Добірка наукової літератури з теми "Metallic channel"

We explore the behavior of persistent current and low-field magnetic response in mesoscopic one-channel rings and multi-channel cylinders within the tight-binding framework. We show that the characteristic properties of persistent current strongly depend on total number of electrons , chemical potential μ, randomness and total number of channels. The study of low-field magnetic response reveals that only for one-channel rings with fixed , sign of the low-field currents can be predicted exactly, even in the presence of disorder. On the other hand, for multi-channel cylinders, sign of the low-field currents cannot be mentioned exactly, even in the perfect systems with fixed as it significantly depends on the choices of , μ, number of channels, disordered configurations, etc.

Due to lack of desirable mechanical properties of silicon substrate; the current trend of micro-fabrication technology is towards metallic materials. In this study, the electrochemical micromachining (EMM) technology is developed to fabricate micro-scale flow channels on thin metallic 316L stainless steel plate. The cathode electrode, the tool, is the mirror image of flow channels. It was produced by the MEMS and UV-LIGA technology and the size is 200μm in width and 500μm in height for the intension to fabricate a serpentine flow channel of 200μm in both depth and width. Because of the electrode size, the process control parameters and geometrical features surpassed conventional and CMOS methods. The flow channels on 0.6mm thick SS 316L plates were fabricated by EMM process within 30 seconds with effective area of 625mm2. The dimensions of flow channel were varying from 1504m to 5004m in width and about 2004m in depth. The results demonstrate the EMM technology produces good quality metallic flow channels efficiently.

In order to evaluate a communication system, we need to model the propagation channel of the relevant environments pertaining to that communication. In this paper, we propose a Geometry-Based Stochastic Channel Modeling approach to build up propagation channel simulations to assess the performance of vehicle-to-vehicle wireless communications. Our methodology allows the simulation of dynamic scenarios, with an electromagnetic simulator, to emulate typical propagation environments (rural, highway and urban-like propagation channels). Simple metallic plates are used to represent scatterers in the simulated geometric configurations. The common characteristics defining a propagation channel such as delay spread, angle of arrival distribution, and the delay-Doppler spectrum are obtained through adjustment of the number and location of those simple metallic plates.

Metallic bipolar plates (BPPs) are key components in the proton-exchange membrane fuel cell (PEMFC), which can replace traditional fossil fuels as a kind of clean energy. However, these kinds of plates, characterized by micro-channels with a high ratio between depth and width, are difficult to fabricate with an ultra-thin metallic sheet. Then, ultrasonic-vibration-assisted stamping is performed considering the acoustic softening effect. Additionally, the influence of various vibration parameters on the forming quality is analyzed. The experimental results show that ultrasonic vibration can obviously increase the channel depth. Among the vibration parameters, the vibration power has the maximum influence on the depth, the vibration interval time is the second, and the vibration duration time is the last. In addition, the rolling direction will affect the channel depth. When the micro-channels are parallel to the rolling direction, the depth of a micro-channel is the largest. This means that the developed ultrasonic-vibration-assisted stamping process is helpful for improving the forming limitation of micro-channels used for the bipolar plates in PEMFC.

Light and thin bipolar plates are essential in increasing the power density of a fuel cell. To construct high-aspect-ratio micro flow channels in such plates is, however, a big challenge. This study reports on machining micro flow channels in metallic bipolar plates using micro electrical discharge machining milling (micro EDMM) with a tungsten carbide electrode. We successfully machined metallic bipolar plates with 500μm channel and rib widths, height of 600μm in a reaction area of 20mm × 20mm, on 1mm thick of SUS316L stainless steel. The optimal operating parameters were explored and discussed. The performance of resulting fuel cell (Metallic-FC) was compared with a commercial available fuel cell composed of graphite bipolar plates (Graphite-FC). The high temperature of Metallic-FC increases its electrochemical reaction rate and consequently yields higher power density (723 mWcm-2) then that of Graphite-FC (687.3 mWcm-2)

Straining to make a transistor The use of carbon nanotubes (CNTs) as short-channel-length transistors will require control of their chirality, which determines whether they are semiconducting or metallic and if they form strong, low-resistance contacts. Tang et al . fabricated CNT intramolecular transistors by progressive heating and straining of individual CNTs within a transmission electron microscope. Changes to chirality along sections of the nanotube created metallic-to-semiconducting transitions. A semiconducting nanotube channel was covalently bonded to the metallic nanotube source and drain regions. The resulting CNT intramolecular transistors had channel lengths as short as 2.8 nanometers. —PDS

