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1
Blackmore, Katherine Ann 1969. "Sintering of heterogeneous glass powder compacts." Thesis, The University of Arizona, 1995. http://hdl.handle.net/10150/291349.
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A modification of Scherer's Self-Consistent model and a new model, the Interlocking Cell model, have been developed to characterize the sintering behavior of mixtures of two glass powders. The theoretical sintering curves predicted by both these models are compared to each other and to experimental densification behaviors. Viscosities extrapolated from homogeneous sintering curves of sol-gel derived powders are transient and cannot be predicted based on composition alone. These transient viscosities have a significant effect on the sintering kinetics. The Self-Consistent and Interlocking Cell models assume very different microstructural changes during sintering. However, differences between the two models can just be distinguished using experimental densification curves of sol-gel cordierite based glass mixtures.
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Jonsén, Pär. "Fracture and stress in powder compacts." Doctoral thesis, Luleå tekniska universitet, Material- och solidmekanik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18300.
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In the field of powder metallurgy (PM), the production methods are constantly developed and improved to produce components with high precision and strength. Cold uniaxial pressing of powder into a green body is a common process in PM. During uniaxial die powder pressing, the volume enclosed between the die and punches is reduced and the powder consolidates until a final height is obtained or a prescribed compacting pressure is reached. Desired properties of the green body are high strength, uniform density, no defects and narrow dimension tolerances. In the development process of new components finite element (FE) modelling and simulations are useful tools, especially to predict density distributions. Today, it is desired to include prediction of fracture and residual stress of powder compacts. The aim of this work is to increase the knowledge of the pressing process and its effect on green body properties. This includes a better understanding of residual stress development in the green body during pressing and the tensile fracture processes of unsintered powder. Both experimental and numerical investigations have been performed to gain knowledge in these fields. An elasto-plastic Cap model has been developed for powder pressing. To improve modelling of strength in the green state a density dependent failure envelope has been used. The model is implemented as a user material subroutine in a nonlinear finite element program. An inverse method is used to adjust the model behaviour to a water atomised metal powder. The fracture process of powder material is studied experimentally with diametral compression test. The properties of conventional and high velocity compacted (HVC) powder is also studied. Methods to determine the tensile strength and fracture energy in metal powder are presented. The test is virtually reproduced with finite element simulations. The residual stress field of a powder compacted rectangular bar is predicted with 3D and 2D finite element models. The effects of kinematics, friction, compacting pressures and die tapers have also been investigated. Numerical results show that the thickness of the small compressive residual stress region close to the side surface varies between 50 ìm and 600 ìm along the surface. Compacting pressure, "upper punch hold down" and die taper geometry have all a significant influence on the residual stress state while die wall friction has only a small influence. The numerical results are in agreement with results from X-ray and neutron diffraction measurements. The diametral compression test is an established method for measurement of the tensile strength in a brittle material. During the test a load, P, is applied along a diameter inducing compressive stresses. Stresses are tensile perpendicular to the compressed diameter. These tensile stresses act until failure. During fracturing a large crack along the compressive loaded diameter in the centre of the disc is visible. The crack development is studied with both experimental and numerical investigations. The results show that both tensile strength and fracture energy is strongly density dependent. A cohesive material behaviour is observed in the experiments. The central crack is virtually introduced in a finite element model and controlled with a proposed energy based fracture model. A numerical investigation of the tensile fracture process in powder compacts is performed and results are in agreement with experimental results. This work has given a better understanding of residual stress development in powder compacts. Another outcome from this work is a refined experimental method to determine tensile strength and fracture energy of powder material. An energy based fracture model is proposed for numerical simulations of tensile fracture in powder material.Godkänd; 2006; 20061205 (haneit)
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Robinson, Jeremy St John. "Extrusion of rapidly solidified powder compacts." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46338.
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Shang, Chenglong. "Modelling powder compaction and breakage of compacts." Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10824.
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Experimental and numerical simulation studies were carried out to enhance the understanding of the compaction behaviour of powder materials and to study the breakage behaviour of tablets after compaction. In order to simulate powder compaction and post compaction behaviour an appropriate constitutive model is required. To calibrate the constitutive model (e.g. a Drucker-Prager Cap model) a series of experiments were carried out including closed die compaction, uniaxial and diametrical compression tests. A newly developed apparatus consisting of a die instrumented with radial stress sensors was used to determine constitutive parameters as well as friction properties between the powder and die wall. The calibration of constitutive models requires accurate stress-strain curves. During die compaction the deformation of the powder material is determined by considering the elastic deformation (or compliance) of the system. The effect of different compliance correction methods was evaluated with regards to the accuracy of models predicting the pressing forces. A method for accounting for non-homogeneous stress states in instrumented die compaction was also developed. A complete data extraction procedure was presented. The breakage behaviour of flat and curved faced tablets was investigated and the breakage patterns of tablets were examined by X-Ray computed tomography. An empirical equation that relates the material strength to the break force was proposed. The constitutive model was implemented into the finite element package Abaqus/Standard to simulate powder compaction and breakage. A range of failure criteria have been evaluated for predicting break force of flat and curved faced tablets under diametrical compression.
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Subrahmanyam, Gowri. "Sintering and its enhancement in ferrous powder compacts." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/32009.
