Heat flux and heat conductance at the metal mold interface plays a key role in controlling the final metal casting strength. It is difficult to obtain these parameters through direct measurement because of the required placement of sensors, however they can be obtained through inverse heat conduction calculations. Existing inverse heat conduction methods are analyzed and classified into three categories, i.e., direct inverse methods, observer-based methods and optimization methods. The solution of the direct inverse methods is based on the linear relationship between heat flux and temperature (either in the time domain or in the frequency domain) and is calculated in batch mode. The observer-based method consists on the application of observer theory to the inverse heat conduction problem. The prominent characteristic in this category is online estimation, but the methods in this category show weak robustness. Transforming estimation problems into optimization problems forms the methods in the third category. The methods in third category show very good robustness property and can be easily extended to multidimensional and nonlinear problems. The unknown parameters in some inverse heat conduction methods can be obtained by a proposed calibration procedure. A two-index property evaluation (accuracy and robustness) is also proposed to evaluate inverse heat conduction methods and thus determine which method is suitable for a given situation. The thermocouple dynamics effect on inverse calculation is also analyzed. If the thermocouple dynamics is omitted in the inverse calculation, the time constant of thermocouple should be as small as possible. Finally, a simple model is provided simulating the temperature measurement using a thermocouple. FEA (Finite Element Analysis) is employed to simulate temperature measurement.

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This dissertation presents control, analysis, and design of silicon carbide (SiC)-based critical conduction mode (CRM) high-frequency soft-switching three-phase ac-dc converters (inverter and rectifier). The soft-switching technique with SiC devices grounded in CRM makes the operation of the ac-dc converter at hundreds of kHz possible while maintaining high efficiency with high power density. This is beneficial for rapidly growing fields such as electric vehicle charging, photovoltaic (PV) systems, and uninterruptable power supplies, etc. However, for the soft-switching technique to be practically adopted to real products in the markets, there are a lot of challenges to overcome. In this dissertation, four types of the challenges are carefully studied and discussed to address them. First, the grid-tied inverters used for distributed energy resources, such as PV systems, must continue operating to deliver power to the grid, when it faces flawed grid conditions such as voltage drop and voltage rise. During abnormal grid conditions, delivering constant active power from the inverter to the grid is essential to avoid large voltage ripples on the dc side because it could trigger over-voltage protection or harm the circuitries, eventually shutting down the inverter. Hence, in such cases, unbalanced ac currents need to be injected into the grid. When the grid voltages and the ac currents are not balanced, there is a chance for the CRM soft-switching inverter to lose its soft-switching capability. Continuous conduction mode operation emerges, causing hard-switching where discontinuous conduction mode (DCM) operation is expected. This leads to huge turn-on loss and high dv/dt noise at the active switch's turn-on moment. To eradicate the hard-switching problem, two improved modulation schemes are developed; one with off-time extension in the CRM phase, the other by skipping switching pulses in the DCM phase. The DCM pulse skipping is applied for a variety of grid imbalance cases, and it is proven that it can be a generalized solution for any kinds of unbalanced grid conditions. Second, the CRM soft-switching scheme with 2-channel interleaving achieves high efficiency at heavy load. Nevertheless, the efficiency plunges as the output load is reduced. This is not suitable for PV inverters, which take account of light load efficiency in terms of "weighted efficiency". Small inductor currents at light load cause the switching frequency to soar because of its CRM-based operation characteristic, causing