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1
Knaust, Stefan. « Microsystems for Harsh Environments ». Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-253558.
Texte intégralRésumé :
When operating microsystems in harsh environments, many conventionally used techniques are limiting. Further, depending on if the demands arise from the environment or the conditions inside the system, different approaches have to be used. This thesis deals with the challenges encountered when microsystems are used at high pressures and high temperatures. For microsystems operating at harsh conditions, many parameters will vary extensively with both temperature and pressure, and to maintain control, these variations needs to be well understood. Covered within this thesis is the to-date strongest membrane micropump, demonstrated to pump against back-pressures up to 13 MPa, and a gas-tight high pressure valve that manages pressures beyond 20 MPa. With the ability to manipulate fluids at high pressures in microsystems at elevated temperatures, opportunities are created to use green solvents like supercritical fluids like CO2. To allow for a reliable and predictable operation in systems using more than one fluid, the behavior of the multiphase flow needs to be controlled. Therefore, the effect of varying temperature and pressure, as well as flow conditions were investigated for multiphase flows of CO2 and H2O around and above the critical point of CO2. Also, the influence of channel surface and geometry was investigated. Although supercritical CO2 only requires moderate temperatures, other supercritical fluids or reactions require much higher temperatures. The study how increasing temperature affects a system, a high-temperature testbed inside an electron microscope was created. One of the challenges for high-temperature systems is the interface towards room temperature components. To circumvent the need of wires, high temperature wireless systems were studied together with a wireless pressure sensing system operating at temperatures up to 1,000 °C for pressures up to 0.3 MPa. To further extend the capabilities of microsystems and combine high temperatures and high pressures, it is necessary to consider that the requirements differs fundamentally. Therefore, combining high pressures and high temperatures in microsystems results in great challenges, which requires trade-offs and compromises. Here, steel and HTCC based microsystems may prove interesting alternatives for future high performance microsystems.
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Resch, Bernd, et Peter Romirer-Maierhofer. « Global Positioning in Harsh Environments ». Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-282.
Texte intégralRésumé :
As global location systems offer only restricted availability, they are not suitable for a world-
wide tracking application without extensions. This thesis contains a goods-tracking solution,
which can be considered globally working in contrast to formerly developed technologies. For
the creation of an innovative approach, an evaluation of the previous efforts has to be made.
As a result of this assessment, a newly developed solution is presented in this thesis that uses
the Global Positioning System (GPS) in connection with the database correlation method
involving Global System for Mobile Communications (GSM) fingerprints. The database
entries are generated automatically by measuring numerous GSM parameters such as Cell
Identity and signal strength involving handsets of several different providers and the real
reference position obtained via a high sensitivity GPS receiver.
3
Glans, Fredrik. « Enhanced positioning in harsh environments ». Thesis, Linköpings universitet, Reglerteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-94523.
Texte intégralRésumé :
Today’s heavy duty vehicles are equipped with safety and comfort systems, e.g. ABS and ESP, which totally or partly take over the vehicle in certain risk situations. When these systems become more and more autonomous more robust positioning is needed. In the right conditions the GPS system provides precise and robust positioning. However, in harsh environments, e.g. dense urban areas and in dense forests, the GPS signals may be affected by multipaths, which means that the signals are reflected on their way from the satellites to the receiver. This can cause large errors in the positioning and thus can give rise to devastating effects for autonomous systems. This thesis evaluate different methods to enhance a low cost GPS in harsh environments, with focus on mitigating multipaths. Mainly there are four different methods: Regular Unscented Kalman filter, probabilistic multipath mitigation, Unscented Kalman filter with vehicle sensor input and probabilistic multipath mitigation with vehicle sensor input. The algorithms will be tested and validated on real data from both dense forest areas and dense urban areas. The results show that the positioning is enhanced, in particular when integrating the vehicle sensors, compared to a low cost GPS.
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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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Pullman, Susan. « Speech recognition in a harsh environment ». Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27992.
Texte intégralRésumé :
Speech Recognition is a rapidly expanding field with many useful applications in man-machine interfacing. One of the main benefits of speech control is the flexibility and ease of use allowed an operator for any number of specific applications. Speech recognition units (SRU) are currently at a high level of accuracy for user dependent, pretrained, isolated word recognition. However, if uncontrollable noise is added to the speech input, recognition degrades rapidly. If the application requires a vast set of control words to be used by many operators, then, there can be inconsistencies in recognition.
The specific application of this study is the secondary control (ie. non-critical control) of heavy machinery (in particular a caterpillar tractor) using an operator - speech interface. The inherent problem of this application is the environmental background noise due to the tractor. It is also important that a robust vocabulary is selected so that no misrecognition occurs between critical control words.
In order to add speech input for control of machines in a harsh environment there are two considerations:
1. The reduction of noise from the input speech signal.
2. The selection of a robust vocabulary dependent upon the specific operator and the specific SRU.
This study investigates many different types of noise reduction filters, including traditional Wiener, Power Spectral Subtraction and Gaussian filters. The results show that the best types of noise reduction filters are adaptive optimization filters which use two input signals or the Power Spectral Subtraction (PSS) filter. It is possible to reduce the noise to a level within the range of the SRU's capacity for noise.
An algorithm for selecting an accurate vocabulary is proposed. This algorithm determines weaknesses for the specific SRU, vocabulary and speaker; and selects the control words around those weaknesses. Testing of this algorithm showed that it was possible to achieve closed to 98% recognition and 0% misrecognition.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Rasulov, Timur. « The book of Job harsh counsel / ». Theological Research Exchange Network (TREN), access this title online, 2006. http://www.tren.com/search.cfm?p091-0058.
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Hennig, Janou. « Generation and analysis of harsh wave environments ». [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975328727.
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Dudukovich, Rachel. « A Wireless Ultraviolet Sensor For Harsh Environments ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1416837540.
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Butler, Jared J. « Highly Compressible Origami Bellows for Harsh Environments ». BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6657.