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Sintering maps have been developed for pure iron compacts. The maps have been drawn as a function of various sintering parameters such as particle size, green density, time and temperature. Two sets of diagrams have been drawn to define the sintering kinetics, namely, the field map and the neck growth/shrinkage map. A new and simple method has been developed to construct the field maps, which define the dominant mechanisms of mass transport that contribute to neck growth under a given set of conditions of sintering. Shrinkage maps, which show how far the neck is growing or give % linear shrinkage for a given neck size and temperature, are generated by numerically integrating, the sum of the contributions to neck growth from the different mechanisms of transport. The model developed is based on ideal geometry and does not take into account complex phenomena such as grain growth, pore coalescence or pore growth.
The sintering equations and diagrams that have been developed for pure iron compacts have been used effectively in the present study to predict and analyze the results of experiments involving various attempts to enhance sintering in such compacts.
Small additions of a selected group of elements were made to iron compacts in an attempt to provide activation of solid state sintering similar to that which is obtained when tungsten powder compacts are doped with nickel. A few of the dopants used with iron compacts produced a small increase in shrinkage and densification for a given set of sintering conditions. Based on the present results and on the several studies of tungsten - nickel compacts which are reported in the literature, a new theory of dopant activated sintering has been proposed. Consistent with this model, it is suggested that certain criteria must be met by the dopant-base metal combination if activated sintering is to be
observed.
Sintering enhancement based on ferrite stabilization in two systems, iron - phosphorus and iron - silicon has been studied. This approach to solid state sintering enhancement proved to be highly effective and it is believed to have important practical applications in the P/M parts industry. The results of these experiments were consistent with predictions
based on the sintering theory and maps appropriate to the conditions of sintering employed.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Çelik, Emrah Güden Mustafa Thesis advisor. "Preparation and characterization of sintered Ti-6A1-4V powder compacts/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000472.doc.
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Candan, Ercan. "Wettability and pressurized infiltration of ceramic powder compacts by metallic melts." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286971.
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Gaboriault, Jr Edward M. "The Effects of Fill-Nonuniformities on the Densified States of Cylindrical Green P/M Compacts." Digital WPI, 2003. https://digitalcommons.wpi.edu/etd-theses/853.
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"We focus attention on single-punch compaction of metal powders in cylindrical dies. In one case, we consider solid cylindrical compacts, and take the die walls to be frictionless in order to isolate the effects of initial nonuniformities in powder fill on the final green density distribution of the compact. First, a model is introduced in which the die is filled with n distinct powders that occupy concentric annular regions within the die. The model requires that the balance of mass, the balance of momentum, and a realistic equation of state be satisfied in each region, and includes a plausible constitutive relation that relates the induced radial pressure in each powder region to the corresponding axial pressure and the relative movements of the interfaces that confine the region. For specified powder properties, the model predicts the movements of the interface between the powders, the final density in each region, the pressure maintained in each region, and the total compaction load required. In the special case of two powders (n=2), we predict how the radial movement of the single interface depends on the mismatch between the properties of the two powders. For large values of n, and for powder properties that change gradually from one powder to the next, the model approximates a single powder filled nonuniformly in the die. Finally, a model is developed for a single powder with continuously varying powder properties. Formally, the model may be obtained by taking the limit of the n-powder model as n becomes unbounded. Employing the continuous model, we determine how nonuniformities in initial fill density can be offset by nonuniformities in other powder properties to yield perfectly uniform green densities. In a second case, we consider axisymmetric, hollow, cylindrical compacts, and include the effects of friction at the die wall and the core rod. The ratio of the induced radial pressure to the applied axial pressure is assumed to be constant throughout the compaction, and Coulomb friction acts between the powder and the die wall as well as between the powder and the core rod. We derive a closed form solution for the axial and radial variation of the axial pressure, radial pressure, and shear stress throughout the compact. This solution is combined with a plausible equation of state to predict the final green density distribution and the variation of applied load throughout the compact."
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Jee, Caroline Siew Yoke. "Experimental investigation and molecular dynamic simulation of binder removal in powder compacts." Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409099.
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Steward, Nigel Ian. "Influence of particle size distribution on the sintering of ceramic powder compacts." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47674.
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Al-Sabbagh, Muhanad Nazar. "Influence of contact strength between particles on constitutive law for powder compaction and the strength of powder compacts." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42788.
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Powder compaction is used in a wide range of industrial applications ranging from powder metallurgy, food, pharmaceuticals, consumer goods, catalysts, fuels briquettes, etc. Powder compaction can be defined in terms of 1) compactibility, which represents the ability to form strong compacts, which is quantified by compact strength and 2) compressibility, which represents the ability of the powder mass to form dense compacts and is described by the constitutive law. The aim of this work is to establish relationships between particle properties, (including mechanical properties of particles and interactions between particles, which are included in the contact law), and bulk powder properties (including compactibility and compressibility). Excipients used in pharmaceutical tablet formulations, such as microcrystalline cellulose, calcium phosphate and mannitol (a sugar) and their mixtures were characterised. Compacts of different densities were manufactured and their compressive and tensile strength was measured. The break force of curved faced tablet made of these materials and mixtures was also measured under an extensive range of conditions. A predictive model was developed and validated to estimate the break force of curved faced tablets using diametrical and uniaxial compression tests only; this has a significant practical importance in the pharmaceutical industry. The mechanical properties of individual particles were characterised using nano-indentation. The data for pharmaceutical excipient were augmented with results for a model powder material consisting of spherical aluminium particles. The now classic micromechanical model of Fleck was used as a theoretical framework to relate particle properties and constitutive laws for compaction. A parameter describing the strength of contact between particles was estimated using the strength of compacts. The contact strength parameter was then related to adhesive contact laws between particles. This work represents the first complete framework for relating contact law (which includes the elastic and plastic properties that determine the deformation of particles in contact and the friction and adhesion between particles) to compact strength.
