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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The research of Taiwan offshore Tuna fishing industry after vessel-reduction by ICCAT

Pan, Chun-wei 24 July 2008 (has links)
ABSTRACT Our Atlantic Ultra-Low-Temperature Tuna Fishing fleets were under attack from Japan during the 2004 ICCAT (International Commission for the Conservation of Atlantic Tunas) Annual Meeting. Japan openly called for tough penalty for our fleet such as significantly cutting our fishing quotas in the Atlantic and revoking our national membership in the ICCAT for over-fishing, violating International Conservation Regulations and washing fish right on the ocean. This resulted in catastrophic damage in our Ultra-Low-Temperature fishing operation in the pacific and undue pressure from our international competitors. Under the strict monitoring of international conservation groups, our government was forced reform its regulations of the fishing industry and focus on the long-neglected area of offshore fishing. To express its sincerity in active management of the industry, the government offered a series of matching measures. The first of these measures was the reduction of the number of ships to achieve cutback in fishing capacity. The three-year plan spanning from 2005 to 2007 involved a joint venture by the government and the offshore industry with joint contribution of 12.5 million US dollars to disassemble 183 large Tuna Long line Fishing Vessels in the three oceans. Fishing vessels in the Atlantic were reduced from 100 to 76. The next measures were to improve the monitoring of the fishing industry and to end any and all illegal, unreported and unregulated fishing. How will our offshore fishing industry recover after a series of attack? How will our industry thrive in the austere environment of conservatism? Do we still possess any competitive advantage after the vessel-reduction measure? This thesis will cover the analysis of the competitive advantage of the Offshore Ultra-Low-Temperature Fishing Industry after the vessel-reduction, the analysis of the supply-and-demand of the Ultra-Low-Temperature market and SWOT analysis. It will also discuss in depth the post-reform fishing industry management strategy for reference.
2

Fabrication de CMOS à basse température pour l'intégration 3D séquentielle / Low thermal budget CMOS processing for 3D Sequential Integration

Lu, Cao-Minh 24 October 2017 (has links)
Alors que la miniaturisation des transistors suivant la loi de Moore semble ralentir dû à des limites physique, technologique et économique, il devient essentiel de trouver des alternatives afin de répondre à la demande croissante en électronique : informatique et télécommunication, objets intelligents et interconnectés, domaine médical et biologique… En cela, l’utilisation de la troisième dimension, par opposition à la fabrication planaire de composants électrique, semble être une option prometteuse. L’intégration 3D permet en effet d’incorporer plus de composants sur une même surface en les empilant à un coût technologique et économique plus faibles que celui de la miniaturisation. En particulier, l’intégration séquentielle ou CoolCubeTM au CEA-Leti permet de profiter pleinement de la troisième dimension en fabriquant successivement les uns sur les autres chaque étage d’une puce, permettant un alignement optimal des transistors unitaires à chaque niveau. Néanmoins, plusieurs verrous technologiques particuliers à l’intégration 3D Séquentielle doivent alors être levés.Dans ce manuscrit, nous nous intéresserons à la