A novel semi-empirical model with an improved single blow method for exploring the heat transfer performance of porous aluminum-foam heat sinks in a channel has been successfully developed. The influencing parameters such as the steady-state air preheating temperature ratio, Reynolds number and medium porosity on local and average heat transfer behavior of porous aluminum-foam heat sinks in a channel are explored. The heat transfer enhancement of using a porous heat sink in a channel to a hollow channel is, (Nu¯b)ss∕(Nu¯b)ε=1, much greater than unity and generally decrease with increasing Re. Furthermore, two new correlations of (Nu¯b)ss and (Nu¯i)ss in terms of ϴ,Re,Da,γ and ε are proposed. As compared with the results evaluated by the transient liquid crystal method, the channel wall temperatures predicted by the present semi-empirical model have a more satisfactory agreement with the experimental data, especially for the cases with smaller porosities. The limitations with relevant error maps of using the transient liquid crystal method in porous aluminum foam channels are finally postulated.

Applications of a metallic material highly depend on its mechanical properties, which greatly depend on the material’s grain sizes. Reducing grain sizes by severe plastic deformation is one of the efficient approaches to enhance the mechanical properties of a metallic material. In this paper, severe plastic deformation of equal channel angular pressing (ECAP) will be reviewed to illustrate its effects on the grain refinement of some common metallic materials such as titanium alloys, aluminum alloys, and magnesium alloys. In the ECAP process, the materials can be processed severely and repeatedly in a designed ECAP mold to accumulate a large amount of plastic strain. Ultrafine grains with diameters of submicron meters or even nanometers can be achieved through severe plastic deformation of the ECAP. In detail, this paper will give state-of-the-art details about the influences of ECAP processing parameters such as passes, temperature, and routes on the evolution of the microstructure of metallic materials. The evolution of grain sizes, grain boundaries, and phases of different metallic materials during the ECAP process are also analyzed. Besides, the plastic deformation mechanism during the ECAP process is discussed from the perspectives of dislocation slipping and twinning.

A bipolar plate is one the most crucial and costliest of the various components of a proton exchange membrane fuel cell (PEMFC). It is important to reduce the cost of bipolar plate, not only in terms of material, but also in terms of the manufacturing process, to allow the commercialization of PEMFC’s. The performance of PEMFC’s is also of importance. Metallic bipolar plates have been the subject of much attention recently, because of their low material cost, formability and excellent thermal and mechanical prosperities. Therefore, this study uses a rubber pad forming process for stainless 316L steel to fabricate a bipolar plate with serpentine channels. A computational fluid dynamics (CFD) analysis is performed, in order to determine the influence of channel geometries, such as channel width, channel height and rib width, on the flow distribution of the reactant. Using the CFD results, finite element analysis models are then constructed and the formability of the micro-flow channel is studied. Finality, experiments are conducted to determine the channel height and thickness distribution of the bipolar plate. The numerical results are verified by the experimental results.

Polymer electrolyte membrane fuel cells (PEMFCs) have emerged as a strong and promising candidate to replace internal combustion engines (ICE) due their high efficiency, high power density and near-zero hazardous emissions. However, their commercialization waits for solutions to bring about significant cost-reductions and significant durability for given power densities. Bipolar plate (BPP) with its multi-faceted functions is one of the essential components of the PEMFC stacks. Stainless steel alloys are considered promising materials of choice for bipolar plate (BPP) applications in polymer electrolyte membrane fuel cells (PEMFC) due to their relatively low cost and commercial availability in thin sheets. Stainless steel materials build a protective passive metal oxide layer on their surface against corrosion attack. This passive layer does not demonstrate good electrical conductivity and increases interfacial electric contact resistance (ICR) between BPP and gas diffusion layer GDL in PEMFC. Lower ICR values are desired to reduce parasitic power losses and increase current density in order to improve efficiency and power density of PEMFC. This study aimed to bring about a broader understanding of manufacturing effects on the BPP contact resistance. In first stage, BPP samples manufactured with stamping and hydroforming under different process conditions were tested for their electrical contact resistance characteristics to reveal the effect of manufacturing type and conditions. As a general conclusion, stamped BPPs showed higher contact conductivity than the hydroformed BPPs. Moreover, pressure in hydroforming and geometry had significant effects on the contact resistance behavior of BPPs. Short term corrosion exposure was found to decrease the contact resistance of bipolar plates. Results also indicated that contact resistance values of uncoated stainless steel BPPs are significantly higher than the respective target set by U.S. Department of Energy. Proper coating or surface treatments were found to be necessary to satisfy the requirements. In the second stage, physical vapor deposition technique was used to coat bipolar plates with CrN, TiN and ZrN coatings at 0.1, 0.5 and 1 μm coating thicknesses. Effects of different coatings and coating thickness parameters were studied as manufactured BPPs. Interfacial contact resistance tests indicated that CrN coating increased the contact resistance of the samples. 1 µm TiN coated samples showed the best performance in terms of low ICR; however, ICR increased dramatically after short term exposure to corrosion under PEMFC working conditions. ZrN coating also improved conductivity of the SS316L BPP samples. It was found that the effect of coating material and coating thickness was significant whereas the manufacturing method and BPP channel size slightly affected the ICR of the metallic BPP samples. Finally, effect of process sequence on coated BPPs was investigated. In terms of ICR, BPP samples which were coated prior to forming exhibited similar or even better performance than coated after forming samples. Thus, continuous coating of unformed stripes, then, applying forming process seemed to be favorable and worth further investigation in the quest of making cost effective BPPs for mass production of PEMFC.