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Gaboriault, Edward M. "The effects of fill-nonuniformities on the densified states of cylindrical green P/M compacts." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0528103-105536.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: powder metallurgy; density distribution; compaction modeling; compact; powder; compaction. Includes bibliographical references (p. 141-142).
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Li, Tao. "Reaction-bonding of Crâ†2Oâ†3 ceramics." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318804.
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Saha, Deepak. "De-lubrication during sintering of P/M compacts : operative mechanism and process control strategy." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-10014-233109.
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Ng, Siak Hong. "Application of conventional machining techniques for green ceramic compacts produced by powder reaction moulding." Thesis, Nottingham Trent University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429429.
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Altındiş, Mustafa Güden Mustafa. "CaP coating of porous sintered Ti6Al4V powder compacts using biomimetic and sol-gel methods." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000544.pdf.
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Petersen, Shaheeda. "Investigation of the hot deformation of sintered titanium compacts produced from direct reduction powder." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/11748.
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Includes bibliographical references (leaves 110-111).The focus of this study was the use of powder metallurgy to produce low cost titanium with comparative mechanical properties to wrought titanium. The objectives of this investigation was to produce sintered titanium compacts that represented metal made by the Direct Powder Rolling method. The critical strain (ɛC) required to induce recrystallization following deformation was determined by hot compressing wrought titanium samples. Finally sintered titanium samples were hot compressed at ɛC and the changes to the microstructure, porosity and mechanical properties was assessed.
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Saha, Deepak. "De-lubrication during sintering of P/M compacts: Operative mechanism and process control strategy." Digital WPI, 2004. https://digitalcommons.wpi.edu/etd-theses/1049.
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"De-lubrication is the first stage in a sintering operation, where the lubricants (higher weight hydrocarbons) are removed from the parts by controlled heating. Improper de-lubrication leads to defects such as blistering, sooting, micro-porosity etc in a sintered part. Most of these problems arise, as there exists a gap in the present understanding of de-lubrication. The primary motive of this work is to direct research towards the development of sensors and controls and thus, mitigate the various problems due to improper de-lubrication. Currently, there exists a myriad of lubricants being used during the process of compaction. They include metallic based lubricants, polymers and non-metallic lubricants. In this work, research was limited in understanding the de-lubrication of EBS (Ethylene Bisstearimide), as, it the most commonly used lubricant in the industry. It has replaced commonly used lubricant due to cleaner burnouts, absence of metallic residue and, cost effectiveness. The entire work is divided into three phases: • Phase 1: Ascertained the most important parameters that affect the kinetics of de-lubrication. • Phase 2: Investigated the type of gases released during the decomposition of EBS. • Phase 3: Recommended a control strategy. TGA (Thermo-gravimetric analysis) was used in the phase I, the results clearly show that the rate of heating is the most important parameter during de-lubrication. Identification of gases was performed using the FTIR (Fourier transform infrared spectroscopy) and DUV (Deep ultraviolet spectroscopy). This constituted the second phase of our experiments. The primary gases identified in Phase II were carbon dioxide and a hydrocarbon (hepta-decane). Finally, an empirical model for de-lubrication has been proposed in Phase III. The model was verified in an industrial furnace. It has been observed that there exists a very good correlation between the proposed empirical model and the experiments performed in Phase II of this study. This study lays down the following guidelines for the development of future sensors and controls: • The development of future sensors should focus in the detection of CO2 and hepta-decane. • Rate of heating determines how fast or slow the lubricant decomposes and finally escapes form the compacted part. • The empirical model may be used, as a means to determine the time a part should reside in a furnace for complete lubricant burnout at a given heating rate."
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Benzerrouk, Souheil. "Feasibility study of infrared detection of defects in green-state and sintered PM compacts." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0427104-165155.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: powder metallurgy; material evaluation; thermal imaging; NDE; IR radiation and detection; nondestructive testing; thermography; infrared imaging. Includes bibliographical references (p. 86-88).
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Benzerrouk, Souheil. "Active and Passive Thermography for the Detection of Defects in Green-State Powdermetallic Compacts." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/386.
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"Despite its maturity, the powder metallurgy (PM) fabrication process continues to rely heavily on indirect methods to determine and predict the quality of its compacts early in the manufacturing line. Currently, the most comprehensive testing is performed on sintered parts, resulting in higher cost and increased waste. This dissertation addresses the need of early inspection by developing a novel approach whereby PM compacts are tested in the green-state without intrusion and with minimal cost per compact tested. The method is based on an infrared detection scheme with two fundamental embodiments. For high resolution applications, or offline testing, an active thermography approach is adopted; electric energy is deposited into the compact in a contact-less fashion to evaluate all parts for cracks, inclusions, or delaminations. As an alternative, for lower resolution high-yield applications, a system based on a passive thermography approach is developed. This system relies on residual heating emanating from the process. Thermal data is then collected and analyzed in an effort to yield part integrity and process stability information. In this dissertation we will discuss our design approach, theoretical modeling aspects, and a proof-of-concept instrument with associated data processing software. We will first describe the underlying physical principles, followed by predictions from the modeling formulation, including a solution of the heat equation. As part of our experimental data processing, we will present results that are collected both in a laboratory setting and in an industrial manufacturing line. The integrity of the compacts is carried out with the aid of a specialized software package."
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Smith, Graham T. "The secondary machining of Fe-Cu-C ferrous powder metallurgy compacts by turning, boring and drilling." Thesis, University of Birmingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395323.
