Bakgrund: Volvo Cars Body Components (VCBC) tillverkar och levererar karosskomponenter till Volvo Cars. För sex år sedan påbörjade VCBC sin implementering av lean production. För att beräkna de kostnader som uppstår i produktionen använder VCBC produktkalkyler. Representanter vid VCBC anser att företaget har problem med höga plåtlager, överproduktion samt problem med att se kostnadssamband. Ett value stream där förbättringsmöjligheter finns är Flöde 1 vid VCBC. Enligt vad Maskell et al. (2011) påstår kan problemen vara effekter av kombinationen mellan lean production och produktkalkyler. Maskell et al. (2011) menar att företag bör beräkna kostnader på hela value stream vid lean production. En modell som gör det och som Maskell et al. (2011) menar att företag bör använda vid lean production är value stream costing. Syfte: Den här studien syftar till att identifiera de kostnader som bör ingå i en VSC-modell för VCBC. Vidare syftar studien till att, med hjälp av första problemformuleringen, beräkna vad den totala kostnaden för Flöde 1 skulle bli om VCBC tillämpar VSC. Studiens syfte är även att undersöka vad införandet av en VSC-modell skulle innebära för VCBC. Metod: Studiens angreppssätt är av kvalitativ art. Då studien har en intervenistisk forskningsstrategi där vi tillämpade aktionsforskning föll det sig naturligt att använda fallstudie som forskningsdesign. För insamling av data har vi använt dokument, arkivmaterial, intervjuer och direkta observationer. Slutsatser: De kostnader som bör ingå i en value stream costing-modell för VCBC är; fastighetskostnad, materialkostnad, avskrivningar, kapitalkostnader, personalkostnader, leasing & hyror samt IT-kostnader. Om VCBC tillämpar value stream costing skulle det resultera i att den årliga kostnaden för Flöde 1 blir; 3 277 524 kronor. Skulle VCBC implementera value stream costing hade det framför allt inneburit att VCBC hade fått en större förståelse för sina value stream, att det hade skapat ett bättre flöde samt att VCBC inte hade behövt spåra historisk data utan att uppföljning kan ske veckovis för att kunna göra förändringar innan det är för sent. Dessutom hade det inneburit att VCBC’s maskiner hade blivit värderade till kalkylmässiga värderingar så att den fysiska kapaciteten är bevarad, samt att genomsnittskostnaden per produkt hade uppgått till 70 kronor per styck istället för den VCBC kalkylerar med idag som är 98 kronor per styck. / Background: Volvo Cars Body Components (VCBC) manufactures and supply body parts for Volvo Cars. It is six years since VCBC began the implementation of lean production. VCBC is using traditional accounting methods to calculate the production costs. Some employees at VCBC consider that the company has problems with high stocks of raw material, overproduction, and trouble seeing relation between costs. One value stream where improvements can be made is at “Flöde 1” at VCBC. As Maskell et al. (2011) say that the problems might be a result from the effects of the combination between lean production and traditional accounting methods. Maskell et al. (2011) argue that costs in lean should be calculated for the entire value stream. A model that makes so and who Maskell et al. (2011) believes should be used in lean is value stream costing. Purpose: This study aims to identify the costs that should be included in a value stream costing-model for VCBC. Furthermore, the study aims to calculate the total cost for “Flöde 1” by using the first research question. Last the study will investigate what the value stream costing model would mean if VCBC includes the method in their lean work. Methodology: The study was performed by using a qualitative research method. Since we used a interventionist research in which we applied action science it was obvious to use case study as a research design. For data collection, we used documents, archival records, interviews and direct observations. Conclusions: The costs that should be included in a value stream costing model for VCBC are; property cost, material cost, depreciation, capital cost, labor cost, costs for leasing and IT cost. If VCBC apply value stream costing it will result in the annual cost for “Flöde 1” to be; 3 277 524 SEK. If VCBC would implement value stream costing it will primary mean that VCBC can get better understanding for their value streams and by this create a better flow. Furthermore, VCBC does not need to track historically data but instead follow-up on a weekly basis to make changes before it is too late. Another change for VCBC if they implement value stream costing is that they have to evaluate their machines so they keep the physical capacity in mind, and that the cost per product will be decreased from 98 SEK to 70 SEK.

Thesis (M. Phil.)--University of Hong Kong, 1974. / Typewritten.