réduction du budget thermique pour la fabrication des transistors supérieurs, nécessaire afin de ne pas endommager les étages inférieurs lors de la réalisation des composants sus-jacents. Nous commencerons par définir le budget thermique maximal afin de ne pas dégrader les couches inférieures avant d’identifier les briques technologiques impactées lors de la fabrication d’un transistor. Nous verrons alors dans ce manuscrit qu’il sera non seulement nécessaire d’étudier de nouveaux matériaux, mais aussi de nouveaux procédés voire de nouvelles techniques de recuit. Plus particulièrement, nous évaluerons tout d’abord l’utilisation des diélectriques low-k comme espaceurs de grille permettant notamment d’améliorer les performances dynamiques des composants. Ensuite, nous présenterons différentes stratégies de préparation de surface et de croissance épitaxiale à basse température pour la réalisation des sources et drains surélevés. Enfin, nous étudierons l’impact d’un budget thermique faible ainsi que de nouvelles techniques de recuits micro-onde et laser sur les propriétés de l’empilement de grille. Nous verrons en particulier que la difficulté principale d’une intégration à bas budget thermique est l’obtention d’une bonne fiabilité des transistors. Toute cette étude nous permettra alors de proposer des solutions à l’intégration d’un transistor à un bas budget thermique compatible avec l’intégration 3D Séquentielle. / As the scaling of transistors following Moore’s law seems to slow down due to physical, technological and economical barriers, it becomes mandatory to find alternatives to cope with the increasing demand in electronics: computing and telecommunication, smart and interconnected objects, medical and biological fields… To that end, the use of the third dimension, in opposition to the planar processing of electronical devices, appears to be a promising option. Indeed, 3D integration allows incorporating more devices per area by stacking them at a lower technological and economical cost than scaling. More specifically, 3D sequential or CoolCubeTM at CEA-Leti allows benefiting fully from the third dimension by processing successively one on top of each other each level of a die, allowing an optimal alignment of single transistors at each layer. However, several technological barriers specific to 3D Sequential Integration need then to be alleviated.In this work, we will study the reduction of thermal budget for the transistors fabrication, which is required to not damage bottom levels during the processing of top devices. First, we will define the maximal thermal budget in order not to degrade bottom layers prior to identifying the technological modules impacted during the fabrication of a transistor. We will then see in this work that not only new materials need to be studied, but also new processes and new annealing techniques. Specifically, we will first evaluate the use of low-k dielectrics as gate offset spacers, allowing the improvement of devices dynamic performance. Then we will present different strategies of surface preparation and epitaxial growth at low temperature for the formation of raised sources and drains. Finally, we will study the impact of a low thermal budget process flow along with novel microwaves and laser annealing techniques on the gate stack properties. In particular, we will see that the biggest challenge in a low thermal budget integration is to get a good reliability of transistors. This study leads to a proposed low thermal budget process flow for transistor fabrication compatible with 3D Sequential Integration.
3