large switching loss. To increase the inductor current dealt with by the first channel, a phase shedding control is proposed. Gate signals for the second channel are not excited, increasing the first channel's inductor current, thus cutting down the first channel's switching frequency. To prevent the unwanted circulating current formed by shared zero-sequence voltage in the paralleled structure, only two phases in the second channel working in high frequency are shed. The proposed phase shedding control achieves a 0.5 to 3.9 % efficiency improvement with light loads. Third, due to the usage of SiC devices, high dv/dt generated at switching nodes over the system parasitic capacitance causes substantial common mode (CM) noise compared to that with Si devices. In this case, a balance technique with PCB winding inductors can effectively reduce the CM noise. First, winding interleaving structure is selected to minimize the eddy current loss in the windings. But the interwinding capacitance caused by the winding interleaving structure aggravates the CM noise. Impact of the interwinding capacitance on the CM noise is analyzed with a new inductor model containing the interwinding capacitance. Then, finally, a novel inductor structure is proposed to remove the interwinding capacitance and to improve the CM noise reduction performance. The soft-switching ac-dc converter built with the final PCB magnetics features almost similar efficiency compared to that with litz-wire inductor and 14 to 18 dB CM noise reduction up to 15 MHz. Lastly, the soft-switching technique is extended to inverters in standalone mode. To meet tight ac voltage total harmonic distortion requirements, a current control in dq-frame is introduced. As for the ac voltage regulation at no-load, on top of the improved phase shedding control, a frequency limiting with fixed frequency DCM method is applied to prevent excessive increase in the switching frequency. Then, how to deal with short-circuit at the output load is investigated. Since the soft-switching modulation violates inductor voltage-second balance during the short-circuit, the modulation method is switched to a conventional sinusoidal PWM at fixed frequency. It is concluded that all the additional requirements for the standalone inverters can be satisfied by the introduced control strategies. / Doctor of Philosophy / The world is facing an unprecedented weather crisis. Global warming is getting more severe because of excessive amount of carbon emission. In an effort to overcome this crisis, paradigm of energy and lifestyle of people have changed. Penetration of distributed energy resources (DERs) such as wind turbines, and photovoltaic systems has been dramatically increased. Instead of internal combustion engine vehicles (EVs), electric vehicles hit the mainstream. In these changes, power electronics plays a critical role as the key element of the systems. Especially, three-phase inverter/rectifiers are essential parts in such applications. Most important aspects of the three-phase inverter/rectifier are efficiency and power density. In the past decades, Silicon (Si) power devices were mostly used for the systems and the technology based on Si has almost reached to its physical limits. The switching frequency of Si-based inverter/rectifier is limited below 20 – 30 kHz to reduce switching loss. This impedes high power density due to bulky passive components such as inductors and capacitors. Nowadays, the advent of wideband gap such as Silicon Carbide (SiC) and Gallium Nitride (GaN) power devices gives us a great opportunity to improve the efficiency and the power density with its high switching speed capability, low switching energy and low on-resistance. The SiC power devices are more suitable for DERs and EVs due to higher voltage rating. Using SiC power devices allows to increase inverter/rectifier' switching frequency about five times to have similar efficiency with those based on Si power devices, making the power density high. However, there is still room to push the switching frequency even higher to hundreds of kHz with soft-switching. In this sense, studies on soft-switching techniques for three-phase inverter/rectifier have been intensively conducted. Particularly, soft-switching techniques based on critical conduction mode (CRM) are regarded as the most promising solutions because it does not have any