Simulation optimization for revenue management of airlines with cancellations and overbooking

This paper develops a model-free simulation-based optimization model to solve a seat-allocation problem arising in airlines. The model is designed to accommodate a number of realistic assumptions for real-world airline systems—in particular, allowing cancellations of tickets by passengers and overbooking of planes by carriers. The simulation–optimization model developed here can be used to solve both single-leg problems and multi-leg or network problems. A model-free simulation–optimization approach only requires a discrete-event simulator of the system along with a numerical optimization method such as a gradient-ascent technique or a meta-heuristic. In this sense, it is relatively “easy” because alternative models such as dynamic programming or model-based gradient-ascent usually require more mathematically involved frameworks. Also, existing simulation-based approaches in the literature, unlike the one presented here, fail to capture the dynamics of cancellations and overbooking in their models. Empirical tests conducted with our approach demonstrate that it can produce robust solutions which provide revenue improvements over heuristics used in the industry, namely, EMSR (Expected Marginal Seat Revenue) for single-leg problems and DAVN (Displacement Adjusted Virtual Nesting) for networks.     

Influence of Trigonella foenum graecum seed extract as root canal irrigation agent on root surfaces: A scanning electron microscope/energy dispersive X‐ray analysis study

The purpose of this in vitro study was to investigate the effect of Trigonella foenum graecum seed extract (TFGSE) as a root canal irrigation agent on the surface of instrumented root canals and on changes in the mineral contents of the root dentin. A total of 90 extracted human mature maxillary central incisor teeth with a single root and without root resorption were selected. The specimens were subdivided into five groups according to irrigation protocol groups G0: distilled water (n = 15): G1: Sodium hypochlorite (5.25% NaOCl); G2: 1% TFGSE G3: NaOCl +17% EDTA (3 min); G4: NaOCl+1% TFGSE; G5: 1% TFGSE +17% EDTA. All the roots were sectioned longitudinally into two halves and examined under scanning electron microscope/energy dispersive X‐ray analysis (SEM/EDX) to assess changes in the mineral content of the tooth. Smear layer removal from root canals was evaluated with scanning electron microscopy (SEM). A statistical analysis was performed using the Kruskal–Wallis test. The most effective irrigation protocols in removing smear layer occurred with TFGSE and NaOCl, both with rinsing with 17% EDTA. TFGSE was more effective than NaOCl for removing the smear layer. The results showed the ability of 1% TFGSE to remove the smear layer from the root canals. TFGSE is a promising alternative irrigation agent for root canals.     

Textile supercapacitors‐based on MnO2/SWNT/conducting polymer ternary composites

This paper describes a simple and fast process for the fabrication of flexible and textile‐based supercapacitors. Symmetric electrodes made up of binder‐free ternary composites of manganese oxide (MnO₂) nanoparticles, single walled carbon nanotubes (SWNT) and a conducting polymer (either polyaniline (PANI) or poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS)) were layer‐by‐layer deposited onto cotton substrates by dip coating method. Solid‐state supercapacitor devices were assembled using a gel electrolyte. Specific capacitances of 294 F/g and 246 F/g were obtained for MnO₂/SWNT/PANI and MnO₂/SWNT/PEDOT:PSS ternary nanocomposite supercapacitors, respectively. Power densities for these supercapacitors were 746.5 W/kg and 640.5 W/kg for MnO₂/SWNT/PANI and MnO₂/SWNT/PEDOT:PSS, respectively. Good capacity retention (more than 70%) upon cycling over 1000 times was achieved for both electrode compositions. Supercapacitors demonstrated in this work would be well suited as disposable power sources for wearable and intelligent textiles. Copyright © 2015 John Wiley & Sons, Ltd.     

Economic and cross-media effect analyses of best available techniques for caustic recovery from mercerization textile wastewater

Clean Technologies and Environmental Policy - Caustic can be recovered from textile mercerization wastewaters by evaporation or membrane filtration. The main objective of this study was to evaluate...     

Collaborative Multi-MSA Multi-Target Tracking and Surveillance: a Divide &; Conquer Method Using Region Allocation Trees

This work deals with the problem of the accurate task space control subject to finite-time convergence. Kinematic and dynamic equations of a rigid robotic manipulator are assumed to be uncertain. Moreover, unbounded disturbances, i.e., such structures of the modelling functions that are generally not bounded by construction, are allowed to act on the manipulator when tracking the trajectory by the end-effector. Based on suitably defined task space non-singular terminal sliding vector variable and the Lyapunov stability theory, we derive a class of absolutely continuous (chattering-free) robust controllers based on the estimation of a Jacobian transpose matrix, which seem to be effective in counteracting uncertain both kinematics and dynamics, unbounded disturbances and (possible) kinematic and/or algorithmic singularities met on the robot trajectory. The numerical simulations carried out for a 2DOF robotic manipulator with two revolute kinematic pairs and operating in a two-dimensional task space, illustrate performance of the proposed controllers.     

Hydropower production without sacrificing environment: a case study of Ilisu Dam and Hasankeyf

The Ilisu Dam and HEPP Project, on the Tigris River in the South-Eastern Anatolia Region of Turkey, has been under debate for more than half a century due to its possible adverse effects on the environment. In particular, the proposed inundation of the archaeological sites around Hasankeyf has prompted strong criticism from national and international organizations. The primary reason for the administration's insistence on construction of the dam is its energy production capacity. The present study is an assessment of an alternative solution that not only saves Hasankeyf with its countless ancient monuments from inundation but also supplies the projected energy production of Ilisu Dam.     

