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1
RESTA, FEDERICA. "Integrated Read-out Front-end for High-Energy Physics Experiments." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/158121.
Texte intégralRésumé :
Le ricerche e le scoperte fatte nell'ambito della fisica sono fortemente dipendenti dall'efficienza e dall'affidabilità degli esperimenti ad alta energia. L'obiettivo principale è lo studio delle particelle che costituiscono la materia in termini di cariche elementari, loro interazioni e prodotti secondari che ne possono derivare. L'LHC (Large Hadron Collider) lavora al CERN ogni giorno con l’obiettivo di scoprire nuovi dettagli su particelle cariche come neutroni e Bosoni di Higgs. Queste sono generate e accelerate all’interno dell’LHC e vengono rilevate da opportuni detector organizzati in una struttura a shell. In questo modo, è possibile avere una caratterizzazione in termini di momento, carica elettrica, energia, tempo di volo e distanza associati alla particella rilevata.
La progettazione dei rilevatori è importante come anche quella dell’elettronica vicina. Un grande esperimento richiede un duro lavoro di scienziati e ingegneri. Negli ultimi anni, l’elettronica è sempre più efficiente e compatta grazie alla sostituzione dei componenti discreti con circuiti integrati CMOS. La progettazione deve essere però fatta considerando sia le reti di interfacciamento con i sensori sia l’ambiente radiattivo circostante. Le radiazioni, infatti, possono modificare parzialmente o totalmente le performance e la scelta della tecnologia scalata può però essere di grande aiuto.
In questo scenario, sono stati progettati, integrati e misurati 3 circuiti di lettura per esperimenti di fisica delle alte energie. 2 prototipi sono stati realizzati in tecnologia 130nm per l'esperimento ATLAS in collaborazione dell’Istituto Max-Plank di Monaco. Questi prototipi sono pensati per rilevare cariche fino a 100fC e convertirle in un segnale di tensione di ampiezza variabile che sarà processato in digitale per avere informazioni sull’istante di arrivo della carica e sulla sua intensità. A tal fine, gli integrati hanno uno stadio di discriminazione ed un Wilkinson ADC in grado di convertire in un tempo il segnale in tensione ricevuto.
Il secondo prototipo è molto simile al primo. Esso è stato migliorato principalmente per poter essere più immune ai disturbi provenienti da masse e alimentazioni.
Il terzo circuito presentato in questa tesi è un sistema di lettura progettato per Pixel detectors in tecnologia
CMOS 28nm. Il canale integrato include un preamplificatore di carica con un comparatore in cascata. L'utilizzo della tecnologia 28nm con la sua ridotta alimentazione comporta una serie di difficoltà nella progettazione ma anche una maggiore resistenza alle radiazioni, consumi ridotti e una minor area occupata.
I circuiti sono stati progettati per due differenti scenari in termini di capacità parassita del rilevatore, cariche di ingresso rilevabili, alimentazioni, soglie, consumi di potenza e rumore. In tutti i casi, però, i sistemi sono in grado di fornire le informazioni sulla carica rilevata in tempi relativamente rapidi (entro 25ns). Questo aspetto è molto importante e permette di evitare errori. Collisioni successive potrebbe causare segnali spuri e si potrebbe rilevare come unico evento due eventi distinti e consecutivi.
Questo lavoro è organizzato come segue. La Parte I include una breve introduzione sull'intera attività svolta nei tre anni di attività di ricerca. La Parte II è dedicata alla descrizione semplificata del campo di applicazione ed ai target previsti per i prossimi esperimenti di fisica. In particolare, sono forniti alcuni dettagli su come l'elettronica può essere influenzata dalla presenza delle radiazioni.
Le parti III e IV rappresentano il core della tesi perché mirano all'analisi dettagliata dei circuiti progettati e descritti precedentemente in maniera generica. L'analisi prevede una caratterizzazione completa degli integrati con simulazioni e misure.
Infine, prima di concludere, la Parte V è dedicata alla pubblicazioni correlate all'attività di ricerca.<br>Physic researches and discoveries depend heavily from efficient and reliability of the High-Energy Physics
(HEP) experiments. The main goal is to study the fundamental constituents of the matter in terms of elementary charge particles, their interactions and their secondary products.
The Large Hadron Collider (LHC) at the CERN works every day to discover details on new charged particles as neutrinos and Higgs Bosons. Charges are generated and accelerated from beam collisions inside the LHC. Different detectors are organized in shell structures and are designed to detect few particles topology. Typically, the parameters useful to identify a charged particle are momentum, electrical charge, energy, time of flight and distance. Detectors design is important but it is enhanced from proper electronic readout systems. In the last years, electronics parts are more and more efficient and compact. CMOS integrated solution are preferred to discrete one allowing major reliability, cost reduction and performance improvement. The design is not trivial but not impossible. Some characteristics depend on the electronic designer and his capability to manage the external parasitic effects, as the parasitic capacitance of the connected detector.
Unfortunately, phenomena as radiation effects on electronics must be taken in account but they are not completely eliminated. CMOS technology influences strongly the integrated circuit performance and radiation hardness.
In this scenario, 3 readout frontend circuits for HEP experiments have been designed, integrated and measured. 2 of them represent 2 different prototypes realized in IBM 130nm technology for ATLAS experiment at CERN laboratory with Max-Plank Institute for Physics collaboration. They include an analog chain in cascade with a digital one. Input charges (up to 100fC) are detected and converted into voltage signals. Their amplitude are proportional to the input and are sent to the following digital part. The digital part provides information about arrival time and amount of the input charge. When the discriminator switches, an event is detected and the Wilkinson ADC starts the voltage-to-time conversion. The full chips have a JTAG section to manage all programmable parameters (i.e. thresholds, hysteresis, deadtime, etc.)
The second prototype is designed improving the previous version in terms of supply rejection noise, deadtime range and hysteresis management. The third circuit presented in this thesis is the first readout frontend for Pixel detectors in 28nm technology. The channel includes a charge sensitive preamplifier with an inverter switched based comparator. Reduced supply voltage and 28nm technology imply some difficult in the design with a major tolerance to the radiations, a lower area occupancy and a lower power consumption.
The circuits are been designed for 2 different scenarios in terms of detector parasitic capacitance, detectable input charges, supply voltage, threshold voltage, power consumption and noise. In overall cases, the integrated systems provide information about amount of detected input charge and arrival time within 25ns.
