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京都大学 / 新制・課程博士 / 博士(医学) / 甲第23754号 / 医博第4800号 / 新制||医||1055(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 木村 剛, 教授 山下 潤, 教授 YOUSSEFIAN Shohab / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>The main focus of this work is to improve the existing clinical machine model within the Pinnacle software planning system (at Juravinski Cancer Center, Hamilton, CA). The incident energy fluence spectrum exiting from the accelerator head is considered an important element of the machine model. Relying on the Pinnacle auto modeling function to determine the relative photon fluence spectrum based on percent depth dose curves fitting for various filed sizes, led to different solutions when the process cycle were repeated. This work presents a new method for determining the Pinnacle photon energy fluence spectrum based on 6 MV Varian 21EX machine. A Monte Carlo simulation spectrum based on BEAMnrc code was attenuated to various depths of water. We determine that, the BEAMnrc spectrum attenuated by 15 cm of water gives the closest agreement between the computed and measured depth dose, similar to the clinical machine spectrum.</p> <p>Implementing the novel spectrum into a machine that retained the same modeling parameters as the clinical machine (21ex-JCC) shows a slight better calculation of the output factor. The MLC model parameters were also investigated, however, adjusting the MLC offset table was found to give significant improvements, especially for the small field geometries.</p> <p>The full impact of adjusting the photon energy spectrum, Off-Axis Softening Factor, MLC rounded leaf tip radius and MLC calibration offsets were investigated individually, resulting in a good model parameter fit. Several proposed supplementary setups were created to further assess our model. This include a geometry sensitive to MLC abutment leakage, the calculation of output factors for long and narrow MLC defined fields, and small square MLC and jaws defined fields. A Sun-Point diode detector was used in the measurement of the output factors for its accurate precision at small geometries. In addition, a GAFCHROMIC EBT2 film dosimetry was used in the measurement of the MLC abutment leakage.</p> <p>Our new model shows superior results in comparison to the clinical 21ex-JCC machine model, especially with MLC small field calculations. We conclude that relying on PDD curves and dose profiles validation method in assessing the model might not necessarily lead to the best machine parameters, since these are not sensitive to subtle changes in parameters that have important dosimetric consequences.</p> / Master of Science (MSc)

Cette thèse contribue à la compréhension des frictions liées aux politiques environnementales et à la manière dont ces frictions affectent la dynamique des industries polluantes ainsi que les agrégats macroéconomiques tels que la productivité. Elle examine également de manière critique comment différents aspects de ces politiques influencent la distribution des entreprises en termes d’emploi, de tailles et d’émissions. Dans le premier chapitre, j’examine les effets à long terme des politiques d’exemption basées sur des seuils dans la réglementation environnementale, qui consistent à exonérer les émetteurs en dessous d’un certain seuil d’émissions. En utilisant des données sur la pollution provenant de divers établissements participant au programme de plafonnement et d’échange de la Californie, j’ai découvert que 40% des entreprises bénéficient de cette exemption, avec une concentration notable autour du seuil, en particulier parmi les nouveaux entrants. Pour comprendre les implications plus larges, j’ai développé un modèle dynamique industriel qui prend en compte des entreprises hétérogènes et un système de tarification du carbone avec des exemptions spécifiques au seuil. En simulant le programme californien de plafonnement et d’échange, j’ai constaté que la suppression de l’exemption conduit à une augmentation de 0,05% de la production en raison du déplacement des ressources vers des entreprises plus productives. Pour mesurer l’impact de la politique d’exemption sur l’allocation des ressources, j’ai analysé la dispersion de la productivité totale des facteurs basée sur les revenus (TFPR) au niveau de l’entreprise. L’analyse a révélé que la volatilité de la TFPR est influencée par la dispersion entre les catégories d’entreprises. Les entreprises ayant une productivité intermédiaire et regroupées autour du seuil ont une moyenne et une dispersion de TFPR plus élevées comparées aux grandes entreprises productives qui supportent les coûts des émissions. Dans le deuxième chapitre, j’examine