1,721,049 research outputs found
Approximate vs. exact algorithms to solve the maximum line length problem
No full textWe present a comparison of different algorithms to solve the problem of minimizing the expectation of the maximum line length of a multiservice system. One of the features of the problem is that the evaluation of the objective function is computationally heavy. In order to find a numerical solution of the problem, we analyze two representations of the objective function that allow some approximations and compare the efficiency of approximate Monte Carlo and deterministic versions of the gradient projection method. Results of a set of simulations are provided. The algorithms we provide appear to solve accurately the problem much faster than the standard gradient projection method
Fleeting extinction? Unraveling the persistence of noise traders in financial markets with learning and replacement
No full textWe describe an agent-based model of a financial market where agents can learn whether to buy costly information on returns, to use noise as if it were information, or to disregard any signals. We show that while learning alone drives all noise traders to extinction in stationary populations, allowing for small rates of replacement of existing agents with new ones suffices to generate substantial levels of persistent noise trading, with the equilibrium share of agents using irrelevant news reaching double digits. Remarkably, the presence of noise traders, when replacement is realistically considered, inflates the share of agents who use costly information relative to the benchmark scenario without replacement
The macro and asset pricing implications of rising Italian uncertainty: Evidence from a novel news-based macroeconomic policy uncertainty index
Full text linkWe develop a new monthly and daily index of economic policy uncertainty for Italy based on articles from the Sole 24 Ore (a popular Italian business daily newspaper). VAR investigations document that an unexpected rise in the Sole 24 Ore news-based EPU index (EPU24) has mild effects on the real economic activity. Cross-sectional asset pricing tests then show that both monthly and daily EPU24 shocks command a positive risk premium. A standard event study finally indicates the presence of statistically significant positive cumulative abnormal returns (CARs) in the energy sector following different categories of policy-related events. Negative and significant CARs in the financial sector are instead found to be generated by international-related events and political elections
The Equity Premium Puzzle: An Application of an Agent-Based Evolutionary Model
Full text linkWe describe an agent-based model of a financial market with a stock and a bond. Agents compete in repeated rounds, decide whether to acquire costly information and can pick one of 16 strategies to allocate their investments, under evolutionary pressure driven by the comparison of the realized short-term revenues from trading. We show that, while in- formed traders survive in some cases, the equilibrium shares are strongly biased in favor of strategies that make little use of information and sys- tematically overestimate the riskiness of the stock. As a consequence, the majority of the population ends up in buying fewer stocks than would be otherwise expected or deemed rational.
This evolutionary dynamics offers a novel way to explain the equity pre- mium puzzle first described by Mehra and Prescott (The equity pre- mium: A puzzle. Journal of Monetary Economics 1985), according to which it’s hard to find reasons for the widespread lack of investment in risky assets. Evolution based on a straightforward comparison of rev- enues is a simple and cognitively appealing avenue to reach a population of traders using (over-)cautious strategies to curb the risk of long-term “financial extinction”. Simulations run in NetLogo also demonstrate that very little information may be used in noisy markets or when the cost of information is substantial
Zero-Intelligence Trading without Resampling
Full text linkThis paper studies the consequences of removing the resampling assumption from the zero-intelligence trading model in Gode and Sunder (1993). We obtain three results. First, individual rationality is no longer sufficient to attain allocative effciency in a continuous double auction; hence, the rules of the market matter. Second, the allocative effciency of the continuous double auction is higher than for other sequential protocols both with or without resampling. Third, compared to zero intelligence, the effect of learning on allocative effciency is sharply positive without resampling and mildly negative with resampling.
Coopetition and complementarities: modelling coopetition strategy and its risks at an individual partner level
No full textThe concept of coopetition is founded on the complementarity-based nature of this strategy. However, coopetition research has devoted relatively little attention to complementarity issues and their impact on coopetition results. By bridging the coopetition and economics of complementarities research fields, we develop a model representing a classical optimization problem in complementarities as applied to coopetition in order to evaluate potential risks deriving at an operational level from implementing a coopetition strategy. The model we develop is a situated one and is based on empirical data from a longitudinal case study of coopetition in the mineral water and soft drinks industry. The results highlight a potential risk of coopetition strategies – namely, thresholds effects – as well as the associated risks a wrong understanding of complementarities in a coopetition setting may entail
ASSESSMENT OF UTERINE ARTERY BLOOD FLOW IN NORMAL FIRST-TRIMESTER PREGNANCIES AND IN THOSE COMPLICATED BY UTERINE BLEEDING
No full textObjective: To compare uterine artery blood flow in normal first-trimester pregnancies with those complicated by uterine bleeding. Methods: Uterine artery blood flow was investigated by transvaginal color Doppler in 46 pregnant women affected by uterine bleeding and in a control group of 35 women with normal intrauterine pregnancy. Gestational age ranged from the 6th to the 12th week. Three blood flow values were calculated, the pulsatility index, the resistance index and the peak systolic velocity. Results were compared between the two groups. Results: Of the 46 patients affected by uterine bleeding, 18 had an incomplete miscarriage, eight had a blighted ovum, five had a missed miscarriage and 15 continued their pregnancy until term and delivered liveborn infants. No significant differences were found in any of the three vascular indices between the normal and the pathological groups of patients. Uterine artery pulsatility and resistance indices decreased with gestational age in both normal and abnormal pregnancies but this change was not statistically significant. The peak systolic velocity significantly increased with gestational age in the control group but not in the pathological group. In patients with a retroplacental hematoma, uterine vascular resistance appeared higher than in those without a hematoma, while the peak systolic velocity showed no difference between the two groups. Conclusion: Doppler analysis of the uterine artery blood flow is unlikely to have a clinical role in the management of early pregnancies complicated by uterine bleeding
COLOUR DOPPLER ANALYSIS OF OVARIAN AND UTERINE ARTERIES IN WOMEN WITH HYPOESTROGENIC AMENORRHOEA
No full textBackground: This is a clinically-controlled study designed to investigate uterine and ovarian blood flow in patients with hypoestrogenic amenorrhoea. Methods: Twelve women with hypoestrogenic amenorrhoea and 13 eumenorrhoeic subjects (controls) were enrolled. Colour and pulsed Doppler was used to visualize the uterine and ovarian arteries and the blood vessels within the ovarian stroma in both groups. Four blood flow indices were calculated: the pulsatility index, the resistance index, the peak systolic velocity and the end-diastolic velocity. Results: Peak systolic velocity underwent the most significant change in amenorrhoeic patients, being significantly lower in comparison with that of controls, both in the uterine (P = 0.0009) and ovarian (P = 0.001) arteries. Compared with controls, the end-diastolic velocity of the ovarian artery was significant lower (P = 0.039) in amenorrhoeic patients, and was also lower in the uterine artery (though not statistically significantly so). A reduction in blood flow was also evident in the ovarian stroma in amenorrhoeic patients. Conclusions: The significant reduction in blood flow observed in hypoestrogenic amenorrhoea suggests that estrogens play an important role in regulating both uterine and ovarian blood flow
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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