On the formation of intermetallics in rapidly solidifying Al–Fe–Si alloys

It is known from previous experimental observations that a rapid solidification of Al–Fe and Al–Fe–Si alloys results in the formation of various metastable phases. Despite attempts to explain why particular intermetallics form and to accurately predict a sequence of their precipitation, a fully satisfactory and prognostic explanation remains to be found. In this communication, it is conjectured that after the concept of the driving forces for the onset of precipitation is adapted to take into account important differences between the Al-rich FCC solution and all other solid phases, it can be used to identify intermetallics whose formation is thermodynamically permissible for a given supercooling. If the composition of some of the “possible phases” is close to the composition of the remaining liquid, then the precipitation of these particular phases is facilitated, because corresponding nucleation events do not require a long-range diffusion, which might be slow in supercooled melts.     

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single-crystal molybdenum oxide (MoO₂) flakes that exhibit unexpected piezoelectric-like response are fabricated, as MoO₂ is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO₂ emerges from an electret-like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out-of-plane piezoresponse is 0.56 pm V⁻¹, which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.     

Zeolite Nanosheets Stabilize Catalyst Particles to Promote the Growth of Thermodynamically Unfavorable,Small‐Diameter Carbon Nanotubes

A challenge in the synthesis of single‐wall carbon nanotubes (SWCNTs) is the lack of control over the formation and evolution of catalyst nanoparticles and the lack of control over their size or chirality. Here, zeolite MFI nanosheets (MFI‐Ns) are used to keep cobalt (Co) nanoparticles stable during prolonged annealing conditions. Environmental transmission electron microscopy (ETEM) shows that the MFI‐Ns can influence the size and shape of nanoparticles via particle/support registry, which leads to the preferential docking of nanoparticles to four or fewer pores and to the regulation of the SWCNT synthesis products. The resulting SWCNT population exhibits a narrow diameter distribution and SWCNTs of nearly all chiral angles, including sub‐nm zigzag (ZZ) and near‐ZZ tubes. Theoretical simulations reveal that the growth of these unfavorable tubes from unsupported catalysts leads to the rapid encapsulation of catalyst nanoparticles bearing them; their presence in the growth products suggests that the MFI‐Ns prevent nanoparticle encapsulation and prologue ZZ and near‐ZZ SWCNT growth. These results thus present a path forward for controlling nanoparticle formation and evolution, for achieving size‐ and shape‐selectivity at high temperature, and for controlling SWCNT synthesis.     

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

The development of pseudocapacitive materials for energy‐oriented applications has stimulated considerable interest in recent years due to their high energy‐storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery‐like to the pseudocapacitive‐like behavior. As a result, it becomes challenging to distinguish “pseudocapacitive” and “battery” materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery‐type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid‐state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state‐of‐the‐art progress in the engineering of active materials is summarized, which will guide for the development of real‐pseudocapacitive energy storage systems.     

Direct numerical inversion method for kinetic ellipsometric data. II. Implementation and experimental verification

A direct numerical inversion method is applied to the monitoring of thin-film growth. Several improvements of the method, including a correction for weakly absorbing materials, are presented. The method has been successfully applied to the inversion of the growth of constant-refractive-index layers andused for the process calibration of plasma-enhanced chemical vapor deposition of silicon oxynitrides. The validity of this calibration has been successfully tested on a linear index gradient and quintic matching layer between a polycarbonate substrate and a scratch-resistant coating.     