Los materiales conocidos como vidrios metálicos han sido sujeto de estudio e todo el mundo desde los años 50, por el cual se ha conseguido un progreso importante en el entendimiento del comportamiento de estos materiales. Como el nombre sugiere, son aleaciones metálicas amorfas en las que no existe el orden a largo alcance. La ausencia de este tipo de orden les dota de propiedades físicas, químicas y mecánicas que son únicas comparadas con las de otros materiales metálicos convencionales.
Sin embargo, los primeros sistemas amorfos fueron obtenidos por técnicas de solidificación rápida, y requerían velocidades de enfriamiento criticas de hasta 106 K s−1. Por consiguiente, se obtenían cintas finas con un espesor limitado hasta unas decenas de micrómetro. Unos treinta a cuarenta años más tarde, una gama de aleaciones multicomponentes, las cuales requiren velocidades de enfríamiento más lentas, fueron desarrolladas, lo cual significó el nacimiento de los vidrios metálicos macizos. Entre estas aleaciones multicomponentes, las que son a base de Zr han sido protagonistas por su capacidad extraordinaria de formar vidrios. Por el mismo, se hicieron como aleaciones modelo para el estudio de propiedades fúndamentales y comportamientos característicos.
Su límite de fluencia excepcionalmente alto, cerca del límite teórico, les proporciona a los vidrios metálicos macizos un potencial para ser utilizados en aplicaciones estructurales. Desafortunadamente, la deformación plástica a temperatura ambiente occure de una manera muy localizada en bandas de cizalladura. En vez de endurecimiento mécanico, los vidrios metálicos sufren un ablandamiento al deformarlos lo cual impide una deformación plástica estable. Así que, a pesar de su límite de fluencia alto, la ruptura occurirá después de una deformación macroscópica limitada. Este mecanismo de deformación inhomogénea a temperatura ambiente limita la fiabilidad de los vídrios metálicos macizos en aplicaciones estructurales. Lógicamente, la mejora de la plasticidad de estos materiales ha sido ampliamente estudiada durante la última década.
El concepto más explorado para evitar la ruptura catastrófica ha sido probablemente el desarollo de una microestructura heterogenea con una segunda fase. Ésta segunda fase puede tener dimensiones tanto a escala micrómetra como la escala nanométrica y puede ser tanto una fase cristalina como una fase amorfa. Varias rutas han sido probadas para obtener ésta segunda fase en la matriz amorfa: añadir directamente una fase reforzante al material fundido, diseñar una composición adecuada que resulta en un material compuesto al solidificarla o precipitar la segunda fase durante un tratamiento térmico después de colar.
Por tratamientos térmicos por debajo de la temperatura de transición vidria, cambios del orden topológico y químico a corto alcance han sido observado en la literatura. El primer efecto suele deteriorar la plasticidad por relajación de la estructura amorfa. La influencia del cambio de orden químico a corto alcanze se ha estudiado en muy poco detalle. Aparte de los tratamientos térmicos, los tratamientos mecánicos pueden inducir cambios estructurales y microestructurales. El estudio del efecto de estos dos tratamientos forma la parte parte de esta tesis.
Los cambios en el orden topólogico y químico de corto alcance de vídrios metálicos a base de Zr, inducidos por tratamientos térmicos y mecánicos, han sido caracterizados por técnicas de calorimetría, difracción de rayos-X y por microscópia electrónica. Luego, la influencia de estos mismos en el comportamiento mecánico de los vídrios se ha estudiado por tests de compresión y de nanoindentación.
Sin embargo, en la primera parte de ésta tesis, se demuestra que al aplicar la técnica de nanoindentación, se debería tomar en cuenta la existencia de un "size-effect", correlacionado directamente con los cambios estructurales que occuren durante la deformación. Este "size-effect" implica que la dureza y el módulo elástico bajan al aumentar la profundidad de la indentación, similar a lo que se observa normalmente para materiales cristalinos. Durante la deformación, aumenta el volumen libre del vídrio metálico. Este crecimiento del volumen libre influirá en la respuesta del material a la nanoindentación. En particular, se observa un ablandamiento dinámico cuando se aplican cargas elevadas al material. Además, concentraciones más altas de volumen libre en el estado inicial después del colado, ocasionan un ablandamiento mayor y por consecuencia, aumentan el "size-effect".
Después, se hizo un estudio sistemático de los cambios de corto y medio alcance, inducido por tratamientos térmicos, en particular por tratamientos a baja temperatura. Aplicando varias técnicas de caracterización, como por ejemplo la calorimetría, difracción de rayos X y microscopía electrónica, cambios importantes de orden quimico han sido observados. Ya durante tratamientos cortos a baja temperatura, se formaban clústers de Cu en una matriz con un contenido de Cu reducido. Más adelante, el estudio se enfocó en la influencia de los cambios microestructurales en las propiedades mecánicas. Aunque los cambios observados eran moderados, su influencia en el comportamiento mecánico, y en particular en la plasticidad en compresión, es enorme cuando los cambios topológicos son todavía moderados (como es el caso durante el tratamiento térmico a baja temperatura). La plasticidad aumenta significativamente, lo que va en contra a la fragilización que suele ocurrir durante los tratamientos térmicos. Durante tratamientos a temperaturas más elevadas, los cambios topológicos empiezan a dominar (disminución del volumen libre) y forman un contrapeso para el efecto positivo de los cambios del orden químico a corto alcance. Posteriormente, se investigó en más detalle la influencia de los cambios de orden químico en la cristalización. Los clústeres de Cu que se forman durante el calentamiento se puede interpretar como fases embrionarias en el proceso de cristalización.
Durante los tratamientos térmicos, se dan tanto cambios de orden topológico como de orden químico, pero tienen un efecto contradictorio en la plasticidad por lo cual puede ser difícil controlarlos. Sin embargo, los cambios beneficiosos de orden químico se pueden obtener por tratamientos mecánicos de deformación severa, por ejemplo por torsión a alta presión (TAP). La deformación no causa una reducción del volumen libre sino la aumenta incluso más. Además, TAP produce una muestra maciza bastante homogenea siempre y cuando el número de revueltas sea menor, lo que es lo contrario de lo que se sabe para materiales cristalinos. Estos materiales suelen requerir más vueltas para evitar una microestructura heterogenea.