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The use of origami-based bellows is of interest in fields where traditional metal bellows are incapable of meeting compression, mass, or flexibility constraints. Metal bellows are often used in space applications but frequently complicate spacecraft design. Origami-based bellows capable of meeting design constraints while adequately shielding sensitive spacecraft parts may be advantageous to space mechanism design. The design and testing of a highly compressible origami bellows for harsh environments is described. Several origami patterns were evaluated and the Kresling fold pattern was designed to meet constraints and selected for use in the bellows design. Origami bellows were prototyped in five different materials and tested in fatigue, thermal cycling, ablation, and radiation. Tested bellows show good fatigue life exceeding 100,000 cycles for some materials and resilience to potential harsh environmental conditions such as thermal cycling, abrasion, and high radiation. The bellows can be designed to fit within a given inner and outer diameter and stroke length depending on the design requirements. The origami bellows shows promise for space application and as an adequate replacement for current metal bellows due to its high compressibility and low mass. The design, testing, and fabrication of an origami-based bellows for microgravity drilling is presented. The benefits of origami created an opportunity for application on NASA's Asteroid Redirect Mission (ARM) to protect sensitive parts from debris. Origami-based bellows were designed to fit spacial limitations and meet needed compression ratios. Designs have demonstrated high mass reductions, improved stroke length, greatly decreased stowed volume, improved flexibility, and reduced reaction forces in comparison with traditional metal bellows. Material and design testing demonstrated that a nylon-reinforced polyvinyl fluoride based bellows with an aramid fiber stitched seam is well suited for debris containment in space conditions. Various epoxies were able to maintain an adequate bond with polyvinyl fluoride below expected environmental temperature for bellows mounting to the ARM drill. Asymmetric compression of the bellows can occur at extreme low temperatures and is preventable by balancing stiffness within the structure.
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Panitzek, Kamill [Verfasser]. « Mobile Service Provision in Harsh Environments / Kamill Panitzek ». Munich : GRIN Verlag, 2016. http://d-nb.info/1118727479/34.
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Boccard, Jean-Michel [Verfasser], et Leonhard M. [Akademischer Betreuer] Reindl. « Interrogation of passive wireless sensors in harsh environments ». Freiburg : Universität, 2015. http://d-nb.info/1119328012/34.
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Zakaria, A. B. « Photothermal studies of surfaces subjected to harsh environments ». Thesis, Swansea University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636724.
Texte intégralRésumé :
In this thesis we have been concerned with photothermal studies of surfaces subjected to harsh environments. In the context of harsh environments we have concentrated on the deleterious effects that atomic oxygen (ATOX) has on different materials. In order to study such effects an ATOX source has been developed which is capable of producing an ATOX flux of 1.5 x 1017 atoms/cm2s when operating at a pressure of 1 to 2 Torr. The characteristics of the source have been studied and the erosion effects on materials at various material temperatures and ATOX fluences have been measured. The erosion in materials may be stopped by coating with gold. However, imperfections in the coating may provide erosion sites. In order to study this, coated polymers were deliberately scratched and exposed so that the damaged areas were eroded and at longer exposures the coatings were found to be undercut at the damage sites. The development of the undercut sites has been monitored by using two dimensional photothermal scans after each exposure to ATOX. Materials studied were Kapton, graphite, Mylar and multi-layered Kapton. For coated Kapton, various conditions of coating imperfection have been studied. The increase of photoacoustic (PA) signal with fluence indicates that during exposure volatile material contaminates the coating surface. At the intact area near the deliberately scratched gold-coated sample there is a disbonded coating due to ATOX attack which increases the PA and decreases the piezoelectric (PZT) signals. The PZT scanned phase images are used to determine the undercut boundary while the scanned magnitude images are used to determined the undercut depth at the opened area, both the width and the depth measurements being cross checked with a profilometer after the final exposure. The new method of scanning by using an open PA cell has been introduced which is inexpensive and suitable for successive ATOX exposures and subsequent scanning.
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Zheng, Deyi. « Advanced piezoceramic actuators for harsh operating environments (APAHOE) ». Thesis, University of Southampton, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548210.
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HILL, BRIAN JAMES. « Common Flight Test Module for Multiple Harsh Environments ». University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1211912322.
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Jones, Wayne. « Modelling the growth and resource allocation dynamics of juvenile salmonids ». Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248333.
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Sacchetti, Allegra. « Novel transparent and flexible transistors for radiation harsh environment ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9204/.
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La scoperta dei semiconduttori amorfi ha segnato l’era della microelettronica su larga scala rendendo possibile il loro impiego nelle celle solari o nei display a matrice attiva. Infatti, mentre i semiconduttori a cristalli singoli non sono consoni a questo tipo di applicazioni e i s. policristallini presentano il problema dei bordi di grano, i film amorfi possono essere creati su larga scala (>1 m^2) a basse temperature (ad es. <400 °C) ottenendo performance soddisfacenti sia su substrati rigidi che flessibili. Di recente la ricerca sta compiendo un grande sforzo per estendere l’utilizzo di questa nuova elettronica flessibile e su larga scala ad ambienti soggetti a radiazioni ionizzanti, come lo sono i detector di radiazioni o l’elettronica usata in applicazioni spaziali (satelliti). A questa ricerca volge anche la mia tesi, che si confronta con la fabbricazione e la caratterizzazione di transistor a film sottili basati su ossidi semiconduttori ad alta mobilità e lo studio della loro resistenza ai raggi X. La micro-fabbricazione, ottimizzazione e caratterizzazione dei dispositivi è stata realizzata nei laboratori CENIMAT e CEMOP dell’Università Nova di Lisbona durante quattro mesi di permanenza. Tutti i dispositivi sono stati creati con un canale n di ossido di Indio-Gallio-Zinco (IGZO). Durante questo periodo è stato realizzato un dispositivo dalle ottime performance e con interessanti caratteristiche, una delle quali è la non variazione del comportamento capacitivo in funzione della frequenza e la formidabile resistenza alle radiazioni. Questo dispositivo presenta 114 nm di dielettrico, realizzato con sette strati alternati di SiO2/ Ta2O5. L’attività di ricerca svolta al Dipartimento di Fisica e Astronomia di Bologna riguarda prevalentemente lo studio degli effetti delle radiazioni ionizzanti su TFTs. Gli esperimenti hanno rivelato che i dispositivi godono di una buona stabilità anche se soggetti alle radiazioni. Infatti hanno mostrato performance pressoché inalterate anche dopo un’esposizione a 1 kGy di dose cumulativa di raggi X mantenendo circa costanti parametri fondamentali come la mobilità, il threshold voltage e la sub-threshold slope. Inoltre gli effetti dei raggi X sui dispositivi, così come parametri fondamentali quali la mobilità, si sono rivelati essere notevolmente influenzati dallo spessore del dielettrico.
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Chedid, Michel. « Wearable Systems in Harsh Environments : Realizing New Architectural Concepts ». Doctoral thesis, Norrköping : Department of Science and Technology, Linköping University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54461.
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Ekström, Martin. « Towards Predictable and Reliable Wireless Communication in Harsh Environments ». Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-16413.