In Situ Electrochemistry of Rechargeable Battery Materials: Status Report and Perspectives

The development of rechargeable batteries with high performance is considered to be a feasible way to satisfy the increasing needs of electric vehicles and portable devices. It is of vital importance to design electrodes with high electrochemical performance and to understand the nature of the electrode/electrolyte interfaces during battery operation, which allows a direct observation of the complicated chemical and physical processes within the electrodes and electrolyte, and thus provides real‐time information for further design and optimization of the battery performance. Here, the recent progress in in situ techniques employed for the investigations of material structural evolutions is described, including characterization using neutrons, X‐ray diffraction, and nuclear magnetic resonance. In situ techniques utilized for in‐depth uncovering the electrode/electrolyte phase/interface change mechanisms are then highlighted, including transmission electron microscopy, atomic force microscopy, X‐ray spectroscopy, and Raman spectroscopy. The real‐time monitoring of lithium dendrite growth and in situ detection of gas evolution during charge/discharge processes are also discussed. Finally, the major challenges and opportunities of in situ characterization techniques are outlined toward new developments of rechargeable batteries, including innovation in the design of compatible in situ cells, applications of dynamic analysis, and in situ electrochemistry under multi‐stimuli. A clear and in‐depth understanding of in situ technique applications and the mechanisms of structural evolutions, surface/interface changes, and gas generations within rechargeable batteries is given here.     

Who plays,how much,and why? Debunking the stereotypical gamer profile

Online games have exploded in popularity, but for many researchers access to players has been difficult. The study reported here is the first to collect a combination of survey and behavioral data with the cooperation of a major virtual world operator. In the current study, 7,000 players of the massively multiplayer online game (MMO) EverQuest 2 were surveyed about their offline characteristics, their motivations and their physical and mental health. These self‐report data were then combined with data on participants’ actual in‐game play behaviors, as collected by the game operator. Most of the results defy common stereotypes in surprising and interesting ways and have implications for communication theory and for future investigations of games.     

Human activity recognition in pervasive health-care: Supporting efficient remote collaboration

Technological advancements, including advancements in the medical field have drastically improved our quality of life, thus pushing life expectancy increasingly higher. This has also had the effect of increasing the number of elderly population. More than ever, health-care institutions must now care for a large number of elderly patients, which is one of the contributing factors in the rising health-care costs. Rising costs have prompted hospitals and other health-care institutions to seek various cost-cutting measures in order to remain competitive. One avenue being explored lies in the technological advancements that can make hospital working environments much more efficient. Various communication technologies, mobile computing devices, micro-embedded devices and sensors have the ability to support medical staff efficiency and improve health-care systems. In particular, one promising application of these technologies is towards deducing medical staff activities. Having this continuous knowledge about health-care staff activities can provide medical staff with crucial information of particular patients, interconnect with other supporting applications in a seamless manner (e.g. a doctor diagnosing a patient can automatically be sent the patient's lab report from the pathologist), a clear picture of the time utilisation of doctors and nurses and also enable remote virtual collaboration between activities, thus creating a strong base for establishment of an efficient collaborative environment. In this paper, we describe our activity recognition system that in conjunction with our efficiency mechanism has the potential to cut down health-care costs by making the working environments more efficient. Initially, we outline the activity recognition process that has the ability to infer user activities based on the self-organisation of surrounding objects that user may manipulate. We then use the activity recognition information to enhance virtual collaboration in order to improve overall efficiency of tasks within a hospital environment. We have analysed a number of medical staff activities to guide our simulation setup. Our results show an accurate activity recognition process for individual users with respect to their behaviour. At the same time we support remote virtual collaboration through tasks allocation process between doctors and nurses with results showing maximum efficiency within the resource constraints.     

Policy-constrained bio-inspired processes for autonomic route management

Autonomic networking systems must be designed to achieve an appropriate balance between the operation of decentralized algorithms and processes that seek to maintain optimal or near-optimal behavior in terms of global stability, improved performance and adaptability, robustness and security, with the requirement for top-down control of the system by humans to ensure business goals are met. Taking a communications networking survivability case study, we show how the operation of decentralized algorithms, inspired by the operation of biological systems, can be controlled and constrained through the deployment of management policies authored by network administrators. We present survivability-related routing algorithms (inspired by chemotaxis, reaction-diffusion and quorum sensing biological processes) which work together to effectively reconfigure network resources when transient link failures occur and demonstrate how these algorithms can be re-parameterized via policies to improve performance given prevailing network conditions. Simulation results show how the combined operation of these algorithms, as controlled by policies, allows the network to react well to survive link failure events.