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Galen, Steven Zavaliangos Antonios. "Path dependence and strength anisotropy of mechanical behavior in cold-compacted powders /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/438.
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Peacock, Simon. "Mechanical properties of rotary forged sintered steel compacts." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319953.
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O'brien, Jonathan. "Medium Power, Compact Periodic Spiral Antenna." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4926.
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Historical, well developed, procedures for RF design have minimal emphasis on exploring the third dimension due to the difficulty of fabrication. Recent material advancements applicable to 3D printing have brought about low-loss thermoplastics with excellent mechanical properties. Research into depositing conductive inks onto arbitrary 3D shapes has achieved resolutions better than 50 μm with conductivity values approaching that of copper cladding. The advancements in additive manufacturing have improved reliability and repeatability of three dimensional designs while decreasing fabrication time. With this design approach other considerations, such as stability and strength, can be concentrated on during the structure design to realize new shapes. The next step in the future of RF research will encompass designing and further understanding the benefits and consequences of using all three dimensions. This could include meandering an antenna element around other electronic components to make the overall package size smaller or integrating an antenna array into a wing.
The design and analysis of the periodic spiral antenna (PSA) takes a look at a specific case of full volume utilization. In this application meandering in the z-dimension allowed the design to become smaller and more efficient than what is achievable with planar methods. This thesis will go into detail on the characterization of the periodic spiral antenna. To exemplify the benefits of meandering in the z-dimension a loop antenna is presented and benchmarked against other miniaturization techniques. Measured results of two different PSA models are presented and remarks on improving fabrication are given. When an antenna is used as a transmitter incident power will cause thermal generation so a study was conducted to understand how material properties can govern the amount of heat generated.
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Kolessar, Rémy. "Compact modeling of Si and SiC power diodes /." Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3186.
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Li, Hongbo. "Modeling Compact High Power Fiber Lasers and VECSELs." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202712.
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Compact high power fiber lasers and the vertical-external-cavity surface-emitting lasers (VECSELs) are promising candidates for high power laser sources with diffraction-limited beam quality and are currently the subject of intensive research and development. Here three large mode area fiber lasers, namely, the photonic crystal fiber (PCF) laser, the multicore fiber (MCF) laser, and the multimode interference (MMI) fiber laser, as well as the VECSEL are modeled and designed.For the PCF laser, the effective refractive index and the effective core radius of the PCF are investigated using vectorial approaches and reformulated. Then, the classical step-index fiber theory is extended to PCFs, resulting in a highly efficient vectorial effective-index method for the design and analysis of PCFs. The new approach is employed to analyze the modal properties of the PCF lasers with depressed-index cores and to effectively estimate the number of guided modes for PCFs.The MCF laser, consisting of an active MCF and a passive coreless fiber, is modeled using the vectorial mode expansion method developed in this work. The results illustrate that the mode selection in the MCF laser by the coreless fiber section is determined by the MMI effect, not the Talbot effect. Based on the MMI and self-imaging in multimode fibers, the vectorial mode expansion approach is employed to design the first MMI fiber laser demonstrated experimentally.For the design and modeling of VECSELs, the optical, thermal, and structural properties of common material systems are investigated and the most reliable material models are summarized. The nanoscale heat transport theory is applied for the first time, to the best of my knowledge, to design and model VECSELs. In addition, the most accurate strain compensation approach is selected for VECSELs incorporating strained quantum wells to maintain structural stability. The design principles for the VECSEL subcavity are elaborated and applied to design a 1040nm VECSEL subcavity that has been demonstrated for high power operation of VECSELs where near diffraction-limited output over 20 W is obtained. Physical modeling of the VECSEL is also discussed and used to compare VECSEL subcavity designs on the laser level.
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Fletcher, Steven. "Protection of physically compact multiterminal DC power systems." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=19507.
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The use of DC for primary power distribution has the potential to bring significant design, cost and effciency benefits to microgrid, ship- board and aircraft applications. The integration of active converter technologies within these networks is a key enabler for these bene ts to be realised, however their in uence on an electrical network's fault response can lead to exceptionally demanding protection requirements. This represents a significant barrier to more widespread adoption of DC power distribution. The principle challenge within the field is to develop protection solutions which do not significantly detract from the advantages which DC networks offer. This objective leads the thesis to not only consider how the protection challenges may be overcome but also how this can be achieved in a manner which can benefit the overall design of a system, inclusive of various system design objectives. The thesis proposes that this objective can be achieved through the operati on of network protection within the initial transient period following the occurrence of a fault. In seeking to achieve this aim, the work presented within this thesis makes a number of contributions. The thesis categorises converter type based on the components which in uence their fault response and then presents an analysis of the natural fault response of compact multiterminal DC power distribution networks containing these converters. Key factors such as the peak magnitudes and formation times of fault current profiles are determined and quantified as a function of network parameters, enabling protection system operating requirements to be established. Secondary fault effects such as voltage transients are also identified and quantified to illustrate the impact of suboptimal protection system operation. The capabilities of different protection methods and technologies for achieving the proposed operating requirements are then analysed. Significant conclusions are: solid state breaking technologies are essential to achieving operating targets and severe limitations exist with the application of protection methods available within literature for this application. To overcome these shortfalls, novel fault detection approaches are proposed and analysed. These approaches enable fault detection time targets to be met as well as aid with the effective integration of future circuit breaking technologies.
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O'Connor, Kevin A. Curry Randy D. "Compact power conditioning and RF systems for a high power RF source." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6285.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 19, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Randy Curry, Thesis Supervisor Includes bibliographical references.
