Software-defined optical networks (SDONs): a survey

This paper gives an overview of software-defined optical networks (SDONs). It explains the general concepts on software-defined networks (SDNs), their relationship with network function virtualization, and also about OpenFlow, which is a pioneer protocol for SDNs. It then explains the benefits and challenges of extending SDNs to multilayer optical networks, including flexible grid and elastic optical networks, and how it compares to generalized multi-protocol label switching for implementing a unified control plane. An overview on the industry and research efforts on SDON standardization and implementation is given next, to bring the reader up to speed with the current state of the art in this field. Finally, the paper outlines the benefits achieved by SDONs for network operators, and also some of the important and relevant research problems that need to be addressed.     

A new mesoporous FeBO3 material having dominant surface magnetism

A new mesoporous iron(III) borate material has been synthesized hydrothermally by using supramolecular assembly of cationic (cetyltrimethylammonium bromide, CTAB) or anionic (sodiumdodecyl sulfate, SDS) surfactant as structure directing agent (SDA) during co-condensation of Fe(III) and H₃BO₃ under controlled pH condition. Powder X-ray diffraction, N₂ sorption, HRTEM, FE-SEM-EDS, AAS, FT-IR and UV–Vis spectroscopic tools, Mössbauer and magnetization measurements are used to characterize the nanostructure, porosity, morphology, chemical composition and magnetic properties. Template molecules can be removed from the as-synthesized material by two consecutive HCl–EtOH extraction and the template-free sample showed good surface area with a peak pore width of ca. 2.6 nm. Spectroscopic results suggested the octahedral coordination of Fe(III) in the FeBO₃ framework. Magnetic measurements suggested the coexistence of antiferromagnetic core and the glassy magnetic behavior. The glassy magnetic behavior is ascribed to the dominant surface magnetism for mesoporous FeBO₃. Acid catalytic properties of this material in liquid phase benzylation of mesityline and anisole have been studied.     

Hand Gesture Recognition Based Omnidirectional Wheelchair Control Using IMU and EMG Sensors

This paper presents a hand gesture based control of an omnidirectional wheelchair using inertial measurement unit (IMU) and myoelectric units as wearable sensors. Seven common gestures are recognized and classified using shape based feature extraction and Dendogram Support Vector Machine (DSVM) classifier. The dynamic gestures are mapped to the omnidirectional motion commands to navigate the wheelchair. A single IMU is used to measure the wrist tilt angle and acceleration in three axis. EMG signals are extracted from two forearm muscles namely Extensor Carpi Radialis and Flexor Carpi Radialis and processed to provide Root Mean Square (RMS) signal. Initiation and termination of dynamic activities are based on autonomous identification of static to dynamic or dynamic to static transition by setting static thresholds on processed IMU and myoelectric sensor data. Classification involves recognizing the activity pattern based on periodic shape of trajectories of the triaxial wrist tilt angle and EMG-RMS from the two selected muscles. Second order Polynomial coefficients extracted from the sensor trajectory templates during specific dynamic activity cycles are used as features to classify dynamic activities. Classification algorithm and real time navigation of the wheelchair using the proposed algorithm has been tested by five healthy subjects. Classification accuracy of 94% was achieved by DSVM classifier on ‘k’ fold cross validation data of 5 users. Classification accuracy while operating the wheelchair was 90.5%.     

Progress in the understanding of NiTi shape memory alloys

Shape memory alloys (SMAs) are a special class of metallic materials which respond with a considerable change in their properties to small changes in temperature or stress. The SMAs offer two interesting characteristics, viz., shape memory effect (SME) and superelasticity (SE), also called pseudoelasticity which make them attractive for applications in engineering and biomedical fields. Among the various SMAs, NiTi base alloys have been the most commercially exploited ones because of their superior SME and SE, mechanical properties, corrosion resistance and biocompatibility. Since the pioneering discovery of NiTi SMA in early 1960s, significant progress has been made in the processing and understanding of the behaviour of these alloys. In spite of these efforts, the NiTi SMAs continue to offer challenges to the scientists and engineers, and new findings are being made continuously. This paper provides an overview of the developments in NiTi SMAs.     

城域网和接入网发展需要的低水峰单模光纤

密集波分复用(DWDM)的出现扩大了长途传输网的容量,但是DWDM技术的复杂性和使用了昂贵的器件,限制了DWDM在城域网的应用.最新研制的光纤,其在整个宽工作带,包括在(1 380±3) nm上都具有低水峰.低水峰光纤与粗波分复用(CWDM)系统比用标准单模光纤(SMF)的同一系统所用的信道间隔宽33%.经过恶劣的环境试验证明,低水峰光纤具有稳定的抗氢气引起的衰减性能,可确保现场安装的低水峰光纤光缆长期可靠地工作.由于低水峰光纤具有优异的弯曲敏感性,使其与最近研制的宽带接入技术,即所谓的光纤到驻地(FTTP)完全相适应.     