This aspect is very important and allows avoiding mistakes. Successive collisions lead to spurious signals presence and a single detection could have information about two different events. Maintaining the processing time within 25ns, consecutive collisions are detected as different events. This work is organized as follows. Part I includes a brief summary of the entire work in order to fix the goals of my activities. Then, the Part II is dedicated on a simplified description of the application field and the next target of the future experiments. In particular, some details on the effects induced by the radiation to integrated electronic component are provided. Part III and Part IV represent the core, including 3 readout frontend circuits design and measurements. Finally, there are correlated publications and conclusions.
2
Riceputi, Elisa (ORCID:0000-0002-0542-553X). "Design and Test of Imaging and Particle Detection Microelectronic System for Frontier Research Applications." Doctoral thesis, Università degli studi di Bergamo, 2018. http://hdl.handle.net/10446/105286.
Texte intégralRésumé :
Over the last decades, the use of CMOS integrated circuits has largely diffused in many different fields and, in particular, in the readout of radiation detectors. Among the advantages of an integrated CMOS technology, high integration density, capability of handling large data rates, small form factor and last but not least, high radiation resistance are crucial to meet the demanding specifications of modern physics experiments using high granularity detectors.
In a well studied realization of an analog readout channel for a radiation detector, three foundamentals steps are needed:
- 1 - characterization of the CMOS nanoscale technology that will be adopted to design the analog channel;
- 2 - desing and simulation of the circuit;
- 3 - characterization and validation of the final chip.
Nanoscale CMOS technology are provided with detailed models capable of perfectly describing the behavior of the transistors for digital applications. Models describing transistors characteristics for analog applications can be not so accurate as far as noise and radiation effects are concerned. In particular noise characteristics, and above all flicker noise, are stongly dependent on the technology, thus an in-depth characterization is needed. Moreover, normally, there are no information regarding the radiation hardness of the technology, thus a detailed analysis at the expected radiation doseis needed depending on the scope of the electronic readout.
Once these peculiar aspects of the chosen technology are defined and analyzed, it is possible to move forward to the second step: design and simulate the circuit meeting the specifications required from the application.
Last but not least, there is the characterization and the validation of the final chip. This step has the goal of verifying the correct functioning of the system. Such phase could also highlight some problems of the designed circuits that ideal simulation did not point out, so that the designers will be able to cope such with defects in the following production steps.
Usually, chip development is not carried out only by one work group, but with a collaboration of different Universities and Institutions. In this thesis, all these steps were taken into account for three different projects: RD53, GAPS and DSSC. All these 3 projects require the design and test of custom integrated circuit for the readout of silicon pixel or strip detectors, with avdanced analog signal processing features providing a low noise performance. Additional requirements such as radiation hardness may depending on the application, as discussed in the following chapters.
In particular, the first part of the work provides an extensive analysis of total dose effects in devices belonging to a commercial 65 nm and 110 nm CMOS process, in the context of designing rad-hard analog integrated circuits for front-end applications in future colliders. This activity has been carried out in the framework of the RD53 collaboration. The aim of this project is to design the next generation of hybrid pixel readout chips for the silicon vertex inner tracker of the ATLAS and CMS detectors of the Lrge Hadron collider (LHC) at CERN facility.
The second part of the work concerns the design of the analog reading channel of a novel cosmic antideuteron detector. This work is carried out for the GAPS project that has the aim to realize a novel approach for indirect dark matter searches. NASA approved GAPS's proposal in September 2016. GAPS experiments is the result of the collaboration of different Universities and Institutes, e.g. MIT, UCLA, INFN and others. The balloon launch is expected by the end of year 2020 from the McMurdo station in Antarctica.
The third part of the work regards the characterization of silicon pixel detectors for DSSC project at European XFEL. The last part of this thesis presents the characterization of the readout ASIC functionality and the backside current of the first and second prototype of the bare modules of such project.
3
CAGLIERO, ROBERTO. "Macro instrumented indentation test for structural materials: experimental and numerical methods." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2641542.
Texte intégralRésumé :
La prova di penetrazione strumentata è stata recentemente proposta per la misura delle proprietà meccaniche di materiali metallici e ceramici, micro e nano-strutturati, mediante campioni di piccole dimensioni. La ISO 14577 specifica il metodo di prova per ricavare il modulo elastico e la durezza Vickers di penetrazione per il campo di misura macro (forze > 2 N). Tale campo, tuttora parzialmente inesplorato, permette di ricavare le proprietà meccaniche massive dei materiali perché la dimensione dell’impronta è in genere maggiore delle caratteristiche microstrutturali. La riferibilità metrologica non è però garantita a causa della mancanza dei relativi blocchetti di riferimento. Vari esperimenti sono stati condotti su un durometro prototipo in grado di applicare forze fino a 2500 N su diversi tipi di acciai e su una lega intermetallica a base gamma TiAl. Gli esperimenti sono stati programmati secondo lo schema del quadrato latino per separare i possibili effetti dovuti allo strumento e al materiale testato. Metodi statistici hanno consentito l'individuazione di errori sistematici e outlier. Successivamente, l'applicazione della GUM ha consentito l'espressione delle incertezze sia dei metodi di misura prescritti dalla ISO 14577 che di ulteriori metodi qui proposti per evitare alcuni svantaggi dei metodi normati. Un’approfondita analisi del comportamento meccanico dei materiali è stata condotta combinando gli esperimenti con l'analisi agli elementi finiti. In particolare, è stato indagato il comportamento elasto-plastico degli acciai in presenza di attrito, è stata ottimizzata la risposta del durometro prototipo (correzione del punto zero) ed è stato valutato l’effetto della microstruttura (dimensione del grano e densità di dislocazioni) sull'andamento delle curve di penetrazione al variare della velocità di deformazione.
4
Gedin, Emanuel. "Hardness of showing hardness of the minimum circuit size problem." Thesis, KTH, Teoretisk datalogi, TCS, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232218.