additional circuits to achieve the soft-switching, keeping the system as straightforward as possible. However, most of the studies for the CRM-based soft-switching three-phase inverter/rectifier mainly focus on limited occasions such as ideal operation conditions. For this technique to be widely used and adopted in industry, more practical cases for the systems need to be studied. In this dissertation, the soft-switching three-phase inverter/rectifier under diverse situations are investigated in depth. First, behavior of the soft-switching inverter/rectifier under unbalanced grid conditions are analyzed and control methods are developed to maintain its soft-switching capability. Second, how to improve light load efficiency is explored. Circulating current issue for the light load efficiency improvement is analyzed and a control method is proposed to eliminate the circulating current. Third, a design methodology and considerations of inductors based on PCB magnetics are discussed to reduce electromagnetic noise and improve system efficiency. Lastly, the soft-switching technique is extended to standalone mode applications dealing with strict voltage regulation, no-load operation, and output short-circuit.

The emergence of silicon-carbide (SiC) devices has been a 'game changer' in the field of power electronics. With desirable material properties such as low-loss characteristics, high blocking voltage, and high junction temperature operation, they are expected to drastically increase the power density of power electronics systems. Recent state-of-the-art designs show the power density over 17 ; however, certain factors limit the power density to increase beyond this limit. In this dissertation, three key factors are selected to increase the power density of SiC-based grid-connected three-phase converters. Throughout this dissertation, the techniques and strategies to increase the power density of SiC three-phase converters were investigated. Firstly, a magnetic integration method was introduced for the coupled inductors in the interleaved three-phase converters. Due to limited current-capacity compared to the silicon insulated-gate bipolar transistors (Si-IGBTs), discrete SiC devices or SiC modules, operate in parallel to handle a large current. When three-phase inverters are paralleled, interleaving can be used, and coupled inductors are employed to limit the circulating current. In Chapter 2, the conventional integration method was extended to integrate three coupled inductors into two; one for differential-mode circulating current and the other for common-mode circulating current. By comparing with prior research work, a 20% reduction in size and weight is demonstrated. From Chapter 3 to Chapter 5, a full-SiC uninterruptible power supply (UPS) was investigated. With the high switching frequency and fast switching dynamics of SiC devices, strategies on electromagnetic inference become more important, compared to Si-IGBT based inverters. Chapter 3 focuses on a common-mode equivalent circuit model for a topology and pulse width modulation (PWM) scheme selection, to set a noise mitigation strategy in the design phase. A three terminal common-mode electromagnetic interference (EMI) model is proposed, which predicts the impact of the dc-dc stage and a large battery-rack on the output CM noise. Based on the model, severe deterioration of noise by the dc-dc stage and battery-rack can be predicted. Special attention was paid on the selection of the dc-dc stage's topology and the PWM scheme to minimize the impact. With the mitigation strategy, a maximum 16 dB reduction on CM EMI can be achieved for a wide frequency range. In Chapter 4, an active PWM scheme for a full-SiC three-level back-to-back converter was proposed. The PWM scheme targets the size reduction of two key components: dc-link capacitors and a common-mode EMI filter. The increase in switching frequency calls for a large common-mode EMI filter, and dc-link capacitors in the three-level topology may take a considerable portion in the total volume. To reduce the common-mode noise emission, different combinations of the voltage vectors are investigated to generate center-aligned single pulse common-mode voltage. By such an alignment of common-mode voltage with different vector combinations, noise cancellation between the rectifier and the inverter can be maximally utilized, while the balancing