Dispersion modeling and analysis for multilayered open coaxial waveguides

This paper presents a detailed modeling and analysis regarding the dispersion characteristics of multilayered open coaxial waveguides. The study is motivated by the need of improved modeling and an increased physical understanding about the wave propagation phenomena on very long power cables which has a potential industrial application with fault localization and monitoring. The electromagnetic model is based on a layer recursive computation of axial-symmetric fields in connection with a magnetic frill generator excitation that can be calibrated to the current measured at the input of the cable. The layer recursive formulation enables a stable and efficient numerical computation of the related dispersion functions as well as a detailed analysis regarding the analytic and asymptotic properties of the associated determinants. Modal contributions as well as the contribution from the associated branch-cut (non-discrete radiating modes) are defined and analyzed. Measurements and modeling of pulse propagation on an 82 km long HVDC power cable are presented as a concrete example. In this example, it is concluded that the contribution from the second TM mode as well as from the branch-cut is negligible for all practical purposes. However, it is also shown that for extremely long power cables the contribution from the branch-cut can in fact dominate over the quasi-TEM mode for some frequency intervals. The main contribution of this paper is to provide the necessary analysis tools for a quantitative study of these phenomena

Taxonomy, distribution and habitats of the Dytiscidae (Coleoptera) of Ethiopia

The 168 species of Dytiscidae known from Ethiopia are listed. For each species are given: original citation, synonyms, gross distribution, and distribution in Ethiopia with special reference to altitude and provinces. Besides literature records and museum specimens, 7300 individuals of 53 species collected by the junior author chiefly in the Arssi highlands in 1988 and 1989 are reported on. One syn. n. is presented: Rhantus longulus Regimbart, 1895 = Rhantus flavicollis Regimbart, 1887. Most of the 38 species endemic to Ethiopia occur only over 2000 m a.s.l., and the proportion of endemic species is highest in the Gondar, Shoa, Arssi and Bale provinces. The fauna of most provinces is poorly known. The Shoa province is best known, with 92 species recorded. In the Arssi highlands, the maximum local diversity was near 20 species in both lentic and lotic biotopes. The species richness of different supraspecific taxa is discussed and information is presented on co-occurrence of congeneric species and proportions of rare and frequent species

An approach to quantitatively estimate biodiversity preservation potential at forest stand level.

For efficient biodiversity preservation planning in forestry we need estimates of the actual and potential conservation value of individual stands. Our approach is based on a relatively good knowledge of the habitat requirements of regionally red-listed and threatened species. The estimation requires also knowledge of habitat availability in the surrounding landscape and the distance and species composition at biodiversity hot-spots nearby. The effects of long-time forest continuity on presumed dispersal-restricted organisms are built into our estimates. We argue that a broad taxonomic knowledge is necessary for an efficient planning of biodiversity preservation. Using only vascular plants and/or vertebrates as guidance will inevitably lead to biased estimates of conservational value at stand level