Metallic glasses have been the subject of widespread research since the 1950's with significant progress in the understanding in their behavior. As the name suggests, they are amorphous metallic alloys, i.e. with the absence of long-range order. The absence of this long-range order offers them unique physical, chemical and mechanical properties compared to conventional metallic materials.
However, the early amorphous systems were obtained typically by rapid quenching techniques, with critical cooling rates up to 106 K s−1, resulting typically in ribbons or thin foils with a thickness limited to a few tens of micrometer. About thirty to forty years later, a large range of multicomponent alloys was developed which required significant lower critical cooling rates leading to the birth of so-called bulk metallic glass (BMG). Among these multicomponent systems, Zr-based alloys have been key players with outstanding glass forming ability, which has made them to model alloys for the study of fundamental properties and characteristic behaviors.
The exceptionally high yield strength, close to the theoretical limit, and yield strain of these amorphous metallic systems in bulk offer them potential for structural applications. However, plastic deformation at room temperature occurs in a highly localized manner by the formation of a few shear bands. Instead of work hardening, metallic glasses soften upon deformation, which prevents stable plastic elongation. Although BMGs possess a high fracture strength, once yielding has set in, early failure after a small percentage of macroscopic deformation appears. This inhomogeneous deformation mechanism at ambient temperature still limits the reliability of BMGs for structural applications. Logically, the enhancement of ductility of this type of materials has been the subject of many research works in the last decade.
Probably the most explored concept to avoid catastrophic failure has been the development of a heterogeneous microstructure, with a second phase on different length scales, both crystalline and amorphous. Various routes have been tried out to obtain this second phase in the amorphous matrix: physically adding a reinforcing phase to the melt, by direct precipitation from the melt of a properly designed composition or by (partial) nano-crystallization of the glass after casting.
Upon annealing below the glass transition, changes in both topological and chemical short range order have been reported. The former is believed to deteriorate plasticity due to structural relaxation of the amorphous structure.
The effect of changes of the chemical short range order on plasticity has hardly been studied into detail. Besides annealing, deformation has been reported to induce structural and microstructural changes. These (micro-)structural changes, induced by annealing and deformation, form the main topic of the work presented in this thesis.
Topological and chemical changes in the short range order of Zr-based bulk metallic glasses upon annealing and deformation treatments have been characterized by calorimetry, X-ray diffraction and electron microscopy. The influence of these changes on the mechanical behavior of these glasses was investigated through compression tests and nanoindentation tests.
However, in a first part of this thesis, it is shown that one should be aware when applying this technique of the existence of a so-called size-effect, directly linked with the structural changes upon deformation.
A decrease of hardness and elastic modulus on the maximum penetration depth was found, similar as what is typically observed for crystalline materials. Upon deformation, free volume typically increases. Due to this increase, free volume will influence the response of the material during nanoindentation testing. In particular, a dynamic softening is observed when being plastically deformed at higher loads. Larger free volume concentrations in the as-cast state result in enhanced mechanical softening and, concomitantly, more pronounced indentation size effects.
Afterwards, a systematic study on changes on the short and medium range order upon annealing was performed, in particular at low temperatures. By means of various characterization techniques, like by calorimetry, X-ray diffraction and electron microscopy, important changes in chemical ordering were found, with the formation of Cu-clusters in a more Cu-depleted matrix, already upon low temperature annealing for a short time. In a next step, the study focussed on the influence of this altered microstructures on the mechanical properties. Although the (compositional) changes observed were moderate, their influence on the mechanical behavior, and in particular plasticity under compression, is great, when the topological changes are still moderate (low temperature annealing). Plasticity is enhanced greatly, in large contrast to the generally assumed embrittlement upon annealing. A too large increase in topological short range order (free volume decrease) counterbalances the effect induced by the chemical short range order upon high temperature annealing. Finally, the influence of these changes of chemical short-range order on the crystallization behaviour was studied in more detail. The formation of the Cu-rich clusters upon annealing can thus be understood as a very embryonic phase towards crystallization.
Upon annealing, topological (densification) and chemical ordering occur simultaneously, but these processes have a contradictory effect on plasticity and it might be difficult to control them. Therefore, it is interesting that the beneficial changes in chemical ordering can be achieved also upon high-deformation treatments, e.g. by high-pressure torsion (HPT). Deformation does not lead to the adverse reduction of free volume but even produces some more. HPT itself is able to produce a rather homogeneous bulky sample, in particular for a low amount of revolution - contrary to what is observed in crystalline materials, where more revolutions are necessary to overcome the undesired inhomogeneous microstructure.