les implications macroéconomiques de l’utilisation complémentaire des instruments de tarification traditionnels avec les Crédits de Compensation (OCs), dont le prix est négocié par les entités couvertes auprès des entreprises non couvertes. Ce processus de négociation peut entraîner un coût marginal d’émission différent par rapport aux instruments de tarification traditionnels. En utilisant les données des entreprises sur les émissions et les modalités de conformité du programme de plafonnement et d’échange de la Californie, j’ai montré trois faits. Premièrement, l’utilisation des OCs augmente avec la taille des émissions des entreprises ; la proportion des entreprises se conformant aux OCs et la proportion des émissions compensées augmentent avec les groupes de quintiles d’émissions. Ainsi, les OCs agissent comme une réduction implicite de la taxe carbone pour les grands émetteurs. Deuxièment, les entreprises établies se conforment plus intensivement aux OCs par rapport aux nouveaux entrants et aux entreprises sortantes. Enfin, le taux de retrait des OCs disponibles diminue progressivement après la réglementation. Pour expliquer ces résultats, j’étends et calibre un modèle de dynamique industrielle incorporant un système de plafonnement et d’échange où les entreprises choisissent entre les permis traditionnels et les OCs, considérés comme des substituts parfaits, le prix de ces derniers étant obtenu par un protocole de négociation de Nash. Je montre quantitativement que compléter le plafonnement et l’échange (enchères) avec des OCs peut affecter positivement les résultats environnementaux et entraîner un gain de bien-être positif (0,021%), bien qu’à un coût léger pour les résultats économiques tels que la productivité totale des facteurs (0,002%). L’effet sur le bien-être lorsque la taxe carbone est combinée avec des OCs est plus faible (0,019%) et est accompagné d’une baisse plus importante du taux d’imposition moyen. Qualitativement, j’ai dérivé les conditions dans lesquelles les taux d’imposition au niveau des entreprises et en moyenne varient en fonction de trois allocations de permis : enchères, attribution gratuite et rabais basé sur la production, en lien avec la conformité aux OCs. Le troisième chapitre examine l’impact des incitations fiscales pour les investissements en dépollution sur la part du travail et l’investissement total en dépollution dans les industries manufacturières en Colombie. En utilisant des données au niveau microéconomique, je constate une forte corrélation négative entre l’investissement en dépollution et la part du travail. En revanche, il n’y a pas d’association significative entre l’investissement en capital et la part du travail. Pour comprendre ces observations, j’étends et calibre un cadre de dynamique industrielle incluant des entreprises hétérogènes investissant dans des mesures de contrôle de la pollution. Les expériences politiques montrent que le passage à des incitations pour le contrôle de la pollution avec une déduction fiscale de 20% réduit la part du travail dans l’industrie de 20% en raison de l’augmentation de la part de marché des entreprises intensives en capital. De plus, l’investissement en dépollution augmente de 45% en raison de l’effet d’équilibre général. Les changements dans les instruments fiscaux créent une corrélation négative entre la part du travail des entreprises et l’investissement en dépollution aux niveaux de l’entreprise et de l’agrégat. Une augmentation de la taxe carbone réduit la part du travail dans l’industrie mais augmente l’investissement total en dépollution, car la part de production des entreprises très intensives en facteurs de production augmente, tandis que les entreprises ayant une intensité de travail médiane perdent du terrain. À l’inverse, une augmentation de l’impôt sur les sociétés réduit l’investissement total en dépollution et augmente la part du travail dans l’industrie, reflétant les changements de distribution observés en l’absence de déduction fiscale. Cette étude met en lumière comment les incitations au contrôle de la pollution par des déductions fiscales influencent la distribution conjointe de la part de production et de l’intensité des facteurs des entreprises. Les résultats soulignent la nécessité de concevoir des incitations fiscales équilibrées pour atteindre les objectifs économiques et environnementaux. / This thesis contributes to the understanding of the frictions associated with environmental policies and how these frictions affect the dynamics of polluting industries and their impact on macroeconomic aggregates such as productivity. It also critically examines how different aspects of these policies influence the