Energy-aware wireless networking with directional antennas: the case of session-based broadcasting and multicasting

We consider ad hoc wireless networks that use directional antennas and have limited energy resources. To explore quantitatively the advantage offered by the use of directional antennas over the case of omnidirectional antennas, we consider the case of connection-oriented multicast traffic. Building upon our prior work on multicasting algorithms, we introduce two protocols that exploit the use of directional antennas and evaluate their performance, We observe significant improvement with respect to the omnidirectional case, in terms of both energy efficiency and network lifetime. Additionally, we show that further substantial increase in the network's lifetime can be achieved by incorporating a simple measure of a node's residual energy into the node's cost function.     

Enhancing Ultrafast Lithium Ion Storage of Li4Ti5O12 by Tailored TiC/C Core/Shell Skeleton Plus Nitrogen Doping

It is of great importance to reinforce electronic and ionic conductivity of Li₄Ti₅O₁₂ electrodes to achieve fast reaction kinetics and good high‐power capability. Herein, for the first time, a dual strategy of combing N‐doped Li₄Ti₅O₁₂ (N‐LTO) with highly conductive TiC/C skeleton to realize enhanced ultrafast Li ion storage is reported. Interlinked hydrothermal‐synthesized N‐LTO nanosheets are homogeneously decorated on the chemical vapor deposition (CVD) derived TiC/C nanowires forming binder‐free N‐LTO@TiC/C core–branch arrays. Positive advantages including large surface area, strong mechanical stability, and enhanced electronic/ionic conductivity are obtained in the designed integrated arrays and rooted upon synergistic TiC/C matrix and N doping. The above appealing features can effectively boost kinetic properties throughout the N‐LTO@TiC/C electrodes to realize outstanding high‐rate capability at different working temperatures (143 mAh g^?1/10 C at 25 °C and 122 mAh g^?1/50 C at 50 °C) and notable cycling stability with a capacity retention of 99.3% after 10 000 cycles at 10 C. Moreover, superior high‐rate cycling life is also demonstrated for the full cells with N‐LTO@TiC/C anode and LiFePO₄ cathode. The dual strategy may provoke wide interests in fast energy storage areas and motivate the further performance improvement of power‐type lithium ion batteries (LIBs).     

A novel method for detection of the transition between atrial fibrillation and sinus rhythm

Automatic detection of atrial fibrillation (AF) for AF diagnosis, especially for AF monitoring, is necessarily desirable for clinical therapy. In this study, we proposed a novel method for detection of the transition between AF and sinus rhythm based on RR intervals. First, we obtained the delta RR interval distribution difference curve from the density histogram of delta RR intervals, and then detected its peaks, which represented the AF events. Once an AF event was detected, four successive steps were used to classify its type, and thus, determine the boundary of AF: 1) histogram analysis; 2) standard deviation analysis; 3) numbering aberrant rhythms recognition; and 4) Kolmogorov-Smirnov (K-S) test. A dataset of 24-h Holter ECG recordings (n = 433) and two MIT-BIH databases (MIT-BIH AF database and MIT-BIH normal sinus rhythm (NSR) database) were used for development and evaluation. Using the receiver operating characteristic curves for determining the threshold of the K-S test, we have achieved the highest performance of sensitivity and specificity (SP) (96.1% and 98.1%, respectively) for the MIT-BIH AF database, compared with other previously published algorithms. The SP was 97.9% for the MIT-BIH NSR database.     

Downlink queuing model and packet scheduling for providing lossless handoff and QoS in AG mobile networks

Next generation mobile networks are expected to provide seamless personal mobile communication and quality-of-service (QoS) guaranteed IP-based multimedia services. Providing seamless communication in mobile networks means that the networks have to be able to provide not only fast but also lossless handoff. This paper presents a two-layer downlink queuing model and a scheduling mechanism for providing lossless handoff and QoS in mobile networks, which exploit IP as a transport technology for transferring datagrams between base stations and the high-speed downlink packet access (HSDPA) at the radio layer. In order to reduce handoff packet dropping rate at the radio layer and packet forwarding rate at the IP layer and provide high system performance, e.g., downlink throughput, scheduling algorithms are performed at both IP and radio layers, which exploit handoff priority scheduling principles and take into account buffer occupancy and channel conditions. Performance results obtained by computer simulation show that, by exploiting the downlink queuing model and scheduling algorithms, the system is able to provide low handoff packet dropping rate, low packet forwarding rate, and high downlink throughput.     