Texte intégralRésumé :
Wireless communication in industrial, scientific and medical applications have several benefits. The main benefits when using wireless technologies include ease-of-deployment, the simplicity to introduce new units into the network and mobility. However it also put higher demands on the communication, including reliability and predictability compared to wired communication. The reliability issues correlate to the radio communication and the possibility to ensure that the user data is received, and within the time frame of the system requirements. This doctoral thesis presents an empirical measurement approach to investigate and model the behaviour linked to reliability and predictability. The focus of the work presented is energy consumption, packet-error-rate and latency studies. This is performed for various radio technologies and standards in (radio?) harsh environments. The main contributions of this thesis are the measurements platforms and procedures that have been developed to meet the requirements to investigate modern radio technologies in terms of predictability and reliability. This thesis show that it is possible to predict wireless communication in radio harsh environments. However it is necessary to determine the characteristics of the environment to be able to choose a suitable radio technology. The measurement procedures presented in this thesis alongside the platform developed enable these types of investigations. In this thesis a model of the energy consumption for a Bluetooth radio in low-duty-cycle applications with point-to-multipoint communication is presented. The measurements show that distance and transmission power will not effect the energy consumption for a Bluetooth nor ZigBee module. However the packet-error-rate and number of retransmissions will affect the overall energy consumption, and these parameters can be correlated to distance and foremost the environmental characteristics. This thesis also presents two application-based solutions, a time synchronized ECG network with reliable data communication as well as a low-latency wireless I/O for a hydro plant.Tesla
Gauss
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Chang, Sung Pil. « Robust micromachined capacitive pressure sensors for mechanically harsh environments ». Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15473.
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De, Luca Andrea. « SOI smart multi-sensor platform for harsh environment applications ». Thesis, University of Cambridge, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709510.
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Buckley, Dave. « The Challenges of Data Acquisition in Harsh Remote Places ». International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596401.
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ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NVIn modern flight test installations there is a continuing trend to move the data acquisition closer to the sensors. As a consequence the data acquisition chassis needs to be mounted in locations that are small, inaccessible and subject to harsh environmental conditions. On top of this there are an increasing number of measurements required for each new flight test campaign. This paper discusses the challenges of designing a small lightweight data acquisition chassis which can provide hundreds of channels of measurement capability while operating in tight spaces which are exposed to fluids, high vibration and extremes of temperature. The paper suggests ways of designing and installing the data acquisition chassis in order to optimize the available installation space while mitigating the effects of the harsh environmental conditions.
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BORDAS, Jean-Claude, et Jean-François LEBLANC. « ULTRA-MINIATURE DIGITAL REMOTE MEASUREMENT SYSTEM FOR HARSH ENVIRONMENTS ». International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612919.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaFor the last dozen years, ELECTRICITE DE FRANCE has been using a digital telematry system mountable on the rotors of its generating machines in case of acceptance tests or after technical hitch, under difficult environmental conditions (125 degrees C and centrifugal acceleration of 100,000 m/s ). This system, manufactured by 2 SCHLUMBERGER, has proved itself in many test programs on high-power electrical motors, primary pumps of PWR reactors, steam turbines, alternators, etc. Today, the need is growing towards operational monitoring of equipment. Using this type of equipment in a monitoring system is a greater challenge. In fact, it is necessary to obtain an MTBF longer than the fuel refilling period (approximately 18 months) to make significant savings in product costs. A technological upgrade of the existing product was undertaken in late 1989. A very effective product capable of meeting the needs expressed is now available on the market. The system can be used to build systems with 1 to 63 channels with pass-bands ranging from 250 Hz to 10 kHz and very high precision (approximately 0.1%), under the above-mentioned environmental conditions. Its size, low power consumption, range of operating temperatures (-20 to 125 degrees C), resolution (12 bits), adaptability and capability of operating under conditions of acceleration and vibrations (100,000 M/s and 1000 m/s from 20 to 1000 Hz), make it a 2 2 unique product of its type. Although designed for use on rotating machines, these devices, thanks to the designs and technologies used, are compatible with other types of applications. The central equipment is also modular, a change in the structure of the rotor-mounted system does not call any of the investments into question; only the equipment’s software configuration is modified. A full line of standard equipment for reception, decommutation, recording and processing is available. This paper is intended to show how this product was developed so as to meet the main constraints of a system mounted on rotating machines. Problems related to installation on the machine, the power supply to the system and data transmission are not dealt with here. A short video film will illustrate our analysis.
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Jia, Tao. « Collaborative Position Location for Wireless Networks in Harsh Environments ». Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26548.
Texte intégralRésumé :
Position location has become one of the more important tasks for improving communication and networking performance for future commercial wireless systems. It is also the enabling technology for many control and sensing applications envisioned by the wireless sensor networks (WSN). Despite its meaningfulness and many algorithms being developed in the past several years, position location in harsh propagation environments remains to be a challenging issue, due mainly to the lack of sufficient infrastructure support and the prominent phenomenon of non-line-of-sight (NLOS) signal propagation.
Recently, adopting the concept of collaborative position location has attracted much research interest due to its potential in overcoming the abovementioned two difficulties. In this work, we approach collaborative position location from two different angles. Specifically, we investigate the optimal performance of collaborative position location, which serves as a theoretical performance benchmark. In addition, we developed a computationally efficient algorithm for collaborative position location and incorporated an effective NLOS mitigation method to improve its performance in NLOS-dense environments. Overall, our work provides insight into both theoretical and practical aspects of collaborative position location.Ph. D.
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Zhu, Yizheng. « Miniature Fiber-Optic Sensors for High-Temperature Harsh Environments ». Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27762.
Texte intégralRésumé :
Measurement of physical parameters in harsh environments (high pressure, high temperature, highly corrosive, high electromagnetic interference) is often desired in a variety of areas, such as aerospace, automobile, energy, military systems, and industrial processes. Pressure and temperature are among the most important of these parameters. A typical example is pressure monitoring in jet engine compressors to help detect and control undesirable air flow instabilities, namely rotating stall and surge. However, the temperatures inside a compressor could reach beyond 600°C for today's large engines. Current fiber-optic sensor can operate up to about 300°C and even the most widely employed semiconductor sensors are limited below 500°C.
The objective of this research is to push the limit of fiber-optic sensing technology in harsh environment applications for both pressure and temperature measurements by developing novel sensing structures, fabrication techniques, and signal processing algorithms. An all-fused-silica pressure sensor has been demonstrated which is fabricated on the tip of a fiber with a diameter no larger than 125μm. The sensor was able to function beyond the current limit and operate into the 600~700°C range. Also a temperature sensor has been developed using sapphire fibers and wafers for ultra-high temperature measurement as high as 1600°C. This effort will generate more understanding regarding sapphire fiber's high temperature properties and could possibly lead to novel designs of pressure sensor for beyond 1000°C. Both sensors have been field tested in real-world harsh environments and demonstrated to be reliably and robust.