Thesis (PhD) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: Currently the reduction of the levelised cost of electricity (LCOE) is the main goal of concentrating solar power (CSP) research. Central to a cost reduction strategy proposed by the American Department of Energy is the use of advanced power cycles like supercritical steam Rankine cycles to increase the efficiency of the CSP plant. A supercritical steam cycle requires source temperatures in excess of 620°C, which is above the maximum storage temperature of the current two-tank molten nitrate salt storage, which stores thermal energy at 565°C. Metallic phase change materials (PCM) can store thermal energy at higher temperatures, and do not have the drawbacks of salt based PCMs. A thermal energy storage (TES) concept is developed that uses both metallic PCMs and liquid metal heat transfer fluids (HTF). The concept was proposed in two iterations, one where steam is generated directly from the PCM – direct steam generation (DSG), and another where a separate liquid metal/water heat exchanger is used – indirect steam generation, (ISG). Eutectic aluminium-silicon alloy (AlSi12) was selected as the ideal metallic PCM for research, and eutectic sodium-potassium alloy (NaK) as the most suitable heat transfer fluid. Thermal energy storage in PCMs results in moving boundary heat transfer problems, which has design implications. The heat transfer analysis of the heat transfer surfaces is significantly simplified if quasi-steady state heat transfer analysis can be assumed, and this is true if the Stefan condition is met. To validate the simplifying assumptions and to prove the concept, a prototype heat storage unit was built. During testing, it was shown that the simplifying assumptions are valid, and that the prototype worked, validating the concept. Unfortunately unexpected corrosion issues limited the experimental work, but highlighted an important aspect of metallic PCM TES. Liquid aluminium based alloys are highly corrosive to most materials and this is a topic for future investigation. To demonstrate the practicality of the concept and to come to terms with the control strategy of both proposed concepts, a storage unit was designed for a 100 MW power plant with 15 hours of thermal storage. Only AlSi12 was used in the design, limiting the power cycle to a subcritical power block. This demonstrated some practicalities about the concept and shed some light on control issues regarding the DSG concept. A techno-economic evaluation of metallic PCM storage concluded that metallic PCMs can be used in conjunction with liquid metal heat transfer fluids to achieve high temperature storage and it should be economically viable if the corrosion issues of aluminium alloys can be resolved. The use of advanced power cycles, metallic PCM storage and liquid metal heat transfer is only merited if significant reduction in LCOE in the whole plant is achieved and only forms part of the solution. Cascading of multiple PCMs across a range of temperatures is required to minimize entropy generation. Two-tank molten salt storage can also be used in conjunction with cascaded metallic PCM storage to minimize cost, but this also needs further investigation.
