Optimum field theory design of broad-band E-plane branchguide phase shifters and 180° couplers

Optimum rectangular waveguide E-plane branch guide phase shifters and 180° branch guide couplers are designed with the rigorous method of field expansion into normalized eigenmodes. The design includes both the higher order mode interaction between the step discontinuities and the finite step and branch heights. The phase shifter design applies the Schiffman principle to branch guide couplers where two ports are short-circuited. The 180° coupler design combines the advantage of the broadband potential of multiple-branch couplers with the low-insertion-loss qualities of E-plane stub-loaded phase shifters. A computer-optimized phase shifter prototype for the waveguide Ku-band (12-18 GHz) shows a 90°±1° differential phase shift with reference to an empty waveguide within about 23% bandwidth. Five-branch three-stub coupler prototypes, designed for 3±0.2 dB coupling, for the waveguide Ku- and Ka-bands (26-40 GHz) achieve a 180°±1° differential phase shift at the output ports within about 19% bandwidth, as well as more than 30 dB isolation and return loss. The theory is verified by measured results     

Hydrodeoxygenation of waste fat for diesel production: Study on model feed with Pt/alumina catalyst

Hydrodeoxygenation of waste fats and oils is a viable method for producing renewable diesel oil. In this study a model feed consisting of oleic acid and tripalmitin in molar ratio 1:3 was hydrotreated at 325 °C with 20 bars H₂ in a stirred batch autoclave with a 5 wt% Pt/γ-Al₂O₃ catalyst, and samples were extracted periodically and analyzed on GC. Despite the significant hydrogen pressure hydrogenation of both reactants were limited and decarboxylation or decarbonylation of the ester and carboxylic acid functionalities were highly favored, yielding carbon chain lengths of odd numbers. Moreover, Pd/γ-Al₂O₃ was observed to be slightly more active than Pt/γ-Al₂O₃ and had a higher ratio of decarboxylation and decarbonylation to hydrogenation, while Ni/γ-Al₂O₃ was substantially less active than Pt and also showed a markedly lower ratio of decarboxylation and decarbonylation to hydrogenation. Variation of the temperature showed that triglycerides as well as free fatty acids were converted at all investigated temperatures, but the conversion of oleic acid increased from 6% to 100% when the temperature was increased from 250 °C to 325 °C. The tripalmitin reacted via a palmitic acid intermediate, and its conversion was limited by formation of this free fatty acid.     

Pulsations During Fires in Tunnels

The existing theoretical modelling of thermoacoustic oscillations has been studied and applied to the case of tunnel fires. The assumptions of the theoretical model were reviewed. It was found that several assumptions are not applicable to tunnel fires and, hence, suggestions for improvement are given. The correlation which expresses the starting conditions for thermoacoustic oscillations is analysed and dependencies on different parameters are presented. The pulsations documented during the large-scale tests in the Runehamar tunnel in 2003 have also been further analysed. The measurements were compared to the theoretical limiting curve for oscillations, showing good agreement. To further study thermoacoustic oscillations in tunnels, more detailed tests in a model-scale tunnel (1:100) were performed. These tests focused on the circumstances which are required to create thermoacoustic oscillations, i.e. the fire was located at different positions along the tunnel and the air flow rate was varied. The tunnel had a length of 4 m, was 8 cm wide and 6 cm high. The results were in good accordance with the theoretical modelling but showed deviations which were most obvious at very low and high air velocities. Both the starting conditions for thermoacoustic oscillations and cases where the thermoacoustic oscillations suddenly stopped, were observed. These findings led to identification of several points in the theoretical model which need to be improved, and to the development of a strategy to avoid such pulsation in fires.     

Conflicts between Perception and Reality in the Management of Alien Species in Forest Ecosystems: A Norwegian Case Study

The vegetation dynamics and landscape management during 20 years of a temperate deciduous forest protected as a nature reserve in western Norway are analysed. Sycamore (Acer pseudoplatanus), an alien species in northern Europe, has become abundant in parts of the forest and the paper discusses how nature management has formulated and interpreted the introduction of sycamore. Scientists and nature managers regard the species as aggressive and a threat to the local natural biodiversity, but in this respect empirical evidence has been replaced by assumption and prejudice, and this is critically reviewed in the paper. The development of the forest has been monitored annually since 1988 and the long-term forest dynamics and behaviour of sycamore are discussed in relation to the attitudes of nature managers. The views held by nature managers are based on their own values and ideas regarding what is valuable nature, and alien species are often assumed to be invasive and aggressive, yet with no reference being made to site ecology and human local history. As an alternative to an a priori understanding of the role of alien species, the paper suggests that proper knowledge of ecosystem dynamics can only be achieved through analysis of ecological variation in space and time. The management of any species should not be according to its status as native or alien, but according to a judgment of its role and long-term behaviour. The values of nature conservationists should not be confused with the intrinsic values of nature.     

