Feed forward rings

Military and other critical (life-threatening/life-saving) systems require performance evaluations from a survivability, reliability, maintainability, and availability (SRMA) perspective. Applying SRMA concepts to commercial token passing ring local area networks (LANs) (e.g., IEEE-802.5, FDDI, SAE-9B) has uncovered several design issues that could impact the utility of these networks in a critical system. This article discloses a new architecture for token passing rings, called “feed forward rings” (FFR), which provides a significant improvement in system survivability, can eliminate “jabber mode” induced ring failures, and provides for passive optical bridging between rings.

The basic “feed forward” concept is that LANs, based on token passing protocols and utilizing multiple, physically separated, fiber optic rings, should have the serial data stream on each ring flowing in the same direction of rotation. This article provides qualitative observations on the performance of current commercial rings and discusses the advantages of several FFR topologies. Implementation issues related to FFRs are also discussed. It is recommended that FFR alternatives to counterrotating rings (CRR) with separated cables be considered for inclusion in LAN standards.     

Network survivability analysis

Advances in fiber optic and local area network (LAN) technologies are providing system designers with many new options for interconnecting computer equipment. A recurring problem for military system designers, who are end-users of a LAN standard, is implementing LANs so that the survivability, reliability, maintainability, and availability (SRMA) of a system is maximized. LAN standards working groups are currently making design decisions about topologies, components, and protocols that directly affect the SRMA of the end-user's system. This article focuses on a new analytic technique, called “network survivability analysis,” that provides the mathematical tools needed to compare the survivability of arbitrary network topologies. For background, several network metrics are described and their limitations for LAN standards development identified. Network survivability is defined, and several token-passing ring case examples are analyzed. The primary strength of network survivability analysis is that it can be used to provide a quantitative comparison among LAN topologies without knowledge of the end-user's equipment, systems, or environments.     

Network survivability analysis

Advances in fiber optic and local area network (LAN) technologies are providing system designers with many new options for interconnecting computer equipment. A recurring problem for military system designers, who are end-users of a LAN standard, is implementing LANs so that the survivability, reliability, maintainability, and availability (SRMA) of a system is maximized. LAN standards working groups are currently making design decisions about topologies, components, and protocols that directly affect the SRMA of the end-user's system. This article focuses on a new analytic technique, called “network survivability analysis,” that provides the mathematical tools needed to compare the survivability of arbitrary network topologies. For background, several network metrics are described and their limitations for LAN standards development identified. Network survivability is defined, and several token-passing ring case examples are analyzed. The primary strength of network survivability analysis is that it can be used to provide a quantitative comparison among LAN topologies without knowledge of the end-user's equipment, systems, or environments.     

Modeling of the dolphin’s clicking sound source: The influence of the critical parameters

A physical and a mathematical models of the dolphin’s source of echolocation clicks have been recently proposed. The physical model includes a bottle of pressurized air connected to the atmosphere with an underwater rubber tube. A compressing rubber ring is placed on the underwater portion of the tube. The ring blocks the air jet passing through the tube from the bottle. This ring can be brought into self-oscillation by the air jet. In the simplest case, the ring displacement follows a repeated triangular waveform. Because the acoustic pressure gradient is proportional to the second time derivative of the displacement, clicks arise at the bends of the displacement waveform. The mathematical model describes the dipole oscillations of a sphere “frozen” in the ring and calculates the waveform and the sound pressure of the generated clicks. The critical parameters of the mathematical model are the radius of the sphere and the peak value and duration of the triangular displacement curve. This model allows one to solve both the forward (deriving the properties of acoustic clicks from the known source parameters) and the inverse (calculating the source parameters from the acoustic data) problems. Data from click records of Odontocetes were used to derive both the displacement waveforms and the size of the “frozen sphere” or a structure functionally similar to it. The mathematical model predicts a maximum source level of up to 235 dB re 1 μPa at 1-m range when using a 5-cm radius of the “frozen” sphere and a 4-mm maximal displacement. The predicted sound pressure level is similar to that of the clicks produced by Odontocetest.     

Ultra-Low-Emittance Light Sources

In this special issue, we delve into the subject of ultra-low-emittance storage ring light sources. While these go under various names, such as “diffraction-limited storage rings” and “ultimate storage rings,” perhaps the most universally applicable name is “fourth-generation storage rings” or 4GSRs. As this name suggests, these rings promise improvements in X-ray brightness that are comparable to those seen in the transition from second- to third-generation rings.     