AFRIKAANSE OPSOMMING: Tans is die minimering van die gemiddelde leeftydkoste van elektrisiteit (GLVE) die hoofdoel van gekonsentreerde son-energie navorsing. In die kosteverminderingsplan wat voorgestel is deur die Amerikaanse Departement van Energie, word die gebruik van gevorderde kragsiklusse aanbeveel. 'n Superkritiese stoom-siklus vereis bron temperature hoër as 620 °C, wat bo die 565 °C maksimum stoor temperatuur van die huidige twee-tenk gesmelte nitraatsout termiese energiestoor (TES) is. Metaal fase veranderingsmateriale (FVMe) kan termiese energie stoor by hoër temperature, en het nie die nadele van soutgebaseerde FVMe nie. ʼn TES konsep word ontwikkel wat gebruik maak van metaal FVM en vloeibare metaal warmteoordrag vloeistof. Die konsep is voorgestel in twee iterasies; een waar stoom direk gegenereer word uit die FVM (direkte stoomopwekking (DSO)), en 'n ander waar 'n afsonderlike vloeibare metaal/water warmteruiler gebruik word (indirekte stoomopwekking (ISO)). Eutektiese aluminium-silikon allooi (AlSi12) is gekies as die mees geskikte metaal FVM vir navorsingsdoeleindes, en eutektiese natrium – kalium allooi (NaK) as die mees geskikte warmteoordrag vloeistof. Termiese energie stoor in FVMe lei tot bewegende grens warmteoordrag berekeninge, wat ontwerps-implikasies het. Die warmteoordrag ontleding van die warmteruilers word aansienlik vereenvoudig indien kwasi-bestendige toestand warmteoordrag ontledings gebruik kan word en dit is geldig indien daar aan die Stefan toestand voldoen word. Om vereenvoudigende aannames te bevestig en om die konsep te bewys is 'n prototipe warmte stoor eenheid gebou. Gedurende toetse is daar bewys dat die vereenvoudigende aannames geldig is, dat die prototipe werk en dien as ʼn bevestiging van die konsep. Ongelukkig het onverwagte korrosie die eksperimentele werk kortgeknip, maar dit het klem op 'n belangrike aspek van metaal FVM TES geplaas. Vloeibare aluminium allooie is hoogs korrosief en dit is 'n onderwerp vir toekomstige navorsing. Om die praktiese uitvoerbaarheid van die konsep te demonstreer en om die beheerstrategie van beide voorgestelde konsepte te bevestig is 'n stoor-eenheid ontwerp vir 'n 100 MW kragstasie met 15 uur van 'n TES. Slegs AlSi12 is gebruik in die ontwerp, wat die kragsiklus beperk het tot 'n subkritiese stoomsiklus. Dit het praktiese aspekte van die konsep onderteken, en beheerkwessies rakende die DSO konsep in die kollig geplaas. In 'n tegno-ekonomiese analise van metaal FVM TES word die gevolgtrekking gemaak dat metaal FVMe gebruik kan word in samewerking met 'n vloeibare metaal warmteoordrag vloeistof om hoë temperatuur stoor moontlik te maak en dat dit ekonomies lewensvatbaar is indien die korrosie kwessies van aluminium allooi opgelos kan word. Die gebruik van gevorderde kragsiklusse, metaal FVM stoor en vloeibare metaal warmteoordrag word net geregverdig indien beduidende vermindering in GLVE van die hele kragsentrale bereik is, en dit vorm slegs 'n deel van die oplossing. ʼn Kaskade van verskeie FVMe oor 'n reeks van temperature word vereis om entropie generasie te minimeer. Twee-tenk gesmelte soutstoor kan ook gebruik word in samewerking met kaskade metaal FVM stoor om koste te verminder, maar dit moet ook verder ondersoek word.