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Ahmed, Shehab. "Compact harsh environment energy conversion systems." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1289.
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Aripirala, Manoj Kumar. "A compact switching mode class-f power amplifier design." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55062.
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Even though there had been extensive research in Switching Mode Power Amplifier design their applications at industry level are quite limited. This is because a Fully-Integrated Switching Mode Power Amplifier using conventional active devices such as Bipolar Junction Transistors (BJT) or Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is challenging due to the inherent design challenges in the Switching Power Amplifier design.
A Fully-Integrated Differential Class-F2,3 Power Amplifier design is explored for this Thesis research. This Power Amplifier has a maximum theoretical efficiency of 90.7% but this value is reduced because of the switching nature of the active device, parasitic effects associated with layout and the quality factor of the passive components used. Waveform shaping required for a Class-F Power Amplifier is done using the stray inductances within a non-ideal transformer instead of individual inductors. This techniques effective reduces the foot prints of two inductors for the tuning network design and make a Fully-Integrated solution more practical.
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Soares, Diogo Lopes. "Design of multidimensional compact constellations with high power efficiency." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/11111.
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Rakhra, Puran. "On the protection of compact DC power systems with high-power energy storage." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28516.
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High-power energy storage systems (ESS) are being considered for future aerospace platforms and other compact DC power system applications to improve the overall transient performance of electrical power distribution systems. These sources are being integrated with advanced bidirectional power electronic converter interfaces with high bandwidth control systems and current limiting functionality. To date, the literature has primarily focused on the control and behaviour of high-power ESS during normal operating conditions with an emphasis on the systems level benefits they offer. Little consideration has been given to their response during network fault conditions. Through simulation and hardware experimentation, this thesis demonstrates that an ESS, by design, can contribute significant levels of current to a fault as it attempts to sustain the network voltage. This behaviour inadvertently reduces the fault current contribution from the primary source of power on the network, reducing the effectiveness of associated protection devices (protection blinding). The impact of several key DC power system design and operation parameters on the ESS fault response is quantified and a new critical fault impedance term, beyond which protection blinding can be expected to occur, is introduced. Building upon this new knowledge, enhancements to typical compact DC power system protection schemes which more effectively account for the presence of ESS are proposed and evaluated. Differential protection schemes are shown to eliminate protection blinding whilst offering the greatest flexibility in increasing protection speed and fault discrimination, and maximising ESS availability. Adaptive protection schemes are shown to be a reliable backup option where a consistent protection system response can be obtained despite the potentially intermittent nature of the ESS fault current contribution. A novel control strategy that actively modifies the fault response of the ESS to facilitate the use of conventional overcurrent schemes is also proposed and demonstrated for applications where communications-based protection is unfavourable. The thesis concludes by proposing a framework to guide protection engineers in the selection of appropriate protection and control strategies when considering the integration of high-power ESS within compact DC power systems.
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Kim, Sunghwan. "Phase shifter approaches for compact low-power phased array transmitters." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3398530.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed May 5, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 103-109).
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Li, Z. M. "Power semiconductor devices : two-dimensional simulation and compact model development." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637903.
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The mixed-mode modelling methodology is essential to extend the benefit of computer-aided design (CAD) techniques to the design of power electronic circuits. The mixed-mode environment can be established in two ways. One is through adopting device circuit models into the two-dimensional device simulator. The other is through introducing finite-element device models into the circuit simulator. In the first method, an effective numerical algorithm has been proposed for adopting advanced compact models for power devices into a general-purpose two-dimensional mixed-mode device/circuit simulator. A suite of compact models for major power devices are implemented into the simulator and validated. In the second method, simplified numerical models for power diodes and insulated gate bipolar transistors (IGBT) for the circuit simulator Saber is proposed. Comparisons of the new models with the other compact model and the experimental result are made and show good agreement. It is also shown that the speed of the numerical models can be increased enormously to be comparable with the speed of other compact models in some cases by using specific numerical techniques. Techniques for measuring fast power devices and extracting the parameters are studied and enhanced, a commercial IGBT device is measured, the parameter extraction procedure applied and device characterised. Two-dimensional device simulation has been used extensively for understanding the devices and to help in the compact model development. Two-dimensional numerical analysis of the quasi-saturation phenomenon in the vertical double-diffused MOS (VDMOS) device is carried out and improved design proposed.
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Colaç̦o, Andrea B. (Andrea Brazilin Immaculate Danielle). "Compact and low-power computational 3D sensors for gestural input." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91437.
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Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2014.87
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 141-150).
Mobile devices have evolved into powerful computing platforms. As computing capabilities grow and size shrinks, the most pronounced limitation with mobile devices is display size. With the adoption of touch as the de facto input, the mobile screen doubles as a display and an input device. Touchscreen interfaces have several limitations: the act of touching the screen occludes the display, interface elements like on-screen keyboards consume precious display real estate, and navigation through content often requires repeated actions like pinch-and-zoom. This thesis is motivated by these inherent limitations of using touch input to interact with mobile devices. Thus, the primary focus of this thesis is on using the space around the device for touchless gestural input to devices with small or no displays. Capturing gestural input in this volume requires localization of the human hand in 3D. We present a real-time system for doing so as a culmination of an exploration of novel methods for 3D capture. First, two related systems for 3D imaging are presented, both relying on modeling and algorithms from parametric sampling theory and compressed sensing. Then, a separate system for 3D localization, without full 3D imaging, is presented. This system, Mime, is built using standard, low-cost opto-electronic components - a single LED and three baseline separated photodiodes. We demonstrate fast and accurate 3D motion tracking at low power enabled by parametric scene response modeling. We combine this low-power 3D tracking with RGB image-based computer vision algorithms for finer gestural control. We demonstrate a variety of application scenarios developed using our sensor, including 3D spatial input using close-range gestures, gaming, on-the-move interaction, and operation in cluttered environments and in broad daylight conditions.
by Andrea B. Colaç̦o.