distribution of firms in terms of employment, firms size and emissions. In the first chapter, I examine the long run effects of threshold-based exemption policies in environmental regulation, which involve exempting emitters below a certain emission threshold. Using pollution data from various establishments under California’s Cap-and-Trade program, I found that 40% of firms benefit from this exemption, with many clustering around the threshold, particularly new entrants. To understand the broader implications, I developed an industry dynamic model that considers heterogeneous firms and a carbon pricing system with threshold-specific exemptions. When simulating California’s Cap-and-Trade, I found that removing the exemption leads to a 0.05% increase in output due to resources shifting towards more productive firms. To measure the impact of the exemption policy on resource allocation, I analyzed the dispersion of Total Factor Productivity Revenue-based (TFPR) at the firm level. The analysis revealed that TFPR volatility is influenced by the dispersion between firm categories, particularly those relative to the exemption threshold. Firms with intermediate productivity, clustered around the threshold, showed higher average and dispersion of TFPR compared to productive firms that bear emission costs. In the second chapter, I quantify the macroeconomic implications of complementing the use of traditional pricing instruments with Offset Credits (OCs), whose price is negotiated by covered entities from non-covered firms. This bargaining process may result in a different marginal emission cost compared to traditional pricing instruments. Using firm data on emissions and compliance modalities from California’s Cap-and-Trade program, I show three facts. First, OC usage increases with firm emission size; the proportion of firms complying with OCs and the proportion of emissions offset increase with emission quintile groups. Thus, OCs act as an implicit carbon tax reduction for large emitters. Second, incumbent firms comply more intensively with OCs compared to new entrants and exiting firms. Lastly, the retirement rate of available OCs drops gradually after the regulation. To explain these findings, I extend and calibrate an industry dynamics model incorporating a cap-and-trade system where firms choose between traditional permits and OCs, viewed as perfect substitutes with the price of the latter obtained through a Nash bargaining protocol. I quantitatively show that complementing cap-and-trade (auction) with OCs can positively affect environmental outcomes and yield a positive welfare gain (0.021%), albeit at a slight cost of total factor productivity (0.002%). The welfare effect when complementing a carbon tax with OCs is smaller (0.019%), accompanied by a larger average tax rate decrease compared to cap-and-trade. Qualitatively, I derived conditions under which firm-level and average tax rates vary depending on three permit allocations: auction, grandfathering, and output-based rebate, in line with the compliance with OCs. The third chapter investigates the impact of tax incentives for investment in abatement on the labor share and aggregate abatement investment in Colombia’s manufacturing industries. Using micro-level data, I find a strong negative correlation between abatement investment and labor share. However, there is no significant association between capital investment and labor share. To understand these facts, I extend and calibrate an industry dynamics framework that includes heterogeneous firms investing in pollution control investments. Policy experiments show that switching to pollution control incentives with a 20% income tax deduction reduces the industry labor share by 20% due to an increase in capital-intensive market share. Additionally, abatement investment rises by 45% due to the general equilibrium effect. Changes in tax instruments create a negative correlation between firms’ labor share and abatement investment at both firm and aggregate levels. An increase in carbon tax reduces the industry labor share but boosts aggregate abatement investment, as the output share of extremely factor-intensive firms grows, while firms around the median labor intensity lose share. Conversely, an increase in corporate tax reduces aggregate abatement investment and raises the industry labor share, mirroring the distribution changes seen with no income tax deduction. This study highlights how pollution control incentives through income tax deductions affect the joint distribution of firms’ output share and factor intensity. The findings emphasize the need for well-designed tax incentives to balance economic and environmental goals.

