Train maintenance personnel shift scheduling: case study.

In this study, the shift scheduling problem of the personnel who maintain the 324 trains operating on the lines of the Ankara Metro, which carry approximately 10 million passengers per month, is discussed. In the problem, daily personnel needs and personnel qualifications are evaluated together according to the fault prediction. Firstly, a total of 1721 fault data for 181 days is analyzed, and the prediction is made according to 8 prediction methods. Then, a 30-day fault prediction is made with the prediction method, which has the least error rate. According to the number of faults obtained as a result of the prediction, the daily personnel requirement is determined. Then, according to the type of fault, the personnel are classified as electronics, electromechanics, and mechanics. It is aimed at distributing the personnel evenly to the shifts. The goal programming model is used to solve the problem, allowing us to add more than one goal to the model. When the solution results of the problem are compared with the current schedule, it is seen that the monthly total working hours are distributed equally, and the shifts are distributed fairly, and a necessary balance is achieved in the shifts according to the personnel qualifications. It is thought that this study, in which personnel qualifications and fault prediction are evaluated together, will contribute to the literature on railway maintenance personnel scheduling.

A Multicriteria Decision-Making Framework for Access Point Selection in Hybrid LiFi/WiFi Networks Using Integrated AHP-VIKOR Technique.

Since light fidelity (LiFi) and wireless fidelity (WiFi) do not interfere with one another, a LiFi/WiFi hybrid network may provide superior performance to existing wireless options. With many users and constant changes, a network can easily become overloaded, leading to slowdowns and fluctuations in data transfer speeds. Access point assignment (APA) is required with the increase of users, which can negatively impact the system performance and quality-of-service (QoS) due to mobility and line-of-sight (LOS) blockage. Many variables could influence the APA process; these variables are considered as criteria, such as the network capacity, the degree of blockage, the speed of the connected user, etc. Unlike conditional APA methods, recent studies have considered treating these variables as "evaluation criteria". Considering these criteria can offer better and more accurate results, eventually enhancing the APA process and QoS. However, the variety of these criteria, the conflict amongst them, their weights (importance), and priority have not been addressed so far. Moreover, treating the criteria equally might result in inaccurate outcomes. Therefore, to solve this issue, it is essential to investigate the impact of each criterion on the APA process. In this work, a multicriteria decision-making (MCDM) problem is formulated to determine a network-level selection for each user over a period of time The decision problem is modeled as a hierarchy that fragments a problem into a hierarchy of simple and small subproblems, and the selection of the AP network among various alternatives is a considered as an MCDM problem. Based on the previous works, we are not aware of any previous research attempts using MCDM methods in the LiFi research area for network selection. Therefore, this work proposes an access point assignment framework using an MCDM approach for users in a hybrid LiFi/WiFi network. The experiment was conducted based on four phases: Five criteria were identified and evaluated with eleven APs (alternatives). The outcome of this phase was used to build the decision matrix and an MCDM was developed and built based on user mobility and blockages with various scenarios using all the criteria; The analytic hierarchy process (AHP) was employed to identify the criterion of the subjective weights of each criterion and to determine the degree of importance supported by experts' judgement. Determining the weights in the AHP process considered various investigations, including the consistency ratio (CR) and the AHP consensus indicator, which is calculated using the rank-based maximum likelihood method (RGMM) and Shannon entropy techniques. The VIekriteri-Jumsko KOmpromisno Rangiranje (VIKOR) method is adopted in the selection of the optimal AP for the proper selection of whether a LiFi or WiFi AP must serve the users. The integrated AHP-VIKOR was effective for solving the APA and was the best solution based on using weighted criteria simultaneously. Moreover, the ranking outcomes of the developed integrated AHP-VIKOR approach were evaluated using sensitivity analysis. The result of this work takes the APA for hybrid LiFi networks to a new perspective.

Current Management of Mirror Distal Anterior Cerebral Artery Aneurysms in Association with Multiple Aneurysms: Case Report with Literature Review.

BACKGROUND: Mirror aneurysms represent 2 adjacent arterial protrusions. Although the size is considered a major risk factor in terms of rupture, sometimes it is the smaller aneurysm that ruptures. Here, we present the contemporary management of mirror distal anterior cerebral artery (DACA) aneurysms associated with multiple aneurysms. Computational fluid dynamic (CFD) analysis was performed when assessing multiple aneurysms using Hemoscope, version 2015. CASE DESCRIPTION: Among multiple aneurysms, a mirror A2/A3 DACA aneurysm was found in a single patient. Surgical treatment was provided for all aneurysms through a single-stage procedure. The left ruptured A2/A3 aneurysm was smaller compared with the right (7.5 × 3.5 mm/10.8 × 3.2 mm). CFD showed greater wall pressure (WP) in the left ruptured A2/A3 aneurysm (left A2/A3 WP 84,000-84,402 Inst. mm Hg/right A2/3 WP 84,224-84,315). WP in the left middle cerebral artery and anterior communicating artery aneurysms showed lesser values compared with the ruptured aneurysm (WP upper values 84,361 and 84,367, respectively). Wall shear stress showed low values for all aneurysms with the lowest flow rate values in the left A2/A3 aneurysm. CONCLUSIONS: In cases of ruptured mirror aneurysms followed by the presence of intracerebral hematoma, surgery is considered the primary option with the best results. A one-stage dual craniotomy procedure was found safe in the associated treatment of other multiple aneurysms. At present, the size of the aneurysm, the hemodynamic influence, and the local configuration are all considerations during the preoperative assessment of multiple aneurysm cases. According to our knowledge, this article presents the first CFD analysis of mirror DACA aneurysms associated with aneurysm multiplicity.