Highly Efficient Pure‐White‐Light‐Emitting Diodes from a Single Polymer: Polyfluorene with Naphthalimide Moieties

Light‐emitting diodes exhibiting efficient pure‐white‐light electroluminescence have been successfully developed by using a single polymer: polyfluorene derivatives with 1,8‐naphthalimide chromophores chemically doped onto the polyfluorene backbones. By adjusting the emission wavelength of the 1,8‐naphthalimide components and optimizing the relative content of 1,8‐naphthalimide derivatives in the resulting polymers, white‐light electroluminescence from a single polymer, as opposed to a polymer blend, has been obtained in a device with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)(50 nm)/polymer(80 nm)/Ca(10 nm)/Al(100 nm). The device exhibits Commission Internationale de l'Eclairage coordinates of (0.32,0.36), a maximum brightness of 11 900 cd m^–2, a current efficiency of 3.8 cd A^–1, a power efficiency of 2.0 lm W^–1, an external quantum efficiency of 1.50 %, and quite stable color coordinates at different driving voltages, even at high luminances of over 5000 cd m^–2.     

Downlink Performance Analysis of MIMO Relaying Networks

In recent years, there has been an upsurge of interest in relay-augmented infrastructure-based networks. On the other hand, multiple-input-multiple-output (MIMO) wireless system becomes a hot topic for it can achieve significant increases in overall system performance. This paper gives a detailed analysis of downlink performance of MIMO relaying networks, in which different channel models and classic MIMO cellular system model with fixed relay are considered. Our results in single cell scenario show that when meeting effective relay system efficiency of 100%, the required relay SNR gain of 2-antenna system can be reduced to less than half of that with only one transceiver antenna. We also observe that MIMO is more tolerant to interference compared with the one-transceiver antenna system. After that, multi-hop architecture is researched and statistics figures out the tolerable number of hops which is supported in wireless communication with a view to real application. In addition, multi-cell scenario is also studied. Statistics results show that there is more 8 dB average spectral efficiency gain in a two-hop fixed relay 4 × 4 MIMO system than that in a SISO system. These results present significant indications in deployment and optimization of relay-based MIMO networks.     

A complete resistance extraction methodology and circuit models for typical TSV structures

Through-silicon via (TSV) is one of the key technologies on three-dimensional integration packaging. In this article, an experimental methodology with circuit models was proposed for electrical characteristic tests on typical TSV structures. To this end, self-developed test patterns such as the via chains, the snake interconnections and the Kelvin structures with different dimensions were designed and manufactured. Suitable electrical measurement methodologies were next employed to characterise the element behaviours of the patterns. Based on the experimental data, electrical circuit models for the TSV structures were introduced and the parameters of the model were exacted. The validity and accuracy of the electrical model were finally verified and the TSV characteristic measurements can be performed through a simpler process.     

应用于光触发晶闸管触发的特种光纤性能分析

对光触发晶闸管应用中使用较广泛的一种特种光纤进行了性能分析,对该光纤的芯层与包层的掺杂和包层/芯层直径比等关键光学特性进行了系统的研究,为光触发晶闸管寻找到性价比较优的特种光纤提供了参考。通过对比分析得出,在光触发晶闸管触发应用中,光纤设计类型为芯层直径200μm,包层直径250μm;采用阶跃折射率分布设计;芯层掺杂为锗氟共掺,芯层掺杂量为锗元素16mol%、氟元素5mol%;包层掺杂为氟元素,包层掺杂量为1mol%的光纤触发性能较优,适合光触发晶闸管的应用。     

断路器弹簧机构现场安装调试常见故障的处理方法

弹簧操动机构是断路器的核心元件,对电力系统的安全性有直接影响.本文对断路器弹簧机构的安装调试过程中常见故障进行分析,并且对故障解决方法进行探讨,旨在提高电力系统运行的安全性.     

Simulation Demonstration and Experimental Fabrication of a Multiple-Slot Waveguide

A multiple-slot waveguide is presented and demonstrated through theoretical simulation. Taking a double-slot waveguide as an example, the results show a nearly 30% enhancement of optical intensity compared with the traditional single-slot waveguide with the same slot gap width. Therefore, the E-field intensity of the slot can be increased by adding another smaller slot. A double-slot waveguide with oxide and air as low index slot materials is realized experimentally and the formation processes of the slots are analyzed.