Theoretical and Experimental Investigation of R-744 Vapor Compression Systems for Cooling Below the Triple Point Temperature

Xu, Yixia 15 June 2023 (has links)
Carbon dioxide (CO2) is a common working fluid for refrigeration systems. The triple point of CO2 (about −56 °C and 0.51 MPa) is often regarded as the lower operating limit for the con-ventional CO2 vapor compression systems, because below this temperature and pressure, solid CO2 could occur and block the system components. However, if the technical issue could be solved and a stable operation of a vapor compression cycle for heat absorption be-low the triple point pressure (or sublimation cycle) could be realized, there would be a great potential for CO2 to replace the common refrigerants with a very high environmental impact such as R-23 for refrigeration applications below −50 °C. The focus of this work is on the dis-cussion of the feasibly of the sublimation cycle regarding the energy efficiency and the block-ing issues. Seven different two-stage and three-stage CO2 sublimation systems are theoretically evalu-ated and compared to a two-stage R-23 system, which serves as a baseline. A calculation model for the systems is developed. The optimum intermediate pressures for each system as well as the high pressure for the systems in transcritical operations are calculated within the given temperature and pressure constraints. Multiple influence factors, such as the ambient temperature, compressor efficiency, are considered in determining the operating limit and evaluating the performance for each system. In order to find out the cause of the blockages in the sublimation system due to the solid CO2, the solid-gas flow is visualized through experiments. Different throttling devices are investi-gated under various inlet conditions. As the sublimator, a heated sight glass assembly is used. It is found that besides the inlet temperature and pressure condition, the tube wall in the down-stream section of the throttling devices has a great influence on the blockages. A larger heat flux also helps to reduce the blockage in the sublimator. Based on the knowledge gained from the theoretical investigation of the cycle variant and preliminary experiments, a cascade sublimation system is designed, constructed and tested. Despite the fact that the system still requires optimization in terms of energy efficiency and operation stability, it is capable of long continuous operation, and thus the basic feasibility of the sublimation cycle is verified. Finally, the further issues and improvement potentials for the heat transfer and sublimator are discussed.:Acknowledgment Abstract Contents Index of figures Index of tables List of abbreviations and symbols 1 Introduction 1.1 Background and Motivation 1.2 Objective and procedure 2 Fundamentals and state of the art 2.1 The R-744 sublimation cycle 2.2 Expansion into solid-gaseous region and critical flow 2.3 Sublimator and solid-gas two-phase flow 2.4 Summary 3 Thermodynamic analysis of sublimation systems 3.1 Definition of the cycle variants 3.1.1 The baseline system 3.1.2 R-744 cascade systems 3.1.3 R-744 booster systems 3.2 Boundary conditions 3.3 Description of the models 3.3.1 Compressor 3.3.2 Heat exchangers 3.3.3 Other components 3.3.4 Fluid properties 3.4 Process calculation and optimization 3.5 Results and discussion 3.5.1 General boundary conditions 3.5.2 Variable temperatures 3.5.3 Variable compressor efficiency 3.5.4 Variable pressure loss and superheating in the sublimator 3.6 Evaluation of the system variants 4 Experimental visualization of the solid-gas flow 4.1 Throttling below the triple point 4.1.1 Experimental setup - test rig I 4.1.2 Results and discussion 4.2 CO2-Sublimation in a horizontal channel 4.2.1 Experimental setup - test rig II 4.2.2 Results and discussion 4.3 Summary 5 Experimental investigation on the performance of a cascade sublimation system 5.1 Experimental setup – test rig III 5.1.1 The refrigerant cycles 5.1.2 The sublimating unit 5.2 Methodology 5.2.1 The measuring procedure 5.2.2 Data evaluation and uncertainty analysis 5.3 Results and discussion 5.3.1 Transient behavior 5.3.2 System performance 5.3.3 Compressor performance 5.3.4 Long period measurements 5.4 Summary 6 Existing issues and optimization potentials 6.1 Blockage-free operation at low wall temperatures 6.1.1 Supplementary experiment 6.1.2 Outlook 6.2 Heat transfer 6.2.1 Supplementary experiment 6.2.2 Outlook 7 Summary Literature Appendix A. Differential evolution A.1 Basics of differential evolution A.2 Convergence of the results for different system variants Appendix B. Mass flow rate from the capillary tubes B.1 Measurement of the mass flow rate B.2. Comparison of the results with the numerical model and correlations Appendix C. Supplement to the measurements of the test rig III C.1 Exemplary measurement of the R-23 operation C.2. Measurement of the air velocity for the sublimator Appendix D. Supplement to the measurements at low wall temperatures D.1. Calculation of the heat transfer coefficients for the airside D.2. Determination of the local sublimation heat transfer coefficients Publications during the PhD study
4

Ultra-low sintering temperature glass ceramic compositions based on bismuth-zinc borosilicate glass