Development of a machine tool selection system using AHP

The selection of appropriate machines is one of the most critical decisions in the design and development of an efficient production environment. In this study, we propose a decision support system for machine tool selection using an effective algorithm, the analytic hierarchy process. In the selection process, we first consider qualitative decision criteria that are related to the machine properties. Reliability and precision analyses may be included in the detailed evaluation procedure. Furthermore, the decision-maker may take into account the economical considerations through cost analysis. In addition, the robustness of the selection procedure may be evaluated using sensitivity analysis. An illustrative example of machine tool selection using the proposed methodology and the software implementation are provided.     

A Cost-Efficient and Simple Plant Oil DNA Extraction Protocol Optimized for DNA-Based Assessment of Product Authenticity

DNA-based assays offer precision in ascertaining the species/cultivar origin of agro-food products. Yet, obtaining DNA of sufficient quality and quantity is the main challenge while performing DNA-based food authentication analyses. The aim of the present work was to standardize a cost-efficient, easy-to-apply, yet effective plant oil DNA isolation protocol that allows reliable downstream PCR-based analyses. Because capillary electrophoresis (CE) separation of species/cultivar discriminating genomic fragments is a widely adopted approach in food genomics, a CE system was utilized in order to assess the performance of the proposed cetyl trimethyl ammonium bromide (CTAB)-based protocol. A plastid intergenic spacer and a nuclear olive gene were used as targets in order to evaluate the amplificability of DNA extracted with the CTAB-based protocol. The plastid barcode not only allowed assessing the reproducibility of PCR amplifications from the extracted oil DNA samples (olive, hazelnut, corn, rapeseed, cottonseed, and soybean oils) but also proved successful in discriminating all tested oil crop species based on amplified fragment length polymorphisms. Moreover, the barcode assay proved successful in correctly identifying the tested olive oil: cottonseed oil blends as admixtures of the two oil species. Thus, it was also feasible to demonstrate the potential of the barcode sequence as a discriminatory analyte to detect adulteration in plant oils. In addition, application of a CAPS (cleaved amplified polymorphic sequence) assay designed to genotype a nuclear SNP (single nucleotide polymorphism) marker resulted in the successful identification of the two single-cultivar olive oils included in the study. As a result of the present work, it was feasible to standardize a reliable and cost-efficient DNA extraction protocol that works well with both unrefined (olive and hazelnut) and refined (corn, rapeseed, cottonseed, and soybean) oils.     

The mechanism of the sudden termination of carbon nanotube supergrowth

The effect of growth conditions and catalyst lifetime on the supergrowth of carbon nanotubes (CNTs) through a water assisted chemical vapor deposition has been investigated. The reasons behind the observed sudden termination of the CNT growth were explored. A proper amount of water was found to improve the activity of the catalyst and enhance the growth rate of CNTs. However, the introduction of water did not extend the catalyst lifetime leading to unavoidable termination of the CNT growth. Further experiments demonstrated that in addition to catalyzing the CNT growth, catalyst particles can also decompose/etch the C sp2/sp3 bonds including those in the CNTs. The existing termination mechanism for the CNT growth fails to explain this. We therefore propose a model based on the catalyst phase transformation using the Johnson–Mehl–Avrami–Kolmogorov theory to predict the growth rate and termination of the CNT growth.     

In-Situ Vibrational Spectroscopic Studies on Model Catalyst Surfaces at Elevated Pressures

Elucidation of complex heterogeneous catalytic mechanisms at the molecular level is a challenging task due to the complex electronic structure and the topology of catalyst surfaces. Heterogeneous catalyst surfaces are often quite dynamic and readily undergo significant alterations under working conditions. Thus, monitoring the surface chemistry of heterogeneous catalysts under industrially relevant conditions such as elevated temperatures and pressures requires dedicated in situ spectroscopy methods. Due to their photons-in, photons-out nature, vibrational spectroscopic techniques offer a very powerful and a versatile experimental tool box, allowing real-time investigation of working catalyst surfaces at elevated pressures. Infrared reflection absorption spectroscopy (IRAS or IRRAS), polarization modulation-IRAS and sum frequency generation techniques reveal valuable surface chemical information at the molecular level, particularly when they are applied to atomically well-defined planar model catalyst surfaces such as single crystals or ultrathin films. In this review article, recent state of the art applications of in situ surface vibrational spectroscopy will be presented with a particular focus on elevated pressure adsorption of probe molecules (e.g. CO, NO, O₂, H₂, CH₃OH) on monometallic and bimetallic transition metal surfaces (e.g. Pt, Pd, Rh, Ru, Au, Co, PdZn, AuPd, CuPt, etc.). Furthermore, case studies involving elevated pressure carbon monoxide oxidation, CO hydrogenation, Fischer–Tropsch, methanol decomposition/partial oxidation and methanol steam reforming reactions on single crystal platinum group metal surfaces will be provided. These examples will be exploited in order to demonstrate the capabilities, opportunities and the existing challenges associated with the in situ vibrational spectroscopic analysis of heterogeneous catalytic reactions on model catalyst surfaces at elevated pressures.