ALBERT

Description: The development of this paper was inspired by the increase in the number of different eco-label like quality assurance schemes established in the European Union in the past few years. These schemes are flooding the market and the researchers raise the question, is there enough credibility in these schemes? This piece of research is based on 58 eco-labeling like food schemes and dissects them into the building blocks of the different factors that makes a scheme credible and analyses the structure of these blocks as well as a literature survey on the perceptions of both the consumers and producers to these schemes. The sort of credibility structure that the building blocks of the schemes (ownership, stakeholder dialogue, traceability, transparency, etc.) have created was discussed and it was questioned if they meet the expectations of the consumers. The main findings of the research indicate that although small groups of consumers may be satisfied with a number of the different schemes, the majority of them fall short of providing a credible quality assurance scheme. Improvements were suggested such as involving a more diverse range of stakeholders and expanding the responsibility of processors and retailers. An alternative to the current form of labeling is also discussed.

Description: Selbstverständlich schafft Windenergie Arbeitsplätze. Betrachtet man die Studie des Bremer Energie-Institutes näher, so zeigen sich einige methodische Schwächen und wenig plausible Annahmen. Von einer "nüchternen Analyse" kann deswegen nicht gesprochen werden.

Description: New energy efficiency policies have been introduced around the world. Historically, most energy models were reasonably equipped to assess the impact of classical policies, such as a subsidy or change in taxation. However, these tools are often insufficient to assess the impact of alternative policy instruments. We evaluate the so-called engineering economic models used to assess future industrial energy use. Engineering economic models include the level of detail commonly needed to model the new types of policies considered. We explore approaches to improve the realism and policy relevance of engineering economic modeling frameworks. We also explore solutions to strengthen the policy usefulness of engineering economic analysis that can be built from a framework of multidisciplinary cooperation. The review discusses the main modeling approaches currently used and evaluates the weaknesses in current models. We focus on the needs to further improve the models. We identify research priorities for the modeling framework, technology representation in models, policy evaluation, and modeling of decision-making behavior.

Description: This book presents important new research on applied eco-efficiency concepts throughout Europe. The aim of eco-efficiency is to achieve market-based measures of environmental protection, in order to enhance the prospects for sustainable development and achieve positive economic and ecological benefits. The distinguished authors discuss a number of themes surrounding eco-efficiency including the necessary conditions for technological dissemination and ecological modernization, and the role of government in enabling businesses and society to participate actively in this process. In particular, they highlight the application of existing European-based policies concerning material flows and energy. The authors also investigate some new concepts of sustainable development and provide a useful introduction to material flows analysis. In further chapters they study the emerging regulatory policies for eco-efficiency, and examine the issues of sustainable business and consumption strategies.

Description: Transnational corporations' (TNCs) economic operations cover numerous countries and can be diverted between several continents. These units have reached a level of significance, having not only economic, but also social and environmental implications. This justifies that they shall be treated separately as a social phenomenon, when considering strategies for the development towards sustainability. This paper presents the concept of Responsible Corporate Governance (RCG), as a strategy to "govern" TNCs. RCG is suggested as a stakeholder based policy instrument, which aims at allocating responsibilities to societal actors aiming at corporate accountability. RCG recognises that the process of societal change is strongly based on what can be called as bottom up-processes. Learning processes take place through the interaction of the different societal members, which eventually leads to macro changes. Therefore, governing TNCs towards sustainability improvements is considered to be a collective process including all stakeholders. Firstly, the paper places the concept of RCG in the ongoing debate of political modernization based on the fact that society develops overtime and the political system must correspondingly modernize. In this context, political overload developed as a consequence of increased resource interdependencies is explained and as a resolution, network approach is discussed. Secondly, demands on the orientation of the TNCs in terms of accountability and innovative action are brought forward. Here, the paper also lists down corporate elements (stakeholder empowered corporate governance, management and performance evaluation systems, transparency enhancement and accountability verification), which need to be in place to attain an accountable orientation in the society. Following, using an analytical framework, the orientation and capabilities of each societal actor (environmental non-governmental organisations, financial institutions, intergovernmental organisations) to affect improvements in the corporate responsibility elements are investigated and recommendations for their effective orientation are listed.

Description: In jedem Unternehmen gibt es Potenziale, um die eigene wirtschaftliche Position zu verbessern und sich gegen zukünftige Krisen abzusichern. Technische, organisatorische oder soziale Innovationen sind der Schlüssel zur dauerhaften Sicherung ihrer Wettbewerbsposition. Diese Broschüre soll kleinen und mittelständischen Unternehmen helfen, Bereiche zu finden, in denen Innovationspotenziale vorhanden sind. Anhand erster Maßnahmen, so genannten Innovationsschritten, werden Ansatzpunkte entwickelt, wie mit möglichst geringem (Zeit- und Kosten-) Aufwand gezielt die eigene Wettbewerbsposition gestärkt werden kann. Sie wendet sich an Unternehmensleitung oder Umweltmanagementbeauftragte und gibt ihnen einen ersten Ein- bzw. Überblick und konkrete Vorschläge, wie sie die Zukunftsfähigkeit ihres Unternehmens verbessern können. Damit hat diese Broschüre konkrete Hilfestellungen für den Praktiker im Unternehmen im Fokus. Mögliche Ansatzpunkte, geeignete Wege sowie passende Instrumente werden für einzelne Bereiche aufgezeigt und erläutert.

Description: Diese Studie untersucht die Medien, die sanktionsbereiten Konsumenten Informationen über die Verantwortung von Unternehmen als Orientierungshilfe für den Einkauf anbieten. Im Brennpunkt stehen dabei sozial-ökologisch orientierte Einkaufsführer, die vergleichende Unternehmensbewertungen mit dem Ziel anbieten, Verbrauchern eine Informationsgrundlage für positive und negative Sanktionen zu geben, um einen positiven Profilierungswettbewerb in Gang zu setzen. Dabei gilt das besondere Interesse dem Übergang vom Printmedium zum Internetauftritt. Ziel der Untersuchung ist eine Analyse fördernder und hemmender Faktoren für den Erfolg, die für die Praxis nützlich sein soll.