In this dissertation, the design, fabrication, and testing of the sensors are discussed in detail. The system and signal processing techniques are presented. The plan and direction for future work are also suggested with an aim of further pushing the operating limit of fiber-optic sensors.Ph. D.
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Arechiga, Austin Podoll. « Sensitivity of Feedforward Neural Networks to Harsh Computing Environments ». Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84527.
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Neural Networks have proven themselves very adept at solving a wide variety of problems, in particular they accel at image processing. However, it remains unknown how well they perform under memory errors. This thesis focuses on the robustness of neural networks under memory errors, specifically single event upset style errors where single bits flip in a network's trained parameters. The main goal of these experiments is to determine if different neural network architectures are more robust than others. Initial experiments show that MLPs are more robust than CNNs. Within MLPs, deeper MLPs are more robust and for CNNs larger kernels are more robust. Additionally, the CNNs displayed bimodal failure behavior, where memory errors would either not affect the performance of the network, or they would degrade its performance to be on par with random guessing. VGG16, ResNet50, and InceptionV3 were also tested for their robustness. ResNet50 and InceptionV3 were both more robust than VGG16. This could be due to their use of Batch Normalization or the fact that ResNet50 and InceptionV3 both use shortcut connections in their hidden layers. After determining which networks were most robust, some estimated error rates from neutrons were calculated for space environments to determine if these architectures were robust enough to survive. It was determined that large MLPs, ResNet50, and InceptionV3 could survive in Low Earth Orbit on commercial memory technology and only use software error correction.Master of Science
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Hedin, Kajsa. « Design of semi-rigid cables for harsh vibration environment ». Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284522.
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This thesis investigates semi-rigid cables exposed to a harsh vibration environment. Thethesis includes the creation of a simulation model of the semi-rigid cables as well asdeveloping a set-up and performing a experimental vibration test. It was shown that thecables could be modeled as a isotropic material with a fitted elastic modulus of 55 GPaand give accurate results in comparison with the experimental vibration test. However itis important that the boundary conditions of the cable are applied correctly. Regardingthe lifetime of the cables it was shown that pre-stress, due to a bending moment, inthe cables did not effect the lifetime of the cables. The amplitude moment, due to theoscillation in the cable from the random vibration, did however effect the lifetime of thecables. With data from the simulations and the vibration test an equation describingrelation between the amplitude moment and the number of cycles the cable was exposedto could be formulated.Den här master rapporten undersöker semi-rigida kablar som utsätts för en hård vibrationsmiljö. Rapporten inkluderar en simulations modellering av de semi-rigida kablarna samt utvecklandet av en fixturmodell som sedan undersökts i ett experimentellt vibrationstest. Det visades att kablarna kunde modelleras som ett isotropiskt material med en elastisk modul på 55 GPa och ge korrekta resultat i jämförelse med det experimentella vibrationstestet. Det var viktigt att analysera randvillkoren så att de applicerades rätt vid modelleringen. Vad gäller livslängden på kablarna visades det att förspänning, på grund av böjmoment, i kablarna inte påverkade livslängden. Amplitudmomentet, på grund av oscillationen som skapas i kablarna vid vibrering, påverkade livslängden och en ekvation som beskriver förhållandet mellan amplitudmomentet och antal cykler som kabeln utsattes för kundes ta fram.
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Ho, Shih-Shian. « Stainless Steel Capacitive Pressure Sensors for Harsh Environment Applications ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1315960232.
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Pakalniskiene, Vilmante. « Harsh or Inept Parenting, Youth Characteristics and Later Adjustment ». Doctoral thesis, Örebro : Örebro universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-1796.
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Kimoto, Daiki. « Characterization and Modeling of SiC Integrated Circuits for Harsh Environment ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223422.
Texte intégralRésumé :
Elektronik för extrema miljöer, som kan användas vid hög temperatur, hög strålning och omgivning med frätande gaser, har varit starkt önskvärd vid utforskning av rymden och övervakning av kärnreaktorer. Kiselkarbid (SiC) är en av kandidaterna inom material för extrema miljöer på grund av sin höga temperatur- och höga strålnings-tolerans. Syftet med denna avhandling är att karakterisera 4H-SiC MOSFETar vid hög temperatur och att konstruera SPICE modeller för 4H-SiC MOSFETar. MOSFET-transistorer karakteriserades till 500°C. Med användande av karaktäristik för en 4H-SiC NMOSFET med L/W = 10 µm / 50 µm, anpassades en SPICE LEVEL 2 kretsmodell. Modellen beskriver DC karakteristiska av 4H- SiC MOSFETar mellan 25ºC och 450ºC. Baserat på SPICE-kretsmodellen simulerades egenskaper för operationsförstärkare och digitala inverterar. Därutöver analyserades driften av pseudo-CMOS vid hög temperatur och principen för konstruktion av pseudo-CMOS föreslogs. Arean och utbytet (s.k. yield) av pseudo-CMOS integrerade kretsar uppskattades och det visar sig att SiC pseudo-CMOS integrerade kretsar kan använda mindre area än SiC CMOS integrerade kretsar.Harsh environment electronics, which can be operated at high-temperature, high-radiation, and corrosive gas environment, has been strongly desired in space exploration and monitoring of nuclear reactors. Silicon Carbide (SiC) is one of the candidates of materials for harsh environment electronics because of its high-temperature and high-radiation tolerance. The objective of this thesis is to characterize 4H-SiC MOSFETs at high- temperature and to construct SPICE models of the 4H-SiC MOSFETs. The MOSFET devices were characterized up to 500ºC. Using the characteristic of a 4H-SiC NMOSFET with L/W = 10 µm/50 µm, a SPICE LEVEL 2 circuit model was constructed. This model describes the DC characteristic of the 4H-SiC MOSFETs in the range of 25 – 450ºC. Based on the SPICE circuit model, the characteristics of operational amplifiers and digital inverters were simulated. Furthermore, the operation of pseudo-CMOS at high-temperature was analyzed and the operation principle of pseudo-CMOS was suggested. The device area and yield of pseudo-CMOS integrated circuits were estimated and it is shown that SiC pseudo-CMOS integrated circuits can use less area than SiC CMOS integrated circuits.
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Unéus, Lars. « Development and characterisation of SiC based sensors for harsh environments / ». Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek736s.pdf.
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Ridenour, Joshua David Evans John L. « Overmolded substrate on aluminum metal backing for harsh environment applications ». Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/FALL/Industrial_and_Systems_Engineering/Thesis/Ridenour_Joshua_26.pdf.
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Khaji, Zahra. « Extending Microsystems to Very High Temperatures and Chemically Harsh Environments ». Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302658.
