Configuring Traffic Grooming VPλNs

A VPN is an optical virtual private network (oVPN) built of wavelength paths within a multihop wavelength routing (WR) dense wavelength division multiplexing (DWDM) network. An efficient and general graph-theoretic model (the wavelength-graph (WG)) has been proposed along with an integer linear programming (ILP) formulation of setting up VPNs with given traffic requirements over a given WR-DWDM network with two protection scenarios. Here, we have exploited the advantages of traffic grooming, i.e., numerous traffic streams of a VPN can share a wavelength path. We have also generalized the model for setting up VPNs over a WR-DWDM system where multiple VPNs can share a single wavelength path. The objective of the optimization is in all cases to reduce resource usage at upper (electrical) layers (i.e., to reduce the load of the virtual routers), subject to constrained amount of capacity of each wavelength channel and limited number of wavelengths. Here, we propose and compare three basic methods for configuring oVPNs and investigate various parameter settings.     

High performance liquid chromatographic detection of a strongly retained pigment fraction in Capsicum annuum

A new colour pigment fraction was detected in Capsicum annuum by high performance liquid chromatography. Surprisingly the pigment was strongly bound both to silica and octadecylsilica surfaces indicating that its molecular mass is probably high. Peak purity tests proved that the fraction is not homogeneous and the degree of inhomogeneity depends on the wavelength used for the peak purity test. The spectra taken at one minute intervals of the peak were strikingly different supporting the above conclusions. It is possible that this highly lipophilic pigment is a secondary product of the ripening and processing procedures and is a mixture of individual pigments covalently bound to each other.     

Research Needs and Challenges in Application of Computer and Information Sciences for Industrial Engineering

By invitation from the Editor of IIE Transactions, a research forum was established in 1987 to develop and prepare this article. The objective: to write on the directions, needs and challenges for research by the IE com-munity in applying computer and information sciences. The motivation: realizing the major advancements in computer and information sciences in the recent decade and their significant impact on the IE profession, it is vital to examine how IE research activities can respond effectively to current and emerging needs. This article is viewed as a useful contribution to such an examination.

Forum members were invited from academia, government and industry based on their experience in and commitment to research in this area. The forum was chaired by Shimon Y. Nof and the members are the co-authors of this article.

Forum members communicated and deliberated throughout 1987 and met for a review and planning session dur-ing the IIE Conference in Washington, D.C. in May, 1987 (Forum, 1987). The following article summarizes the contributions and recommendations of the forum members, and was reviewed by four guest reviewers. The re-viewers, invited by the Editor, have provided comments that have been incorporated into this article     

Engineering model of a passive planar air breathing fuel cell cathode

The behavior of an air breathing fuel cell (ABFC) operated on dry-hydrogen in dead-ended mode is studied using theoretical analysis. A one-dimensional, non-isothermal, combined heat and mass transport model is developed that captures the coupling between water generation, oxygen consumption, self-heating and natural convection at the air breathing cathode. The model is validated against planar ABFC experimental measurements over a range of ambient temperatures. The model confirms the strong effect of self-heating on the water balance within passive ABFCs. Model analysis provides several conclusions: (1) thermal runaway caused by inadequate heat rejection predominantly limits ABFC performance. (2) The natural convection boundary layer represents a significant barrier to cathode mass and heat transfer. (3) Because the mass and heat transport numbers associated with natural convection are small, even slight forced convection dramatically affects cell behavior. (4) Performance optimization requires maximizing heat rejection while minimizing flooding. Decoupling the latter two phenomena is challenging due to the exponential relationship between water vapor saturation and temperature.     

Beurteilung von hals-verbindungen

QUALIFICATION OF HALS COMPOUNDS A complex method of examination has been developed suitable for the qualification of light stabilizers; by this method, according to experience, the efficacy of HALS compounds can be extensively and expediently characterized. Several light stabilizers of the HALS-type were examined and qualified, used alone or together with a UV-absorber. It has been found that, when selecting the appropriate structure for a given polymer, the weatherability of polyolefine foils is effectively increase to six-eightfold; the increase is even tenfold when the stabilizer is combined with a benzophenone-type compound. As a utilization of these experiences, a contract with the industry, led to the production of an LDPE based agricultural foil with a life-time of several years.     

The reinitiation mechanism of HCl catalysis in PVC degradation

Summary The effect of HCl on the thermal degradation of PVC has been studied. Changes in UV and visible spectra and kinetics of HCl loss indicate that HCl is able to reinitiate the allyl-activated zip elimination by proton exchange with polyenes. Also polyene-consuming secondary reactions are accelerated by HCl.     

Thermooxidative degradation of PVC in solution in the presence of metal stearate stabilizers

Detailed research has been carried out to determine the effect of metal stearates (PbSt₂, CdSt₂, BaSt₂, CaSt₂, and ZnSt₂) on the thermooxidative degradation of PVC in inert dilute solution. The induction periods of free HCl evolution increase in the presence of PbSt₂, CdSt₂, CdSt₂, BaSt₂, and CaSt₂, while ZnSt₂, due to ZnCl₂ formation, leads to fast HCl loss without induction period. The induction periods are much shorter than those obtained during thermal degradation, but the relative order of effectiveness of these stabilizers is the same as in inert atmosphere: PbSt₂ > CdSt₂ > BaSt₂ > CaSt₂ > ZnSt₂. After the induction period, the initial rates of free HCl evolution decrease as metal stearate concentrations increase. Surprisingly, this dependence is independent of the kind of metal. At higher stabilizer concentrations, the initial rates of free HCl loss during the thermooxidative degradation approach the initial dehydrochlorination rate of thermally degraded PVC. As UV and visible spectra indicate, there is a sharp change in the normalized integral absorption versus time plots at the end of the induction periods in the presence of PbSt₂, CdSt₂, and BaSt₂. Based on these experimental results, it has been concluded that effective metal stearates have manifold roles in the course of PVC stabilization under thermooxidative conditions. The main role of these compounds is not the replacement of labile structures and HCl-scavenging, but the blocking of the rapid zip-elimination is the most important event of the stabilization process. However, this blocking is reversible, which becomes effective mainly right after the consumption of the metal soaps (reversible blocking mechanism). Another important effect of these stabilizers is that they destroy peroxides and/or peroxy radicals (antioxidant effect).