Description: Infrastrukturen und Infrastrukturpolitik nehmen einen entscheidenden Einfluss auf die Nachhaltigkeit eines Landes. Betrachtet man die (Fehl-) Entwicklungen des letzten Jahrhunderts in den Industrieländern, so ist zu erkennen, dass die derzeitigen Energie-, Verkehrs- und Wasserinfrastrukturen selbst den Anforderungen einer ökonomischen Nachhaltigkeit nicht gewachsen sind. Ihre sozialen und ökologischen Folgen wurden zudem meist vernachlässigt und spielten bei Entscheidungsprozessen nur eine nachrangige Rolle. Große Herausforderungen liegen vor den Industrieländern, wenn sie nachhaltige Infrastrukturen schaffen wollen - und gar eine Leitbildfunktion für Schwellen- und Entwicklungsländer im 21. Jahrhundert einnehmen möchten. Denn durch die Intensivierung der weltweiten Austauschbeziehungen werden die nicht-nachhaltigen Infrastrukturkonzepte und -politiken der Industrieländer zunehmend auf Entwicklungsländer übertragen. Eine Umorientierung muss deshalb auch im Süden erfolgen. Dieses Wuppertal Paper bietet am Beispiel der drei wichtigen Sektoren Energie, Verkehr und Wasser Ansätze einer nachhaltigen Infrastrukturpolitik. Dazu gehören sowohl globale Lösungsstrategien als auch spezifische Instrumente für die Länder des Nordens oder des Südens. Im Rahmen von sektoralen Fallstudien werden die Schwellenländer Brasilien (Energie), China (Verkehr) und Indonesien (Wasser) betrachtet. Zudem werden Strategien und Erfolgsfaktoren für eine an Nachhaltigkeitszielen orientierte Transferpolitik skizziert, wobei auch auf die Bedeutung von Bildung und die Rolle internationaler Finanzinstitutionen (am Beispiel der Weltbank) eingegangen wird. Um die großen Herausforderungen einer globalen nachhaltigen Entwicklung zu bewältigen, schlägt dieses Papier vor, mehrere Strategien parallel zu verfolgen. Im Norden sind die gegenwärtigen ressourcenintensiven, nicht-nachhaltigen Infrastrukturen zu überdenken. Im Süden sollte der Pfad der "nachholenden Entwicklung" verlassen und im Sinne eines ökologischen "leapfrogging" der Sprung in post-fossile Infrastrukturen angestrebt werden, um nicht die Fehler des Nordens zu wiederholen. Länderspezifische Lösungen sollten dabei an die Stelle eines Imports nicht-angepasster Infrastrukturen treten. Der Transfer und Austausch von Ideen, Konzepten und Lösungen kann dabei einen wesentlichen Beitrag leisten, wobei eine unidirektionale Entwicklungszusammenarbeit von Nord nach Süd nicht ausreicht. Auch Süd-Süd oder Süd-Nord-Kooperationen eröffnen wichtige Chancen. Zudem ist der industrieländerzentrische, Technologie orientierte Ansatz einer einfachen Optimierung der supply-side zu verlassen zugunsten einer Handlungsstrategie, die ein nachhaltiges demand-side-management integriert.

Description: An increasing number of publications about theoretical approaches and new findings illustrate the relevance of the topic environmental risk assessment. The actual discussion about high oil prices is not incorporated under this headline; but it should be, as natural resource scarcity is a crucial economic factor. In practical experience, more and more banks, insurance companies as well as investors realize that there are certain areas with a high correlation between sustainable development and corporate success, corporate risk exposure and corporate performance. In this discussion one of the most obvious topics are risks related to climate change. According to the findings of surveys evaluated in this paper climate change starts to affect economic development and companies' performance in various ways. Over the next decade, economic losses due to climate change are estimated by US$ 150 billion per year. As result world's business leaders have described climate change as the biggest challenge of the 21st century. Hence, the incorporation of climate change as a risk factor is essential, but risks related to climate change feature a severe issue of complex structure and uncertainty; traditional risk assessment tools appear in the light of not being able to either reflect the multifaceted system nor provide sufficient outcomes. Environmental risk assessments in general so far have mainly emphasized - if at all - on actual and possible impacts of the release of materials or emissions (external effects). But an overall sustainable risk assessment has also to take into account the risks related to the inflow of materials. The main reason for neglecting the inflow risks from an environmental perspective can be seen in the fact that these risks seem to be less tangible and more uncertain. Nevertheless, in a world where economic development and the use of natural resources is not uncoupled yet, a steadily increasing economic power will result in a continually rising extraction of resources. As all resources are limited, the risk of scarcity will rise; and the example of water illustrates that it already exists. Indeed, scarcity is not tangible for all kind of resources from a present point of view. Hence, a specified analysis is needed considering different market and supply conditions. A comprehensive analysis of environmental risks needs to encompass risks affecting the output as well as the input side of a value chain. This paper enlarges the discussion on environmental risk assessments upon the input dimension using the example of carbon risks. Firstly, carbon risks are defined as risks related to climate change at the corporate level with a focus on the input as well as the output dimension. Secondly, an analysis of the current discussion on the topic of carbon risk evaluates the status quo of scientific work in this field. Thirdly, in terms of developing a practically oriented tool, the Value-at-Risk approach and it's application to measure input oriented carbon risks are scrutinized. The results discuss how future volatility and market prices can be utilized to describe the uncertainty resulting from markets acknowledging and pricing oil scarcity as a risk factor. Finally recommendations with a focus on strategic management decisions and financial performance analysis are given and further research opportunities are drawn. The conclusion is; once markets have acknowledged the depletion mid-point as a measure of oil scarcity, natural scarcity will result in a significant higher Value-at-Risk. The Value-at-Risk of one barrel of crude oil could then be as high as US$ 15.5 in the short term and even US$ 17.2 in the long term. The scope of this paper is neither intended to predict one likely development nor to demonstrate how this tool can actually work in terms of forecasting single companies' performance. But in order to point the way ahead, this paper provides scenarios for potential future developments and sets a frame for risk assessments due to oil scarcity.