Deployment of high temperature (>500 °C) thermal energy storage in solar power plants will make solar power more cost competitive and pave the way towards a sustainable future. In this research, a unique metallic encapsulation has been presented for thermal energy storage at high temperatures, capable of operation in aerobic conditions. This goal was achieved by employing low cost materials like carbon steel. The research work presents the unique encapsulation procedure adopted, as well as various coatings evaluated and optimized for corrosion protection. Experimental testing favored the use of 150 μm of nickel on carbon steel for corrosion protection in these conditions. These metallic encapsulations survived several thermal cycles at temperatures from 580 °C to 680 °C with one encapsulation surviving for 1700 thermal cycles.

Purpose: The purpose of this thesis is to investigate Stena Metall’s values and how they are communicated within the organization.

Background: In the Fall of 2008, the world was shocked by the worst financial crisis in decades. The crisis had deep effects on the Swedish economy, and many companies suffered heavily. The recycling and environmental service company Stena Metall experienced their first negative result in 30 years, and 900 employees had to leave the company. An action program, including an altered culture was established with the purpose to adapt the operations to the new business environmental conditions. Values, which are a part of the organizational culture, were decided to be an important part of the change. To implement these in the entire organization a well-structured communication process is needed. Within these subjects; values and communication, a qualitative study at Stena Metall has been conducted.

Method: To fulfill the purpose, a qualitative method has been used. Thirteen interviews were conducted to collect data from different levels of the organization. The interviews were designed differently based on the employee’s level of responsibility in the organization. The theoretical framework used when analyzing the empirical material includes earlier research in the areas of culture, with emphasis on values, and communication.

Conclusion: Two set of values have been identified, core values and aspiration values. The findings indicate a gap in the communicational process at Stena Metall. Part of the new information communicated about Stena Metall´s values is lost on its way from the management to the lower levels in the organization. The perception of what the values mean, both core and aspiration values, differs depending on level in the organization.

This article describes the identification and separation of metallic and semiconducting carbon nanotubes according to their electric properties. It first provides an overview of the electronic structure of nanotubes, focusing on how their metallic and semiconducting properties arise. It then considers the most widely used characterization techniques used in determining metallic or semiconducting behavior, including Raman spectroscopy and photoluminescence measurements. It also discusses specific chirality-selective growth techniques, physical postgrowth selection methods, enrichment by chirality-sensitive chemical reactions, and modification of transport properties without change in chirality. The article concludes with a review of some applications of metallic and semiconducting carbon nanotubes as transparent conductive coatings.

This article discusses the modulation design of plasmonics for diagnosis and drug screening applications. It begins with an overview of the advances made in terms of theoretical insights, focusing on the origins of surface plasmon wave and manipulation, admittance loci design method, and surface plasmon grating coupled emission. It then considers how prism coupler, Ge-doped silica waveguide, nanograting and active plasmonics can trigger the excitation of surface plasmon resonance (SPR). It also examines the metallic effect of long-range surface plasmon resonance and conducting metal oxide as adhesive layer before describing three SPR waveguide biosensors that were developed for the realization of a hand-held SPR system. In particular, it presents a lateral-flow microfluidic channel based on a nitrocellulose membrane and integrated with a SPR waveguide biosensor to achieve dynamic detection. Finally, the article evaluates the biomolecular layer effect, with emphasis on kinetics analysis of antibody binding.

Rechargeable Energy Storage Technologies for Automotive Applications Abstract This paper provides an extended summary of the available relevant rechargeable energy storage electrode materials that can be used for hybrid, plugin and battery electric vehicles. The considered technologies are the existing lithium-ion batteries and the next generation technologies such as lithium sulfur, solid state, metal-air, high voltage materials, metalair and sodium based. This analysis gives a clear overview of the battery potential and characteristics in terms of energy, power, lifetime, cost and finally the technical hurdles. Inhalt Seite Vorwort 1 Alternative Energiespeicher – und Wandler S. Hävemeier, Neue Zelltechnologien und die Chance einer deutschen 3 M. Hackmann, Zellproduktion – Betrachtung von Technologie, Wirtschaft- R. Stanek lichkeit und dem Standort Deutschland N. Omar, Rechargeable Energy Storage Technologies for 7 R. Gopalakrishnan Automotive Applications – Present and Future ...