Ph. D.
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Lim, Yong Chuan Mark. "Slotted cylindrical ring (SCR) resonator for compact microwave filters." Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364497.
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Todeschini, Fabien. "Dimensionnement énergétique de réseaux de capteurs ultra-compacts autonomes en énergie." Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0008/document.
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Les capteurs sans fil ont un avenir prometteur c’est pourquoi leur développement est àl’origine de nombreuses recherches. Leur autonomie reste cependant un problème à résoudre.Les travaux de cette thèse se concentrent précisément sur cette problématique : trouverune stratégie permettant aux capteurs d’être autonomes en énergie.L’énergie nécessaire à l’alimentation du capteur, quel que soit son mode de fonctionnement,doit en effet être récupérée de l’environnement dans lequel le capteur se trouve. Deplus, en cas d’absence ou d’insuffisance d’énergie environnante, le fonctionnement du capteurdoit pouvoir perdurer. À cela s’ajoute la nécessité de connaitre à tout instant la quantitéd’énergie disponible afin de pouvoir maintenir un niveau de charge constant et ainsi prolongerla vie du capteur. Enfin, toute cette gestion de l’énergie doit pouvoir garantir le meilleurrendement possible.Cette étude a conduit à la conception et au test d’un circuit en technologie CMOS 90nm.Ce même circuit a été intégré dans les capteurs sans fil d’un réseau en cours de développement.Et enfin, une méthode permettant de connaitre le niveau d’énergie embarquée a étémise au point et pourra permettre à l’avenir la conception d’un nouveau circuit de power managementpour capteurs autonomes en énergieWireless sensors have a bright future so their development is causing a lot of research.However, their autonomy is still an issue.This work focuses on this problem : find a strategy for the sensors to be autonomous.The energy required to power the sensor, whatever its working mode, must indeed be harvestedfrom the environment wherein the sensor is located. Moreover, in case of absence ora lack of available energy, the sensor has to keep working. Additionnaly the state-of-chargehas to be known in real time in order to extend the sensor lifetime. Finally, the energy managementhas to give the highest efficiency.This study led to the design and the test of a circuit in CMOS 90nm technology. Thiscircuit was integrated in wireless sensors for networks under development. Finally, a methodto estimate the level of energy in the sensor has been developed and will allow to design anew circuit of power management for wireless sensor network
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Aston, Steven David. "Acoustic techniques for property estimation in green and fired ceramic powder compact components." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323738.
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A commonly used process for the formation of ceramic wall tile bodies is powder compaction. Variations in density in wall tile bodies introduced by the compaction process can cause rejection at later stages of production. Quality control equipment currently employed does not identify reject bodies in the unfired state. Scope exists to reduce production costs by the timely removal of reject bodies in the unfired state. In this thesis an ultrasonic non-destructive technique is presented which allows the mapping of the density variations found in wall tile bodies in the unfired and fired states to an accuracy of ± 0.5%. An effective medium theory for the propagation of ultrasound in porous media is developed. The significance of the dependence of Young's modulus on density in determining the relationship between compression wave propagation velocity and density is explored. Using a vibrational resonance technique, it is shown that the evolution of Young's modulus and Poisson's ratio in the wall tile body material are very sensitive to the conditions used for the firing operation. The Biot two-phase theory of acoustic propagation in fluid saturated porous media which considers dissipation due to friction between the fluid and porous frame is reviewed, and the applicability to the wall tile body material assessed. It is shown that this dissipation mechanism is insignificant for this particular material. A modification is made to the model in an attempt to include dissipation due to the inelasticity and scattering of the porous frame. The results show that the two-phase theory reduces to an effective medium theory in the limit of the saturating fluid being air. The thesis concludes that density variations in wall tile bodies can be measured using and ultrasonic technique and that an effective medium theory can be used to describe the propagation of ultrasound in porous media.
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Li, Li. "Extremely Compact High-Power Er3+-Yb3+-Codoped Phosphate Glass Fiber Lasers." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/193824.
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Extremely compact high-power fiber lasers operating at eye-safe telecom wavelength of 1.5 μm have been achieved by systematic experimental studies. Heavily Er3+-Yb3+-codoped phosphate glasses have been chosen as the host glass for our fibers and 1.5 μm lasers have been realized when pumped with 975 nm laser diodes.The first short-length cladding-pumped fiber laser with watt-level CW output power has been demonstrated by an 11-cm-long doped step-index phosphate fiber. Without active cooling, 1.5 W output power at 1535 nm has been obtained.Thermoelectric cooler has been used for heavily doped phosphate step-index fibers. A dual-end-pumped actively cooled fiber laser has generated more than 11 W CW output power at 1535 nm from an 11.9 cm long active fiber. A fully 3-dimensional thermal analysis has been performed to calculate the internal temperature distribution of the short-length fiber laser and the simulated results have been experimentally verified.Phosphate glass microstructured optical fibers (MOFs) with large active cores have been fabricated. The first demonstrated short phosphate MOF laser has generated > 3 W single-mode CW output power from an 11-cm-long fiber. The impacts of depressed-core-index and annealing upon MOF's modal property have been systematically investigated. Extremely compact high-power fiber laser is demonstrated by a heavily doped MOF laser and > 4.5 W single-mode CW output power is delivered from a 3.5 cm long fiber. Finally, a high-power single-frequency fiber laser is realized by splicing a FBG with a 3.8 cm long MOF, which achieves > 2 W single-frequency output power.