Description: Der neoliberalen Globalisierung liegen Rationalitätsmuster zugrunde, die weder neu, noch liberal sind. Dies gilt für herrschaftliches Denken über Natur (als Ressource) ebenso wie für den sich verstärkenden Zugriff auf Naturgüter und die Ausblendung reproduktiver Elemente aus der Debatte über Umgangsweisen mit Natur. Mit Blick auf Landnutzung und Livelihood wird lokale Vielfalt durch Globalisierung zerstört. Der Absolutheitsanspruch eines weltweit entfesselten Marktes mit seinem grenzenlos freien Wettbewerb untergräbt das Recht auf- und die Möglichkeit zu je eigener, der Lokalität gemäßer Naturnutzung. Wenn immer mehr Menschen ihrer an die jeweiligen Lokalitäten gebundenen Produktionsmittel beraubt werden, können sich Gesellschaften nicht von innen heraus nachhaltig entwickeln.

Description: This paper examines the connection between globalisation, with its growth in world trade links, and certain ecological effects especially concerning "North-South" relations. Although world trade in the mid-nineties was significantly uncoupled from growth trends in the world economy, so that since then it has increased nearly three times faster than the global GDP, certain indicators of energy use and CO2 emissions have not developed proportionately to world trade; globalisation evidently does not lead to a situation where pressures on the environment are increasing to the same extent worldwide. This de-linking may, however, result in the kind of shifts that we examine here with reference to the material trade flows of the European Union. It will be shown that, in the course of globalisation, the countries of the EU have increasingly shifted environmental burdens on to the countries of the South, especially in the form of ecological rucksacks of imported raw materials, while at the same time reducing the pressure on their own domestic environment by extracting fewer material resources. Furthermore, goods whose production places intensive pressure on the environment (industrial emissions into the atmosphere and water, heavy metal emissions, etc.) have been increasingly imported from newly industrializing or developing countries. The greater covering of material requirements from foreign resources has served not so much the EU's internal consumption as its own production of export goods; this shows that the EU has an increasing share in the resource requirement of other economies. The paper concludes that it is absolutely necessary to consider the international dimension in any strategy for more productive use of resources in industrial countries. In the long term, the EU's resource use should also be reduced in absolute terms. This will also be necessary in order to reduce the pressure on the environment due to imports and exports.

Description: Die "Ökonomie der Aufmerksamkeit" hat zur Herausbildung spezifischer Märkte für Kommunikations-, Media- und Marketingdienstleistungen geführt. Ein dynamisch wachsender Markt ist der Markt für Live-Kommunikation, der in dieser Arbeit vertiefend untersucht wird. Hierbei werden drei Fragen diskutiert: 1. Was sind die treibenden Faktoren und Trends der Live-Kommunikation? 2. Nach welchen Maßstäben werden Events, insbesondere im Bereich der Unternehmenskommunikation, beauftragt? 3. Welche Chancen bestehen in diesem Markt, Events für Nachhaltigkeit als Marktsegment zu etablieren und zu stärken? Bei der Beantwortung dieser Fragen werden aktuelle Trendstudien ausgewertet, aber auch auf Untersuchungen und Fallstudien zurückgegriffen, die im Rahmen des Projektes "Eventkultur und Nachhaltigkeit" durchgeführt wurden. Die Autoren kommen zu dem Ergebnis, dass die Markt- und Trendstudien eine wichtige Orientierungsfunktion für die Eventwirtschaft haben. Aus der Perspektive eines kulturökonomischen Ansatzes wird kritisiert, dass diese Orientierungsfunktion auf Marken und Marketingtechniken beschränkt ist und der Einfluss der gesellschaftlichen Wertbildung auf die Marketingpraxis ausgeblendet bleibt. Nachhaltige Ziele und Inhalte werden mit den Mitteln des Event-Marketings erst vereinzelt vermittelt. Aus diesen ersten Aktivitäten kann aber ein neuer Kommunikationsmarkt entstehen, wenn seitens der Nachhaltigkeitsakteure eine Verständigung über Kriterien und Anforderungen an dieses Marketinginstrument erfolgt sowie der Symbolebene in der Nachhaltigkeitskommunikation eine stärkere Beachtung geschenkt wird. Informationsbündelung und symbolisches Management sind wichtige Ansatzpunkte, um in der Marketingpraxis von Unternehmen, öffentlichen Einrichtungen, Verbänden, NGOs und von Kommunikations- und Eventagenturen eine nachhaltige Eventkultur zu verankern.

Description: During the period December 23,1997 and December August 31,2004, we accomplished the development of 2 CFD codes for DNS/LES/RANS simulation of turbine cascade flows, namely LESTool and UNCLE. LESTool is a structured code making use of 5th order upwind differencing scheme and UNCLE is a second-order-accuracy unstructured code. LESTool has both Dynamic SGS and Spalart's DES models and UNCLE makes use of URANS and DES models. The current report provides a description of methodologies used in the codes.

Description: The Hubble Space Telescope (HST) was launched April 24, 1990, and was deployed April 25 into low Earth orbit (LEO). It was soon discovered that the metal poles holding the solar arrays were expanding and contracting as the telescope orbited the Earth passing between the sunlight and the Earth s shadow. The expansion and contraction, although very small, was enough to cause the telescope to shake because of thermal-induced jitters, a detrimental effect when trying to take pictures millions of miles away. Therefore, the European Space Agency (ESA, the provider of the solar arrays) built new solar arrays (SA-11) that contained bi-stem thermal shields which insulated the solar array metal poles. These thermal shields were made of 2 mil thick aluminized-Teflon fluorinated ethylene propylene (FEP) rings fused together into a circular bellows shape. The new solar arrays were put on the HST during an extravehicular activity (EVA), also called an astronaut space walk, during the first servicing mission (SM1) in December 1993. An on-orbit photograph of the HST with the SA-11, and a close up of the bellows-like structure of the thermal shields is provided in Figure 1.