一种通用的时隙环网时隙调度机制

提出一种新颖的时隙环网公平机制——环分布式时隙调度(DTSR), 该机制是分布式的, 适合所有目的节点剥离业务的时隙环网。DTSR通过在单向信道上循环传输的时隙控制头(TCH)内增加一个简单的域, 实现对环上“饿死”节点信息的动态收集, 协调各个节点占用资源的时间, 确保各节点之间的公平性; 在发现环上有“饿死”节点后, DTSR利用时隙环网空间重用的特性, 调度相关节点向不经过“饿死”节点的其他节点发送数据, 充分利用了环网资源; 此外DTSR机制具有良好的算法收敛性, 且接入时延较传统算法更小。最后,对DTSR的性能进行仿真, 并和几个典型的时隙环网的公平机制进行了比较。     

A New 1×K Tunable Multi-wavelength Router and its Features

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｗａｖｅｌｅｎｇｔｈｒｏｕｔｅｒｓ (ＷＲｓ)ａｒｅｋｅｙｄｅｖｉｃｅｓｉｎｗａｖｅｌｅｎｇｔｈ ｒｏｕｔｉｎｇａｌｌ ｏｐｔｉｃａｌｎｅｔｗｏｒｋｓ.Ｒｅｃｅｎｔｌｙ ,ｒｅｓｅａｒｃｈｆｏｒｔｈｅＷＲｓｈａｓｂｅｅｎｏｎｅｏｆｈｏｔｓｐｏｔｓｉｎｗａｖｅｌｅｎｇｔｈｄｉｖｉｓｉｏｎｍｕｌｔｉｐｌｅｘｉｎｇ (ＷＤＭ )ｎｅｔｗｏｒｋｔｅｃｈｎｏｌｏｇｉｅｓ[1,2 ] .Ｂｙｄｉｆｆｅｒｅｎｔｒｏｕｔｉｎｇｐａｔｔｅｒｎｓ,ｔｈｅＷＲｓｃａｎｂｅｄｉｖｉｄｅｄｉｎｔｏｔｗｏｋｉｎｄ…     

A New 1×K Tunable Multi-wavelength Router and its Features

Tunable wavelength routers (TWRs) for multiple wavelength selection are key devices in dynamic wavelength-routing wavelength division multiplexing (WDM) networks. In this paper, by cascading conventional 2×2 TWRs, a new 1×K TWR is proposed for large-scale dynamic wavelength-routing WDM networks. When the cascading numbers are smaller, the 1×K TWR can be directly applied to networking WDM networks. When the cascading numbers are larger, the 1×K TWR can be carried out by the integrating method and be extensively used to networking various multi-wavelength optical networks by the way of “EDFA+TWR”. Though the cascading method proposed is based on the acousto-optic TWRs, it can be also applied to cascading other kinds of TWRs.     

Performance evaluation of survivable WDM based SANs in a metro ring network

Storage area networks (SANs) are an essential part of enterprise computing today. There is no comprehensive business continuity plan without SANs in the picture. This paper proposes and evaluates network survivability of optical paths in wavelength division multiplexing (WDM) based storage area networks in a metro ring network. The paper begins with a background on network survivability in metro WDM ring network. Subsequently, the network and node architectures along with their medium access control (MAC) protocols are described. In this work, one link failure (a single cable cut) in metro WDM based SANs in a ring network architecture is considered. Performance evaluation for network survivability in metro WDM SAN is carried out by means of discrete-event computer simulation. Network throughput and packet delay are investigated. The network performance is evaluated for asymmetric (unbalanced) traffic scenarios under Poisson and self-similar traffic.     

On synchrotron radiation in non-uniform magnetic fields

We study the conditions in which a charged particle in an inhomogeneous magnetic field (particularly at the edges of a “long” uniform magnet or in a “short” magnet) can emit synchrotron radiation with a spectrum extending beyond the “critical frequency”. We suggest that this effect should be clearly visible (and also useful) in the case of very high energy proton storage rings.     

Opportunities for wavelength conversion with on‐chip diamond ring resonators

Recent progress in the fabrication of high‐quality synthetic diamond and of diamond waveguide structures has enabled photonics researchers to start exploiting the unique optical properties of diamond for various applications. In this article the promise of on‐chip diamond ring resonators for wavelength conversion based on Kerr and Raman‐resonant four‐wave mixing is numerically demonstrated. After examining to what extent both dispersion‐engineered phase‐matching and “automatic” quasi‐phase‐matching can be established in diamond ring converters, it is shown that such a “double‐matching” approach can yield high conversion efficiencies for a wide range of wavelengths in the near‐infrared/mid‐infrared domain, as well as in the ultraviolet/visible domain.     

Capacity enhancement in packet switched slotted ring wavelength division multiplexed transport networks

In this paper, all-optical WDM networks based on a slotted multichannel ring topology have been investigated. The nodes are equipped with one fixed-wavelength receiver, wavelength-tunable transmitter and provide packet-mode transport in WDM network. The topology provides one logical channel to be associated with each destination node. Each channel is shared in statistical time division by all nodes transmitting to a given destination. The capacity enhancement has been demonstrated by comparing all optical WDM network by increasing the number of nodes. It is concluded that by increasing the number of nodes in the topology, the token queue length capacity, the token arrival rate are increased and the token arrival period is decreased which results in overall increase in the performance and capacity of the logical WDM network.     