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Mostaghim, Besarati Saeb. "Analysis of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrated Solar Power Applications." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5431.
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Solar power tower technology can achieve higher temperatures than the most common commercial technology using parabolic troughs. In order to take advantage of higher temperatures, new power cycles are needed for generating power at higher efficiencies. Supercritical carbon dioxide (S-CO2) power cycle is one of the alternatives that have been proposed for the future concentrated solar power (CSP) plants due to its high efficiency. On the other hand, carbon dioxide can also be a replacement for current heat transfer fluids (HTFs), i.e. oil, molten salt, and steam. The main disadvantages of the current HTFs are maximum operating temperature limit, required freeze protection units, and complex control systems. However, the main challenge about utilizing s-CO2 as the HTF is to design a receiver that can operate at high operating pressure (about 20 MPa) while maintaining excellent thermal performance. The existing tubular and windowed receivers are not suitable for this application; therefore, an innovative design is required to provide appropriate performance as well as mechanical strength.
This research investigates the application of s-CO2 in solar power tower plants. First, a computationally efficient method is developed for designing the heliostat field in a solar power tower plant. Then, an innovative numerical approach is introduced to distribute the heat flux uniformly on the receiver surface. Next, different power cycles utilizing s-CO2 as the working fluid are analyzed. It is shown that including an appropriate bottoming cycle can further increase the power cycle efficiency. In the next step, a thermal receiver is designed based on compact heat exchanger (CHE) technology utilizing s-CO2 as the HTF. Finally, a 3MWth cavity receiver is designed using the CHE receivers as individual panels receiving solar flux from the heliostat field. Convective and radiative heat transfer models are employed to calculate bulk fluid and surface temperatures. The receiver efficiency is obtained as 80%, which can be further improved by optimizing the geometry of the cavity.
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Wang, Wenhai Zavaliangos Antonios. "Towards an improved understanding of strength and anisotropy of cold compacted powder /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1865.
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Ghanadi, Mehdi [Verfasser], and Heino [Akademischer Betreuer] Henke. "A New Compact Broadband Radial Power Combiner / Mehdi Ghanadi. Betreuer: Heino Henke." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1019398558/34.
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Hasan, Md Naimul. "A Compact Low Power Bio-Signal Amplifier with Extended Linear Operation Range." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1358074945.
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Sajedin, M., Issa T. Elfergani, Jonathan Rodriguez, Raed A. Abd-Alhameed, M. Fernandez-Barciela, and M. Violas. "Ultra-Compact mm-Wave Monolithic IC Doherty Power Amplifier for Mobile Handsets." MDPI, 2021. http://hdl.handle.net/10454/18600.
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YesThis work develops a novel dynamic load modulation Power Amplifier (PA) circuity that can provide an optimum compromise between linearity and efficiency while covering multiple cellular frequency bands. Exploiting monolithic microwave integrated circuits (MMIC) technology, a fully integrated 1W Doherty PA architecture is proposed based on 0.1 µm AlGaAs/InGaAs Depletion- Mode (D-Mode) technology provided by the WIN Semiconductors foundry. The proposed wideband DPA incorporates the harmonic tuning Class-J mode of operation, which aims to engineer the voltage waveform via second harmonic capacitive load termination. Moreover, the applied post-matching technique not only reduces the impedance transformation ratio of the conventional DPA, but also restores its proper load modulation. The simulation results indicate that the monolithic drive load modulation PA at 4 V operation voltage delivers 44% PAE at the maximum output power of 30 dBm at the 1 dB compression point, and 34% power-added efficiency (PAE) at 6 dB power back-off (PBO). A power gain flatness of around 14 ± 0.5 dB was achieved over the frequency band of 23 GHz to 27 GHz. The compact MMIC load modulation technique developed for the 5G mobile handset occupies the die area of 3.2.
This research was funded by the European Regional Development Fund (FEDER), through COMPETE 2020, POR ALGARVE 2020, Fundação para a Ciência e a Tecnologia (FCT) under i-Five Project (POCI-01-0145-FEDER-030500). This work is also part of the POSITION-II project funded by the ECSEL joint Undertaking under grant number Ecsel-345 7831132-Postitio-II-2017-IA. This work is supported by FCT/MCTES through national funds and when applicable co-funded EU funds under the project UIDB/50008/2020-UIDP/50008/2020. The authors would like to thank the WIN Semiconductors foundry for providing the MMIC GaAs pHEMT PDKs and technical support. This work is supported by the Project TEC2017-88242-C3-2-R- Spanish Ministerio de Ciencia, Innovación e Universidades and EU-FEDER funding.
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Bonnet, Sebastien. "Combinaison de puissance hyperfréquence à faibles pertes et compacte." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0072/document.