Description: A computational heat transfer design methodology was developed to study the dual-engine linear aerospike plume-induced base-heating environment during one power-pack out, in ascent flight. It includes a three-dimensional, finite volume, viscous, chemically reacting, and pressure-based computational fluid dynamics formulation, a special base-bleed boundary condition, and a three-dimensional, finite volume, and spectral-line-based weighted-sum-of-gray-gases absorption computational radiation heat transfer formulation. A separate radiation model was used for diagnostic purposes. The computational methodology was systematically benchmarked. In this study, near-base radiative heat fluxes were computed, and they compared well with those measured during static linear aerospike engine tests. The base-heating environment of 18 trajectory points selected from three power-pack out scenarios was computed. The computed asymmetric base-heating physics were analyzed. The power-pack out condition has the most impact on convective base heating when it happens early in flight. The source of its impact comes from the asymmetric and reduced base bleed.

Description: This paper details a novel three-dimensional (3D) hydro-focusing micro cell sorter for micro flow cytometry applications. The unit was microfabricated by means of SU-8 3D lithography. The 3D microstructure for coaxial sheathing was designed, microfabricated, and tested. Three-dimensional hydro-focusing capability was demonstrated with an experiment to sort labeled tanned sheep erythrocytes (red blood cells). This polymer hydro-focusing microstructure is easily microfabricated and integrated with other polymer microfluidic structures.

Description: The Sensors and Electronics Technology Branch of the NASA Glenn Research Center is developing thin-film-based sensors for surface measurement in propulsion system research. Thin-film sensors do not require special machining of the components on which they are mounted, and they are considerably thinner than wire- or foil-based sensors. One type of sensor being advanced is the thin-film thermocouple, specifically for applications in high-temperature combustion environments. Ceramics are being demonstrated as having the potential to meet the demands of thin-film thermocouples in advanced aerospace environments. The maximum-use temperature of noble metal thin-film thermocouples, 1500 C (2700 F), may not be adequate for components used in the increasingly harsh conditions of advanced aircraft and next-generation launch vehicles. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically in the form of bulky rods or probes. As part of ASTP, Glenn's Sensors and Electronics Technology Branch is leading an in-house effort to apply ceramics as thin-film thermocouples for extremely high-temperature applications as part of ASTP. Since the purity of the ceramics is crucial for the stability of the thermocouples, Glenn's Ceramics Branch and Case Western Reserve University are developing high-purity ceramic sputtering targets for fabricating high-temperature sensors. Glenn's Microsystems Fabrication Laboratory, supported by the Akima Corporation, is using these targets to fabricate thermocouple samples for testing. The first of the materials used were chromium silicide (CrSi) and tantalum carbide (TaC). These refractory materials are expected to survive temperatures in excess of 1500 C. Preliminary results indicate that the thermoelectric voltage output of a thin-film CrSi versus TaC thermocouple is 15 times that of the standard type R (platinum-rhodium versus platinum) thermocouple, producing 20 mV with a 200 C temperature gradient. The photograph on the left shows the CrSi-TaC thermocouple in a test fixture at Glenn, and the resulting output signal is shown on the right. The temperature differential across the sample, from the center of the sample inside the oven to the sample mount outside the oven, is measured using a type R thermocouple on the sample.

Description: The unsteady, incompressible Navier-Stokes equations are used for the direct numerical simulation (DNS) of spatially evolving disturbances in a three-dimensional (3-D) attachment-line boundary layer. Two-dimensional (2-D) disturbances are introduced either by forcing at the in ow or by harmonic-source generators at the wall; 3-D disturbances are introduced by harmonic-source generators at the wall. The DNS results are in good agreement with both 2-D non-parallel theory (for small-amplitude disturbances) and weakly nonlinear theory (for finite-amplitude disturbances), which validates the two theories. The 2-D DNS results indicate that nonlinear disturbance growth occurs near branch II of the neutral stability curve; however, steady suction can be used to stabilize this disturbance growth. For 3-D instabilities that are generated o the attachment line, spreading both toward and away from the attachment line causes energy transfer to the attachment-line and downstream instabilities; suction stabilizes these instabilities. Furthermore, 3-D instabilities are more stable than 2-D or quasi-2-D instabilities.

Description: A fast multigrid solver for the steady incompressible Euler equations is presented. Unlike time-marching schemes, this approach uses relaxation of the steady equations. Application of this method results in a discretization that correctly distinguishes between the advection and elliptic parts of the operator, allowing efficient smoothers to be constructed. Solvers for both unstructured triangular grids and structured quadrilateral grids have been written. Computations for channel flow and flow over a nonlifting airfoil have computed. Using Gauss-Seidel relaxation ordered in the flow direction, textbook multigrid convergence rates of nearly one order-of-magnitude residual reduction per multigrid cycle are achieved, independent of the grid spacing. This approach also may be applied to the compressible Euler equations and the incompressible Navier-Stokes equations.

Description: The structural analysis results for a graphite/epoxy quasi-isotropic circular plate subjected to a forced rotation at the boundary and pressure is presented. The analysis is to support a specialized material characterization test for composite cryogenic tanks. Finite element models were used to ensure panel integrity and determine the pressure necessary to achieve a predetermined equal biaxial strain value. The displacement results due to the forced rotation at the boundary led to a detailed study of the bending stiffness matrix [D]. The variation of the bending stiffness terms as a function of angular position is presented graphically, as well as, an illustrative technique of considering the laminate as an I-beam.

Description: Various artificial compressibility methods for calculating the three-dimensional incompressible Navier-Stokes equations are compared. Each method is described and numerical solutions to test problems are conducted. A comparison based on convergence behavior, accuracy, and robustness is given.

Description: This study provides systematic method for reducing power consumption in reduced gravity systems by adopting minimum velocity required to provide adequate CHF and preclude detrimental effects of reduced gravity . This study proves it is possible to use existing 1 ge flow boiling and CHF correlations and models to design reduced gravity systems provided minimum velocity criteria are met

Description: Recent workshops to define strategic research on critical issues in microgravity fluids and transport phenomena in support of mission orientated needs of NASA and many technical conferences over the years in support of fundamental research targeting NASA's long range missions goal have identified several phase change processes needed to design advanced space and planetary based systems for long duration operations Recommendation noted that phase change processes are profoundly affected by gravitational environment.

