On routing in large WDM networks

An important problem in WDM network design is to construct a logical topology and determine an optimal routing over that topology. Mixed Integer Linear Program (MILP) formulations to generate optimal solutions for this problem have been presented. Such formulations are computationally intractable, even for moderate sized networks. A standard approach is to decouple the problem of logical topology design and the problem of routing the traffic on this logical topology. Heuristics for finding the logical topology exist and a straight-forward linear program (LP), based on the node-arc formulation can be used to solve the routing problem over a given logical topology. We have found that such LP formulations become computationally infeasible for large networks. In this paper, we present a new formulation, based on the arc-chain representation, for optimally routing the specified traffic over a given logical topology to minimize the congestion of the network. We have used the revised simplex method incorporating an implicit column generation technique, and exploited the special Generalized Upper Bounding structure as well as the possibility of eta-factorization for efficiently updating the dual variables and finding the solution. Experimental results on a number of networks demonstrate the suitability of this approach.     

Rheological properties of wheat flour and quality characteristics of pan bread as modified by partial additions of wheat bran or whole grain wheat flour

The use of bran and whole grain flour changes dough rheology and causes difficulties in manufacturing bakery products. The aim of this study was to analyse the influence of substituting refined wheat flour (WF) by wheat bran (WB; 5%, 10%, 20%, 30% and 40%) or whole grain wheat flour (WGWF; 10%, 20%, 30%, 40% and 50%) on dough rheological properties and pan bread quality characteristics. The addition of WB and WGWF increased water absorption and resistance to extension and decreased stability, extensibility and peak viscosity. Effects with WB were more pronounced. The presence of WB or WGWF increased crumb moisture content, firmness and hardness and decreased specific volume of pan bread. It is important to set new farinographic and extensographic standards when using WB and WGWF, allowing for a correct correlation between rheology and quality characteristics of bakery products, as the same standards used for WF are not valid.     

General Description and Assessment Concept for Magnetic Field Distributions Caused by Switchgear Installations

The subject of power frequency magnetic fields has become very popular in recent years. This is mainly due to two facts: the increasing usage of display units which represent a very sensitive interference victim and the increasing public concern with respect to adverse health effects caused by those fields. Switchgear installations act as one of the prominent sources of power frequency magnetic fields and, therefore, knowledge of the fields produced by them is required in order to assess any potential effects. On the other hand, switchgear installations are often very individual ones with consequently very individual magnetic-field distributions. This basically requires an individual investigation of each installation-a procedure which, in practice, has been shown as a very involved and cost consuming one. This paper describes a basic assessment method which can be used to evaluate magnetic-field distributions around switchgear installations from a general point of view, where the emphasis is on systems with a medium voltage level. The resulting field distributions can be utilized to derive and to determine appropriate distances required between switchgear and areas under consideration in order to comply with any limits concerning people or equipment     

Analysis of glycerophosphonolipids in egg yolk

Glycerophosphonolipids are a relatively unknown class of polar lipids. Little information is available on any special biological function of these substances or specific technological use for them. Since glycerophosphonolipids have been reported to occur in egg yolk, further studies are needed in order to determine their relevancy. However, analysis of these lipids is rather difficult, due both to their chemical similarity to phospholipids and the lack of commercially available reference substances. Therefore, a reference substance for phosphono analogues of phosphatidylethanolamine (PnE)—1,2-dioctadecanoyl-glycero-3-aminoethylphosphonate—has been synthesized and an HPLC/ELSD method to separate PnE from its phosphonoanalog was developed. Although the present results showed no evidence of glycerophosphonolipids in egg yolk (limit of detection <0.02% for PnE), the spectroscopic data gathered here do point to an approach for further analysis of glycerophosphonolipids. Furthermore, a characteristic ESI–MS² fragmentation pattern for PnE was established, which can be used as a “fingerprint” for the identification of this substance in other biological systems. It was found to be characteristic for a fatty acid fragment to be split off as an internal anhydride (ketene) [M–H–RCH=C=O]⁻ along with the whole fatty acid fragment [M–H–RCH₂COOH]⁻ in the negative ion mode. In the positive mode, there was a selective loss of only the head group of the phosphonolipid [PO₃H₂–C₂H₄–NH₃]⁺, resulting in the so-called “diacylglycerol-like fragment ion” [DAG]⁺.     