Texte intégralRésumé :
The problem of finding the smallest size of a circuit that computes a given boolean function, usually referred to as the minimum circuit size problem (MCSP), has been studied for many years but it is still unknown whether or not the problem is NP-hard. With this in mind we study properties of potential reductions to this problem. The reductions in focus are local natural reductions which has been common in other well-known proofs of NP-hardness. We present a generalized method that shows the existence of an algorithm solving any problem which has a local natural reduction to MCSP. In particular we show that if the decision problem of distinguishing satisfiable 3-SAT instances from those where at most 7/8 + o(1) of the clauses can be satisfied has a reduction to MCSP where any arbitrary bit of the output can be computed in O(n1 - ε) time for any ε > 0 then k-SAT can be solved by a circuit of depth 3 and size 2o(n).<br>Problemet att finna den minsta storleken på en krets som beräknar en given boolesk funktion, ofta kallat minimum circuit size problem (MCSP), har studerats i många år men det är fortfarande okänt om problemet är NP-svårt eller inte. Med detta i åtankte studerar vi egenskaper hos potentiella reduktioner till det här problemet. Vi fokuserar på naturliga lokala reduktioner som är vanliga i många bevis av NP-svårighet. Vi presenterar en method som visar att det finns en algorithm för att lösa varje problem som har en lokal naturlig reduktion till MCSP. Vi visar att om beslutsproblemet att skilja satisfierbara instanser av 3-SAT från de där som mest 7/8 + o(1) av klausulerna går att satisfiera har en reduktion till MCSP där en godtycklig bit av utdata kan beräknas i O(n1 - ε) tid för varje ε > 0 då kan k-SAT lösas av en krets med djup 3 och storlek 2o(n).
5
Budík, Tomáš. "Zakružovačka na Hardox." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231242.
Texte intégralRésumé :
This work describes the design of a dedicated three-rolls hydraulic bending for Hardox 500 without the possibility of bending sheet metal for the manufacture of pipes. The work will analyze the problem of proposed three-rolls bending, bending technology and creating of the pre-bending, the design of the adjusting hydraulic servo-cylinder, planetary gearboxes with hydraulic motors to drive the bottom rollers, a partial draft of the hydraulic circuit and the complete frame structure of bending machine with its covers.
6
Click, Sally Evelyn. "Melvene Draheim Hardee music maker and dreamer of dreams /." Bowling Green, Ohio : Bowling Green State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1237838404.
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Arana, Miranda Rodrigo, Ward Adrian Benavides, Takamura Ricardo Andrés Jiménez, Mori Willy Roosevelt Vásquez, and Rodríguez Pamela Carolina Vital. "Harina de grillo - Crickie." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/652248.
Texte intégralRésumé :
Las tendencias en la actualidad indican un aumento en el consumo de productos orgánicos debido a una mayor preocupación en las personas por cambiar su dieta y cuidar su salud. Aquello hace que las personas estén más dispuestas a buscar constantemente productos con un alto contenido nutricional y propiedades beneficiosas, así como a averiguar acerca de alternativas distintas a las tradicionales y estar dispuestos a desembolsar una mayor cantidad de dinero para adquirir dichos productos.
A raíz de ello surge Crickie, dicho producto es una harina de grillo de alta calidad que es bastante útil para los deportistas o personas con un estilo de saludable que buscan consumir un insumo que tenga un alto contenido proteico, sostenible con el medioambiente y diferente a las alternativas tradicionales de suplementos en el mercado.
En el trabajo que estamos realizando se procederá a desarrollar una investigación con el fin de ver la viabilidad y rentabilidad del proyecto con el fin de poder proceder a comercializar dicho producto. Asimismo, se aplicará y desarrollará los conocimientos aprendidos durante el transcurso de la carrera al tratar temas relacionados a distintas áreas como finanzas, marketing, negocios internacionales, logística, entre otros
8
Jahnke, Carsten. "Das Silber des Meeres : Fang und Vertrieb von Ostseehering zwischen Norwegen und Italien (12.-16.Jahrhundert) /." Köln ; Weimar ; Wien : Böhlau, 2000. http://catalogue.bnf.fr/ark:/12148/cb388275261.
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Mamani, Choque Claudia. "Obtención de harina de tarwi." Universidad Mayor de San Andrés. Programa Cybertesis BOLIVIA, 2009. http://www.cybertesis.umsa.bo:8080/umsa/2009/mamani_cc/html/index-frames.html.
Texte intégralRésumé :
El tarwi (Lupinus Mutabilis), es una leguminosa que posee un alto contenido de proteínas y grasas, puede jugar un rol importante en la alimentación humana, ya que en los últimos años se busca nuevas fuentes alimenticias que reúnan esas condiciones. Sin embargo el tarwi posee sustancias no proteicas como los alcaloides que impiden su consumo directo, siendo importante desde el punto de vista industrial realizar el desamargado. Si bien en Bolivia existen productos elaborados a base de tarwi, estos no utilizan la harina sino el grano desamargado de tarwi como tal incorporándolo luego a sus ingredientes. Por esto el presente proyecto de investigación, propone la obtención de harina de tarwi que reúna todas las características nutritivas. Para llevar a cabo esta investigación se adecuaron métodos tecnológicos hasta la obtención de la harina. Se inició con una clasificación de la variedad Carabuco del departamento de La Paz. Se incluyó en los métodos tecnológicos la etapa de desamargado (hidratado, cocción y lavado), estudiándose en éste diferentes variables como volúmenes de agua, tiempos, condiciones de tratamiento, pH, etc. Para luego el grano desamargado ser secado y molido. Obteniéndose la harina de tarwi, se caracterizó fisicoquímica y microbiológicamente, posterior a esto se estudió su aplicación en productos de panificación, encontrándose un porcentaje de sustitución adecuado, obteniéndose así un producto con alto valor nutritivo.
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Harder, Michael [Verfasser]. "Exchangeability of copulas / Michael Harder." Ulm : Universität Ulm, 2016. http://d-nb.info/1106329910/34.
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Bohman, Jerker. "En kritik av Hardins livbåtsetik." Thesis, Uppsala universitet, Filosofiska institutionen, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-350226.
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Bruasse, Laurent. "Stabilité et filtration de Harder-Narasimhan." Phd thesis, Université de Provence - Aix-Marseille I, 2001. http://tel.archives-ouvertes.fr/tel-00004129.
