The lithiation/delithiation in LiFePO4 is highly anisotropic with lithium-ion diffusion being mainly confined to channels along the b-axis. Controlling the orientation of LiFePO4 crystals therefore plays an important role for efficient mass transport within this material. We report here the preparation of single crystalline LiFePO4 nanosheets with a large percentage of highly oriented {010} facets, which provide the highest pore density for lithium-ion insertion/extraction. The LiFePO4 nanosheets show a high specific capacity at low charge/discharge rates and retain significant capacities at high C-rates, which may benefit the development of lithium batteries with both favorable energy and power density.

Single-Crystalline LiFePO4 Nanosheets for High-Rate Lithium Batteries

Smart grid communication and information technologies in the perspective of Industry 4.0: Opportunities and challenges

Since the inception of IEEE 802.11 wireless local area networks (WLANs) in 1997, wireless networking technologies have tremendously grown in the last few decades. The fundamental IEEE 802.11 physical (PHY) and medium access control (MAC) protocols have continuously been enriched with new technologies to provide the last mile wireless broadband connectivity to end users. Consequently, several new amendments of the basic IEEE 802.11 gradually came up in the forms of IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g. More recently, IEEE 802.11n, IEEE 802.11ac, and IEEE 802.11ad are introduced with enhanced PHY and MAC layers that boost up physical data rates to the order of Gigabit per second. So, these amendments are generally known as high throughput WLANs (HT-WLANs). In HT-WLANs, PHY layer is enhanced with multiple-input multiple-output antenna technologies, channel bonding, short guard intervals, enhanced modulation and coding schemes. The MAC sublayer overhead is reduced by introducing frame aggregation and block acknowledgement technologies. However, several existing studies reveal that, many a time, the aforesaid PHY and MAC enhancements yield negative impact on various upper layer protocols, that is end-to-end transport and application layer protocols. As a consequence, a large number of researchers have focused on improving the coordination among PHY/MAC and upper layer protocols. In this survey, we discuss impact of HT-WLAN PHY and MAC layer enhancements on various transport and application layer protocols. This paper also summarizes several research works that use aforesaid enhancements effectively to boost up data rate of end-to-end protocols. We also point out limitations of the existing researches and list down different open challenges that can be meaningfully explored for the development of the next generation HT-WLAN technologies.

Impact of IEEE 802.11n/ac PHY/MAC High Throughput Enhancements on Transport and Application Protocols—A Survey

Smart tourism is an important component of smart cities. However, in many cities, insecurity, safety, fraud, and the lack of availability of proper information about resources are the biggest hurdles toward independent mobility. These issues can be overcome via proactive participation of local citizens to help tourists as well as by cooperation between citizens, city administration, and tourists. As a result, a number of components of smart cities can be strengthened, from sustainable mobility in tourism development to economic development. This is very challenging, as it requires a combination of societal inputs and advanced smart and effective tools. This article presents a viable Internet of Things (IoT)-based solution called iTour that is a framework for independent tourist mobility. In the process, we analyze the difficulties in initiatives and lessons, exploring possible roles of the IoT.

iTour: The Future of Smart Tourism: An IoT Framework for the Independent Mobility of Tourists in Smart Cities

A well-crystallized (NH4)[Fe2(OH)(PO4)2]·2H2O particle with a red-blood-cell-like (RBC-like) shape has been synthesized via a simple sonochemical method, and is employed as the precursor to fabricate LiFePO4/C as a cathode material for Li-ion batteries. The morphology evolution of (NH4)[Fe2(OH)(PO4)2]·2H2O from a nanoparticle to a nanoplate (∼50 nm in thickness) and to a RBC-like discoid is observed by increasing the reaction time. The formation mechanism of this kind of RBC-like shape can be understood as nucleation, crystallization, formation of thin plates, and self-assembly. The precursor and corresponding LiFePO4/C are characterized by XRD, SEM, TEM, charge–discharge tests and CV measurements. The results show that the morphology of the (NH4)[Fe2(OH)(PO4)2]·2H2O precursor turns from a RBC-like structure into an irregular structure and the size becomes much smaller for LiFePO4/C during the solid-state reaction process. The fabricated LiFePO4/C exhibits excellent rate performance with a discharge capacity of 113.4 mA h g−1 even at 10C and a capacity fading rate of 3.5% after 300 cycles. Thus, this kind of uniquely shaped (NH4)[Fe2(OH)(PO4)2]·2H2O shows potential application in high-power Li-ion batteries.

Red-blood-cell-like (NH4)[Fe2(OH)(PO4)2]·2H2O particles: fabrication and application in high-performance LiFePO4 cathode materials