香辛料提取物及其在肉制品抑菌防腐中的应用进展

肉品腐败被认为是食品工业中最重要的经济和健康问题之一,而抑菌防腐剂的应用是阻止化学变质和微生物腐败的主要手段.由于消费者对化学防腐剂安全性的担忧,相对更为安全的天然或"绿色"的替代品越来越受到关注.研究表明,天然香辛料提取物具有显著的抑菌性和抗氧性,其作用机理是基于对微生物细胞壁的降解、细胞膜的破坏、膜蛋白的损伤,以及...     

Multi-Agent Radio Resource Allocation

This paper presents a spatially distributed and dynamic billing, pricing and allocation mechanism for which a user terminal requires Cognitive Radio abilities. That is, the Cognitive Radio abilities will be applied to the economical environment. The radio resource goods are allocated to the users by a multi-unit sealed-bid auction. Intelligent entities like the bidding strategy have to represent operator’s and users’ behavior and to make decisions for them in order to fulfill the preferences and QoS. The main functionalities, used to execute the dynamic auction sequence and located in the MAC are described, assuming the entities possess Cognitive Radio abilities.

Resource efficient network design and traffic grooming strategy with guaranteed survivability

In WDM networks, path protection has emerged as a widely accepted technique for providing guaranteed survivability of network traffic. However, it requires allocating resources for backup lightpaths, which remain idle under normal fault-free conditions. In this paper, we introduce a new design strategy for survivable network design, which guarantees survivability of all ongoing connections that requires significantly fewer network resources than protection based techniques. In survivable routing, the goal is to find a Route and Wavelength Assignment (RWA) such that the logical topology remains connected for all single link failures. However, even if the logical topology remains connected after any single link fault, it may not have sufficient capacity to support all the requests for data communication, for all single fault scenarios. To address this deficiency, we have proposed two independent but related problem formulations. To handle our first formulation, we have presented an Integer Linear Program (ILP) that augments the concept of survivable routing by allowing rerouting of sub-wavelength traffic carried on each lightpath and finding an RWA that maximizes the amount of traffic that can be supported by the network in the presence of any single link failure. To handle our second formulation, we have proposed a new design approach that integrates the topology design and the RWA in such a way that the resulting logical topology is able to handle the entire set of traffic requests after any single link failure. For the second problem, we have first presented an ILP formulation for optimally designing a survivable logical topology, and then proposed a heuristic for larger networks. Experimental results demonstrate that this new approach is able to provide guaranteed bandwidth, and is much more efficient in terms of resource utilization, compared to both dedicated and shared path protection schemes.     

Algorithms for Dynamic Routing in All-Optical Networks

In this paper, we have studied a number of algorithms for routing in all-optical wavelength routed networks. We have considered situations where a lightpath is dynamically created in response to a request for communication and the WDM channels constituting the lightpath are reclaimed when the communication is over. We have looked at two schemes for dynamic wavelength allocation. In the first scheme we have assumed the existence of a central agent to maintain a database of existing lightpaths where the central agent attempts to generate a new lightpath in response to a request for communication. In the second scheme, we attempt to generate a new lightpath using a distributed algorithm. In the first scheme we have exploited the existence of multiple paths between any pair of nodes in a network in order to reduce the blocking probability. For the second scheme, we have proposed three distributed strategies to determine, if possible, a lightpath when there is a request for communication. Each of these strategies have their advantages and disadvantages in terms of the expected blocking probability and the set-up time. We have studied the performances of both the schemes using Monte Carlo simulation.