of neutral point voltage can be achieved by the transition between the combinations. Also, to reduce the size of the dc-link capacitor for the three-level back-to-back converter, a compensation algorithm for neutral point voltage unbalance was developed for both differential-mode voltage and the common-mode voltage of the ac-ac stage. The experimental results show a 4 dB reduction on CM EMI, which leads to a 30% reduction on the required CM inductance value. When a 10% variation of neutral point voltage can be handled, the dc-link capacitance can be reduced by 56%. In Chapter 5, a 20 kW full-SiC UPS prototype was built to demonstrate a possible size-reduction with the proposed PWM scheme, as well as a selection of topologies and PWM schemes based on the model. The power density and efficiency are compared with the state-of-the-art Si-IGBT based UPSs. Chapter 6 seeks to improve power density by a change in a modulation method. Triangular conduction mode (TCM) operation of the three-level full-SiC inverter was investigated. The switching loss of SiC devices is reported to be concentrated on the turn-on instant. With zero-voltage turn-on of all switches, the switching frequency of a three-level three-phase SiC inverter can be drastically increased, compared to the hard-switching operation. This contributes to the size-reduction of the filter inductors and EMI filters. Based on the design to achieve a 99% peak efficiency, a comparison was made with a full-SiC three-level inverter, operating in continuous conduction mode (CCM), to verify the benefit of the soft switching scheme on the power density. A design procedure for an LCL filter of paralleled TCM inverters was developed. With 3.5 times high switching frequency, the total weight of the filter stage of the TCM inverter can be reduced by 15%, compared to that of the CCM inverter. Throughout this dissertation, techniques for size reduction of key components are introduced, including coupled inductors in parallel inverters, an EMI filter, dc-link capacitors, and the main boost inductor. From Chapter 2 to 5, the physical size or required value of these key components could be reduced by 20% to 56% by different schemes such as magnetic integration, EMI mitigation strategy through modeling, and an active PWM scheme. An optimization result for a full-SiC UPS showed a 40% decrease in the total volume, compared to the state-of-the-art Si-IGBT solution. Soft-switching modulation for SiC-based three-phase inverters can bring a significant increase in the switching frequency and has the potential to enhance power-density notably. A three-level three-phase full-SiC 40 kW PV inverter with TCM operation contributed to a 15% reduction on the filter weight. / Doctor of Philosophy / The power density of a power electronics system is regarded as an indicator of technological advances. The higher the power density of the power supply, the more power it can generate with the given volume and weight. The size requirement on power electronics has been driven towards tighter limits, as the dependency on electric energy increases with the electrification of transportation and the emergence of grid-connected renewable energy sources. However, the efficiency of a power electronics system is an essential factor and is regarded as a trade-off with the power density. The size of power electronics systems is largely impacted by its magnetic components for filtering, as well as its cooling system, such as a heatsink. Once the switching frequency of power semiconductors is increased to lower the burden on filtering, more loss is generated from filters and semiconductors, thus enlarging the size of the cooling system. Therefore, considering the efficiency has to be maintained at a reasonable value, the power density of Si-based converters appears to be saturated. With the emergence of wide-bandgap devices such as silicon carbide (SiC) or gallium nitride (GaN), the switching frequency of power devices can be significantly increased. This is a result of superior material properties, compared to Si-based power semiconductors. For grid-connected applications, SiC devices are adopted, due to the limitations of voltage ratings in GaN devices. Before commercial SiC devices were available, the power density of SiC- based three-phase inverters was expected to go over 20 𝑘𝑊 𝑑𝑚3 ⁄ . However, the state-of-the art designs shows the