The work presented in this thesis encompasses the design, development, realization and testing of novel magnetoelectric thin film elements that do not rely on ferromagnets, but are based entirely on magnetoelectric antiferromagnets such as Cr2O3. Thin film spintronic elements, and in particular magnetoelectric transducers, are crucial building blocks of high efficiency data processing schemes that could complement conventional electronic data processing in the future. Recent developments in magnetoelectrics have revealed, that exchange biased systems are ill-suited to electric field induced switching of magnetization due to the strong coupling of their ferromagnetic layer to magnetic fields. Therefore, ferromagnet-free magnetoelectric elements are proposed here in an effort to mitigate the practical problems associated with existing exchange biased magnetoelectric elements. This goal is achieved by establishing an all-electric read-out method for the antiferromagnetic order parameter of thin films, which allows to omit the ferromagnet from conventional exchange biased magnetoelectric elements. The resulting ferromagnet-free magnetoelectric elements show greatly reduced writing thresholds, enabled operation at room temperature and do not require a pulsed magnetic field, all of which is in contrast to state-of-the-art exchange biased magnetoelectric systems. The novel all-electric read-out method of the magnetic field-invariant magnetization of antiferromagnets, so-called spinning-current anomalous Hall magnetometry, can be widely employed in other areas of thin film magnetism. Its high precision and its sensitivity to previously invisible phenomena make it a promising tool for various aspects of thin solid films. Based on this technique, a deep understanding could be generated as to what physical mechanisms drive the antiferromagnetic ordering in thin films of magnetoelectric antiferromagnets. As spinning-current anomalous Hall magnetometry is an integral probe of the magnetic properties in thin films, it offers no intrinsic scale sensitivity. In order to harness its great precision for scale related information, a statistical framework was developed, which links macroscopic measurements with microscopic properties such as the antiferromagnetic domain size.:TABLE OF CONTENTS Abbreviations 9 1 Introduction 11 1.1 Motivation 11 1.2 Objectives 12 1.3 Organization of the thesis 13 2 Background 15 2.1 History of magnetoelectric coupling 15 2.2 Long range magnetic ordering 16 2.2.1 Magnetic order parameter and field susceptibility 17 2.2.2 Magnetic proximity effect 19 2.2.3 Exchange bias 20 2.3 Phenomenology of magnetoelectric coupling 21 2.3.1 The linear magnetoelectric effect 21 2.3.2 Magnetoelectric pressure on the antiferromagnetic order parameter 22 2.3.3 Switching the antiferromagnetic order parameter 23 2.4 Realized magnetoelectric thin film elements 24 2.4.1 BiFeO3/CoFe system 24 2.4.2 Cr2O3/Co/Pt system 25 3 Experimental methods 27 3.1 Development of ferromagnet free magnetoelectric elements 28 3.1.1 The substrate 29 3.1.2 The Cr2O3 bulk and top surface 31 3.1.3 The V2O3 or Pt bottom electrodes 33 3.1.4 Epitaxial relationships 34 3.1.5 The Cr2O3 bottom interface 39 3.1.6 Twinning of Cr2O3 39 3.1.7 Hall crosses and patterning processes 43 3.2 Magnetotransport measurements 44 3.2.1 Hall effects 45 3.2.2 Anomalous Hall effect 46 3.2.3 Magnetoelectric writing 47 3.2.4 All electric read out 49 3.3 The experimental setup 50 3.3.1 Temperature control 50 3.3.2 Magnetic field control 51 4 Spinning-current anomalous Hall magnetometry 53 4.1 Characteristics of the technique 53 4.1.1 Operational principle 53 4.1.2 Advantages 55 4.1.3 Magnetic hysteresis loops and field-invariant magnetization 55 4.1.4 Measurement of field-invariant magnetization 56 4.1.5 Limitations 58 4.2 Application of SCAHM to Cr2O3(0001) thin films 59 4.2.1 Criticality and distribution of the antiferromagnetic phase transition 61 4.2.2 Evaluation of the magnetic proximity effect 64 4.3 SCAHM with thin metallic antiferromagnetic IrMn films 65 4.3.1 [Pt/Co]4/IrMn exchange bias system 65 4.3.2 Isolated antiferromagnetic IrMn thin films 67 5 Magnetoelectric performance 69 5.1 Magnetoelectric field cooling 69 5.2 The gate bias voltage 71 5.3 Isothermal binary magnetoelectric writing in Cr2O3 72 6 Order parameter selection in magnetoelectric antiferromagnets 77 6.1 Uncompensated magnetic moment 77 6.2 Extrinsic causes for broken sublattice equivalence 81 6.3 The V2O3 gate electrode 83 7 Measurement of microscopic properties with an integral probe 87 7.1 Interentity magnetic exchange coupling 87 7.2 Ensemble formalism for the entity size determination 90 7.3 Estimation of the entity sizes 94 7.4 Microscopic confirmation of the ensemble model 97 8 Summary and Outlook 101 8.1 Goal-related achievements 101 8.1.1 All-electric read-out of the AF order parameter 101 8.1.2 Electric field induced writing of the AF order parameter 102 8.2 Further achievements 103 8.2.1 Foreseen impact of SCAHM on thin film magnetism 103 8.2.2 Practical optimization routes of magnetoelectric Cr2O3 systems 104 8.2.3 Theoretical work 105 8.3 Future directions 105 8.3.1 Development of Cr2O3-based magnetoelectric systems 105 8.3.2 Applications of SCAHM 106 References 107 Erklärung 113 Acknowledgements 115 Curriculum Vitae 117 Scientific publications, contributions, patents 119