Description: We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid and liquid-solid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients kLa and kGa (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Description: One particular characteristic observed in unsteady shear layers is the phase shift relative to the main flow. In attached boundary layers this will have an effect both on the instantaneous skin friction and heat transfer. In separation bubbles the contribution to the drag is dominated by the pressure distribution. However, the most significant effect appears to be the phase shift on the transition process. Unsteady transition behaviour may determine the bursting of the bubble resulting in an un-recoverable full separation. An early analysis of the phase shift was performed by Stokes for the incompressible boundary layer of an oscillating wall and an oscillating main flow. An amplitude overshoot within the shear layer as well as a phase shift were observed that can be attributed to the relatively slow diffusion of viscous stresses compared to the fast change of pressure. Experiments in a low speed facility with the boundary layer of a flat plate were evaluated in respect to phase shift. A pressure distribution similar to that on the suction surface of a turbomachinery aerofoil was superimposed generating a typical transitional separation bubble. A periodically unsteady main flow in the suction type wind tunnel was introduced via a rotating flap downstream of the test section. The experiments covered a range of the three similarity parameters of momentum-loss-thickness Reynolds-number of 92 to 226 and Strouhal-number (reduced frequency) of 0.0001 to 0.0004 at the separation point, and an amplitude range up to 19 %. The free stream turbulence level was less than 1% .Upstream of the separation point the phase shift in the laminar boundary layer does not appear to be affected significantly bay either of the three parameters. The trend perpendicular to the wall is similar to the Stokes analysis. The problem scales well with the wave velocity introduced by Stokes, however, the lag of the main flow near the wall is less than indicated analytically. The separation point comes closest to the Stokes analysis but the phase is still 20 degrees lower at the wall.

Description: Among the numerous causes for unsteadiness in turbo machinery flows are turbulence and flow environment, wakes from stationary and rotating vanes, boundary layer separation, boundary layer/shear layer instabilities, presence of shock waves and deliberate unsteadiness for flow control purposes. These unsteady phenomena may lead to flow-structure interactions such as flutter and forced vibration as well as system instabilities such as stall and surge. A major issue of unsteadiness relates to the fact that a fundamental understanding of unsteady flow physics is lacking and requires continued attention. Accurate simulations and sufficient high fidelity experimental data are not available. The Glenn Research Center plan for Engine Component Flow Physics Modeling is part of the NASA 21st Century Aircraft Program. The main components of the plan include Low Pressure Turbine National Combustor Code. The goals, technical output and benefits/impacts of each element are described in the presentation. The specific areas selected for discussion in this presentation are blade wake interactions, flow control, and combustor exit turbulence and modeling.

Description: The Effects of elevated free-stream turbulence (FST) on the natural and periodically excited separation bubbles were studied experimentally, due to the relevance of this flow to low-pressure turbine blades at low Reynolds numbers. A bubble was formed at the leading edge of a flat plate and the FST level was altered by placing a grid across the flow at different locations upstream of the plate. The mixing across the separated shear-layer, forming the free boundary of the bubble, increased due to the elevated FST and due to nominally two-dimensional periodic excitation, both flattening and shortening the bubble. Periodic excitation at frequencies that were at least an order of magnitude lower than those associated with the initial shear-layer instability, were very effective at low FST, because the amplitudes of the excitation frequency and its harmonic were amplified over the bubble. High frequency excitation (F+ 3, based on the length of the baseline low FST bubble) had a major effect close to the separation location, while farther downstream the excited fluctuations rapidly decayed in the reattachment region. Low frequency excitation, that generated waves comparable to the length of the unperturbed bubble (F+ 1) were less effective and their magnitude decayed at a slower rate downstream of reattachment. An increase in the level of the FST reduced the net effect of the periodic excitation on the mixing enhancement and subsequent reattachment process, probably due to a destructive interference between the nominally 2D excitation and the random (in space and time) FST, reducing the spanwise coherence and therefore the effectiveness of the current control strategy. However, even at the reduced effectiveness of 2D periodic excitation at elevated FST, it accelerated the reattachment process and the recovery rate of the reattached boundary layer, enhancing the boundary layer resistance to repeat separation and reducing its momentum loss further downstream.

Description: In this brief, we investigate the turbulent condensation of a population of droplets by means of a direct numerical simulation. To that end, a coupled Navier-Stokes/Lagrangian solver is used where each particle is tracked and its growth by water vapor condensation is monitored exactly. The main goals of the study are to find out whether turbulence broadens the droplet size distribution, as observed in in situ measurements. The second issue is to understand if and for how long a correlation between the droplet radius and the local supersaturation exists for the purpose of modeling sub-grid scale microphysics in cloud-resolving codes. This brief is organized as follows. In Section 2 the governing equations are presented, including the droplet condensation model. The implementation of the forcing procedure is described in Section 3. The simulation results are presented in Section 4 together with a sketch of a simple stochastic model for turbulent condensation. Conclusions and the main outcomes of the study are given in Section 5.

Description: Three-dimensional computational techniques, in particular the uncoupled CFD-DSMC of the present study, are available to be applied to problems such as jet interactions with variable density regions ranging from a continuum jet to a rarefied free stream. When the value of the jet to free stream momentum flux ratio approximately greater than 2000 for a sharp leading edge flat plate forward separation vortices induced by the jet interaction are present near the surface. Also as the free stream number density n (infinity) decreases, the extent and magnitude of normalized pressure increases and moves upstream of the nozzle exit. Thus for the flat plate model the effect of decreasing n (infinity) is to change the sign of the moment caused by the jet interaction on the flat plate surface.

