Li‐Rich Li[Li1/6Fe1/6Ni1/6Mn1/2]O2 (LFNMO) Cathodes: Atomic Scale Insight on the Mechanisms of Cycling Decay and of the Improvement due to Cobalt Phosphate Surface Modification

Lithium‐rich Li[Li_1/6Fe_1/6Ni_1/6Mn_1/2]O₂ (0.4Li₂MnO₃‐0.6LiFe_1/3Ni_1/3Mn_1/3O₂, LFNMO) is a new member of the xLi₂MnO₃·(1 ? x)LiMO₂ family of high capacity–high voltage lithium‐ion battery (LIB) cathodes. Unfortunately, it suffers from the severe degradation during cycling both in terms of reversible capacity and operating voltage. Here, the corresponding degradation occurring in LFNMO at an atomic scale has been documented for the first time, using high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM), as well as tracing the elemental crossover to the Li metal anode using X‐ray photoelectron spectroscopy (XPS). It is also demonstrated that a cobalt phosphate surface treatment significantly boosts LFNMO cycling stability and rate capability. Due to cycling, the unmodified LFNMO undergoes extensive elemental dissolution (especially Mn) and O loss, forming Kirkendall‐type voids. The associated structural degradation is from the as‐synthesized R‐3m layered structure to a disordered rock‐salt phase. Prior to cycling, the cobalt phosphate coating is epitaxial, sharing the crystallography of the parent material. During cycling, a 2–3 nm thick disordered Co‐rich rock‐salt structure is formed as the outer shell, while the bulk material retains R‐3m crystallography. These combined cathode–anode findings significantly advance the microstructural design principles for next‐generation Li‐rich cathode materials and coatings.     

Thermal stability of Al-1%Si-0.5%Cu/TiSi2 contact structure

Stable TiSi₂ was formed by rapid thermal annealing (RTA) on single-crystal Si. Subsequently a 600 nm-thick Al-1%Si-0.5%Cu layer was deposited on the top of the formed TiSi₂ followed by furnace annealing for 30 min at 400–600 C in N₂ ambient atmosphere. The thermal stability of Al-1%Si-0.5%Cu/TiSi₂ bilayer and interfacial reaction were investigated by employing four-point probe, scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The composition and the phase of precipitates formed by the reaction of Al-1%Si-0.5%Cu with TiSi₂ were studied by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). It was found that the TiSi₂ layer was consumed by the reaction between TiSi₂ and Al-1%Si-0.5%Cu layer, resulting in precipitates at 550 C. The results from EDS revealed that the precipitates were composed of Ti, Al and Si. The precipitates were identified as Ti₇Al₅Si₁₂ ternary compound from XRD analysis.     

Compiler transformations for effectively exploiting a zero overhead loop buffer

A Zero Overhead Loop Buffer (ZOLB) is an architectural feature that is commonly found in DSP processors. This buffer can be viewed as a compiler managed cache that contains a sequence of instructions that will be executed a specified number of times without incurring any loop overhead. Unlike loop unrolling, a loop buffer can be used to minimize loop overhead without the penalty of increasing code size. In addition, a ZOLB requires relatively little space and power, which are both important considerations for most DSP applications. This paper describes strategies for generating code to effectively use a ZOLB. We have found that many common code improving transformations used by optimizing compilers on conventional architectures can be easily used to (1) allow more loops to be placed in a ZOLB, (2) further reduce loop overhead of the loops placed in a ZOLB, and (3) avoid redundant loading of ZOLB loops. The results given in this paper demonstrate that this architectural feature can often be exploited with substantial improvements in execution time and slight reductions in code size for various signal processing applications. Copyright © 2004 John Wiley & Sons, Ltd.     

Code optimizations for a VLIW-style network processing unit

The explosive growth in network bandwidth and Internet services such as QoS (quality of service) and SLA (service level agreement) monitoring have created the need for new networking hardware called a Network Processing Unit (NPU). In order to rapidly reconfigure the NPU for frequently varying Internet services and technologies, a high-performance C compiler is urgently needed. Several code generation techniques, which are intended to meet the high code quality demands of other types of application specific instruction-set processors (ASIPs) like digital signal processors (DSPs), have already been developed. However, these techniques are insufficient for NPUs due to striking architectural differences such as asymmetric data paths. The main purpose of this paper is to discuss our recent experience with the development of a commercial compiler for a new NPU called the Paion PPII, which is basically a packet engine for NPU to meet the growing need for new high-bandwidth communication equipment targeted for Internet routers and ethernet adapters. For this purpose, we will first show the architectural challenges posed by the target NPU. Then, we will describe several compiler techniques that we found to be effective for the target NPU with various unorthogonal architectural features. The current implementations of the PPII use a VLIW (Very Long Instruction Word) architecture. So, we handled this VLIW-style architecture by employing a simple code compaction scheme which packs multiple parallel instructions into one long instruction word. The experimental results show that our techniques are effective for significantly reducing the dynamic instruction count. Copyright © 2004 John Wiley & Sons, Ltd.     