Texte intégralRésumé :
Née sur les variétés algébriques, la notion de stabilité s'est ensuite généralisée aux variétés kähleriennes, puis, au variétés holomorphes compactes grâce à l'utilisation des métriques de Gauduchon. L'étude du comportement des fibrés (ou des faisceaux) non semi-stables n'a été faite de façon complète que dans le cas algébrique à travers la notion de filtration de Harder-Narasimhan (FHN). Nous poursuivons ici cette étude pour des variétés holomorphes compactes quelconques. Nous montrons qu'il est possible de définir le sous-faisceau de pente maximale d'un fibré vectoriel complexe. Ce sous-faisceau est obtenu comme limite au sens des sous-fibrés holomorphes faibles, notion déjà utilisée par Uhlenbeck et Yau pour la correspondance de Kobayashi-Hitchin, qui nous donne ici ``la bonne notion de convergence''. Nous démontrons l'existence d'une FHN dans ce cadre. Nous généralisons ensuite le résultat aux faisceaux cohérents sans-torsion. On est alors confronté à des problèmes de convergence liés à la non compacité de la base (lieu où le faisceau est localement libre). Nous montrons ensuite comment ces méthodes s'appliquent à une famille de fibrés (ou une famille plate de faisceaux sans-torsion) définie sur une déformation de variété holomorphe compacte pour obtenir des résultats d'existence de sous-faisceaux limites de type Bishop. On obtient par là-même une nouvelle démonstration de l'ouverture de la stabilité en déformation qui n'utilise pas la difficile correspondance de Kobayashi-Hitchin. Dans une deuxième partie, nous donnons des conditions équivalentes de simplicité et de stabilité pour les fibrés tangents des surfaces holomorphes compactes de la classe $VII$. Nous obtenons, en particulier, un exemple de déformation de surface à coquille sphérique globale qui illustre la non ouverture de la non semi-stabilité en déformation.
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Deniz, Tansel. "Ballistic Penetration Of Hardened Steel Plates." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613534/index.pdf.
Texte intégralRésumé :
Ballistic testing is a vital part of the armor design. However, it is impossible to test every
condition and it is necessary to limit the number of tests to cut huge costs. With the intro-
duction of hydrocodes and high performance computers<br>there is an increasing interest on
simulation studies to cutoff these aforementioned costs. This study deals with the numerical
modeling of ballistic impact phenomena, regarding the ballistic penetration of hardened steel
plates by 7.62 mm AP (Armor Piercing) projectile. Penetration processes of AP projectiles
are reviewed. Then, a survey on analytical models is given. After the introduction of fun-
damentals of numerical analysis, an intensive numerical study is conducted in 2D and 3D.
Johnson Cook strength models for the four different heat treatments of AISI 4340 steel were
constructed based on the dynamic material data taken from the literature. It was found that
2D numerical simulations gave plausible results in terms of residual projectile velocities, con-
sidering the literature review. Then, 3D numerical simulations were performed based on the
material properties that were selected in 2D studies. Good agreement was obtained between
the numerical and test results in terms of residual projectile velocities and ballistic limit thick-
nesses. It was seen that the ballistic protection efficiency of the armor plates increases with
the increasing hardness, in the examined range.
This study is a part of T¨<br>ubitak project 106M211 of MAG.
14
Evans, Paul Done. "The hardness and abrasion of polymers." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38305.
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Baldie, Keith David. "Crack growth in hardened cement paste." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37934.
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Breckel, Daniel W. "The process of hardness of heart." Theological Research Exchange Network (TREN), 1991. http://www.tren.com.
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Borsub, Jatesada. "Hardened Registration Process for Participatory Sensing." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247886.
Texte intégralRésumé :
Participatory sensing systems need to gather information from a largenumber of participants. However, the openness of the system is a doubleedgedsword: by allowing practically any user to join, the system can beabused by an attacker who introduces a large number of virtual devices.This work proposes a hardened registration process for participatory sensingto raise the bar: registrations are screened through a number of defensivemeasures, towards rejecting spurious registrations that do not correspondto actual devices. This deprives an adversary from a relatively easytake-over and, at the same time, allows a flexible and open registrationprocess. The defensive measures are incorporated in the participatorysensing application.<br>Deltagande avkännings system behöver samlas från ett stort antal aktörer.Systems öppenhet är dock en dubbelsidigt värd: Genom att låta alla praktiskaanvändare deltagit, kan system utnyttja en av angripare som introducera ett stortantal virtuella enheter. I det här arbetet föreslå en härda registreringsprocess fördeltagare att identifiera höjning av ribban: registrering screenas genom ett antaldefensiva åtgärders, för att avvisa falska registreringar som inte motsvara aktuellaenheter. Detta berövar en motståndare från en relativt lätt övertagande och gersamtidigt en flexibel och öppen registreringsprocess. De defensiva åtgärdernainförlivas i deltagande avkännings applikation.
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Persu, Elena-Mădălina. "Tensors, sparse problems and conditional hardness." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120418.
Texte intégralRésumé :
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 101-108).<br>In this thesis we study the interplay between theoretical computer science and machine learning in three different directions. First, we make a connection between two ubiquitous sparse problems: Sparse Principal Component Analysis (SPCA) and Sparse Linear Regression (SLR). We show how to efficiently transform a blackbox solver for SLR into an algorithm for SPCA. Assuming the SLR solver satisfies prediction error guarantees achieved by existing efficient algorithms such as those based on the Lasso, we show that the SPCA algorithm derived from it achieves state of the art performance, matching guarantees for testing and for support recovery under the single spiked covariance model as obtained by the current best polynomial-time algorithms. Second, we push forward the study of linear algebra properties of tensors by giving a tensor rank detection gadget for tensors in the smoothed model. Tensors have had a tremendous impact and have been extensively applied over the past few years to a wide range of machine learning problems for example in developing estimators for latent variable models, in independent component analysis or blind source separation. Unfortunately, their theoretical properties are still not well understood. We make a step in that direction. Third, we show that many recent conditional lower bounds for a wide variety of problems in combinatorial pattern matching, graph algorithms, data structures and machine learning, including gradient computation in average case neural networks, are true under significantly weaker assumptions. This highlights that the intuition from theoretical computer science can not only help us develop faster practical algorithms but also give us a better understanding of why faster algorithms may not exist.<br>by Elena-Mădălina Persu.<br>Ph. D.
19
Faulstich, Raymond J., Lawrence W. Jr Burke, and William P. D’Amico. "HARDENED SUBMINIATURE TELEMETRY AND SENSOR SYSTEM." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/607637.