Description: InSPACE is a microgravity fluid physics experiment that was operated on the International Space Station (ISS) in the Microgravity Science Glovebox from late March 2003 through early July 2003. (InSPACE is an acronym for Investigating the Structure of Paramagnetic Aggregates From Colloidal Emulsions.) The purpose of the experiment is to obtain fundamental data of the complex properties of an exciting class of smart materials termed magnetorheological (MR) fluids. MR fluids are suspensions, or colloids, comprised of small (micrometer-sized) superparamagnetic particles in a nonmagnetic medium. Colloids are suspensions of very small particles suspended in a liquid. (Examples of other colloids are blood, milk, and paint.) These controllable fluids can quickly transition into a nearly solid state when exposed to a magnetic field and return to their original liquid state when the magnetic field is removed. Controlling the strength of the magnetic field can control the relative stiffness of these fluids. MR fluids can be used to improve or develop new seat suspensions, robotics, clutches, airplane landing gear, and vibration damping systems. The principal investigator for InSPACE is Professor Alice P. Gast of the Massachusetts Institute of Technology (MIT). The InSPACE hardware was developed at the NASA Glenn Research Center. The InSPACE samples were delivered to the ISS in November 2002, on the Space Shuttle Endeavour, on Space Station Utilization Flight UF-2/STS113. Operations began on March 31, 2003, with the processing of three different particle size samples at multiple test parameters. This investigation focused on determining the structural organization of MR colloidal aggregates when exposed to a pulsing magnetic field. On Earth, the aggregates take the shape of footballs with spiky tips. This characteristic shape may be influenced by the pull of gravity, which causes most particles initially suspended in the fluid to sediment, (i.e., settle and collect at the bottom of the cell). In the absence of sedimentation effects on the ISS, the behavior and shape of these MR aggregate structures are dominated exclusively by magnetic and surface tension forces. The microscopic detail of these structures was imaged under two orthogonal camera views. The video was downlinked to the InSPACE team at Glenn's Telescience Support Center and to MIT and also recorded onboard the ISS on videotapes that will be brought back to the ground by the space shuttles. The study examined the effect on the structure formation by varying the magnetic field strength and pulse frequency, and particle size. Fundamental data that characterized the structure formation were obtained. InSPACE completed its last planned test run on July 2, 2003. Operations occurred on 21 days over approximately a 3-month period. Forty-one test points were completed during 26 test runs. During the initial testing, the procedures followed by the crew were modified to maximize the observation of some unexpected and interesting aggregate behavior. As a result Dr. Gast has reported on the formation of aggregate shapes that are more extended and diverse than those observed on the ground. Sheets of magnetic material folded over in a labyrinth pattern and large columnar aggregates with complex interfaces with the surrounding fluid are examples of the interesting structures that have been observed on the ISS. In light of these early findings, the understanding of the fundamental properties of MR fluids on the basis of ground-based observations may need to be reconsidered.The experiments on the ISS have provided a vast amount of video data for analysis. While this analysis is ongoing, plans are being made for additional experimental runs. For this purpose, additional hardware and cells containing samples of different magnetic particles and sizes are being fabricated for a future launch to the ISS. The InSPACE hardware will remain on orbit until this testing is completed.

Description: Leakage and wear are two fundamental problems in all traditional turbine seals that contribute to an engine's inefficiency. The solutions to seal leakage and wear conflict in the conventional design space. Reducing the clearance between the seal and rotating shaft reduces leakage but increases wear because of increased contact incidents. Increasing the clearance to reduce the contact between parts reduces wear but increases parasitic leakage. The goal of this effort is to develop a seal that restricts leakage flow using acoustic pressure while operating in a noncontacting manner, thereby increasing life. In 1996, Dr. Timothy Lucas announced his discovery of a method to produce shock-free high-amplitude pressure waves. For the first time, the formation of large acoustic pressures was possible using dissonant resonators. A pre-prototype acoustic seal developed at the NASA Glenn Research Center exploits this fundamental acoustic discovery: a specially shaped cavity oscillated at the contained fluid's resonant frequency produces high-amplitude acoustic pressure waves of a magnitude approaching those required of today's seals. While the original researchers are continuing their development of acoustic pumps, refrigeration compressors, and electronic thermal management systems using this technology, the goal of researchers at Glenn is to apply these acoustic principles to a revolutionary sealing device. When the acoustic resonator shape is optimized for the sealing device, the flow from a high-pressure cavity to a low-pressure cavity will be restricted by a series of high-amplitude standing pressure waves of higher pressure than the pressure to be sealed. Since the sealing resonator cavity will not touch the adjacent sealing structures, seal wear will be eliminated, improving system life. Under a cooperative agreement between Glenn and the Ohio Aerospace Institute (OAI), an acoustic-based pre-prototype seal was demonstrated for the first time. A pressurized cavity was attached to one end of the resonator while the other end remained open to ambient pressure. Measurements were taken at several values of applied pressure with the assembly stationary, oscillated at an off-resonance frequency, and then oscillated on-resonance. The three cases show that the flow through the conical resonator can be reduced by oscillating the resonator at the resonance frequency of the air contained within the cavity. The results are currently being compared with results obtained from a commercial computational fluid dynamics code. The objective is to improve the design through numerical simulation before fabricating a next-generation prototype sealing device. Future work is aimed at implementing acoustic seal design improvements to further reduce the leakage flow rate through the device and at reducing the device's overall size.

Description: A new technology for reducing turbulent skin friction, called the Microblowing Technique (MBT), is presented. Results from proof-of-concept experiments show that this technology could potentially reduce turbulent skin friction by more than 50% of the skin friction of a solid flat plate for subsonic and supersonic flow conditions. The primary purpose of this review paper is to provide readers with information on the turbulent skin friction reduction obtained from many experiments using the MBT. Although the MBT has a penalty for obtaining the microblowing air associated with it, some combinations of the MBT with suction boundary layer control methods are an attractive alternative for a real application. Several computational simulations to understand the flow physics of the MBT are also included. More experiments and computational fluid dynamics (CFD) computations are needed for the understanding of the unsteady flow nature of the MBT and the optimization of this new technology.

Description: Solve the time-dependent inviscid flow equations for this geometry subject to the specified inflow/outflow mean conditions and the fluctuating inflow velocity distortion. (1) Compute the unsteady solution until periodicity in pressure is achieved by showing that at least two successive periods are identical. Periodicity must be achieved on both the airfoil surface and the inflow/outflow boundaries. (2) Once periodicity is achieved, compute the pressure frequency spectra on the reference airfoil on both the upper and lower surfaces at x=(-0.25c,0.00, +0.25c), on the inflow boundary at (x,y)={1.5c,-0.3c), (-1.5c,0.0),(-1.5c,0.3c)} and on the outflow boundary at (x,y)= {(1.5c,-0.3c),(1.5c,0.0), (1.5c,0.3c)}. Express the spectral results in dB using the standard definition 20 log(P(sub(r.m.s)/P(sub ref), where p(sub ref) == 20 microPa. (3) Extract the harmonic pressure distributions on the inflow and outflow boundaries (i.e., on x= -/+ 1.5c lines) at the fundamental frequency omega and apply a Fourier transform in y direction to identify the spatial (i.e., mode order) structure of the pressure perturbations. Express the result in dB for each mode order. Repeat the process for the frequencies 2omega and 3omega.

