to be properly rebalanced to meet the demand of users and to operate successfully. However, the problem of Balancing Bike Sharing Systems (BBSS) is a demanding task: it requires the design of optimal tours and operating instructions for relocating bikes among stations to maximally comply with the expected future bike demands. In this paper, we tackle the BBSS problem by means of Constraint Programming (CP). First, we introduce two different CP models for the BBSS problem including two custom branching strategies that focus on the most promising routes. Second, we incorporate both models in a Large Neighborhood Search (LNS) approach that is adapted to the respective CP model. Third, we perform an experimental evaluation of our approaches on three different benchmark sets of instances derived from real-world bike sharing systems. We show that our CP models can be easily adapted to the different benchmark problem setups, demonstrating the benefit of using Constraint Programming to address the BBSS problem. Furthermore, in our experimental evaluation, we see that the pure CP (branch & bound) approach outperforms the state-of-the-art MILP on large instances and that the LNS approach is competitive with other existing approaches.     

Iridoid glycoside sequestration byThessalia leanira (Lepidoptera: Nymphalidae) feeding onCastilleja integra (Scrophulariaceae)

A small population of a polyvoltine checkerspot butterfly,Thessalia leanira fulvia (also known asChlosyne leanira ssp.fulvia), was found to useCastilleja integra as a larval food plant at a localized site (Burnt Mill) southwest of Pueblo, Colorado. Field-captured adult butterflies contained the major iridoid glycosides (catalpol and macfadienoside) of theCastilleja. The content of a third iridoid glycoside, methyl shanzhiside, was also relatively high in the collected butterflies even though most individualCastilleja plants at Burnt Mill contained little or no methyl shanzhiside. Only a few plants, restricted to a small area, did contain appreciable methyl shanzhiside. Most of the plants that lacked the ester methyl shanzhiside contained shanzhiside, the corresponding free carboxylic acid.Thessalia larvae did not normally methylate the acid to produce methyl shanzhiside. Larvae that stopped feeding at an early instar, but yet survived several weeks, did contain major amounts of methyl shanzhiside. It is suggested that only larvae that overwinter or otherwise enter diapause convert shanzhiside to methyl shanzhiside. TheCastilleja food plant also contained iridoids other than catalpol and macfadienoside, sometimes in major amounts, but these were never found in larvae, pupae, or butterflies.Paper 27 in the series Chemistry of the Scrophulariaceae. Paper 26: Stermitz, F.R., Foderaro, T.A., and Li, Y.-X., 1993.Phytochemistry 32:1151