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Ces travaux de thèse concernent le développement de combineur de puissance faibles pertes et compact selon une architecture planaire pour des applications amplificateur de forte puissance à état solide en bande X. La conception du combineur de puissance s’appuie sur l’étude de structures multicouches faibles pertes et compactes en triplaque à air suspendu. Une étude électromagnétique et thermique est proposée pour déterminer les performances de ces structures de transmission dans la bande X. Un système de refroidissement est également mis en place pour permettre aux structures de transmission de tenir des puissances moyenne de l’ordre de 50 W. La réalisation et la caractérisation de ces structures triplaques à air ont permis de démontrer les caractéristiques de faibles pertes et de compacité de ces circuits imprimés. Cette technologie triplaque à air suspendue est alors compatible pour des applications de forte puissance comme les émetteurs à état solideThis PhD thesis deals with planar architecture design development of low loss and compact power combiner for solid-state high power amplification in X-band. The design is based on the study of innovative multilayer air dielectric stripline transmission structures. A reliable printed circuit process allows to obtain low loss, compact and replicable stripline structures. Electromagnetic FEM and thermal studies are proposed to evaluate transmission structures performances in X-band. Two compact and scalable structures were developed and may be integrated into complex multilayer systems. Finally a cooling system with periodic ceramic contacts is developed to improve the power handling capability of these stripline structures up to 50 W. The study, development and benchmark of these stripline structures demonstrated their compactness and low loss behaviour. Ultimately, these attributes make them excellent candidates for high power solid-state emitters
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Cunningham, John C. Zavaliangos Antonios. "Experimental studies and modeling of the roller compaction of pharmaceutical powders /." Philadelphia, Pa. : Drexel University, 2006. http://dspace.library.drexel.edu/handle/1860%20/837.
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Scarpignato, Gerardo Cristian. "Conception, fabrication et caractérisation d'un amplificateur de puissance à base de verres spéciaux pour les sources LIDAR." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT008.
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L'objectif de ce travail de recherche est l'étude, la réalisation et la caractérisation d'un amplificateur de puissance à base de verres spéciaux devant être inséré dans un dispositif laser impulsionnel à cohérence élevée opérant a la longueur d'onde de 1550 nm en configuration MOPA (Master Oscillator Power Amplifier). Il aura pour fonction d'amplifier le signal provenant d'un laser source afin de pouvoir le propager sur des distances élevées sans pour autant dégrader ses caractéristiques spectrales ou sa cohérence. Le dispositif ainsi obtenu sera utilisé comme source laser pour des systèmes LIDAR compact pouvant soit être embarqués à bord d'avions ou de voitures; soit être utilisés dans des stations météorologiques ou des aéroports. Un tel projet représente une innovation majeure dans le domaine des capteurs laser fonctionnant en espace libre. Il s'agit en effet de réaliser des dispositifs compacts qui n'existent pour l'instant pas aussi bien de façon commerciale que des les laboratoires de rechercheThe objective of the present research is the study, fabrication and characterization of a power amplifier based on special glasses to be implemented as an embedded module inside a pulsed laser device with high coherence working at 1550 nm wavelength. The optical amplifier represents the second module of a laser in configuration MOPA (Master Oscillator Power Amplifier). The device must amplify the signal proceeding from a seed laser and allow the propagation of the signal at high distances while maintaining the spectral characteristics of the high coherent source. The device obtained with this approach will be employed as a source for a monitoring LIDAR system, which will be installed in train monitoring portals. The results can be extended to other applications as well, such as aeroplanes, meteorological stations or airports. The current research work is intended to contribute to the fabrication of compact devices that seems not be still available even in laboratories
Lo scopo della presente ricerca `e lo studio, la realizzazione e la caratter-izzazione di un amplificatore di potenza a base di vetri speciali da utiliz-zare come modulo da implementare all’interno di un dispositivo laser adimpulsi ad elevata coerenza operante alla lunghezza d’onda di 1550 nm.L’amplificatore ottico rappresenta il secondo modulo di un laser in configu-razione MOPA (Master Oscillator Power Amplifier): esso ha la funzione diamplificare il segnale proveniente da un laser “seed” e permette di propa-gare il suo segnale ad elevate distanze, mantenendo tuttavia le caratteris-tiche spettrali di elevata coerenza della sorgente. Il dispositivo cos`ı ottenutosar`a utilizzato come sorgente per un sistema LIDAR di rilevazione a bordodi aerei, autoveicoli e stazioni meteorologiche o aeroporti. Questi sistemisembrano non essere ancora disponibili neanche a livello dei laboratori diricerca
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Counihan, Patrick John. "Nanostructured single-phase Ti₅Si₃ produced by crystallization of mechanically amorphized and shock densified powder compact." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19984.
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Dora, Venkata Mohana Murali Krishna [Verfasser]. "Compact storage-based resistance spot welding power supplies / Krishna Dora Venkata Mohana Murali." Paderborn : Universitätsbibliothek, 2016. http://d-nb.info/1117642097/34.
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Hoa, Xuyen D. 1976. "An investigation of a compact micro-optic and micromirror-based optical power equalizer /." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81539.
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This thesis examines the design and characterisation of a compact optical power equalizer module for optical fiber telecommunication applications. The various components of the modules are separately examined in terms of their impact on the overall dimension, performance and loss of the equalizer module. Two components are studied in greater details, namely the micro diffractive optical elements (DOEs), responsible for the multiplexing/demultiplexing of the wavelength channels, and the micromirrors, responsible for creating the beam displacements and thus controlling the attenuation. The DOEs allow for the spatial separation of 64 wavelengths into a two-dimensional array with a compact module. MUMPs surface-micromachined micromirrors have good optical properties: 0.29 dB (93.5%) reflectance, low surface sag and negligible curvature. At operating voltages of less than 15 V, tilts of 16 mrad are obtained, sufficient to provide over 50 dB attenuation for the equalizer. Simulation results show that the diffractive elements have low efficiency due to fabrication limitations. The power loss due to beam clipping is 2.81 dB with overall system efficiency at above 5 dB. Major areas of improvement in the device packaging, assembly and efficiency have been identified for future works.