Na2FeP2O7 as a Promising Iron‐Based Pyrophosphate Cathode for Sodium Rechargeable Batteries: A Combined Experimental and Theoretical Study

Considering the promising electrochemical performance of the recently reported pyrophosphate family in lithium ion batteries as well as the increasing importance of sodium ion batteries (SIBs) for emerging large‐scale applications, here, the crystal structure, electrochemical properties, and thermal stability of Na₂FeP₂O₇, the first example ever reported in the pyrophosphate family for SIBs, are investigated. Na₂FeP₂O₇ maintains well‐defined channel structures (triclinic framework under the P1 space group) and exhibits a reversible capacity of ≈90 mAh g^?1 with good cycling performance. Both quasi‐equilibrium measurements and first‐principles calculations consistently indicate that Na₂FeP₂O₇ undergoes two kinds of reactions over the entire voltage range of 2.0–4.5 V (vs Na/Na⁺): a single‐phase reaction around 2.5 V and a series of two‐phase reactions in the voltage range of 3.0–3.25 V. Na₂FeP₂O₇ shows excellent thermal stability up to 500 °C, even in the partially desodiated state (NaFeP₂O₇), which suggests its safe character, a property that is very critical for large‐scale battery applications.     

Context‐aware hybrid satellite‐terrestrial broadband access

One of the key performance targets on the European Commission's Digital Agenda is to provide at least 30‐Mbit/s broadband coverage to all European households by 2020. The deployment of existing terrestrial technologies will not be able to satisfy the requirements in the most difficult‐to‐serve locations, either due to a lack of coverage in areas where the revenue potential for terrestrial service providers is too low or due to technological limitations that diminish the available throughput in rural environments. In this paper, we investigate a hybrid broadband system combining satellite and terrestrial access networks. The system design and the key building blocks of the intelligent routing entities (referred to as intelligent gateways) are presented. To justify the hybrid broadband system's performance subjectively, lab trials have been performed with an integrated multiple access network emulator and a variety of typical multimedia applications that have varying requirements. The results of the lab trials suggest that the quality of experience is consistently improved thanks to the utilisation of intelligent gateway devices, when compared with using a single access network at a time.     

Valence number transition and silicate formation of cerium oxide films on Si(100)

Interface reactions of a Ce-oxide layer with Si(100) wafers have been characterized by X-ray photoelectron spectroscopy. The ratio of Ce atoms in Ce³⁺ states within the Ce-oxide layer has been found to decrease from 47% at as-deposited sample to 26% after annealing. From detailed reaction analysis of valence number transitions of Ce atoms and the creation of SiO₂ layer at the interface, the reacted Ce³⁺ atoms are converted into silicates and Ce⁴⁺ with a ratio of 2:1. The energy bandgap of Ce-silicate layer has been determined as 7.67 eV and the valence band offset with respect to Si(100) wafer has been extracted as 4.35 eV.     

Laser cutting of Kevlar laminates: First and second law analysis

Kevlar laminates are difficult to machine using conventional machining methods because of their thermal and mechanical properties. Laser cutting offers advantages over conventional machining methods, such as precision of operation, non-frictional processing, and operational cost. This provides the motivation for the present study, which reports on laser cutting of Kevlar laminates of different thicknesses. The first and second law efficiencies of the cutting process are formulated and predicted in line with the experimental parameters. The laser cut surfaces are examined using optical and electron scanning microscopes. It is demonstrated that the first and second law efficiencies improve at high laser cutting speeds and low laser output power levels. For these conditions parallel sided kerfs with no sideways burning are produced.     

On sample preparation for surface-enhanced raman scattering (SERS) of bacteria and the source of spectral features of the spectra

The characterization, detection, and identification of bacteria using surface-enhanced Raman scattering (SERS) spectroscopy is drawing considerable attention due to its ability to provide rich intrinsic molecular information about molecules and molecular structures in close proximity to noble metal surfaces. However, sample preparation methods and experimental conditions must be carefully evaluated in order to obtain healthy, interpretable, and comparable results. In this study, several bacterial species including E. coli, B. megaterium, S. aureus, and S. cohnii were systematically evaluated to demonstrate the source of the spectral features of bacterial SERS spectra. It was found that the features observed in bacterial SERS spectra originate mostly from the bacteria surface with some contributions from metabolic activity or molecular species detached from the bacteria surface during sample preparation.     