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Aiming at applications in space exploration as well as for monitoring natural hazards, this thesis focuses on understanding and overcoming the challenges of extending the applicability of microsystems to temperatures above 600°C as well as chemically harsh environments. Alumina and zirconia high-temperature co-fired ceramics (HTCC) with platinum as the conductor material, have in this thesis, been used to manufacture a wide range of high-temperature tolerant miniaturized sensors and actuators, including pressure and flow sensors, valves, a combustor, and liquid monopropellant microthrusters. Interfacing for high temperatures is challenging. One solution is to transfer the signal wirelessly. Here, therefor, wireless pressure sensors have been developed and characterized up to 1000°C. It is usually unwanted that material properties change with temperature, but by using smart designs, such changes can be exploited to sense physical properties as in the gas flow sensor presented, where the temperature-dependent electrical conductivity of zirconia has been utilized. In the same manner, various properties of platinum have been exploited to make temperature sensors, heaters and catalytic beds. By in-situ electroplating metals after sintering, even more capabilities were added, since many metals that do not tolerate HTCC processing can be added for additional functionality. An electroplated copper layer that was oxidized and used as an oxygen source in an alumina combustor intended for burning organic samples prior to sample analysis in a lab on a chip system, and a silver layer used as a catalyst in order to decompose hydrogen peroxide in a microthuster for spacecraft attitude control, are both examples that have been explored here. Ceramics are both high-temperature tolerant and chemically resistant, making them suitable for both thrusters and combustors. The corresponding applications benefit from miniaturization of them in terms of decreased mass, power consumption, integration potential, and reduced sample waste. Integrating many functions using as few materials as possible, is important when it comes to microsystems for harsh environments. This thesis has shown the high potential of co-fired ceramics in manufacturing microsystems for aggressive environments. However, interfacing is yet a major challenge to overcome.
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Angaragsuren, Odkhuu. « Conservation of a decorated ancient tomb in harsh climate conditions ». Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/265207.
Texte intégralRésumé :
京都大学新制・課程博士
博士(人間・環境学)
甲第23435号
人博第1008号
新制||人||238(附属図書館)
京都大学大学院人間・環境学研究科共生文明学専攻
(主査)教授 高妻 洋成, 准教授 山崎 健, 教授 小椋 大輔, 教授 松川 節
学位規則第4条第1項該当
Doctor of Human and Environmental Studies
Kyoto University
DFAM
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Zhang, Yibing. « Novel Optical Sensors for High Temperature Measurement in Harsh Environments ». Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28392.
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Accurate measurement of temperature is essential for the safe and efficient operation and control of a vast range of industrial processes. Many of these processes involve harsh environments, such as high temperature, high pressure, chemical corrosion, toxicity, strong electromagnetic interference, and high-energy radiation exposure. These extreme physical conditions often prevent conventional temperature sensors from being used or make them difficult to use. Novel sensor systems should not only provide accurate and reliable temperature measurements, but also survive the harsh environments through proper fabrication material selections and mechanical structure designs.
This dissertation presents detailed research work on the design, modeling, implementation, analysis, and performance evaluation of novel optical high temperature sensors suitable for harsh environment applications. For the first time to our knowledge, an optical temperature sensor based on the broadband polarimetric differential interferometric (BPDI) technology is proposed and tested using single crystal sapphire material. With a simple mechanically structured sensing probe, in conjunction with an optical spectrum-coded interferometric signal processing technique, the proposed single crystal sapphire optical sensor can measure high temperature up to 1600 oC in the harsh environments with high accuracy, corrosion resistance, and long-term measurement stability. Based on the successfully demonstrated sensor prototype in the laboratory, we are confident of the next research step on sensor optimization and scale-up for full field implementations. The goal for this research has been to bring this temperature sensor to a level where it will become commercially viable for harsh environment applications associated with industries.Ph. D.
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Twedt, Jason Christopher. « Fiber-Optics Based Pressure and Temperature Sensors for Harsh Environments ». Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/42782.
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Monitoring accurate temperature and pressure profiles in harsh environments is currently in high demand in aerospace gas turbine engines and nuclear reactor simulators. Having the ability to measure both quantities continuously over a region, without thermal coupling, using a sensor with a small size (envelope) is also highly desirable. Currently available MEMS (microelectromechanical systems) provide effective small scale pressure and temperature measurement devices, however, they have only been shown to be effective up to 600C and lack the ability to perform distributed measurements unless combined with fiber-optic techniques. In general, fiber-optics provide many advantages over electrical based sensors and are the ideal choice for high temperature regimes and distributed sensing. In this thesis, preliminary designs and suggested future work are presented for a sensor built within an 3.175 mm radius envelope and capable of distributed pressure and temperature sensing up to temperatures reaching 800C. Finite element analysis via ANSYS, along with analytical verification models have been used for the design evolution. Diaphragm based designs, seem to provide easy fabrication methods and good sensitivity, however, for this design to be realized at high temperature operation, a robust bonding method must be chosen to avoid unwanted deformation due to misfit strains.Master of Science
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Szabo, Nicholas F. « DEVELOPMENT OF HARSH ENVIRONMENT NITROGEN OXIDES SOLID-STATE GAS SENSORS ». The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1046980412.
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Branch, Shirmir D. « Fluorescence-based spectroscopic sensor development for technetium in harsh environments ». University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521192977626836.
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Pham, Tuan Anh. « Multifunctional silicon carbide nanowires for sensing applications in harsh environments ». Thesis, Griffith University, 2022. http://hdl.handle.net/10072/414588.
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Wide bandgap semiconductors are currently considered as the building blocks which revolutionized many areas of nanoscience and nanotechnologies. Among them, silicon carbide has been quickly emerging as one of the most interesting materials due to its remarkable physical, chemical, mechanical, electrical properties along with its biocompatibility and its feasibility for a wafer-scale production using standard MEMS processes. Inspired by these advantages, considerable number of studies have been devoted to the development of various SiC-based electronic devices over the past years. Despite these great achievements, however, it is realized that existing sensing devices usually rely on SiC in the forms of bulk or thin film, which still exhibit relatively poor sensitivity and unstable operation due to the limitation of their surface-to-volume ratios. Another key bottleneck of these existing sensing devices lies in the impossibility to integrate SiC onto soft and stretchable substrates due to its rigid and brittle nature, which significantly hamper the broader applications of SiC in the fast-emerging field of bioelectronics. Therefore, the research activities in the framework of my Ph.D. candidature aimed to establish reliable and sustainable protocols to overcome these two critical challenges. The focuses of my research work are placed on the fabrication of SiC nanowires on SiO2 insulators and stretchable SiC microstructures integrated onto polymeric substrates with a high level of structural perfection. Towards these goals, I have successfully fabricated Si NWs on insulator by using a combination of electron beam lithography and thermal wet oxidation techniques. The temperature sensing devices based on SiC NWs exhibit a high TCR compared to their bulk counterparts. On the other hand, I successfully established an effective protocol to transfer rigid SiC microstructures onto polymeric substrates and subsequently, enhanced their stretchability by taking advantages of structural design approaches.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Zhang, Chen. « Piezoelectric-Based Gas Sensors for Harsh Environment Gas Component Monitoring ». Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538769/.