拉丝环境湿度对高强度光纤动态疲劳的影响

文章研究了高强度石英玻璃光纤的动态疲劳性能与拉丝环境相对湿度的函数关系。光纤是在采用石墨感应加热炉加热,并在控制温度、相对湿度和拉丝环境尘埃粒子数的条件下拉制的。所谓拉丝环境指的是从感应加热拉丝炉至涂覆点之间的空间。通常,人们采用两种不同的加载方式,即拉伸和两点弯曲来测量拉制的光纤的动态疲劳。业已发现,拉丝湿度对用张力法加载方式测得的光纤的动态疲劳起着决定性的影响。     

Comparative structural morphometry and elemental composition of three marine sponges from Western Coast of India

Three marine sponges Halichondria glabrata, Cliono lobata, and Spirastrella pachyspira from the western coastal region of India were compared for their morphometry, biochemical, and elemental composition. One‐way analysis of variance was applied for spicule morphometry results. Length, width, and length:width ratio were calculated independently. The ratio of length:width varied from 35 to 42 among the grown samples, which remained in the range of 10–22 in young sample at the beginning of studies. However, no significant change was observed in spicule width compared to length. Elemental compositions of marine sponges were determined by field emission gun‐scanning electron microscope. Scanning electron microscopy data revealed that the spicules of all the three sponges were mostly composed of O (47–56%) and Si (30–40%), whereas Al (14.33%) was only detected in the spicules of C. lobata. Apart from these, K, Ni, Ca, Fe, Mg, Na, and S were additionally detected in all the three samples. Presence of heavy metals in the sponges was analyzed by inductively coupled plasma‐atomic emission spectroscopy. Results showed that iron was present in a large amount in samples, followed by zinc, lead, and copper. Microsc. Res. Tech. 77:296–304, 2014. © 2014 Wiley Periodicals, Inc.     

Continuous‐discrete filters for bearings‐only underwater target tracking problems

In this work, we develop a continuous‐discrete shifted Rayleigh filter (CD‐SRF) and a continuous‐discrete sparse‐grid Gauss‐Hermite filter (CD‐SGHF) for a real‐life passive underwater bearings‐only target tracking problem. The stochastic difference equation describing the process model is derived from its continuous equivalent using Ito‐Taylor expansion of order 1.5. The performance of the proposed filters is compared in terms of root mean square error (RMSE), track divergence and computational time. For a fair comparison, popular filters like the unscented Kalman filter (UKF), cubature Kalman filter (CKF) and Gauss–Hermite filter (GHF) are implemented. The effect of initial uncertainty, measurement noise covariance and sampling time on filtering accuracy is also studied. Finally, RMSEs of all the filters are evaluated in comparison with the Cramer–Rao lower bound (CRLB). From simulation results, it was observed that CD filters performed with higher accuracy than their discrete equivalents, with CD‐SRF proving to be the most accurate among all the filters.     

A transmission electron microscopy study of WC-10Co cemented carbides with modified hard and binder phases

The alloy design of WC-10Co cemented carbide, modified with addition of a hard carbide phase, TiC, and with Ni and Mo in the binder phase, has been highlighted by the authors in a number of publications. The present article deals with the fine microstructural features of various phases in such cemented carbides. WC grains in all the investigated cemented carbide compositions appear to develop straight facets during sintering because of their anisotropic nature. In contrast, the TiC phase is characterized by its rounded shape. Dislocations are present in both WC and TiC grains, being of lesser density in the latter. The binder phase is always associated with stacking faults. The nature of the hard phase/binder interfaces has been found to be dependent on the binder phase chemistry. The observed changes in microstructures and mechanical properties have been correlated with the wettability and solubility of the hard phases in the binder melt, and with the different strengthening mechanisms in the binder phase.     

FPGA based area efficient RS(23, 17) codec

Generally in digital communication systems and storage mediums, Reed–Solomon (RS) codes are employed to detect and correct errors. RS code is a promising code for Ultra Wide Band (UWB) which is ideally suitable for wireless application. Design of compact, high-speed and low-power RS(23, 17) code is challenging for today’s wireless communication systems. Here, an optimization algorithm is introduced which is very simple and it is employed to reduce the number of XOR gates required to design constant Galois Field (GF) multipliers. In this paper, a compact RS(23, 17) encoder and decoder circuit is designed and implemented for Ultra Wide Band(UWB) application. The number of two input XOR gates is reduced by 29.27 (20.00) and 56.10 (66.15) % respectively for local and global optimization compared to unoptimized RS encoder (syndrome block) without increasing its delay. The proposed algorithm is also employed to design the RS(204, 188) and RS(255, 223) encoder. All designs are simulated and synthesized for Vertex4 FPGA platform. Proposed algorithm is also used for the design of Chien Search and Forney blocks. Implemented RS(23, 17) codec requires lesser number of slices and LUTs over the unoptimized RS codec. The synthesis results reflect that the proposed design is suitable for resource constraint applications.