Personalizing influence diagrams: applying online learning strategies to dialogue management

We consider the problem of adapting the parameters of an influence diagram in an online fashion for real-time personalization. This problem is important when we use the influence diagram repeatedly to make decisions and we are uncertain about its parameters. We describe learning algorithms to solve this problem. In particular, we show how to modify various explore-versus-exploit strategies that are known to work well for Markov decision processes to the more general influence-diagram model. As an illustration, we describe how our techniques for online personalization allow a voice-enabled browser to adapt to a particular speaker for spoken dialogue management. We evaluate all the explore-versus-exploit strategies in this domain.     

Adsorption of cobalt(II) ion by titanium-based oxides in high temperature water

Titanium-based adsorbents such as TiO₂ and Fe-Ti-O were prepared by hydrolysis of Ti(OC₃H₇)₄ and alkalinizing an equimolar mixed solution of TiCL₄ and FeCl₂ followed by heat treatment of their hydroxides, respectively. The prepared Fe-Ti-O adsorbent was found to be stable nonstoichiometric ferrous and ferric titanium oxides with pseudobrookite and rutile structures. The Co²⁺ adsorption characteristics of the adsorbent in high temperature water were investigated in the autoclave.Co ²⁺ adsorption capacity of the Fe-Ti-O adsorbent was determined to be larger man that of TiO₂ at high temperatures. The enthalpy changes of 34 and 49 kJ-mol^-1 due to the adsorption of Co²⁺ on the TiO₂ and Fe-Ti-O adsorbents indicate that the adsorption is endothermic in the experimental temperature range (15-280 ‡C). From this preliminary study, titanium-based oxides are shown to have good potential applicability for reactor water purification as high temperature adsorption media.     

Improving command and control speech recognition on mobile devices: using predictive user models for language modeling

Command and control (C&C) speech recognition allows users to interact with a system by speaking commands or asking questions restricted to a fixed grammar containing pre-defined phrases. Whereas C&C interaction has been commonplace in telephony and accessibility systems for many years, only recently have mobile devices had the memory and processing capacity to support client-side speech recognition. Given the personal nature of mobile devices, statistical models that can predict commands based in part on past user behavior hold promise for improving C&C recognition accuracy. For example, if a user calls a spouse at the end of every workday, the language model could be adapted to weight the spouse more than other contacts during that time. In this paper, we describe and assess statistical models learned from a large population of users for predicting the next user command of a commercial C&C application. We explain how these models were used for language modeling, and evaluate their performance in terms of task completion. The best performing model achieved a 26% relative reduction in error rate compared to the base system. Finally, we investigate the effects of personalization on performance at different learning rates via online updating of model parameters based on individual user data. Personalization significantly increased relative reduction in error rate by an additional 5%.     

Acoustically steered and rotated true-time-delay generator based on wavelength-division multiplexing

The acoustically steered and rotated (ASTRO) true-time-delay (TTD) generator, capable of two-dimensional (2D) multiple beam generation without causing extraneous beams, is described. It is based on wavelength-division multiplexing to encode and decode various linear chirp time delays with wavelengths. An array of equally spaced light stripes with linear chirp time delays among them is formed and is subsequently rotated to a desired angle by use of our nonmechanical acousto-optic dove prism, believed to be novel. Our architecture reduces hardware complexity significantly by avoiding redundancy in conventional TTD generators. Experimental results to prove the concept of 2D multiple beam generation are shown. Also, an extension of the system for bidirectional communications is proposed. Various technical issues for practical applications are discussed.     

High-strength silica fibres in a long length coated at a speed of 5 m/s

We report the strength characteristics of high-speed coated optical fibres. We used synthetic drawn 125 ?m-diameter-fibre silica rods coated in-line with a 50 ?m-thick single-layer coating at a rate of 5 m/s. A 50.8 km length of fibre was drawn into sample lengths ranging from ~ 5 to 7 km from each rod. All the fibres were proof tested at three different stress levels up to 2.1 GN/m2, resulting in an average survival length of ~ 10 and 3 km, respectively, at 1 4 GN/m2 (200 kpsi) and 2.1 GN/m2 (300 kpsi).