Texte intégralRésumé :
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California<br>The Army development and test community must demonstrate the functionality and
reliability of gun-launched projectiles and munitions systems, especially newer smart
munitions. The best method to satisfy this requirement is to combine existing optical and
tracking systems data with internal data measured with on-board instrumentation (i.e. spin,
pitch, and yaw measurements for standard items and terminal sensor, signal processor, and
guidance/navigation system monitoring for smart munitions). Acquisition of internal data is
usually limited by available space, harsh launch environments, and high associated costs.
A technology development and demonstration effort is underway to provide a new
generation of products for use in this high-g arena. This paper describes the goals,
objectives, and progress of the Hardened Subminiature Telemetry and Sensor System
(HSTSS) program.
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Caldas, Miguel. "Characterization of Hardly e-Open functions." Pontificia Universidad Católica del Perú, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/97022.
Texte intégralRésumé :
A function is dened to be hardly e-open provided that theinverse image of each e-dense subset of the codomain that is contained in a proper open set is e-dense in the domain. Characterizations and properties of hardly e-open functionsare presented.
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Kohlhöfer, Walter. "Dynamic hardness testing challenges conventional tests." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/15981.
Texte intégralRésumé :
Bibliography: pages 69-71.<br>The design and use of a portable dynamic hardness tester is described. The thesis begins with a description of the more common static hardness tests and the usefulness of such tests in industry. It shows a correlation between the different types of hardness and also between hardness and other material parameters such as tensile strength. A thorough investigation of the principles involved in the indentation processes using conical and spherical indenters under static and dynamic loading is given so that the reasons for the correlations may be more clearly understood. A series of test specimens tested by conventional static hardness tests (Brinell, Vickers and Rockwell) are used as calibration specimens for the dynamic tester. Both a spherical and conical tip are used. The results of these tests are compared and analyzed. The dynamic tester may then be programmed so that it correlates with the results of the static tests. A set of guidelines for the use of such a portable tester is then given.
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Smith, Michael Reed. "An empirical study of instance hardness /." Diss., CLICK HERE for online access, 2010. http://contentdm.lib.byu.edu/ETD/image/etd3239.pdf.
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Smith, Michael Reed. "An Empirical Study of Instance Hardness." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2012.
Texte intégralRésumé :
Most widely accepted measures of performance for learning algorithms, such as accuracy and area under the ROC curve, provide information about behavior at the data set level. They say nothing about which instances are misclassified, whether two learning algorithms with the same classification accuracy on a data set misclassify the same instances, or whether there are instances misclassified by all learning algorithms. These questions about behavior at the instance level motivate our empirical analysis of instance hardness, a measure of expected classification accuracy for an instance. We analyze the classification of 57 data sets using 9 learning algorithms. Of the over 175000 instances investigated, 5% are misclassified by all 9 of the considered learning algorithms, and 15% are misclassified by at least half. We find that the major cause of misclassification for hard instances is class overlap, manifested as outliers and border points which can be exacerbated by class skew. We analyze these causes and show to what extent each leads to misclassifications, both in isolation and jointly. 19.8% of all misclassified instances are outliers; 71.3% are border points; 21% belong to a minority class. We also find that 91.6% of all outliers and 38.3% of all border points are misclassified whereas only 3.5% of instances without class overlap are misclassified. We propose a set of heuristics to predict when an instance will be hard to correctly classify. Additionally, we analyze how different learning algorithms perform on tasks with varying degrees of outliers, border points and class skew.
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Zure, Marina [Verfasser], Jens [Akademischer Betreuer] Harder, and Ramsay [Akademischer Betreuer] Paul. "Biogeography of Rhodopirellula in European coastal sediments / Marina Zure. Betreuer: Jens Harder. Gutachter: Jens Harder ; Ramsay Paul." Bremen : Staats- und Universitätsbibliothek Bremen, 2015. http://d-nb.info/1082343269/34.
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Pahl, Jürgen [Verfasser], Sjoerd [Akademischer Betreuer] Harder, and Sjoerd [Gutachter] Harder. "Lewis Acidic Magnesium Complexes: Development, Synthesis, Characterization and Reactivity / Jürgen Pahl ; Gutachter: Sjoerd Harder ; Betreuer: Sjoerd Harder." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2019. http://d-nb.info/1182034713/34.
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Fischer, Tanja [Verfasser], Jens [Akademischer Betreuer] Harder, Jens [Gutachter] Harder, and Rudolf [Gutachter] Amann. "Surface structures and taxonomy of marine Flavobacteriia / Tanja Fischer ; Gutachter: Jens Harder, Rudolf Amann ; Betreuer: Jens Harder." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1169299016/34.
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Elsen, Holger [Verfasser], Sjoerd [Akademischer Betreuer] Harder, Sjoerd [Gutachter] Harder, and Ralph [Gutachter] Puchta. "Imine Reduction with Main Group Metal Catalysts / Holger Elsen ; Gutachter: Sjoerd Harder, Ralph Puchta ; Betreuer: Sjoerd Harder." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1229194193/34.
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Hart, Alan D. "THE APPLICATION OF HARDENED CRYSTAL REFERENCE OSCILLATORS INTO THE HARDENED SUBMINIATURE TELEMETRY AND SENSOR SYSTEM (HSTSS) PROGRAM." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608741.
Texte intégralRésumé :
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>This paper briefly reports on concepts for hardening (physically toughening) crystal reference oscillators for the highly integrated program known as HSTSS. Within the HSTSS program is the L & S band transmitter development contract. The harshest requirements for this contract are surviving and functioning, to within 20 ppm of its center frequency, 30 ms after sustaining a shock pulse of 100,000 (g) for 0.5 ms on any axis. Additional requirements call for the transmitter to be no larger than 0.2 in3, and to operate within a 20 ppm frequency stability throughout the temperature range of -400 to +850 centigrade and during centrifugal spins of up to 300 Hz or 25,000 (g). Fundamentally the question is, is it feasible for any telemetry system to be capable of withstanding such harsh conditions and, to be practical on all DoD Test Ranges, still adhere to the stability tolerance guidelines set forth by the Range Commanders Council on Telemetry Standards - IRIG 106-96? Under "normal" conditions, stability requirements for "Range" transmitters are easily satisfied through the use of off-the-shelf crystal reference oscillators which provide the reference frequencies required within a transmitter’s phase lock loop circuitry. Unfortunately, the oscillator is also the most vulnerable part of a transmitter to the conditions listed and is the key to this problem. The oscillator’s weak points are in its resonator’s fragile quartz structure (the blank) and support mechanism. The challenge is to invent and adapt this area to these newer harsher conditions and to do it in the smallest space ever required.