AbstractIn this chapter, the most promising techniques to observe oil slicks and to detect metallic targets at sea using polarimetric synthetic aperture radar (SAR) data are reviewed and critically analysed. The detection of oil slicks in SAR data is made difficult not only by the presence of speckle but also by the presence of, e.g. biogenic films, low-wind areas, rain cells, currents, etc., which increase the false alarm probability. The use of polarimetric features has been shown to both observe oil slicks and distinguish them from weak-damping look-alikes but also to extract some of their properties. Similarly to oil slicks, the same factors can hamper the detection of metallic targets at sea. The radiometric information provided by traditional single-channel SAR is not generally sufficient to unambiguously detect man-made metallic targets over the sea surface. This shortcoming is overcome by employing polarimetry, which allows to fully characterize the scattering mechanism of such targets.

Abstract In this work, a conjugate heat transfer model was established to numerically investigate the conjugate thermal performance of a steam-cooled ribbed channel with thick metallic walls. By employing the software of ANSYS CFX, the flow field in the channel and the temperature field in the solid channel were calculated. The flow behavior, heat transfer performance and temperature gradient distributions of ribbed channels with wall thickness (δ) of 1–5 mm, rib height-to-hydraulic diameter (e/D) of 0.047–0.188, rib pitch-to-height ratio (P/e) of 5–15 and rib angle-of-attack (α) of 30°–90° were compared and analyzed. The optimum structure parameters of thick-wall ribbed channel with higher heat transfer performance and lower maximum temperature gradient were obtained. The results show that the SST k-ω turbulence model is more suitable for the conjugate heat transfer problem of steam in the thick-wall ribbed channels. The friction factor reduces gradually with the increase of Re, increases greatly with the increase of e/D and α, and first increases then decreases with the increase of P/e. The average Nusselt number increases up to 8.81 times, while the maximum temperature gradient decreases about 45.35% when Reynolds number varies from 10,000 to 70,000. The rib angle of about 45°–60°, e/D of 0.188, and P/e of 10 are suitable to obtain the optimum thermal performance of steam flow in the ribbed channel. The influence of δ on the flow and heat transfer characteristics is non-significant.

Soil resistivity is one of the most important variables that is used to ascertain the corrosivity of an electrolyte around a pipe. This is crucial information that enhances the classification, prioritization and selection of locations prone to external corrosion during External Corrosion Direct Assessment (ECDA) or pipeline integrity assessment when combined with results from cathodic protection and coating surveys. The Wenner Four-Pin method is commonly used in the industry for soil resistivity measurements. It entails perpendicular measurements with four equidistant pins away from the pipe to avoid any interference from the buried metallic pipe. However, the resistivity of soil samples taken away from the pipe might not be similar to the actual soil condition at the pipe location, possibly due to environmental polarization and changes in soil mixing due to previous construction activities. This could lead to an erroneous prioritization of coating faults and soil corrosivity assessment during pipeline integrity corrosion evaluations. In this study, measurements of soil resistivity conducted at different depths on top of and adjacent to a buried coated pipe using the Wenner Four-Pin method indicated that this method is less susceptible to errors arising from interference from the buried coated metallic pipe. The resistance of the coating actually increased the measured resistivity. This confirms that soil resistivity measurements should be taken on top of the pipe whenever possible to improve the prioritization of coating faults and ensure pipeline integrity.

Infrared spectroscopy (IR) is a highly effective method for the analysis of minerals, rocks and ores, capable of solving a whole range of problems when choosing innovative solutions for the technological processing of various types of mineral raw materials. The article considers the main directions of using the infrared spectroscopy method in assessing the technological properties of minerals and their behavior in technological processes: evaluation of the grade (quality) of mineral raw materials; analysis of the behavior of minerals in the technological process with prediction of their technological properties; analysis of changes in the structure and properties of minerals in technological processes; operational analysis of mineral substances at various stages of technological processing. The article illustrates all aspects of the use of infrared spectroscopy at various stages of studying the material composition of mineral raw materials in its enrichment assessment by specific examples of solving problems arising from the technological redistribution of various types of ore and non-metallic minerals.