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In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.
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Walker, Rodney A. « The operation and simulation of GPS positioning in harsh environments ». Thesis, Queensland University of Technology, 1999.
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Alexandru, Mihaela. « 4H-SiC Integrated circuits for high temperature and harsh environment applications ». Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/129635.
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Silicon Carbide (SiC) has received a special attention in the last decades thanks to its superior electrical, mechanical and chemical proprieties. SiC is mostly used for applications where Silicon is limited, becoming a proper material for both unipolar and bipolar power device able to work under high power, high frequency and high temperature conditions. Aside from the outstanding theoretical and practical advantages still to be proved in SiC devices, the need for more accurate models for the design and optimization of these devices, along with the development of integrated circuits (ICs) on SiC is indispensable for the further success of modern power electronics.
The design and development of SiC ICs has become a necessity since the high temperature operation of ICs is expected to enable important improvements in aerospace, automotive, energy production and other industrial systems. Due to the last impressive progresses in the manufacturing of high quality SiC substrates, the possibility of developing ICs applications is now feasible. SiC unipolar transistors, such as JFETs and MESFETs show a promising potential for digital ICs operating at high temperature and in harsh environments.
The reported ICs on SiC have been realized so far with either a small number of elements, or with a low integration density. Therefore, this work demonstrates that by means of our SiC MESFET technology, multi-stage digital ICs fabrication containing a large number of 4H-SiC devices is feasible, accomplishing some of the most important ICs requirements. The ultimate objective is the development of SiC digital building blocks by transferring the Si CMOS topologies, hence demonstrating that the ICs SiC technology can be an important competitor of the Si ICs technology especially in application fields in which high temperature, high switching speed and harsh environment operations are required.
The study starts with the current normally-on SiC MESFET CNM complete analysis of an already fabricated MESFET. It continues with the modeling and fabrication of a new planar-MESFET structure together with new epitaxial resistors specially suited for high temperature and high integration density. A novel device isolation technique never used on SiC before is approached. A fabrication process flow with three metal levels fully compatible with the CMOS technology is defined. An exhaustive experimental characterization at room and high temperature (300ºC) and Spice parameter extractions for both structures are performed.
In order to design digital ICs on SiC with the previously developed devices, the current available topologies for normally-on transistors are discussed. The circuits design using Spice modeling, the process technology, the fabrication and the testing of the 4H-SiC MESFET elementary logic gates library at high temperature and high frequencies are performed. The MESFET logic gates behavior up to 300ºC is analyzed. Finally, this library has allowed us implementing complex multi-stage logic circuits with three metal levels and a process flow fully compatible with a CMOS technology.
This study demonstrates that the development of important SiC digital blocks by transferring CMOS topologies (such as Master Slave Data Flip-Flop and Data-Reset Flip-Flop) is successfully achieved. Hence, demonstrating that our 4H-SiC MESFET technology enables the fabrication of mixed signal ICs capable to operate at high temperature (300ºC) and high frequencies (300kHz). We consider this study an important step ahead regarding the future ICs developments on SiC.
Finally, experimental irradiations were performed on W-Schotthy diodes and mesa-MESFET devices (with the same Schottky gate than the planar SiC MESFET) in order to study their radiation hardness stability. The good radiation endurance of SiC Schottky-gate devices is proven. It is expected that the new developed devices with the same W-Schottky gate, to have a similar behavior in radiation rich environments.
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Minhas, Inam-Ul-Haq. « WIRELESS SENSOR NETWORK PERFORMANCE IN HIGH VOLTAGE AND HARSH INDUSTRIAL ENVIRONMENTS ». Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4186.
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The applications of wireless sensor networks, WSN, are getting popular in the different areas reaching from daily usage to industrial usage. The performance evaluation of WSN deployed in industrial and high-voltage areas is receiving a great attention and becoming an interesting area of research. This thesis addresses the performance issues of WSN in high-voltage and harsh industrial environments. This study has been carried out at the facilities of High Voltage Test Lab of ABB. Typically, wireless sensor network contains wireless field devices (nodes) connected to a base station via a central gateway. The gate way centralizes information gathered and processed by the nodes. The nodes can communicate with each other and with the gateway via radio wave. The quality and usability of the data sent by WSN can be degraded due to the packet loss and delay. In the presence of high-voltage, the electromagnetic interference, EMI, can affect the performance of WSN. In this study the performance of WSN is evaluated in terms of packet loss and delay. We also focus on the effect of EMI on hardware devices as well as on signal transmission. EMI was expected at wide frequency band due to harsh industrial and high voltage environments. It was expected that EMIs could increase a bit error rate and/or packet loss. The EMI can also change the sensitivity of the nodes. For the performance evaluation of WSN network throughput, latency, path stability, data reliability and average value of the received signal strength indicator, RSSI, are used and measured. The results show that the electromagnetic frequencies of harsh industrial and high voltage environments affect the wireless sensor network performance.0046700375216
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Thompson, Tristan Nicholas. « Moral lessons from the harsh teacher : Thucydides, Nietzsche, and the sophists ». Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43412.
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This paper suggests an unconventional solution to the “moral question” regarding Thucydides' History of the Peloponnesian War. The term “moral question” refers to the fact that a significant number of current leading commentators on Thucydides think that the historian must have some form of moral outlook, but experience difficulty when they attempt to decipher a moral perspective from the historian's text.
To find a solution to the “moral question”, this paper looks back to a short passage written by Friedrich Nietzsche titled “What I Owe to the Ancients.” In this short and highly personal essay, Nietzsche suggests that the key to properly reading Thucydides is to interpret him in the context of the sophists, teachers of rhetoric and moral philosophers prominent in Thucydides' 4th century Athens. By comparing statements on the sophists that appear throughout Nietzsche's body of work to the surviving writings of the sophists and their contemporaries, a picture of “sophist culture” is established, in order to test the hypothesis that Thucydides can be profitably interpreted as expressing a sophistic understanding of morality.
A “sophistic understanding of morality”, in the simplest terms, centers on the the relativity of morals, the idea that morality has no real, concrete, and universal existence, and that morality is thus a fragile and changeable human construct. By following Nietzsche's picture of Thucydides as the “highest expression of sophist culture” to its fullest extent, we are able to answer the “moral question” of Thucydides' History, and to perceive a work that is itself a bold and challenging statement on the nature of morality, while containing relatively little explicit commentary on questions of right and wrong.