Approved for public release; distribution is unlimited / OFDM systems have experienced increased attention in recent years and have found applications in a number of diverse areas including telephone-line based ADSL links, digital audio and video broadcasting systems, and wireless local area networks (WLAN). Orthogonal frequency-division multiplexing (OFDM) is a powerful technique for high data-rate transmission over fading channels. However, to deploy OFDM in a WLAN environment, precise frequency synchronization must be maintained and tricky frequency offsets must be handled. In this thesis, various techniques to improve the data throughput of OFDM WLAN are investigated. A simulation tool was developed in Matlab to evaluate the performance of the IEEE 802.11a physical layer. We proposed a rapid time and frequency synchronization algorithm using only the short training sequence of the IEEE 802.11a standard, thus reducing the training overhead to 50%. Particular attention was paid to channel coding, block interleaving and antenna diversity. Computer simulation showed that drastic improvement in error rate performance is achievable when these techniques are deployed. / Lieutenant, Hellenic Navy

Approved for public release, distribution is unlimited / Orthogonal frequency division multiplexing (OFDM) is being successfully used in numerous applications. It was chosen for IEEE 802.11a wireless local area network (WLAN) standard, and it is being considered for the fourthgeneration mobile communication systems. Along with its many attractive features, OFDM has some principal drawbacks. Sensitivity to frequency errors is the most dominant of these drawbacks. In this thesis, the frequency offset and phase noise effects on OFDM based communication systems are investigated under a variety of channel conditions covering both indoor and outdoor environments. The simulation performance results of the OFDM system for these channels are presented. / Lieutenant Junior Grade, Turkish Navy

No description available.

Multiuser and cooperative orthogonal frequency division multiplexing(OFDM) systems are being actively researched and adopted in wireless standards, owing to their advantages of robustness to multipath fading, modularity, and ability to achieve high data rates. In OFDM based systems, perfect frequency and timing synchronization is essential to maintain orthogonality among the subcarriers at the receiver. In multiuser OFDM on the uplink, timing offsets (TOs) and/or carrier frequency offsets (CFOs) of different users, caused due to path delay differences between different users, Doppler and/or poor oscillator alignment, can destroy orthogonality among subcarriers at the receiver. This results in multiuser interference (MUI)and consequent performance degradation. In this thesis, we are concerned with the analysis and mitigation of the effect of large CFOs and TOs in multiuser OFDM systems, including uplink orthogonal frequency division multiple access (OFDMA),uplink single-carrier frequency division multiple access(SC-FDMA), and cooperative OFDM. Uplink OFDMA: In the first part of this thesis, we analytically quantify the effect of large CFOs and TOs on the signal-to-interference plus noise ratio(SINR) and uncoded bit error rate(BER) performance of uplink OFDMA on Rayleigh and Rician fading channels, and show analytical results to closely match with simulation results. Such an SINR/BER analysis for uplink OFDMA in the presence of both large CFOs as well as TOs has not been reported before. We also propose interference cancelling(IC) receivers to mitigate the performance degradation caused due to large CFOs and TOs of different users. SC-FDMA versus OFDMA: An issue with uplink OFDMA is its high peak-to-average power ratio(PAPR).Uplink SC-FDMA is proposed in the standards as a good low-PAPR alternative to uplink OFDMA; e.g., SC-FDMA has been adopted in the uplink of 3GPP LTE. A comparative investigation of uplink SC-FDMA and OFDMA from a sensitivity to large CFOs and TOs view point has not been reported in the literature. Consequently, in the second part of the thesis, we carry out a comparative study of the sensitivity of SC-FDMA and OFDMA schemes to large CFOs and TOs of different users on the uplink. Our results show that while SC-FDMA achieves better performance due to its inherent frequency diversity advantage compared to OFDMA in the case of perfect synchronization, its performance can get worse than that of OFDMA in the presence of large CFOs and TOs. We further show that use of low-complexity multistage IC techniques, with the knowledge of CFOs and TOs of different users at the receiver, can restore the performance advantage of SC-FDMA over OFDMA. Cooperative OFDM: Cooperative OFDM is becoming popular because of its ability to provide spatial diversity in systems where each node has only one antenna. In most studies on cooperative communications, perfect time synchronization among cooperating nodes is assumed. This implies that the transmissions from different cooperating nodes reach the destination receiver in orthogonal time slots. In practice, however, due to imperfect time synchronization, orthogonality among different nodes’ signals at the destination receiver can be lost, causing inter-symbol interference(ISI).In the third part of the thesis, we investigate cooperative OFDM communications using amplify-and-forward(AF) protocol at the relay, in the presence of imperfect timing synchronization. We derive analytical expressions for the ISI as function of timing offset for cooperative OFDM with AF protocol, and propose an IC receiver to mitigate the effects of timing offset induced ISI.