The excessive deposition of fine inorganic sediment (<2 mm) is a major pathway by which agricultural land uses exert pressure on stream ecosystems. However, less well understood are the underlying mechanisms driving threshold biotic responses and the ecological consequences of community changes to sedimentation. Reviewing the literature, I found that sedimentation can affect algal and detrital pathways, and invertebrate community composition may show abrupt shifts with increased sediment. Moreover, functional changes to communities potentially leads to simpler food webs, with altered interactions and decreased ecosystem function. After identifying these knowledge gaps, I conducted survey and experimental research using agricultural streams on the Canterbury Plains of New Zealand’s South Island. Results from my survey of 30 streams along a sedimentation gradient showed that pollution-sensitive invertebrates (% EPT; Ephemeroptera, Plecoptera, Trichoptera) demonstrated threshold responses to sediment that varied with spatial scale, and change-point analysis indicated marked declines beyond 20% fine sediment covering streambed reaches. Structural equation modeling indicated that decreased habitat availability was a key mechanism contributing to these changes. To better understand the functional consequences of altered community structure, I investigated food webs in 12 streams along the gradient. The results showed a compression of community trophic niche space, suggesting that in particular, primary consumers became trophically more equivalent. The simplification of stream food webs with increasing sediment appeared to be the result of functional changes to invertebrate communities, with fewer specialised consumers, and shifts in the availability of basal resources. Using field and laboratory experiments investigating litter breakdown and invertebrate feeding, I found that the net consequence of functionally less diverse stream communities with increased sediment was impaired ecosystem function, demonstrated by a reduction in litter breakdown rates. The reduction of detrital resource availability through burial by sediment in laboratory mesocosm experiments strongly influenced detrital consumption rates, thus leading to reduced growth and survival of detritivorous caddisflies. The survey and experimental results support my postulate that sediment deposition causes environmental stress by degrading benthic habitat and making associated food resources (e.g., periphyton and leaves) less available. Overall, my results have provided new insights into sediment impacts on stream communities and have furthered our understanding of how these changes affect the structure and functioning of stream ecosystems.

Thesis (M.S.)--State University of New York at Binghamton, Department of Geological Sciences and Environmental Studies, 2009. / Includes bibliographical references.

Subglacial hydrology is known to influence the flow of ice. However, difficulty in accessing the base of large ice sheets has made determining the interaction between ice streams, basal sediment and water difficult to discern. The aim of this thesis is to determine the influence of subglacial hydrology on the flow of the West Antarctic ice streams. This is achieved through development of a numerical flowline model, the Hydrology, Ice and Till (HIT) model. Ice thermodynamics are coupled to a till layer of Coulomb plastic rheology. The porosity of the till changes with basal melt and freeze and can be augmented by water transported through a subglacial conduit system. Water availability strongly affects ice flow, as till porosity influences the till failure strength and thereby the basal resistance of the ice. The model was developed in four stages and a number of sensitivity tests were performed. It was then applied to Kamb Ice Stream (Ice Stream C) and Whillians Ice Stream (Ice Stream B), West Antarctica. Results confirm that ice streams are capable of oscillating between fast and slow velocity states. Cycles are generated at the grounding line of an ice stream and the speed of the transition from slow to fast flow is governed by water availability. The period of oscillation of the cycles for the West Antarctic ice streams was found to be several hundred years, which is in line with observations of stagnation and reactivation of these ice streams. This shows that subglacial hydrology has a role in modulating the flow variability of ice streams and that rather large changes in the flow of the West Antarctic ice streams are likely to occur this century.

North American prairie headwater streams are highly threatened and relatively poorly studied. Most studies on prairie streams have occurred at the Konza Prairie Biological Station, a tallgrass prairie Long Term Ecological Research site in the Flint Hills ecoregion near Manhattan, KS. According to the Stream Biome Gradient Concept, several ecosystem factors vary along a gradient from more allochthonous forested streams to more autochthonous desert streams, with grassland streams often intermediate in several key ecological factors including litter inputs, primary production, and invertebrate abundance and biomass. However, few studies have examined the degree of variation that exists within prairie headwater streams, and whether this variation occurs along a longitudinal gradient as well, with more mesic tallgrass prairie streams differing from more xeric shortgrass prairie streams, and mixed-grass sites intermediate between the two. I examined thirteen prairie headwater stream sites in the central United States from 2014 to 2017. My objective was to determine whether basal resource composition – including standing stocks of coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and very fine particulate organic matter (VFPOM), sestonic and benthic chlorophyll-a levels, and sources of CPOM – differed significantly among streams in tallgrass, mixed-grass, and shortgrass prairie regions. In addition, I examined whether invertebrate communities differed among tallgrass, mixed-grass, and shortgrass prairie regions, and whether this was reflected in the functional feeding group composition, habit composition, voltinism, and dispersal ability of invertebrate communities. There were no significant differences in total CPOM, FPOM, and VFPOM standing stocks among regions. However, CPOM composition did differ with region, with tallgrass sites having higher standing stocks of leaf litter, but lower standing stocks of grass litter and macrophyte litter than the other regions. Benthic chlorophyll-a did not differ significantly among regions, but there were lower sestonic chlorophyll-a levels in tallgrass sites. Given higher light availability and nutrient levels in shortgrass and mixed-grass streams, lack of stable substrata may be limiting benthic algae in these regions. Invertebrate abundance and biomass were highest in mixed-grass sites and lowest in tallgrass sites, with shortgrass sites intermediate. Mixed-grass sites also had significantly higher Shannon diversity and taxa richness than tallgrass sites. A NMDS revealed that sites differed in overall community structure. Functional feeding group composition did not differ significantly across regions, with collector-gatherers, followed by predators, dominating in all sites. High Predator-Prey Index (predator biomass: other invertebrate biomass) values in each region indicates strong top-down pressure and high turnover rates of prey taxa. While there was a weak correlation between leaf litter AFDM and invertebrate community structure, the correlation between latitude and longitude and invertebrate community structure was much higher, indicating that basal resources may not be the main drivers in these systems. Invertebrate habit composition did not differ with region; all regions were dominated by taxa preferring fine substrata (burrowers and sprawlers). All regions showed selection against semivoltine invertebrates and were dominated by high dispersing insect taxa, though the proportion of the insect community that consisted of high dispersers did not differ significantly with region. My results suggest that generalizing about prairie streams based on studies from one or a handful of sites may not be prudent, at least for some aspects. The higher proportion of autochthonous inputs in shortgrass and mixed-grass regions may drive increased invertebrate abundance, biomass, richness, and diversity, but the relative hydrologic stability of the mixed-grass sites might also explain these results or have an interactive or additive relationship with primary production. Overall, the link between basal resources and communities across prairie types was somewhat weak, and all regions were dominated by collector-gatherers with rapid life-cycles and high dispersal abilities, indicating that disturbance may be a more important community filter than basal resource composition. Streams in all three regions have highly variable hydrology, and this may be an overriding factor that results in similarity in communities.