Development of a System for Temperature Profile Characterization of Baths

Liquid baths are the main calibration equipment to directly affect the measurement uncertainty in temperature calibrations. Therefore, the characteristics of baths need to be well investigated and understood. The temperature profile and stability of liquid baths are one of the most important contributions to the calibration uncertainty of platinum resistance thermometers, digital thermometers, liquid-in-glass thermometers, and thermocouples. Commercial baths only present stability and uniformity data in two dimensions in general; however, thermometers and thermocouples are immersed into the body of the bath, so the depth or z-axis is also very important. In this study, a measurement system has been designed using three-stepper motors and a data acquisition system (DAS). The DAS is developed using object-oriented algorithms to form a three-dimensional (3-D) scanning system. The 3-D scanning system is home-made and used in conjunction with a reference platinum thermometer. The temperature profiles and stability of several types of baths: water, oil, and salt were obtained in the temperature range from 30???C to 450???C. Therefore, this contributed toward a more accurate uncertainty budget evaluation.     

Determination of heavy metals (Cd,Pb) and trace elements (Cu,Zn) in sediments and fish of the Southeastern Aegean Sea (Turkey) by atomic absorption spectrometry

The Bay of Güllük in Southeastern Aegean Sea (Turkey) is very important by the potential of marine product in the Aegean Sea. There are various polluting elements in Güllük Bay. The current situation of the bay and impact of pollutants have became necessity. Dicentrarchus labrax are frequently used for human consumption. In this study, heavy metals (Pb, Cd) and trace elements (Cu, Zn) were analyzed in fish (D. labrax) and sediments in the Bay of Güllük by atomic absorption spectrometry. The average metal concentrations in the fish varied in the following ranges: Pb; <0.02–0.4, Cd; <0.01–0.04, Cu; <0.1, Zn; <0.5–7.2 mg kg⁻¹. In addition, seven sediment samples were analyzed and avarage concentrations of them were found as Zn; 80.8 ± 0.45, Cu; 25.2 ± 0.14, Pb; 20.0 ± 2, Cd; 0.560.08 mg kg⁻¹. The accuracy and precision of our results were checked by using International Certified Reference samples (fish: DORM-2, sediment: HISS-1).     

An efficient and adaptive channel handover procedure for cognitive radio networks

In designing cognitive radio systems, one of the most critical issues is handling the channel handover process (CHP). The CHP consists of spectrum sensing, spectrum decision, negotiation on the common control channel, and adjustment of frequency and modulation settings, and such, it can be a time‐consuming process. Consequently, initiating the CHP after each detected user activity (UA) can decrease the aggregate spectrum utilization. To alleviate this problem, we introduce a novel handover strategy to find the optimal trade‐off between the durations of the CHP and UAs. With the use this model, secondary users (SUs) track only local information on their current data channel to make the decision to initiate the CHP or to wait for the termination of the ongoing UA. The system adapts to the dynamic conditions of the data channels and reduces the frequency of handovers to increase throughput and decrease access delay. We give analytical utilization bounds for SUs and also compare the performance of our model to those of other channel handover strategies by using extensive simulations. Our results for channels with heterogeneous loads and dynamic environments show that this model can clearly decrease the frequency of handover and consequently increase the aggregate SU utilization. Copyright © 2013 John Wiley & Sons, Ltd.     

Propylene polymerization in slurry catalyzed by titanium trichloride–diethyl aluminum chloride

Propylene is polymerized in a slurry over a TiCl₃ · ?AlCl₃ catalyst with a DEAC cocatalyst, approaching conditions of industrial relevance. The effects of various parameters such as temperature, pressure, cocatalyst-to-catalyst ratio, hydrogen concentration, and polymerization time are investigated with particular emphasis on the yield, tacticity, molecular weight, bulk density, and particle size of the resulting polymer. The highest yield and isotactic content are obtained at an Al/Ti ratio of 6, temperature of 70°C, and pressure of 9 kg/cm²g. The polymerization rate is found to be first order up to a monomer concentration of 2.5 mol/L. The overall activation energy of polymerization calculated from an Arrhenius plot is found to be 11.6 kcal/mol. A correlation between MFI and molecular weight is also presented. © 1994 John Wiley & Sons, Inc.