power density around 3 ~ 4 𝑘𝑊 𝑑𝑚3 ⁄ , and at most 17 𝑘𝑊 𝑑𝑚3 ⁄ . The SiC devices could increase the power density, but they have not reached the level expected. The adoption of SiC devices with faster switching was not a panacea for power density improvement. This dissertation starts with an analysis of the factors that prevent power density improvement of SiC-based, grid-connected, three-phase inverters. Three factors were identified: a limited increase in the switching frequency, large high-frequency noise generation to be filtered, and smaller but still significant magnetic components. Using a generic design procedure for three-phase inverters, each chapter seeks to frame a strategy and develop techniques to enhance the power density. For smaller magnetic components, a magnetic integration scheme is proposed for paralleled ac-dc converters. To reduce the size of the noise filter, an accurate modeling approach was taken to predict the noise phenomena during the design phase. Also, a modulation scheme to minimize the noise generation of the ac-ac stage is proposed. The validity of the proposed technique was verified by a full-SiC three-phase uninterruptible power supply with optimized hardware design. Lastly, the benefit of soft-switching modulation, which leads to a significant increase in switching frequency, was analyzed. The hardware optimization procedure was developed and compared to hard-switched three-phase inverters.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Der knochenleitende Hörverlust, der auf eine mögliche Schädigung des Hörorgans durch die Operation hinweist, ist eine unerwünschte postoperative Komplikation in der Hals-Nasen-Ohren-Heilkunde. Lärm, der durch das Bohren verursacht wird, könnte die Hauptursache für diese Komplikation sein. Um diese Hypothese zu überprüfen, ist der erste Schritt die Quantifizierung dieses Lärms. In den meisten früheren Studien wurde ein Schallpegelmesser als quantitatives Werkzeug verwendet, das jedoch nur die Messung von Luftschall ermöglicht und durch den Abstand zur Schallquelle beeinflusst wird. Neben Luftschall scheint der Knochenschall während der Ohroperation intuitiv wahrscheinlicher zu iatrogenener Hörverlust zu führen. Die Schwierigkeit bei der Messung von Knochenschall besteht darin, dass es kein Standardinstrument wie einen Schallpegelmesser gibt, das den Geräuschwert direkt messen kann. In früheren begrenzten Untersuchungen des Knochenschalls wurde ein Kompromissweg eingeschlagen, bei dem eine Korrelation zwischen dem knochenleitenden Schalldruck bei einer bestimmten Frequenz und der Beschleunigung um das Ohr herum hergestellt wurde. Ersteres wurde durch den Knochenwandler des Audiometers ausgeübt, während letzteres durch den Beschleunigungssensor protokolliert wurde. Durch die Messung der Beschleunigung ist es somit möglich, indirekt auf den knochenleitenden Schallpegel zu schließen. In Übereinstimmung mit diesem Gedanken hat unser Forschungsteam in einer früheren Studie ein Messsystem für knochenleitenden Lärm entwickelt, das aus einem Beschleunigungssensor, einem Piezovibrator und einem Kraftsensor besteht, wobei die Kombination der beiden letzten Komponenten als gleichwertig zum Knochenwandler des Audiometers betrachtet werden kann. Mit diesem Gerät können wir im Vergleich zu einem Audiometer diese entsprechende Beziehung über einen größeren Frequenzbereich hinweg abtasten und die Überlagerung von Schalldruckpegeln mit unterschiedlichen Phasen bei jeder Frequenz berechnen. In dieser Studie wurde die Beziehungskurve (FRF) zwischen Kraft und Beschleunigung weiter optimiert, um den Einfluss abnormal hoher Werte zu reduzieren. Darüber hinaus wurde ein Kalibrierungskoeffizient, der aus einer Gruppe von Experimenten an Felsenbeinen gewonnen wurde, eingeführt, um den knochenleitenden Lärm beim Bohren am runden Fensternische genauer widerzuspiegeln. Alle diese Verbesserungen wurden angewendet, um den durch das Bohren verursachten knochenleitenden Lärm bei einer Serie von 25 Cochlea-Implantationsverfahren zu quantifizieren, was bisher die umfangreichste Studiengruppe in diesem Bereich darstellt. Gemäß den Messergebnissen wurden die maximalen Schalldruckpegel mit A-Bewertung und schneller Zeitbewertung (LAF) zwischen 111 dB und 122 dB aufgezeichnet. LAF trat am häufigsten bei etwa 95 dB auf. Die tägliche Lärmdosis, die die Gesamtmenge des Lärms in der Operation widerspiegelt, variierte