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Grudén, Mathias. « Wireless Sensor Network Systems in Harsh Environments and Antenna Measurement Techniques ». Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-218891.
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Wireless sensor network (WSN) has become a hot topic lately. By using WSN things that previously were difficult or impossible to measure has now become available. One of the main reasons using WSN for monitoring is to save money by cost optimization and/or increase safety by letting the user knowing the physical status of the monitored structure. This thesis considers four main topics, empirical testing of WSN in harsh environments, antenna designs, antenna measurements and radio environment emulation. The WSN has been tested in train environment for monitoring of ball bearings and inside jet engines to monitor strain of blades and temperatures. In total, two investigations have been performed aboard the train wagon and one in the jet engine. The trials have been successful and provide knowledge of the difficulties with practical WSN applications. The key issues for WSN are robust communication, energy management (including scavenging) and physical robustness. For the applications of WSN in harsh environments antennas has to be designed. In the thesis, two antennas has been designed, one for train environment and one for the receiver in the jet engine. In the train environment, a more isotropic radiation pattern is preferable; hence a small dual layered patch antenna is designed. The antenna is at the limit of being electrically small; hence slightly lower radiation efficiency is measured. For the WSN in the jet engine, a directive patch array is designed on an ultra-thin and flexible substrate. The thin substrate of the antenna causes rather lower radiation efficiency. But the antenna fulfils the requirements of being conformal and directive. In reverberation chambers are used to measure antennas, but there are difficulties to provide a realistic radio environment, for example outdoor or on-body. In this thesis, a large reverberation chamber is designed and verified. It enables measurement between 400 MHz and 3 GHz. Also, a sample selection method is designed to provide a post processing possibilities to emulate the radio environment inside the chamber. The method is to select samples from a data set that corresponds to a desired probability density function. The method presented in this thesis is extremely fast but the implementation of the method is left for future research.WISENET
WiseJet
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Schwerter, Martin [Verfasser]. « Micro sensor systems for aeronautical application in harsh environment / Martin Schwerter ». Aachen : Shaker, 2018. http://d-nb.info/1161307524/34.
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Lerch, Marc Alger. « Using Decoys as a Resiliency Mechanism in Spectrally Harsh DSA Environments ». Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25842.
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As wireless communication mediums develop and Dynamic Spectrum Access (DSA) is implemented as a means to increase capacity on a limited spectrum, the threat of reactive interference becomes real. The motivation for this thesis is to address this problem by suggesting a mechanism which could be used in these spectrally harsh DSA environments.
Overcoming certain types of interference in DSA environments requires unique approaches to transmitting and receiving data. This thesis discusses a decoy-based approach to mitigate conditions in which interference reacts to the spectral movement of the transmitting DSA radio as it hops around the frequency spectrum. Specifically using a polyphase channelizer, multiple replicas of the information signal are simultaneously transmitted at separate frequencies to lure reactive interference away from the main source of transmission. Using either serial or parallel transmission (splitting the signal in time or splitting the signal's energy) with the decoy signals and the original signal can either maximize data throughput in a minimal-interference environment or can add necessary robustness in the presence of multiple sources of reactive interference.
This decoy-based approach is verified with network simulation. An event-based simulator written in C++ was used to define the capacity or maximum throughput. Configuration files loaded with the necessary presets are used to run three network simulation scenarios: First Responder, Military Patrol, and Airborne Network.Master of Science
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Tran, Thi-Phuong-Yen. « CMOS 180 nm Compact Modeling Including Ageing Laws for Harsh Environment ». Thesis, Bordeaux, 2022. http://www.theses.fr/2022BORD0185.
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Au cours des dernières décennies, la demande de fonctionnalités complexes et d'intégration haute densité pour les Circuits Intégrés (CI) a mené à une réduction de la taille des dispositifs métal-oxyde-silicium (MOS). Dans ce scénario, les problèmes de fiabilité sont les préoccupations considérables par suite de la miniaturisation de l'appareil, telles que Hot Carrier Injection (HCI) et Bias Temperature Instability (BTI) qui ont un impact sérieux sur les performances de l'appareil. Dans certains domaines d'application où le coût des pannes est extrêmement élevé, comme l'espace, les champs pétrolifères ou les soins de santé, l'appareil doit pouvoir fonctionner de manière stable et fiable, en particulier dans une plage de températures étendue. Bien que les mécanismes de défaillance des dispositifs aient été intensivement étudiés dans le passé, les investigations de ces mécanismes à hautes températures sont rarement étudiées.L'objectif de cette thèse est de développer les lois de vieillissement de la technologie CMOS 0.18µm afin d'optimiser la conception des circuits pour une durée de vie ciblée sous des températures extrêmes. Nous avons mené une campagne intensive de tests de vieillissement pour nMOS et pMOS avec plusieurs longueurs de grille. Les mécanismes HCI et BTI intrinsèques ont été caractérisés et modélisés sous des tensions de polarisation de fonctionnement typique pour éviter le risque de sur-accélération d'autres mécanismes d'usure qui ne sont pas censés être expérimentés dans l'application pratique. Notre expérimentation est un test à longue durée avec un temps de stress allant jusqu'à 2,000 heures. Cette thèse présente des résultats de mesure jusqu'à 230°C qui n'ont jamais été étudiés auparavant dans la littérature pour cette technologie.Les lois de vieillissement sont finalement intégrées dans un environnement de conception assistée par ordinateur (EDA) pour prédire l'évolution des paramètres électriques dégradés du transistor/circuit et l'estimation de la durée de vie en conséquence des effets du vieillissement. De plus, le test de fiabilité au niveau du circuit a été réalisé pour valider et vérifier les modèles de vieillissement proposés. Cette approche offre la possibilité d'évaluer et de simuler la dérive de spécification du CI due à l'effet du vieillissement dans la phase de conception précoceIn the past decades, the demand for complicated functionality and high-density integration for Integrated Circuits (ICs) has resulted in metal-oxide-silicon (MOS) devices' scaling down. In this scenario, the reliability problems are the considerable concerns due to the device miniaturization, such as Hot Carrier Injection (HCI) and Bias Temperature Instability (BTI) that seriously impact the device performance. In some application fields where the cost of failure is extremely high such as space, oilfield, or healthcare, the device must be able to stably and reliably work, especially at an extensive temperature range. Although device failure mechanisms have been intensively investigated in the past, the investigations of these mechanisms at high temperatures are seldom studied.This thesis aims to develop the aging laws for 0.18µm CMOS technology to optimize circuit design for a targeted lifetime under extreme temperatures. We conducted an intensive aging test campaign for both nMOS and pMOS featuring several gate lengths. The intrinsic HCI and BTI mechanisms were characterized and modeled under typical operating voltage biases to avoid the risk of overaccelerating other wear-out mechanisms that are not supposed to be experienced in practical application. Our experiment is a long-term test with a stress time of up to 2,000 hours. This thesis presents measurement results up to 230°C that have never been studied before in the literature for this technology.The aging laws are finally integrated into an electronic design automation (EDA) environment to predict the evolution of the degraded transistor/circuit electrical parameters and the lifetime estimation due to the aging effects. In addition, the reliability test at the circuit level has been performed to validate and verify the proposed aging models. This approach offers the possibility to assess and simulate the IC specification drift due to the aging effect in the early design phase and optimize the circuit design over lifetime
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Behera, Amiya Ranjan. « Diode Laser Spectroscopy for Measurements of Gas Parameters in Harsh Environments ». Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84930.