Chen, M.-Y. (Mei-Yu) 06 June 2017 (has links)
Abstract In the first part of the thesis, novel glass-ceramic compositions based on Al2O3 and BaTiO3 and bismuth-zinc borosilicate (BBSZ) glass, sintered at ultra-low temperatures, were researched. With adequate glass concentration, dense microstructures and useful dielectric properties were achieved. The composite of BaTiO3 with 70 wt % BBSZ sintered at 450 °C exhibited the highest relative permittivity, εr, of 132 and 207 at 100 kHz and 100 MHz, respectively. Thus, the dielectric properties of the composites were dominated by the characteristics of glass, BaTiO3, and Bi24Si2O40 phase, especially the contribution of Bi24Si2O40 for the samples with 70-90 wt % glass. Actually, the existence of the secondary phase Bi24Si2O40 may not hinder but enhance the dielectric properties. The Al2O3-BBSZ composition samples showed a similar situation, not only for densification but also for their microstructures and phases (Al2O3, BBSZ, Bi24Si2O40), explaining the achieved dielectric properties. The second part of the thesis mainly discusses the composite of BaTiO3 with 50 wt % BBSZ with different thermal treatments. After sintering at 720 °C, dense microstructures and the existence of Bi4BaTi4O15, BaTiO3, Bi24Si2O40 phases were observed. The results also showed that the size of glass powder particles did not influence the dielectric properties (εr = 263-267, tan δ = 0.013 at 100 kHz) of sintered samples, but the addition of LiF degraded the dielectric properties due to the features and amount of Bi4BaTi4O15. These results demonstrate the feasibility of the BBSZ based composites for higher sintering temperature technologies as well. At the end, a novel binder system, which enables low sintering temperatures close to 300 °C, was developed. A dielectric multilayer module containing BaTiO3-BBSZ and Al2O3-BBSZ composites with silver electrodes was co-fired at 450 °C without observable cracks and diffusions. These results indicate that these glass-ceramic composites provide a new horizon to fabricate environmentally friendly ULTCC materials, as well as multilayers for multimaterial 3D electronics packages and high frequency devices. / Tiivistelmä Väitöstyön ensimmäisessä osassa tutkittiin ja kehitettiin uudentyyppisiä, ultramatalissa sintrauslämpötiloissa (ULTCC) valmistettuja lasi-keraami komposiitteja käyttäen vismuttisinkkiborosilikaatti -pohjaista lasia (BBSZ). Täyteaineina olivat alumiinioksidi (Al2O3) ja bariumtitanaatti (BaTiO3). Materiaaleille saatiin riittävän suuren lasipitoisuuden avulla tiheät mikrorakenteet ja sovelluskelpoiset dielektriset ominaisuudet. BaTiO3:n komposiitti, joka sisälsi 70 p-% BBSZ lasia, saavutti 450 °C lämpötilassa sintrattuna korkeimman suhteellisen permittiivisyyden: εr=132 (@100 kHz) ja εr=207 (@100 MHz). Komposiittien dielektrisiä ominaisuuksia määrittivät tällöin lasi-, BaTiO3- ja Bi24Si2O40- faasien ominaisuudet ja erityisesti Bi24Si2O40 -faasi näytteissä, joissa on 70-90 p-% lasia. Sekundäärinen faasi Bi24Si2O40 ei välttämättä heikentänyt, vaan jopa paransi dielektrisiä ominaisuuksia. Vastaavilla Al2O3-BBSZ –komposiiteilla saavutettiin samanlaisia tuloksia tihentymisen, mikrorakenteiden ja faasien (Al2O3, BBSZ, Bi24Si2O40) suhteen. Lisäksi tässä tapauksessa saavutetut dielektriset ominaisuudet voidaan selittää näiden kolmen faasin yhdistelmän olemassaololla. Väitöstyön toinen osa käsitteli pääasiassa eritavoin lämpökäsiteltyjä BaTiO3:n komposiitteja, joissa on 50 p-% BBSZ-lasia. Näillä saavutettiin tiheä mikrorakenne sintrattaessa 720 °C lämpötilassa ja havaitiin Bi4BaTi4O15-, Bi24Si2O40-faasien muodostuminen BaTiO3 lähtöfaasin rinnalle. Tulokset osoittivat myös, että lasijauheen partikkelikoko ei vaikuttanut sintrattujen näytteiden dielektrisiin ominaisuuksiin (εr = 263-267, tan δ = 0.013 (@100 kHz)). LiF -lisäys sen sijaan heikensi dielektrisiä ominaisuuksia ja vähensi Bi4BaTi4O15 faasin muodostumista. Tämä aiheutui Bi4BaTi4O15-faasin ominaisuuksista ja oli riippuvainen kyseisen faasin määrästä. Nämä tulokset osoittivat BBSZ -pohjaisten komposiittien käytettävyyden myös korkeampien sintrauslämpötilojen teknologioihin. Viimeisenä kehitettiin uudentyyppinen sideainesysteemi, joka mahdollistaa ultramatalien keraamien yhteissintraamisen jopa noin 300 °C lämpötilassa. Hyödyntäen kehitettyä sideainesysteemiä monikerrosrakenne, jossa käytettiin dielektrisiä BaTiO3-BBSZ- ja Al2O3-BBSZ-komposiitteja ja hopeaelektrodeja, yhteissintrattiin 450 °C lämpötilassa. Valmistetuissa rakenteissa ei havaittu murtumia eikä diffuusioita. Tulokset osoittavat, että kehitetyt lasi-keraami komposiitit mahdollistavat ympäristöystävällisten ULTCC -materiaalien valmistuksen. Lisäksi osoitettiin kehitettyjen materiaalien soveltuvuus monikerroksisten rakenteiden käyttöön monimateriaali-3D-elektroniikan pakkauksissa ja suurtaajuuskomponteissa.

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