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Martin, Johannes [Verfasser], Sjoerd [Akademischer Betreuer] Harder, Sjoerd [Gutachter] Harder, and Ralph [Gutachter] Puchta. "Alkene Activation and Hydrogenation with Alkaline Earth Metals / Johannes Martin ; Gutachter: Sjoerd Harder, Ralph Puchta ; Betreuer: Sjoerd Harder." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1233867474/34.
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Zhang, JingYing. "Process Optimization for Machining of Hardened Steels." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7248.
Texte intégralRésumé :
Finish machining of hardened steel is receiving increasing attention as an alternative to the grinding process, because it offers comparable part finish, lower production cost, shorter cycle time, fewer process steps, higher flexibility and the elimination of environmentally hazardous cutting fluids. In order to demonstrate its economic viability, it is of particular importance to enable critical hard turning processes to run in optimal conditions based on specified objectives and practical constraints.
In this dissertation, a scientific and systematic methodology to design the optimal tool geometry and cutting conditions is developed. First, a systematic evolutionary algorithm is elaborated as its optimization block in the areas of: problem representation; selection scheme; genetic operators for integer, discrete and continuous design variables; constraint handling and population initialization. Secondly, models to predict process thermal, forces/stresses, tool wear and surface integrity are addressed. And then hard turning process planning and optimization are implemented and experimentally validated. Finally, an intelligent advisory system for hard turning technology by integrating experimental, numerical and analytical knowledge into one system with user friendly interface is presented.
The work of this dissertation improves the state of the art in making tooling solution and process planning decisions for hard turning processes.
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Pang, Thiam-Sun [Verfasser], and Stefan [Akademischer Betreuer] Kebekus. "The Harder-Narasimhan filtrations and rational contractions." Freiburg : Universität, 2015. http://d-nb.info/1119328241/34.
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Schlapobersky, Paul Harry 1966. "Hardness in motion : retrieving Johannesburg after Apartheid." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/70353.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.<br>Includes bibliographical references (p. 91-92).<br>This thesis seeks to engage with the city of Johannesburg on terms that break decisively with the linear-historical methods that have been used to both catalogue and decipher the city up to the present. The city is, itself, in its second incarnation - that of the post-apartheid, post-gold mining metropolis - and the fact of this historic overturning demands reappraisal of what Johannesburg is, and more importantly, what it can become. Its complexities stand in stark opposition to an apparent banality that arises from the ease with which it is visually apprehended. Words form a core of this thesis, used not only in their capacity to reveal through what they say, but through the possibilities created in the spaces between unrelated and related texts (what they do not say). The thesis has thus been concerned with the juxtaposition of words - fiction and non· fiction - as well as their mapping and diagramming, in order to foster new conceptualizations of a city whose blatancy is simultaneously its lifeblood and its problem. The generative words in this context have been those of the thirteen fictions written specifically for the thesis. These stand as a representation of the creative act that is here seen as being fundamental to the re-imagining of Johannesburg; to get beyond the image/face of the city in order to view the human substrata. Additionally, two architectural "provocations" are offered as vehicles for ways in which the city can begin to be re ·imagined . Both of these projects engage with the idea of "absorption" (removal from contingency, to focus on transcendental endeavors), and the notion of the architectural project as a generator, not specifically for what it is, but for what it represents. These architectural projects are, within the context of t he thesis, Brecht's "fragile instruments".<br>by Paul Harry Schlapobersky.<br>S.M.
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Degwekar, Akshay (Akshay Dhananjai). "Structure vs. hardness through the obfuscation lens." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105578.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 71-[77]).<br>Cryptography relies on the computational hardness of structured problems. While one-way functions, the most basic cryptographic object, does not seem to require much structure, as we advance up the ranks into public-key cryptography and beyond, we seem to require that certain structured problems are hard. For example, factoring, quadratic residuosity, discrete logarithms, and approximate shortest and closest vectors in lattices all have considerable algebraic structure. This structure, on the one hand, enables useful applications such as public-key and homomorphic encryption, but on the other, also puts their hardness in question. Their structure is exactly what puts them in low complexity classes such as SZK or NP [set-theoretic intersection symbol] coNP, and is in fact the reason behind (sub-exponential or quantum) algorithms for these problems. The question is whether such structure is inherent in different cryptographic primitives, deeming them inherently easier. We study the relationship between two structured complexity classes, statistical zero-knowledge (SZK) and NP [set-theoretic intersection symbol] coNP, and cryptography. To frame the question in a meaningful way, we rely on the language of black-box constructions and separations. Our results are the following: -- Cryptography vs. Structured Hardness: Our two main results show that there are no black-box constructions of hard problems in SZK or NP [set-theoretic intersection symbol] coNP starting from one of a wide variety of cryptographic primitives such as one-way and trapdoor functions, one-way and trapdoor permutations (in the case of SZK), public-key encryption, oblivious transfer, deniable encryption, functional encryption, and even indistinguishability obfuscation; -- Complexity-theoretic Implications: As a corollary of our result, we show a separation between SZK and NP[set-theoretic intersection symbol]coNP and the class PPAD that captures the complexity of computing Nash Equilibria; and -- Positive Results: We construct collision-resistant hashing from a strong form of SZK-hardness and indistinguishability obfuscation. It was previously known that indistinguishability obfuscation by itself does not imply collision-resistant hashing in a black-box way; we show that it does if one adds SZK-hardness as a "catalyst". Our black-box separations are derived using indistinguishability obfuscation as a "gateway", by first showing a (separation) result for indistinguishability obfuscation and then leveraging on the fact that indistinguishability obfuscation can be used to construct the above variety of cryptographic primitives and hard PPAD instances in a black-box manner.<br>by Akshay Degwekar.<br>S.M.
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Fretwell, Daniel. "Level p paramodular congruences of Harder type." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9683/.