Texte intégralRésumé :
The detection and measurement of gas properties has become essential to meet rigorous criteria of environmental unfriendly emissions and to increase the energy production efficiency. Although low cost devices such as pellistors, semiconductor gas sensors or electrochemical gas sensors can be used for these applications, they offer a very limited lifetime and suffer from cross-response and drift. On the contrary, gas sensors based on optical absorption offer fast response, zero drift, and high sensitivity with zero cross response to other gases. Hence, over the last forty years, diode laser spectroscopy (DLS) has become an established method for non-intrusive measurement of gas properties in scientific as well as industrial applications. Wavelength modulation spectroscopy (WMS) is derivative form of DLS that has been increasingly applied for making self-calibrated measurements in harsh environments due to its improved sensitivity and noise rejection capability compared to direct absorption detection. But, the complexity in signal processing and higher scope of error (when certain restrictions on operating conditions are not met), have inhibited the widespread use of the technique.
This dissertation presents a simple and novel strategy for practical implementation of WMS with commercial diode lasers. It eliminates the need for pre-characterization of laser intensity parameters or making any design changes to the conventional WMS system. Consequently, sensitivity and signal strength remain the same as that obtained from traditional WMS setup at low modulation amplitude. Like previously proposed calibration-free approaches, this new method also yields absolute gas absorption line shape or absorbance function. Residual Amplitude Modulation (RAM) contributions present in the first and second harmonic signals of WMS are recovered by exploiting their even or odd symmetric nature. These isolated RAM signals are then used to estimate the absolute line shape function and thus removing the impact of optical intensity fluctuations on measurement. Uncertainties and noises associated with the estimated absolute line shape function, and the applicability of this new method for detecting several important gases in the near infrared region are also discussed. Absorbance measurements from 1% and 8% methane-air mixtures in 60 to 100 kPa pressure range are used to demonstrate simultaneous recovery of gas concentration and pressure. The system is also proved to be self-calibrated by measuring the gas absorbance for 1% methane-air mixture while optical transmission loss changes by 12 dB.
In addition to this, a novel method for diode laser absorption spectroscopy has been proposed to accomplish spatially distributed monitoring of gases. Emission frequency chirp exhibited by semiconductor diode lasers operating in pulsed current mode, is exploited to capture full absorption response spectrum from a target gas. This new technique is referred to as frequency chirped diode laser spectroscopy (FC-DLS). By applying an injection current pulse of nanosecond duration to the diode laser, both spectroscopic properties of the gas and spatial location of sensing probe can be recovered following traditional Optical Time Domain Reflectometry (OTDR) approach. Based on FC-DLS principle, calibration-free measurement of gas absorbance is experimentally demonstrated for two separate sets of gas mixtures of approximately 5% to 20% methane-air and 0.5% to 20% acetylene-air. Finally, distributed gas monitoring is shown by measuring acetylene absorbance from two sensor probes connected in series along a single mode fiber. Optical pulse width being 10 nanosecond or smaller in the sensing optical fiber, a spatial resolution better than 1 meter has been realized by this technique.
These demonstrations prove that accurate, non-intrusive, single point, and spatially distributed measurements can be made in harsh environments using the diode laser spectroscopy technology. Consequently, it opens the door to practical implementation of optical gas sensors in a variety of new environments that were previously too difficult.Ph. D.
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Ige, Emmanuel. « Facial expression recognition under harsh lighting using high dynamic range imaging ». Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/90327/.
Texte intégralRésumé :
Facial information can reveal the emotional status of individuals. Although traditional cameras can capture this information, such cameras struggle to acquire the necessary information in extreme lighting conditions. This thesis aim to investigate whether High Dynamic Range (HDR) imaging can capture human facial expression under complex lighting conditions, and in doing so, enhance Facial Expression Recognition (FER) performance. The techniques presented in this thesis focus on developing a baseline for images captured in scenes with harsh lighting conditions, where Low Dynamic Range (LDR) images have difficulty capturing the full range of light in a single exposure. The thesis considers unprocessed images and a variety of pre-processing methods to examine whether reducing the impact of large lighting variations could improve the quality of an input image. In addition, realistic facial data plays a key role in validating facial expression analysis systems. Today, the majority of FER algorithms are evaluated only on images generated in highly controlled laboratory environments. The variability of a facial appearance in an image could be dominated by changes in head pose and illumination conditions. This can effectively hide features that are necessary to discriminate different subjects or different facial articulations. New HDR imaging techniques are thus introduced to help ensure that all the details in a scene is captured no matter what the lighting conditions present, and all this detail is then available to the FER algorithms. This is also investigated on Face recognition algorithms.
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John, Dylan Boone. « Atomistic Modeling of AlN/GaN HEMTs for Applications in Harsh Environments ». OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/572.
Texte intégralRésumé :
AlN/GaN high-electron mobility transistors (HEMT) are subject to internal structural and electrostatic fields originating mainly from: (i) the fundamental crystal atomicity and the interface discontinuity between dissimilar materials, (ii) atomistic strain, (iii) piezoelectricity, and (iv) spontaneous polarization (pyroelectricity). In this thesis, through numerical simulations, we have studied the origin and effects of these competing internal fields on the electrostatics and the I-V characteristic of scaled nitride HEMT structures. It is shown that strain in these devices is asymmetric and long-ranged (demanding simulations using millions of atoms). The resulting piezoelectric polarization is arge and atomistic in nature. However, the pyroelectric potential is significantly larger than the piezoelectric counterpart and opposes the latter at the InN/GaN interface as opposed to AlGas which only produces a piezoelectric potential. The polarization induced charge density is computed using a three-dimensional Poisson solver and shown to be strongly dependent on the thickness of the AlN barrier layer. This finding has been validated using available experimental data. We have also demonstrated that the olarization fields alone can induce channel carriers at zero external bias and lead to a significant increase in the ON current.