Content removed due to copy right restriction: Dewson, Z.S., Death, R.G. & James, A.B.W. (2003) The effects of water abstractions on invertebrate communities in four small North Island streams. New Zealand natural Sciences 28, 51-65. / Small streams are often used for small-scale water abstractions, but the effects of these water abstractions on the instream environment, invertebrate communities and ecosystem functioning of small permanent streams is poorly understood. This research extends current knowledge by surveying existing water abstractions and completing flow manipulation experiments in the field. Reduced discharge often decreases water velocity, water depth, and wetted channel width and can increase sedimentation, modify the thermal regime and alter water chemistry. In a survey of sites upstream and downstream of existing water abstractions, I found that downstream sites had higher densities of invertebrates, but fewer taxa sensitive to low water quality compared with upstream sites. There were greater differences in physicochemical characteristics such as velocity and conductivity and in invertebrate communities between upstream and downstream sites on streams where a larger proportion of total discharge was abstracted. Using before-after, control-impact (BACI) designed experiments, weirs and diversions were created to experimentally decrease discharge by over 85% in each ot three small streams, ranging from pristine to low water quality. The response of invertebrates to short-term (one-month) discharge reduction was to accumulate in the decreased available area, increasing local invertebrate density. After a year of reduced flow, the density of invertebrates and percentage of mayflies, stoneflies and caddisflies decreased at the pristine site, whereas only taxonomic richness decreased at the mildly polluted stream. Reduced discharge had no affect on the invertebrate community at the stream with the lowest water quality. Reduced discharge had little influence on leaf decomposition rates, but distances travelled by released coarse particulate organic matter (CPOM) increased with increasing discharge. The effects of reduced discharge on primary production were not consistent between streams. Overall, the severity (magnitude/duration) of flow reduction appeared to influence invertebrate responses to water abstraction although the outcomes of water abstraction were dependent on the invertebrate assemblage present in each stream.

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Sept. 23, 2009). Thesis advisor: John S. Schwartz. Vita. Includes bibliographical references.

Dynamic expansions and contractions of stream networks can play an important role for hydrologic processes as they can connect different parts of the landscape to the stream channels. However, we know little about the temporal and spatial variations of stream networks during different flow and wetness conditions. This study focuses on the contraction and expansion of stream networks during different flow conditions in the boreal Krycklan catchment, located in Northern Sweden. The stream network and initiation points were extracted from a gridded digital elevation model (DEM) of 5-meter resolution, and then compared with the stream network initiation points (heads) observed during the spring flood (freshet) period in 2012. From the results of the study, it was clearly seen that the observed stream heads and the stream heads appearing in the stream network map extracted from DEM did not agree very well. 49% of the total observed stream heads (49) fell onto the low order stream branches and headwater streams derived from the DEM. Only few of them exactly matched the modeled stream heads. Moreover, the modeled stream network was much denser than the observed stream network, and so the simple raster based dynamic model developed could not well represent the dynamic stream network extension in the real system. Most headwater streams in the study catchment were man-made ditches, which were dug to drain water wetlands and to increase forest productivity. The majority of observed stream heads were formed by seepage from the saturated surrounding soils, while only a few of them were formed by saturation overland flow.  On the other hand, the dynamic stream network derived from the DEM suggested that the number of streams of lower order and their lengths was sensitive to change in streamflow, especially during the high flow episode.

No description available.