Vad gäller reglerna om tidigare års underskott utgör koncernbidragsspärren en spärregel till den annars gällande huvudregeln att tidigare års förluster får kvittas mot framtida vinster. Koncernbidragsspärren inträder vid ägarförändringar och innebär förenklat att ett underskottsföretag är förhindrat att, under en period om fem år, kvitta kvarstående underskott mot koncernbidrag som underskottsföretaget mottar från företag som inte ingick i koncernen före ägarförändringen (nya företag). Underskott som uppkommer efter ägarförändringen får dock kvittas mot koncernbidrag från nya företag. Uppsatsen syftar till att analysera och granska reglerna om koncernbidragsspärren ur ett företagsperspektiv, vilket innebär att uppsatsen ser till reglernas bakomliggande syfte och till hur reglerna fungerar vid en praktisk tillämpning. Uppsatsen har ett särskilt fokus kring i vilken turordning koncernbidrag ska beaktas vid avräkning mot befintliga underskott när ett underskottsföretag mottar koncernbidrag både från gamla och nya företag i en koncern. I RÅ 2008 ref. 69 ställdes frågan på sin spets och Högsta Förvaltningsdomstolen befäste en ny turordningsprincip där koncernbidrag från gamla företag ska beaktas före koncernbidrag från nya företag i koncernen. Det har genom uppsatsens analys av reglerna om koncernbidragsspärren påvisats att reglerna är svåra att tillämpa och i många fall råder det osäkerhet om hur reglerna ska tolkas. Det kan konstateras att problematik kvarstår avseende frågan om i vilken turordning koncernbidrag från så kallade gamla respektive nya företag ska beaktas vid avräkning mot befintliga underskott även efter RÅ 2008 ref. 69. En rådande osäkerhet om hur reglerna ska tolkas kan inte anses tillfredsställande ur ett företagsperspektiv och en översyn av reglerna vore välkommen. / According to the Swedish legislation tax losses can normally be carried forward and settled against future profits in the same company unlimited of time. However, a restriction of losses being carried forward may occur in situations where change of ownership is at hand. The restrictive rule prohibits offsetting tax losses in an acquired loss-making company against group contributions received from other group companies. The restrictive rule applies up until, and including, the end of the fifth year after the year when the restriction occurred. However, losses that occur after the change of ownership are possible to offset against group contributions from other group companies. The thesis aims to analyze and review the restrictive rule from a business perspective which means that the underlying purpose of the restrictive rule and how it works in practice is examined. The thesis has a particular focus on in what order group contributions should be considered when being offset against existing deficits when the deficit company receives group contributions from old and new companies in the corporate group. In the Swedish case law RÅ 2008 ref. 69 the Supreme Administrative Court laid down a new principle of order where group contributions from an old company should be regarded before a group contribution from a new company. Through the analysis of the restrictive rule it has been demonstrated that the rule is difficult to conform to and that there is an uncertainty regarding the interpretation of it. Through the analysis of this thesis it is established that, even after RÅ 2008 ref. 69, the complexity of problems remains concerning in what order group contributions from old respectively new companies should be considered when being offset against existing deficits. A such prescribed uncertainty regarding the interpretation of the restrictive rule cannot be considered satisfactory from a business perspective and a review of the rules would be preferable.