A survey of swarm intelligence for portfolio optimization: Algorithms and applications

In portfolio optimization (PO), often, a risk measure is an objective to be minimized or an efficient frontier representing the best tradeoff between return and risk is sought. In order to overcome computational difficulties of this NP-hard problem, a growing number of researchers have adopted swarm intelligence (SI) methodologies to deal with PO. The main PO models are summarized, and the suggested SI methodologies are analyzed in depth by conducting a survey from the recent published literature. Hence, this study provides a review of the SI contributions to PO literature and identifies areas of opportunity for future research. © 2018 Elsevier B.V

Bee colony intelligence in fatigue life estimation of simulated magnesium alloy welds

The fatigue life of magnesium alloy is influenced by many factors such as stress concentration factor, stress ratio and stress amplitude as well as different material states. Since all these factors affect the fatigue life of the alloy, the effects of these parameters need to be investigated. This study aims to obtain fatigue life values with satisfactory results on the samples of magnesium alloy AZ31. In order to solve the problem, firstly an exponential-trigonometric function model is constructed. Secondly, an artificial bee colony algorithm is used to optimize the weights of this function. Sample data of the alloy is used to verify the correctness of the fatigue life estimation model. The estimated results are compared with the results of experimental studies. Simulation results show that the fatigue life prediction model proposed in this paper can fit the experimental Wöhler lines with high estimation accuracy. The model based on artificial bee colony is a good candidate to estimate the fatigue life of magnesium alloy. © 2019 Elsevier Lt

A perturbation based variable neighborhood search heuristic for solving the Vehicle Routing Problem with Simultaneous Pickup and Delivery with Time Limit

The Vehicle Routing Problem with Simultaneous Pickup and Delivery with Time Limit (VRPSPDTL) is a variant of the basic Vehicle Routing Problem where the vehicles serve delivery as well as pick up operations of the clients under time limit restrictions. The VRPSPDTL determines a set of vehicle routes originating and terminating at a central depot such that the total travel distance is minimized. For this problem, we propose amixed-integer mathematical optimization model and a perturbation based neighborhood search algorithm combined with the classic savings heuristic, variable neighborhood search and a perturbation mechanism. The numerical results show that the proposed method produces superior solutions for a number of wellknown benchmark problems compared to those reported in the literature and reasonably good solutions for the remaining test problems. © 2014 Elsevier B.V. All rights reserved

A prospective randomized study comparing perioperative outcome variables after epidural or general anesthesia for lumbar disc surgery

General and regional anesthesia (spinal and epidural) can be performed successfully for lumbar disc surgery. The aim of this study was to assess the superiority of general anesthesia or epidural anesthesia techniques in lumbar laminectomy and discectomy. Sixty patients undergoing lumbar partial hemilaminectomy and discectomy were randomly divided into two groups receiving standardized general anesthesia (GA) or epidural anesthesia (EA). Demographically, both groups were similar. Surgical onset time (36.72 ± 5.47 vs. 25.40 ± 7.83 minutes) was longer in the EA group, but total anesthesia time (154.32 ± 35.73 vs. 162.40 ± 26.79 minutes) did not differ between the two groups. Surgical time (118.80 ± 35.42 vs. 139.60 ± 26.80 minutes) was longer in the GA group. The heart rate and mean arterial pressure values of the EA group measured 15, 20, and 25 minutes after local anesthetic administration to the epidural catheter were found to be lower than in the GA group measured after induction of general anesthesia. The frequency of bradycardia (EA vs. GA, 3 vs. 2), tachycardia (3 vs. 7), and hypotension (6 vs. 4) during anesthesia did not differ between the groups, but the occurrence of hypertension (1 vs. 7) was higher in the GA group. Blood loss was less in the EA group than in the GA group (180.40 ± 70.38 vs. 288.60 ± 112.51 mL). Postanesthesia care unit (PACU) heart rate and mean arterial pressure were higher in the GA group. Peak pain scores in PACU and postoperative 24 hours were higher in the GA group when compared with the EA group. Nausea was more common in the GA group both in PACU and 24 hours after surgery. There was no difference between the hospitalization duration of the groups. In conclusion, this study suggests that EA is an important alternative to GA during lumbar disc surgery

Allergen immunotherapy for allergic asthma: Protocol for a systematic review.

BACKGROUND: The European Academy of Allergy and Clinical Immunology (EAACI) is in the process of developing the EAACI Guidelines for Allergen Immunotherapy (AIT) for Allergic Asthma. We seek to critically assess the effectiveness, cost-effectiveness and safety of AIT in the management of allergic asthma. METHODS: We will undertake a systematic review, which will involve searching international biomedical databases for published, in progress and unpublished evidence. Studies will be independently screened against pre-defined eligibility criteria and critically appraised using established instruments. Data will be descriptively and, if possible and appropriate, quantitatively synthesised. DISCUSSION: The findings from this review will be used to inform the development of recommendations for EAACI's Guidelines on AIT

Erratum to: Allergen immunotherapy for allergic asthma: Protocol for a systematic review.

International audience[This corrects the article DOI: 10.1186/s13601-016-0094-y.]