Description: Three benchmark problems from the current and previous CAA workshops involving tone noise generated in viscous flows are investigated using the CE/SE finite volume method. The CE/SE method is first briefly reviewed. Then, the benchmark problems, namely, flow past a single cylinder (CAA Workshop II problem), flow past twin cylinders (from the current CAA Workshop IV, Category 5, Problem 1) and flow past a deep cavity with overhang (CAA Workshop III problem) are investigated. Generally good results are obtained in comparison with the experimental data.

Description: The effects of gravity on the bubble formation in an annular jet were studied. The experiments were conducted in the 2.2-second drop tower at the NASA Glenn Research Center. Terrestrial gravity experiments were conducted at the Fluid Dynamics Research Laboratory at the University of Oklahoma. Stainless steel tubing with inner diameters of 1/8" (gas inner annulus) and 5/16" (liquid outer annulus) served as the injector. A rectangular test section, 6" x 6" x 14" tall, made out of half-inch thick Lexan was used. Images of the annular jet were acquired using a high-speed camera. The effects of gravity and varying liquid and gas flow rates on bubble size, wavelength, and breakup length were documented. In general, the bubble diameter was found to be larger in terrestrial gravity than in microgravity for varying Weber numbers (0.05 - 0.16 and 5 - 11) and liquid flow rates (1.5 ft/s - 3.0 ft/s). The wavelength was found to be larger in terrestrial gravity than in microgravity, but remained constant for varying Weber numbers. For low Weber numbers (0.05 - 0.16), the breakup length in microgravity was significantly higher than in terrestrial gravity. Comparison with linear stability analysis showed estimated bubble sizes within 9% of experimental bubble sizes. Bubble size compared to other terrestrial gravity experiments with same flow conditions showed distinct differences in bubble size, which displayed the importance of injector geometry on bubble formation.

Description: The objective of the present study is to develop a two-fluid model formulation with interfacial area transport equation applicable for microgravity conditions. The new model is expected to make a leapfrog improvement by furnishing the constitutive relations for the interfacial interaction terms with the interfacial area transport equation, which can dynamically model the changes of the interfacial structures. In the first year of this three-year project supported by the U.S. NASA, Office of Biological and Physics Research, the primary focus is to design and construct a ground-based, microgravity two-phase flow simulation facility, in which two immiscible fluids with close density will be used. In predicting the two-phase flow behaviors in any two-phase flow system, the interfacial transfer terms are among the most essential factors in the modeling. These interfacial transfer terms in a two-fluid model specify the rate of phase change, momentum exchange, and energy transfer at the interface between the two phases. For the two-phase flow under the microgravity condition, the stability of the fluid particle interface and the interfacial structures are quite different from those under normal gravity condition. The flow structure may not reach an equilibrium condition and the two fluids may be loosely coupled such that the inertia terms of each fluid should be considered separately by use of the two-fluid model. Previous studies indicated that, unless phase-interaction terms are accurately modeled in the two-fluid model, the complex modeling does not necessarily warrant an accurate solution.

Description: Flow regime and pressure drop data was obtained and analyzed. Pulse flow exists at lower liquid flow rates in 0-g compared to 1-g. 1-g flow regime maps do not apply in microgravity. Pressure drop is higher in microgravity (enhanced interfacial effects).

Description: In fiscal year 2003, test cell 23 of the Research Combustion Laboratory (RCL 23) at the NASA Glenn Research Center was upgraded with the addition of gaseous hydrogen as a working propellant and the addition of a 450-psig air-supply system. Test flexibility was further enhanced by upgrades to the facility control systems. RCL 23 can now test with gaseous hydrogen flow rates up to 0.05 lbm/sec and jet fuel flow rates up to 0.62 lbm/sec. Research airflow rates up to 3 lbm/sec are possible with the 450-psig supply system over a range of inlet temperatures. Nonvitiated, heated air is supplied from a shell and tube heat exchanger. The maximum nonvitiated facility air temperature is 1100 F at 1.5 lbm/sec. Research-section exhaust temperatures are limited to 3200 F because of material and cooling capacity limits. A variety of support systems are available depending on the research hardware configuration. Test section ignition can be provided via either a hydrogen air torch system or an electronic spark system. Emissions measurements are obtained with either pneumatically or electromechanically actuated gas sample probes, and the electromechanical system allows for radial measurements at a user-specified axial location for measurement of emissions profiles. Gas analysis data can be obtained for a variety of species, including carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NO and NOx), oxygen (O2), unburnt hydrocarbons, and unburnt hydrogen. Facility control is accomplished with a programmable logic control system. Facility operations have been upgraded to a system based on graphical user interface control screens. A data system is available for real-time acquisition and monitoring of both measurements in engineering units and performance calculations. The upgrades have made RCL 23 a highly flexible facility for research into low emissions gas turbine combustor concepts, and the flame tube configuration inherently allows for a variety of fuel nozzle configurations to be tested in a cost-effective manner. RCL 23 is poised to be a leading facility for developing modern low-emission fuel nozzles for use with jet fuel and alternative fuels.

Description: The operation of a packed bed reactor (PBR) involves gas and liquid flowing simultaneously through a fixed-bed of solid particles. Depending on the application, the particles can be various shapes and sizes but are generally designed to force the two fluid phases through a tortuous route of narrow channels connecting the interstitial space. The PBR is the most common type of reactor in industry because it provides for intimate contact and high rates of transport between the phases needed to sustain chemical or biological reactions. The packing may also serve as either a catalyst or as a support for growing biological material. Furthermore, this type of reactor is relatively compact and requires minimal power to operate. This makes it an excellent candidate for unit operations in support of long-duration human space activities.