Small World Properties Generated by a New Algorithm Under Same Degree of All Nodes

Based on the model of the same degree of all nodes we proposed before, a new algorithm, the so-called “spread all over vertices” (SAV) algorithm, is proposed for generating small-world properties from a regular ring lattices. During randomly rewiring connections the SAV is used to keep the unchanged number of links. Comparing the SAV algorithm with the Watts-Strogatz model and the “spread all over boundaries” algorithm, three methods can have the same topological properties of the small world networks. These results offer diverse formation of small world networks. It is helpful to the research of some applications for dynamics of mutual oscillator inside nodes and interacting automata associated with networks.     

Routing Algorithms for Translucent Networks

Abstract

After a discussion on hybrid optical-electronic networks, the so-called “translucent” networks, this article presents routing algorithms for an efficient use of resources in dynamic traffic demands.     

Super-FM and analogue-to-digital-conversion technologies for next-generation wireless access in optical fibres

Fibre-in-the-loop (FITL) or hybrid fibre coaxial (HFC) networks are the ideal transmission infrastructure for next-generation wireless communication networks, such as digital microcells, personal communication networks (PCNs) and wireless local area networks (LANs). In this paper, the feasibility of two cost-effective optical fibre transmission technologies, super-frequency-modulation (FM) and analogue-to-digital conversion, for wireless access in broadband optical fibres are experimentally demonstrated. Associated circuit and system implementation issues are investigated. Furthermore, by using a statistical model of multiple access in different microcellular environments, we find that both transmission technologies can meet the dynamic range requirements with a significant safe margin.     

Theoretical analysis of the experimental UV-Vis absorption spectra of some phenolic Schiff bases

The time-dependent density functional theory (TDDFT) was applied in conjunction with the natural bond orbital analysis to examine the UV-Vis properties of 10 phenolic Schiff bases. The calculations were performed with different functionals, but main discussion refers to results obtained at the B3LYP/6-311+G(d,p) level of theory. The approach based on the natural localised molecular orbital clusters indicates similar behaviour for majority of examined compounds. The HOMO (“highest occupied molecular orbital”) cluster is delocalised over the ring which is electron richer, the HOMO-1 cluster is spread over the other ring, whereas the LUMO (“lowest unoccupied molecular orbital”) cluster is situated on the imino group. The two bands at long wavelengths correspond to the HOMO → LUMO and HOMO-1 → LUMO transitions, i.e. from both A and B rings to the imino group. The next band originates from a transition from the imino group to the imino group. The band at the smallest wavelengths originates from a transition from the A ring to the A ring, or from the B ring to the B ring. Our findings are in very good agreement with the existing literature data.     

From Atoms to Aerosols: A Workshop on Opportunities for Chemical Physics at the ALS

Can the capabilities of the “big three” synchrotron radiation facilities still be “big” in the future? The three third-generation synchrotron radiation facilities — ESRF, APS, and SPring-8 — were inaugurated with performances significantly beyond that of smaller, lower-energy machines. For the past few years, though, mid-scale (～3 GeV) low-emittance machines, both operating and planned, have been gaining ground, in part taking advantage of the technological developments at the larger rings. The future competitiveness of the big three was one of the issues addressed during the ESRF/APS/SPring-8 Three-Way Meeting.     

Practical considerations in determining the installed cost of LAN optical fiber cables

The development and introduction of fiber-optical-based local area networks (LANs) has required system designers and end users to seriously evaluate their cost-effectiveness. The installed optical fiber cable represents a significant part of the system cost. This article reviews current and future costs of the media.     

Practical considerations in determining the installed cost of LAN optical fiber cables

The development and introduction of fiber-optical-based local area networks (LANs) has required system designers and end users to seriously evaluate their cost-effectiveness. The installed optical fiber cable represents a significant part of the system cost. This article reviews current and future costs of the media.     

Theory of the Kapitza-Dirac diffraction effect

We treat the Kapitza-Dirac diffraction effect observed recently by Batelaan et al. using a newly developed nonperturbative quantum-field scattering theory. Our theory shows that an electron beam passing perpendicularly through a focused standing light wave can produce diffraction patterns. Our theory predicts (1) the minimum value of the ponderomotive energy is (Planck's over 2 pi omega)(2)/m(e)c(2), (2) the critical laser intensity above which the first pair of electron diffraction peaks will occur, and (3) the existence of sidebands in the electron spectra separated far from the central band by a momentum of several hundred photons. Our theory provides a unified explanation of the experimental results of Bucksbaum et al. and Batelaan et al.