Texte intégralRésumé :
In this thesis we will produce and investigate certain congruences, as predicted by Harder, between Hecke eigenvalues of Siegel and elliptic modular forms. Such congruences form a natural generalisation of the famous 691 congruence of Ramanujan. In direct comparison the moduli of our congruences will come from critical values of L-functions of elliptic modular forms. In particular we will be interested in congruences between level p paramodular Siegel forms and Gamma0(p) elliptic forms. Evidence for such congruences in these cases is rare (the only known examples being of level 2, due to Bergstrom et al). In order to simplify matters on the Siegel side we move into spaces of algebraic modular forms for the group GU2(D) for a quaternion algebra D/Q ramified at p,∞. Here we can use a web of conjectures and results due to Ibukiyama along with trace formulae of Dummigan to produce Hecke eigenvalues of level p paramodular forms (allowing the congruences to be tested with ease). I provide new algorithms for finding explicit descriptions of these spaces of algebraic forms. In order to provide justification for the paramodular nature of the congruence we will also consider the interplay between associated Galois representations and automorphic representations.
35
Harding, Affeld Martín Ignacio [Verfasser]. "Essays in Macroeconomics / Martín Ignacio Harding Affeld." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1215571984/34.
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Caldwell, Anita M. "Hard Times Hit Elderly Harder Than Most." College of Agriculture, University of Arizona (Tucson, AZ), 1993. http://hdl.handle.net/10150/295717.
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Danaki, Paraskevi. "Radiation hardness of thin film solar cells." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-386054.
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Hardee, Bailey Alice Anne. "Effects of Stereotype Threat on Females in Math and Science Fields: An Investigation of Possible Mediators and Moderators of the Threat-Performance Relationship." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-11162004-111432/unrestricted/hardee-bailey%5Falice%5Fa%5F200412%5Fphd.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--Psychology, Georgia Institute of Technology, 2005.<br>Amy Bruckman, Committee Member ; Jack Feldman, Committee Chair ; Dianne Leader, Committee Member ; Larry James, Committee Member ; Ruth Kanfer, Committee Member. Includes bibliographical references.
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Frank, Carsten S. [Verfasser], Jens [Akademischer Betreuer] Harder, and Rudolf [Akademischer Betreuer] Amann. "Polyphasische Taxonomie, Kerngenom und Lebenszyklus von Rhodopirellula-Stämmen / Carsten S. Frank. Gutachter: Jens Harder ; Rudolf Amann. Betreuer: Jens Harder." Bremen : Staats- und Universitätsbibliothek Bremen, 2011. http://d-nb.info/1071897888/34.
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Gentner, Thomas [Verfasser], Sjoerd [Akademischer Betreuer] Harder, and Sjoerd [Gutachter] Harder. "Novel Strongly Donating and Superbulky Ligands in s-Block Metal Chemistry / Thomas Gentner ; Gutachter: Sjoerd Harder ; Betreuer: Sjoerd Harder." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2019. http://d-nb.info/119199399X/34.
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Kizina, Jana [Verfasser], Jens [Akademischer Betreuer] [Gutachter] Harder, and Rudolf [Gutachter] Amann. "Insights into the biology of Candidate Division OP3 LiM populations / Jana Kizina ; Gutachter: Jens Harder, Rudolf Amann ; Betreuer: Jens Harder." Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/1142314294/34.
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Puentes, Cala Edinson Andres [Verfasser], Jens [Akademischer Betreuer] Harder, Jens [Gutachter] Harder, and Michael [Gutachter] Friedrich. "The anaerobic monoterpene metabolism in Castellaniella defragrans 65Phen / Edinson Andres Puentes Cala ; Gutachter: Jens Harder, Michael Friedrich ; Betreuer: Jens Harder." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1159699895/34.
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Guntermann, Bernd [Verfasser], Frank [Akademischer Betreuer] Hardtke, Frank [Gutachter] Hardtke, and Olaf [Gutachter] Hohmann. "Das wirtschaftsstrafrechtliche Mandat unter der Strafrechtsschutzversicherung für Unternehmen und Manager / Bernd Guntermann ; Gutachter: Frank Hardtke, Olaf Hohmann ; Betreuer: Frank Hardtke." Greifswald : Universität Greifswald, 2021. http://d-nb.info/1236693728/34.
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Tukuta, Marian. "An evaluation of impact of co-operative societies on poverty alleviation among the urban poor in Harare, Zimbabwe during the period 2008-2010." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/506.
Texte intégralRésumé :
The main purpose of this study was to evaluate the impact of co-operative societies on poverty alleviation among the urban poor in Zimbabwe with particular reference to consumer co-operative societies in areas of agriculture, housing and micro- finance. The co-operative sector plays an important role in poverty alleviation since many unemployed people have turned to co-operative activities as a way of earning a lawful and decent living during a period in which Zimbabwe generally suffered immense impoverishment in the midst of the national economic meltdown that was characterised by hyper-inflation, de-industrialisation and mass unemployment. The period of study was as from January 2008 to August 2010. This period is significant in that many co-operative societies were formed with the following broad objectives: (a) economic power and through this power; (b) control of socio-economic institution, to eliminate exploitation of man by man to make the people of Zimbabwe self reliant; (c) skills management, goods and services and establish in themselves a sense of confidence, initiative and high development aspirations; (d) to provide an opportunity to develop the community; and a (e) collective way of living that provides a sound base for socialism and national solidarity ix In this study, two hundred and seventy four respondents were used as research subjects. This consisted of one hundred and sixty respondents from housing, twenty four from micro- finance, and eighty eight from agricultural co-operative societies which covered dairy, poultry and fishing co-operative societies. This also included the Registrar of Co-operatives and the Harare City Council Co-operative officer. The research instruments that were used for the purpose of this research study were questionnaires, field visits, interviews and observations. Use was also made of secondary data that was obtained from the offices of Registrar of Co-operatives and the Town clerk of the Harare City Council as well as from the various co-operative societies that constitute the research study’s sample. The key factors that account for the failure of co-operative societies included the lack of adequate funding, lack of relevant knowledge and experience about co-operative activities, conflict among co-operative society members, failure to follow co-operative principles, mixing politics with co-operative activities and lack of education and training. The study also found out that the key to the success of any co-operative venture includes some of the following factors: Proper application of co-operative principles, the provision of co-operative education to both the membership and management of co-operative societies and proper keeping of institutional records. Most important of which include membership, financial and asset registers. x The study recommends that the government should give adequate administrative and financial support to co-operative societies since they have a potential of alleviating poverty if properly managed. It is also further recommended that research be done in order to enhance the strategic management of co-operative societies since empirical evidence tends to suggest that they are a viable tool for broad –based participatory and democratic sustainable livelihoods development. The study also recommended further studies to be carried out on the applicability of cooperative principles in all environments since some co-operative societies that have followed these principles especially in the developed countries have proved to be suitable instruments for poverty alleviation.
