Switched reluctance motor(SRM)drives are favored in many industrial applications because of their cost advantage and ruggedness. However, the torque ripple and bus current ripple of SRM restrict its application range  compared with traditional AC and DC motors due to the doubly salient pole structure and the highly non-linear coupling between torque, rotor position and phase current. As a result of the torque ripple on the shaft, unwilling large acoustic noises are generated. The large current ripple at the DC bus input requires large electrolytic capacitors for attenuation. However, electrolytic capacitors are of low reliability, which will reduce the duration of the control system. Because of these disadvantages, the acceptance of SRM by the industry, especially in servo-type applications which require stationary torque at low speed, is quite slow. In order to obtain high quality control, there have been many efforts in developing techniques for torque ripple attenuation. Primarily, two approaches are used to give a smooth torque. One is to improve the magnetic design, the other is to use sophisticated control techniques. Some torque control techniques have been proved to obtain a relatively good performance by simulations and experimental results. This thesis gives an alternative torque ripple minimization technique. Simulations and Experiments are conducted to show the effectiveness of this new control scheme. Under this new control scheme, the current controller are much easier to be designed under high speed application, which could be an advantage of it. First, the SRM operating principle is presented. The torque of SRM is produced by the tendency of its moveable part shifting to a position where the inductance of the exited winding is maximized. The torque ripple origin is discussed in terms of both magnetization and control. The torque ripple is produced during phase commutation interval because the phase current cannot rise from zero to the nominal value instantaneously due to the existence of the phase inductance. Second, a new torque control scheme is proposed. The new torque control of SRM is split into two cascade sub-tasks. At first, a current reference for ripple free torque is determined. Then a current controller is designed to regulate the current in the stator winding to reference value. Simulations are conducted to verify the effective of this torque control scheme in both ideal 'sinusoidal' SRM and a 'Pseudo-Sinusoidal' SRM. Finally, a motor drive control system is built to implement the new control scheme. The motor is tested under different speeds to see the torque ripple produced in different speed ranges. As a conclusion, the new control algorithm for constant torque and damped input bus current ripple is investigated. The advantages of this new torque control method are listed in the paper. Simulation and experimental results show the effectiveness of this new control method. / Master of Science

Masters in Public Administration - MPA / This study was about the change of the National Student Financial Aid Scheme (NSFAS) administration system from a decentralised to a centralised one. The aim was to investigate the shift of the NSFAS administration system and its effect on the students' academic progress and overall well-being in the learning process at a historically Black university in the Western Cape Province. The study had three objectives. Firstly, to examine the efficacy of the NSFAS centralised application process. Secondly, to determine the impact of the process on the students' academic progress and overall well-being in the learning process. Lastly, to propose recommendations for the streamlining of the application process so that the negative impact on the students' academic performance be minimised or prevented.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19166号 / 理博第4106号 / 新制||理||1591(附属図書館) / 32158 / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 加藤 周, 教授 並河 良典, 教授 雪江 明彦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20341号 / 工博第4278号 / 新制||工||1662(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 立川 康人, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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In this work we present the first implementation of the incremental scheme for coupled cluster linear-response frequency-dependent dipole polarizabilities. The implementation is fully automated and makes use of the domain-specific basis set approach. The accuracy of the approach is determined on the basis of a test suite of 47 molecules and small clusters. The local approximation in the coupled cluster singles and doubles polarizability exhibits a mean error of 0.02% and a standard deviation of 0.32% when using a third-order incremental expansion. With the proposed approach, it is possible to compute polarizabilities with larger basis sets compared to the canonical implementation and thus it is possible to obtain higher total accuracy. The incremental scheme yields the smallest errors for weakly-bound and quasi-linear systems, while two- and three-dimensional (cage-like) structures exhibit somewhat larger errors as compared to the full test set. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Android and iOS are the world leading mobile operating systems in today’s growing market of handheld devices. Third-party applications are an important aspect of these systems but can also provide an attack-vector for exploiting other installed applications. Previous studies have shown that the Android inter- app communication (IAC) mechanism Intent can be used for causing harm to other apps. In contrast, research involving iOS app communication have been sparse because of the closed nature of the iOS ecosystem. One of the previous studies showed the possibility of using Android Intents for hijacking and forging payments between a company application providing payments via the Swedish payment application Swish and their App2App API. This study extends this previous work by creating an artifact that performs the same exploit on the iOS platform. iOS uses a URL-scheme for opening and sending data between applications. This mechanism is used for creating the communication between apps and finding out if payment information sent via the URL- scheme can be hijacked instead of arriving at the intended Swish application. The experiences drawn from the exploit were used in combination with the previous work to find differences between the IAC mechanisms. Finally, a literature study is presented with the latest mitigation techniques for IAC vulnerabilities.

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Responsible investing has become a trend throughout financial markets. As World’s economies pledge to decrease the amount of greenhouse gas (GHG) emissions, environmental policies like carbon pricing (CP) are expected to be strengthened; the above is attributed to the effort of internalizing the environmental costs of the current economic system. In the same context where asset owners have been demanding to the private sector for greater coverage of Environmental Social Governance (ESG) issues, understanding exposure and risk to carbon taxation and emission trading schemes (ETS) could be a major driver for responsible investing. Nonetheless, it has been found that this environmental policy to price emissions, falls behind from a harmonized cost per emission across sectors and geographies. Defined and assessed through a quantitative scenario analysis on scope 1 emissions, all information on carbon pricing set the basis for the model. From an investing perspective, the results showed higher exposure for the electricity sector by 2030 and 2050; nonetheless, the riskiest sector to invest at, was shown as industry. The above is based on the current and expected carbon dependency, and the expected increase in coverage from carbon pricing mechanisms respectively. In addition, aviation, which is a sub-sector from offroad transportation, showed to be the main source for this sector´s exposure and risk. It is concluded that the research carried out is a first step from a complete analysis on CP, as scope 2 emissions need to be assessed. / Att investera ansvarsfullt är en trend som ökar stadigt genom finansmarknader i världen idag. Då flera ekonomier i världen utlovar att minska mängden utsläpp av växthusgaser i linje med vissa klimatscenarion, så förstärks miljöpolicys som koldioxidutsläppspriser i ett försök att internalisera externaliteter i dagens ekonomiska system. I kontexten av när ägare av tillgångar börjar kräva större täckning i miljö, socialt ansvar och ägarstyrning, kan exponering och risk i koldioxidutsläppsbeskattning och handel av utsläppsoptioner vara en drivande faktor i ansvarsfullt investerande. En utmaning i att prissätta utsläpp genom miljöpolicys ligger i hur separerade båda mekanismerna är från en harmoniserad kostnad per utsläpp genom olika sektorer och geografier. Definierad och utvärderad genom en kvantitativ scenarioanalys av Scope 1-utsläpp, verkade all information om koldioxidutläppspriser som grund till modellen. Från ett investeringsperspektiv visade resultaten en högre exponering för elkraftssektorn till 2030 och 2050. Emellertid påvisades även att industrisektorn har störst risk för investeringar. Detta är baserat på elkraftens nuvarande och förväntade koldioxidutsläppsberoende och den förväntade ökningen i täckning från koldioxidutsläppsprismekanismer i industrisektorn. Vidare påvisades flygindustrin, som är en sidosektor av offroad-transport, vara den huvudsakliga källan för denna sektors exponering och risk. Avslutningsvis fastställs det att denna undersökning endast är ett första steg i en komplett analys av koldioxidpriser, då Scope 2 utsläpp även bör undersökas.