Environmental and Economic Benefits of using Multi-Echelon Inventory Control

Summary This master thesis evaluates the benefits of using multi-echelon control instead of single-echelon control of a multi-echelon inventory system. The multi-echelon inventory system studied in this thesis is a one-warehousemultiple- retailer inventory system. Multi-echelon inventory control is defined as a method to optimize the inventory system by taking the interdependencies between different stock locations in the system into consideration. Single-echelon control on the other hand is defined as optimizing each stock point in isolation and disregarding the interdependencies that exists. There has been extensive research in this area, and the fact that large potential cost reductions exist is well documented. However, little research has been performed to evaluate the environmental benefits that can be rendered by implementing multiechelon inventory control. The purpose of this master thesis is to evaluate the environmental and economic benefits of using a more advanced multi-echelon control method in a real case instead of the commercial single-echelon control method currently used. The hypothesis is that by fulfilling the fill-rates better, the amount of emergency orders can be reduced significantly, and by this also the total CO2-emissions can be reduced. The company studied is Lantmännen Maskin AB (LM) who provides their retailers in Sweden, Norway and Denmark with spare parts for agricultural machinery. The methodology used have been that of an operations research study where both mathematical models and simulations have been used. As a base model a commercial single-echelon model currently used at Lantmännen Maskin has been used, called SCP in this thesis. This model was compared to a more sophisticated multi-echelon model developed at Production Management, Lund University, Faculty of Engineering by Berling and Marklund (2012;2013), called MEM in this thesis. The approach of the project can be divided into five steps; first the data from the case company was gathered. Secondly, an existing simulation model was extended to fit the needs of this study. Thirdly, a stratified sampling was performed on the gathered data to find a representative sample of the case company’s items. Fourthly, the inventory system was optimized with SCP and MEM respectively. Finally, the results from the SCP-model and the MEM-model was simulated and compared. The results show that the average fill-rate was increased with 8.3% from 92.0% to 99.6%, the holding costs went down with 18.1% and the CO2- emissions were reduced with 57.0%. Further, the MEM model shows to be more consistent on achieving target fill-rate, whereas the SCP model varies a lot and delivers some fill-rates which are well below target and some that are above. Sensitivity analysis of the results concerning the CO2-emissions shows that for this case study the emergency orders sent by air do not affect the system very much. The reason is that the emergency transports by air are very few compared to the ones sent by truck. To really examine the benefits that could be achieved with the MEM model compared to the SCP model, a modified case set up was investigated where all emergency orders were assumed to be sent by air. In this case the reduction of CO2-emissions can be as high as 90%. Another important aspect found during this thesis concerning the CO2-emissions is that certain item attributes can make some items affect the CO2-emissions of the whole system in a non-proportional way. Two important factors were found, weight and mean demand. All CO2-emissions are linearly dependent on the weight, and consequently, this is a very important factor. But the second factor has even more influence. The reason for this is that if the mean demand for an item is high compared to other items then this item can have relatively many emergency orders even if the fill-rate is high. This was found during the study where one item, which had a high fill-rate, emitted CO2-emissions equivalent to 68% of the CO2-emissions of all of the studied items. Consequently, the conclusion from the results is that implementing the MEM model instead of the SCP model will reduce the environmental impact. Further, there are other aspects which are important to consider; firstly the MEM model will be more consistent on achieving target fillrates than the SCP model, secondly the reduction of CO2-will be greater in a system using air transport for emergency orders instead of land transport, and finally, the weight and mean demand are important aspects to consider if the environmental impact is to be reduced

The hoverfly Criorhina ranunculi – a biodiversity indicator at the landscape level?

The hoverfly Criorhina ranunculi – a biodiversity indicator at the landscape level? The hoverfly Criorhina ranunculi is rare and red-listed in Sweden, but it may be overlooked. I made a detailed inventory of the species in the parish of Stenbrohult, southern Sweden, where the species was found at nine localities in 2006, at one of these with at least ten individuals. The study area, with many other redlisted woodliving insects (Nilsson & Baranowski 2003), contains over 500 old hollow trees. I suggest that Criorhina ranunculi may indicate valuable areas for conservation action at the landscape level. The species was found at many flowering shrubs and trees (Salix, Malus, Prunus, Acer, Crataegus, Syringa) from the beginning of May to the beginning of June. Spring was relatively late in 2006

Parallel searching on m rays☆☆This research is supported by the DFG-Project “Diskrete Probleme”, No. Ot 64/8-3.

AbstractWe investigate parallel searching on m concurrent rays. We assume that a target t is located somewhere on one of the rays; we are given a group of m point robots each of which has to reach t. Furthermore, we assume that the robots have no way of communicating over distance. Given a strategy S we are interested in the competitive ratio defined as the ratio of the time needed by the robots to reach t using S and the time needed to reach t if the location of t is known in advance.If a lower bound on the distance to the target is known, then there is a simple strategy which achieves a competitive ratio of 9—independent of m. We show that 9 is a lower bound on the competitive ratio for two large classes of strategies if m⩾2.If the minimum distance to the target is not known in advance, we show a lower bound on the competitive ratio of 1+2(k+1)k+1/kk where k=⌈logm⌉ where log is used to denote the base-2 logarithm. We also give a strategy that obtains this ratio