The chemistry of the noble metal fission product, ruthenium is very complex due to the existence of many oxidation states in addition to forming a large number of co-ordination complexes. In the PUREX process for the separation of U and Pu from the spent nuclear fuels from fast breeder reactors, owing to the high volatile nature of RuO4 problems arise not only during the extraction stages but also in the treatment of high active liquid waste and subsequent vitrification. As this volatile RuO4 can deposit in cooler parts, there is an increase in the radiation field due to the presence of 106Ru. The problem is very acute in the reprocessing of fast reactor fuels due to the increased concentration of ruthenium in the spent fuel. In nitric acid medium Ru can exist in various nitroso nitrate complexes and nitroso complexes are more stable than nitrates. The nitrates are non-extractable by the solvent TBP; however, they are extractable to a higher degree by DBP (the primary degradation product of TBP). The extractability of Ru nitrates into the solvent is inhibited by high acid content, temperature and prolonged hold-up time. Nevertheless, these factors promote the volatilization of Ru as RuO4. The volatilization is enhanced by the addition of phosphate ions, but is suppressed by phosphite or hypophosphite ions. Thus, it would be advantageous if ruthenium is removed so that not only the purity of the product (Pu) is improved, but also the problem related to volatilisation can be resolved. High molecular weight amines (tertiary amines) capable of forming co-ordinate bonds are reported to be ideal extractants for Ru. Gas phase separation is an effective method for the recovery of Ru from catalysts, lead button and from other platinum group metals. Separation and pre-concentration of noble metals can be accomplished from non-metals by simple sorbents like coconut shell activated carbon to complicated chelating resins, aromatic polymers and zeolites. In the electro-oxidation of active Ru from nitroso salts, Pd was found to interfere and removal of Pd prior to oxidation of Ru is recommended. Redox catalysts such as Ag2+ and Ce4+ are found to play a prominent role in the electro-oxidation of Ru. Though, various methods and extractants are reported in the literature for the separation of Ru, R&D is being pursued for the removal of Ru during aqueous reprocessing of spent fuels using extractants and methods which are conducive to plant conditions. Hence, an exhaustive survey of literature was made and the different methods reported for the removal of Ru with emphasis towards reprocessing applications are discussed in this report as a review. Attempts made by the authors in separating Ru from simulated waste solution are also included in this review.

Separation and recovery of ruthenium: a review

Carbon coating on the current collector and LiFePO 4 nanoparticles – Influence of sp 2 and sp 3 -like disordered carbon on the electrochemical properties

The IEEE 802.11 standard defines a power management algorithm for wireless LAN. In the power management for Independent Basic Service Set (IBSS), time is divided into Beacon Intervals (BIs) and each BI is divided into an Announcement Traffic Indication Message (ATIM) window and a data window. The stations that have successfully transmitted an ATIM frame within the ATIM window compete to transmit data frames in the rest of the BI. This paper analyzes the performance of the IEEE 802.11 Power Save Mode (PSM) in single hop ad hoc networks using a discrete-time Markov chain for a data frame transmission together with the corresponding ATIM frame transmission. The paper presents an analytical model to compute the throughput, average delay and power consumption in IEEE 802.11 IBSS in PSM under ideal channel and saturation conditions. The impact of network size on the throughput, delay and power consumption of the IEEE 802.11 DCF in Power Save Mode is also analyzed. This can be used to find an efficient scheme that can maximize the network throughput while saving power consumption for resource constrained ad hoc wireless networks. The analytical work is validated with simulation results obtained from Qualnet 5.0.1 network simulator.

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Performance modeling and evaluation of IEEE 802.11 IBSS power save mode

Fairness provisioning in IEEE 802.11s EDCA based Wireless Mesh Networks (WMNs) is a very challenging task due to relayed traffic and traffic load variation among mesh routers. Because of bursty traffic in general purpose community wireless mesh networks, proportional fairness is more suited than max-min fairness, where mesh routers and clients should get channel access proportional to their traffic load. However, proportional fairness is hard to achieve by solving optimization function because of non-linearity and non-concave property of the objective function. In this paper, a probabilistic approach is proposed to provide proportional fairness without solving global non-linear and non-concave optimization. Every mesh node use a load estimation strategy to estimate total traffic load that it needs to forward. The required channel share of a mesh node should be proportional to its traffic load, whereas, the total normalized channel share for all the contending mesh nodes should be kept less than unity to satisfy the clique constraint. The network architecture and contention property in WMN are explored to deduce the required channel share of mesh nodes. A probabilistic approach is used to tune the contention window based on the difference between actual channel share and required channel share, so that the node with more traffic load gets more channel share. A discrete time Markov Chain based modeling is used to deduce the overall network throughput for the proposed scheme. Simulation result shows that the proposed scheme works better than the standard IEEE 802.11s based EDCA MAC in terms of fairness and throughput.

Proportional fairness in MAC layer channel access of IEEE 802.11s EDCA based wireless mesh networks

The IEEE 802.11 standard for wireless local area networks defines a power management algorithm for Independent Basic Service Set (IBSS) allowing it to save critical battery energy in low powered wireless devices. The power management algorithm for IBSS uses beacon intervals (BIs) as the time unit, where every BI consists of an Announcement Traffic Indication Message (ATIM) window and a data window. The stations that have data to send need to go through a handshaking procedure in the ATIM window. If this handshaking is successful, the station remains awake in the data window and participates in the data communication. Otherwise, it goes into the sleep mode. This paper presents an analytical model to compute the throughput, expected delay and expected power consumption in an IEEE 802.11 IBSS in power save mode (PSM) for different traffic conditions in the network. The impact of data arrival rate, network size, and size of the BI on the performance of the IEEE 802.11 DCF in PSM is also analyzed. This analysis reveals a clear trade-off among throughput, delay, and average power consumption. The trade-off analysis is useful for designing efficient power consumption algorithms while maintaining the consistence performance of the network in terms of throughput and delay.

Pravati Swain

Papers

Separation and recovery of ruthenium: a review

Carbon coating on the current collector and LiFePO 4 nanoparticles – Influence of sp 2 and sp 3 -like disordered carbon on the electrochemical properties

Performance modeling and evaluation of IEEE 802.11 IBSS power save mode

Proportional fairness in MAC layer channel access of IEEE 802.11s EDCA based wireless mesh networks

Performance Modeling and Analysis of IEEE 802.11 IBSS PSM in Different Traffic Conditions