Description: Recent research efforts within the Microgravity Fluid Physics Branch of the NASA Glenn Research Center have necessitated the development of a microscope capable of high-resolution, three-dimensional imaging of intracellular structure and tissue morphology. Standard optical microscopy works well for thin samples, but it does not allow the imaging of thick samples because of severe degradation caused by out-of-focus object structure. Confocal microscopy, which is a laser-based scanning microscopy, provides improved three-dimensional imaging and true optical sectioning by excluding the out-of-focus light. However, in confocal microscopy, out-of-focus object structure is still illuminated by the incoming beam, which can lead to substantial photo-bleaching. In addition, confocal microscopy is plagued by limited penetration depth, signal loss due to the presence of a confocal pinhole, and the possibility of live-cell damage. Two-photon microscopy is a novel form of laser-based scanning microscopy that allows three-dimensional imaging without many of the problems inherent in confocal microscopy. Unlike one-photon microscopy, it utilizes the nonlinear absorption of two near-infrared photons. However, the efficiency of two-photon absorption is much lower than that of one-photon absorption because of the nonlinear (i.e., quadratic) electric field dependence, so an ultrafast pulsed laser source must typically be employed. On the other hand, this stringent energy density requirement effectively localizes fluorophore excitation to the focal volume. Consequently, two-photon microscopy provides optical sectioning and confocal performance without the need for a signal-limiting pinhole. In addition, there is a reduction in photo-damage because of the longer excitation wavelength, a reduction in background fluorescence, and a 4 increase in penetration depth over confocal methods because of the reduction in Rayleigh scattering.

Description: Many valuable advances in combustion science have come from observations of microgravity flames. This research is contributing to the improved efficiency and reduced emissions of practical combustors and is benefiting terrestrial and spacecraft fire safety. Unfortunately, difficulties associated with microgravity have prevented many types of measurements in microgravity flames. In particular, temperature measurements in flames are extremely important but have been limited in microgravity. A novel method of measuring temperatures in microgravity flames is being developed in-house at the National Center for Microgravity Research and the NASA Glenn Research Center and is described here. Called thin-filament pyrometry, it involves using a camera to determine the local gas temperature from the intensity of inserted fibers glowing in a flame. It is demonstrated here to provide accurate measurements of gas temperatures in a flame simultaneously at many locations. The experiment is shown. The flame is a laminar gas jet diffusion flame fueled by methane (CH4) flowing from a 14-mm round burner at a pressure of 1 atm. A coflowing stream of air is used to prevent flame flicker. Nine glowing fibers are visible. These fibers are made of silicon carbide (SiC) and have a diameter of 15 m (for comparison, the average human hair is 75 m in diameter). Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. The flame and glowing filaments were imaged with a digital black-and-white video camera. This camera has an imaging area of 1000 by 1000 pixels and a wide dynamic range of 12 bits. The resolution of the camera and optics was 0.1 mm. Optical filters were placed in front of the camera to limit incoming light to 750, 850, 950, and 1050 nm. Temperatures were measured in the same flame in the absence of fibers using 50-m Btype thermocouples. These thermocouples provide very accurate temperatures, but they generally are not useful in microgravity tests because they measure temperature at only one location at a time. Thermocouple measurements at a height of 11 mm above the burner were used to calibrate the thin-filament pyrometry system at all four wavelengths. This calibration was used to perform thin-filament pyrometry at other heights above the burner. One such profile is shown in this graph; this is for a height of 21 mm. The agreement between the pyrometry measurements and thermocouple results at this height is excellent in the range of 1000 to 2000 K, with an estimated uncertainty of 50 K and an estimated upper limit of 2500 K. Neither the thermocouple nor the thin-filament pyrometry temperatures have been corrected for radiation, but the correction is expected to be nearly the same for both methods. We anticipate that thin-filament pyrometry similar to that developed here will become an important diagnostic for studies of microgravity flames owing to its accuracy and its ability to simultaneously measure finely spaced temperatures.

Description: When discharged into an International Space Station (ISS) payload rack, a carbon dioxide (CO2) portable fire extinguisher (PFE) must extinguish a fire by decreasing the oxygen in the rack by 50 percent within 60 sec. The length of time needed for this oxygen reduction throughout the rack and the length of time that the CO2 concentration remains high enough to prevent the fire from reigniting is important when determining the effectiveness of the response and postfire procedures. Furthermore, in the absence of gravity, the local flow velocity can make the difference between a fire that spreads rapidly and one that self-extinguishes after ignition. A numerical simulation of the discharge of CO2 from PFE into the Combustion Integrated Rack (CIR) in microgravity was performed to obtain the local velocity and CO2 concentration. The complicated flow field around the PFE nozzle exits was modeled by sources of equivalent mass and momentum flux at a location downstream of the nozzle. The time for the concentration of CO2 to reach a level that would extinguish a fire anywhere in the rack was determined using the Fire Dynamics Simulator (FDS), a computational fluid dynamics code developed by the National Institute of Standards and Technology specifically to evaluate the development of a fire and smoke transport. The simulation shows that CO2, as well as any smoke and combustion gases produced by a fire, would be discharged into the ISS cabin through the resource utility panel at the bottom of the rack. These simulations will be validated by comparing the results with velocity and CO2 concentration measurements obtained during the fire suppression system verification tests conducted on the CIR in March 2003. Once these numerical simulations are validated, portions of the ISS labs and living areas will be modeled to determine the local flow conditions before, during, and after a fire event. These simulations can yield specific information about how long it takes for smoke and combustion gases produced by a fire to reach a detector location, how large the fire would be when the detector alarms, and the behavior of the fire until it has been extinguished. This new capability could then be used to optimize the location of fire detectors and fire-suppression ports as well as to evaluate the effectiveness of fire suppressants and response strategies. Numerical data collected from these simulations could also be used to develop a virtual reality fire event for crew training and fire safety awareness. This work is funded by NASA's Bioastronautics Initiative, which has the objective of ensuring and enhancing the health, safety, and performance of humans in space. As part of this initiative, the Microgravity Combustion Science Branch at the NASA Glenn Research Center is conducting spacecraft fire safety research to significantly improve fire safety on inhabited spacecraft.