Resuspension and settling of helminth eggs in water: Interactions with cohesive sediments

Helminth parasite eggs in low quality water represent main food safety and health hazards and are therefore important indicators used to determine whether such water can be used for irrigation. Through sedimentation helminth eggs accumulate in the sediment, however resuspension of deposited helminth eggs will lead to increased concentration of suspended eggs in the water. Our study aimed to determine the erodibility (erosion rate and erosion threshold) and settling velocity of Ascaris and Trichuris eggs as well as cohesive sediment at different time points after incorporation into the sediment. Cohesive sediment collected from a freshwater stream was used to prepare a sediment bed onto which helminth eggs were allowed to settle. The erodibility of both sediment and helminth eggs was found to decrease over time indicating that the eggs were incorporated into the surface material of the bed and that this material was stabilized through time. This interaction between eggs and bulk sediment was further manifested in an increased settling velocity of suspended eggs when sediment was present in the suspension as compared to a situation with settling in clean water. The incorporation into the sediment bed and the aggregation with sediment particles decrease the mobility of both helminth egg types. Our findings document that helminth eggs should not be viewed as single entities in water systems when modelling the distribution of eggs since both erodibility and settling velocity of eggs are determined by mobility of the sediment present in the water stream. Recalculation of the erosion threshold for helminth eggs and sediment showed that even at relatively low current velocities i.e. 0.07-0.12 m s⁻¹ newly deposited eggs will be mobile in open irrigation channels. These environmental factors affecting resuspension must be taken into account when developing models for sedimentation of helminth eggs in different water systems.     

Removal of estrogenicity in Swedish municipal sewage treatment plants

The human estrogen receptor alpha-test, hosted in a yeast strain, was used to quantify estrogenicity in three-week composite samples of untreated and treated effluents from 20 Swedish municipal sewage treatment plants. The treatment plants were selected to represent different treatment processes regarding chemical precipitation and microbial procedures. The discharge from Swedish domestic sewage treatment plants contained estrogenic compounds corresponding to <0.1-15 ng estradiol equivalents/L. Low levels of estrogenic activity were also found in a river receiving municipal effluents, 3.5-35 km downstream the outlet from a sewage treatment works. The range of estrogenicity in untreated, raw sewage effluents was found to be 1-30 ng estradiol equivalents/L. Generally, wastewater treatment reduced the estrogenicity and extended biological treatment was most effective in its removal. Activated sludge treatment tended to be more effective than trickling filters, whereas chemical precipitation using iron or aluminium salts without biological treatment showed little effectivity. The study showed that treatment methods in current use are able to eliminate or largely reduce estrogenicity in domestic wastewater.     

Cost and Energy Effective Management of EAF with Flexible Charge Material Mix

Within the framework of the project FLEXCHARGE, performed within the RFCS steel research program, a team including research institutes and steel producers developed and tested in an industrial environment a methodology to effectively manage the EAF charged with variable materials. Statistical and deterministic methods were used together to determine yield and composition of different scrap types as well as the influence of the scrap mix on the off-gas emission and the slag composition. The paper summarizes the most relevant results obtained at four different EAF plants by applying the improved process control and by performing industrial trials for different steel grades. It also shows how the use of low quality scrap types in the charge mix has been maximized, considering the tramp element restrictions and scrap availability, yield as well as specific energy consumption.     

Degradation of microcystin in sediments at oxic and anoxic, denitrifying conditions

The potent toxin microcystin is frequently released during cyanobacterial blooms in eutrophic waters and may impose a risk to human health, when surface water is used for drinking water. For removal of microcystin in surface waters, infiltration through sediment is commonly used. In the present study, mineralization of 14C-labelled microcystin (accumulation of 14CO(2)) and concentration changes (protein phosphatase inhibition assay) demonstrated that indigenous microorganisms in the sediment of a water recharge facility were capable of degrading microcystin. At oxic or microaerophilic (<2% O(2)) conditions, microcystin added to sediment slurries at 70 microg l(-1) was reduced to <20 microg l(-1) in 1-2 weeks, and less than 3 microg l(-1) after 7 weeks. At anoxic conditions (<0.3% O(2)) and with addition of nitrate, the degradation was significantly stimulated, reducing microcystin from 100 to <20 microg l(-1) within 1 day. The simultaneous production of N(2)O in the samples suggests that the microcystin degradation was coupled to dissimilative nitrate reduction (denitrification). Since aquifers and sediments beneath drinking water reservoirs often are anoxic, nitrate respiration may be an important process in removal and detoxification of microcystin.     

Are Perceived Sensory Dimensions a Reliable Tool for Urban Green Space Assessment and Planning?

Environmental psychologists have developed varying methods for landscape assessment according to how it is perceived and experienced. In the Nordic countries, eight perceived sensory dimensions are increasingly being used as a methodological framework for expert assessments. These are serene, nature, rich in species, space, prospect, refuge, social and culture. Using an onsite questionnaire distributed to green space visitors in Helsingborg, Sweden, this study is the first to examine the representation of the eight sensory dimensions in different types of urban green spaces as experienced by lay people and their relationships with green space attributes. The results showed that (1) prospect then serene and space were the most common, and culture and social the least; (2) the experience of the sensory dimensions varied across the six study sites and was related to their diversity of biotopes and overall size; and (3) respondent experience of the sensory dimensions was consistent across gender, age and frequency and type of recreational use. These results grant legitimacy to the method in assessment and mapping of recreational experience of urban green space.