Terahertz Spoof Surface Plasmon Polariton Waveguides: A Comprehensive Model with Experimental Verification.

Spoof surface plasmon polariton waveguides are perfect candidates to enable novel, miniaturized terahertz integrated systems, which will expedite the next-generation ultra-wideband communications, high-resolution imaging and spectroscopy applications. In this paper, we introduce, for the first time, a model for the effective dielectric constant, which is the most fundamental design parameter, of the terahertz spoof surface plasmon polariton waveguides. To verify the proposed model, we design, fabricate and measure several waveguides with different physical parameters for 0.25 to 0.3 THz band. The measurement results show very good agreement with the simulations, having an average and a maximum error of 2.6% and 8.8%, respectively, achieving 10-to-30 times better accuracy than the previous approaches presented in the literature. To the best of our knowledge, this is the first-time investigation of the effective dielectric constant of the terahertz spoof surface plasmon polariton waveguides, enabling accurate design of any passive component for the terahertz band.

An efficient resource utilization scheme within PMIPv6 protocol for urban vehicular networks.

Recently, the mobility management of urban vehicular networks has become great challenges for researchers due to its unique mobility requirements imposed by mobile users when accessing different services in a random fashion. To provide a ubiquitous Internet and seamless connectivity, the Internet Engineering Task Force (IETF) has proposed a Proxy Mobile IPv6 (PMIPv6) protocol. This is meant to address the signaling of the mobility transparent to the Mobile Node (MN) and also guarantee session continuity while the MN is in motion. However, performing a handoff by tens of thousands of MNs may harm the performance of the system significantly due to the high signaling overhead and the insufficient utilization of so-called Binding Cash Entry (BCE) at the Local Mobility Anchor (LMA). To address these issues, we propose an efficient scheme within the PMIPv6 protocol, named AE-PMIPv6 scheme, to effectively utilize the BCE at the LMA. This is primarily achieved by merging the BCEs of the MNs, thus, reducing the signaling overhead. Better utilization of the BCEs has been attained by employing virtual addresses and addressing pool mechanisms for the purpose of binding information of the MNs that are moving together towards the same network at a specific time, during their handoff process. Results obtained from our simulation demonstrates the superiority of AE-PMIPv6 scheme over E-PMIPv6 scheme. The AE-PMIPv6 succeeds in minimizing the signaling overhead, reduces the handover time and at the same time efficiently utilize the buffer resources.

Quality of Service Class Identifier (QCI) radio resource allocation algorithm for LTE downlink.

The increasing demand for network applications, such as teleconferencing, multimedia messaging and mobile TV, which have diverse requirements, has resulted in the introduction of Long Term Evolution (LTE) by the Third Generation Partnership Project (3GPP). LTE networks implement resource allocation algorithms to distribute radio resource to satisfy the bandwidth and delay requirements of users. However, the scheduling algorithm problem of distributing radio resources to users is not well defined in the LTE standard and thus considerably affects transmission order. Furthermore, the existing radio resource algorithm suffers from performance degradation under prioritised conditions because of the minimum data rate used to determine the transmission order. In this work, a novel downlink resource allocation algorithm that uses quality of service (QoS) requirements and channel conditions to address performance degradation is proposed. The new algorithm is formulated as an optimisation problem where network resources are allocated according to users' priority, whereas the scheduling algorithm decides on the basis of users' channel status to satisfy the demands of QoS. Simulation is used to evaluate the performance of the proposed algorithm, and results demonstrate that it performs better than do all other algorithms according to the measured metrics.

Anti-plaque Efficacy of Herbal Mouthwashes Compared to Synthetic Mouthwashes in Patients Undergoing Orthodontic Treatment: A Randomised Controlled Trial.

PURPOSE: The present study compared the antiplaque effects of two herbal mouthwashes containing Salvadora persica and Azadirachta indica, respectively, with two synthetic mouthwashes containing either chlorhexidine or cetylpyridinium. MATERIALS AND METHODS: In this triple-blind, randomised controlled trial, 100 patients undergoing orthodontic treatment underwent scaling and polishing at baseline to obtain a plaque score of zero. In the first phase, they were given oral hygiene instructions and were provided with a standard toothpaste to be used twice daily for a period of three weeks. In the second phase, following scaling and polishing, they were randomly allocated to 4 groups according to 4 different types of mouthwash (A: chlorhexidine; B = cetylpyridinium; C = extracts of Salvadora persica miswak; D: extract of Azadirachta indica miswak) along with previously taught toothbrushing protocol for three more weeks. Plaque accumulation was scored three times according to the Modified Bonded Bracket Plaque Index: at the start, after the toothbrush-toothpaste trial, and at the end of mouthwash trial. The paired t-test was used to compare the pre-plaque and post-plaque indices in all groups. Analysis of mean differences of post-plaque indices between and within groups was performed using the post-hoc Tukey test. Qualitative variables were compared by Crosstab. RESULTS: Eighty participants completed the study - 63 females and 17 males. There was a statistically significant decrease in mean plaque scores after using mouthwashes in all four groups at follow-up when compared to the baseline plaque score (p = 0.001). The greatest reduction of plaque score was found in group C (extract of Salvadora persica) when compared with group A, chlorhexidine (p = 0.016). CONCLUSION: Compared to other mouthwashes, Salvadora persica miswak-based mouthwash showed a maximum reduction in the plaque scores among orthodontic patients.