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Kuivinen, Fredrik. "Algorithms and Hardness Results for Some Valued CSPs." Doctoral thesis, Linköpings universitet, TCSLAB - Laboratoriet för teoretisk datalogi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51687.
Texte intégralRésumé :
In the Constraint Satisfaction Problem (CSP) one is supposed to find an assignment to a set of variables so that a set of given constraints are satisfied. Many problems, both practical and theoretical, can be modelled as CSPs. As these problems are computationally hard it is interesting to investigate what kind of restrictions of the problems implies computational tractability. In this thesis the computational complexity of restrictions of two optimisation problems which are related to the CSP is studied. In optimisation problems one can also relax the requirements and ask for an approximatively good solution, instead of requiring the optimal one. The first problem we investigate is Maximum Solution (Max Sol) where one is looking for a solution which satisfies all constraints and also maximises a linear bjective function. The Maximum Solution problem is a generalisation of the well-known integer linear programming problem. In the case when the constraints are equations over an abelian group we obtain tight inapproximability results. We also study Max Sol for so-called maximal constraint languages and a partial classification theorem is obtained in this case. Finally, Max Sol over the boolean domain is studied in a setting where each variable only occurs a bounded number of times. The second problem is the Maximum Constraint Satisfaction Problem (Max CSP). In this problem one is looking for an assignment which maximises the number of satisfied constraints. We first show that if the constraints are known to give rise to an NP-hard CSP, then one cannot get arbitrarily good approximate solutions in polynomial time, unless P = NP. We use this result to show a similar hardness result for the case when only one constraint relation is used. We also study the submodular function minimisation problem (SFM) on certain finite lattices. There is a strong link between Max CSP and SFM; new tractability results for SFM implies new tractability results for Max CSP. It is conjectured that SFM is the only reason for Max CSP to be tractable, but no one has yet managed to prove this. We obtain new tractability results for SFM on diamonds and evidence which supports the hypothesis that all modular lattices are tractable.<br>I ett villkorsprogrammeringsproblem är uppgiften att tilldela värden till variabler så att en given mängd villkor blir uppfyllda. Många praktiska problem, så som schemaläggning och planering, kan formuleras som villkorsprogrammeringsproblem och det är därför önskvärt att ha effektiva algoritmer för att hitta lösningar till denna typ av problem. De generella varianterna av dessa problem är NP-svåra att lösa. Detta innebär att det antagligen inte finns effektiva algoritmer för problemen (om inte P = NP vilket anses vara mycket osannolikt). Av denna anledning förenklar vi problemet genom att studera restriktioner av det och ibland nöjer vi oss med approximativa lösningar. I den här avhandlingen studeras två varianter av villkorsprogrammeringsproblemet där man inte bara ska hitta en lösning utan hitta en så bra lösning som möjligt. I den första varianten är målet att hitta en tilldelning där samtliga villkor uppfylls och att en viktad summa av variablerna maximeras. Detta problem kan ses som en generalisering av det välkända linjära heltalsprogrammeringsproblemet. I den andra varianten är målet att hitta en tilldelning som uppfyller så många villkor som möjligt. Då det gäller den första varianten, då man ska hitta en lösning som uppfyller samtliga villkor som också maximerar summan av variablerna, presenteras nya resultat för ett antal specialfall. De så kallade maximala villkorsmängderna studeras och komplexiteten för ett antal av dessa bestäms. Vi studerar också en variant av problemet över den Boolska domänen då antal variabelförekomster är begränsat. I detta fall ger vi en partiell klassifikation över vilka villkorsmängder som är hanterbara och vilka som inte kan lösas effektivt. För den andra varianten, då man ska uppfylla så många villkor som möjligt, presenteras några nya effektiva algoritmer för vissa restriktioner. I dessa algoritmer löses det mer generella problemet av minimering av submodulära funktioner över vissa ändliga latticar. Vi bevisar också ett resultat som beskriver exakt när det finns effektiva algoritmer då man endast har tillgång till en typ av villkor.
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Howe, Lisa A. "Spirited Pioneer: The Life of Emma Hardinge Britten." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2292.
Texte intégralRésumé :
Emma Hardinge Britten’s life encompassed and reflected many of the challenges and opportunities afforded to women in the Victorian world. This dissertation explores the multi-layered Victorian landscape through the life of an individual in order not only to tell her individual story, but also to gain a more nuanced understanding of how nineteenth-century norms of gender, class, religion, science and politics combined to create opportunities and obstacles for women in Britten’s generation. Britten was an actor, a musician, a writer, a theologian, a political activist, a magazine publisher, a spirit medium, a lecturer, and a Spiritualist missionary. Taking into account her multiple subjectivities, this dissertation relies on historical biography to contextualize Britten’s life in a number of areas, including Modern Spiritualism and political and civic engagement in the second half of the nineteenth century in Britain, the U.S., and Australia.
The dissertation is organized thematically in a quasi-chronological manner. Time frames overlap between chapters, as Britten travels from the realm of politics to that of science and to religion. Each chapter reflects this transformation of Britten’s multiple intellectual and spiritual engagements, including performance, religion, politics and science.
Emma Hardinge Britten challenged, whether consciously or not, gendered expectations by attaining a presence in a male-dominated public. Even though her life and accomplishments pre-date the New Woman of the fin de siècle, Britten established a successful career and her life creates a foreshadowing of the larger movements to come. She was an extraordinarily politically active woman whose influence reached three continents in her lifetime and beyond.
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Zhaojiang, Li. "Hardness characteristics in electrodeposited Cu/Ni multilayer systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0020/MQ52687.pdf.
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Marcum, Frank. "Analysis of a test technique for hardness surveillance." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182866116.
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Raghavan, Satyanarayanan. "Laser-based hybrid process for machining hardened steels." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47550.
Texte intégralRésumé :
Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material.
The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish.
First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %).
Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field
induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region.
Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.
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Richardson, I. G. "The microstructure and composition of hardened cement pastes." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302868.
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