zwischen 15,8% und 494,8% mit einem Durchschnitt von 138,4%. Trotz der Hinzufügung des Korrekturwerts, der aus dem Felsenbeinexperiment erhalten wurde, wies die Vorbereitung des Implantatbett immer noch die höchste Lärmdosis und Lärmintensität (Dosis/Zeit) unter den 4 geteilten Bohrschritten auf: Implantatbett, Mastoidektomie, Tympanotomie und Cochleotomie (Bohren am Rundfensternische). Basierend auf den obigen Daten und gemäß den Lärmschutzstandards des NIOSH wird die Lärmbelastung durch das Bohren während des CI-Verfahrens nicht als besonders gefährlich eingestuft, und solange der Bohrer die innere Membran nicht berührt, ist das Entfernen des runden Fensterfachs durch Bohren ein relativ sicherer Eingriff zur Erhaltung des Resthörens. Es ist erwähnenswert, dass alle Arten von Lärmschutzstandards auf Messungen mit einem Schallpegelmesser basieren, der den Schalldruck in der Luft direkt misst. Jedoch, in der Branche der Knochenleitungsvorrichtungen, z.B. Knochenleitungskopfhörer, entspricht der Parameter, der in diesem Kontext den Schalldruck darstellt, der vom Wandler ausgeübten Kraft. Angesichts der Tatsache, dass es an Forschungen und Schutzstandards bezüglich der Schäden fehlt, die Überlastkräfte unserem Gehör zufügen können, wird in dieser Studie die ISO 389-3 Norm im Bezug auf Audiometer verwendet, um die Kraft indirekt in den Schallpegel umzurechnen. Daher werden alle Schalldruckwerte aus den Kraftwerten abgeleitet. Gleichzeitig werden alle Kraftwerte aus den Beschleunigungswerten durch die etablierte Frequenzgangfunktion abgeleitet. In Zukunft würden Bemühungen, die Anzahl der Schritte in diesem Umwandlungsprozess zu reduzieren oder die Umwandlungspräzision zu verbessern, dazu beitragen, die Genauigkeit der Messungen von knochenleitendem Lärm zu erhöhen. Es wird auch erwartet, eine Korrelationsstudie zwischen dem protokollierten Lärmpegel und dem postoperativen knochenleitenden Hörpegel bei Patienten durchzuführen, die über praktisches Hörvermögen verfügen.:1. Introduction 2. Theoretical Basis 2.1. Sound Energy 2.2. Fourier transform of signals and parameter settings 2.2.1. Conversion between time-domain signals and frequency-domain signals 2.2.2. Transform velocity to acceleration or displacement in frequency domain 2.3. Frequency response function 2.4. Reflection and Transmission of sound wave 2.5. Loudness simulation: ISO 389-3:2016 and A-weighting 2.6. Sound level meter: Fast, Slow and Impulse time weighting 3. Method 3.1. Overall road map 3.2. Calibration 3.2.1. General layout 3.2.2. Signal configuration and parameters 3.2.3. Optimization of calibration curve 3.3. Acquisition of correction coefficient by temporal bone experiment. 3.3.1. General 3.3.2. Anatomy approach and equipment layout 3.3.3. Signal configuration and parameters 3.4. Loudness stimulation, Sound level meter stimulation and Noise value evaluation 3.5. Measurements in the cochlear implantation operation 3.5.1. Patients 3.5.2. Cochlear Implantation 3.5.3. Burrs 4. Results 4.1. Correction of LAF derived from cochleotomy 4.2. General condition 4.3. Maximum LAF 4.4. Time distribution of LAF above 85dB. 4.5. Drilling-induced noise production by different surgeons 4.6. Noise comparison between different drilling location 4.7. Noise comparison between different burrs 5. Discussion 5.1. Error analysis 5.1.1. The error from calibration 5.1.2. The error from correction coefficient 5.1.3. The error from ISO389-3 and A-weighting 5.1.4. The error from the standard of NIOSH 5.2. In comparison with other bone-conducted noise measurements 5.2.1. Method comparison 5.2.2. Results comparison 5.2.3. In comparison with air-conducted noise measurements 5.2.4. Can this level of noise exposure cause hearing impairment? 5.2.5. Drilling at the round window niche 5.2.6. Factors affecting drilling-induced noise 6. Summary/Zusammenfassung References Supplementary calculation code for this project Acknowledgments Anlage 1: Erklärungen zur Eröffnung des Promotionsverfahrens Anlage 2: Bestätigung über Einhaltung der aktuellen gesetzlichen Vorgaben / Bone conductive hearing decline which implies possible damage to the hearing organ caused by the surgery, is an undesirable postoperative complication in otolaryngology. Drilling-induced noise may be the primary cause of this complication. To verify this hypothesis, the first step is to quantify this noise. Sound level meter has been used as a quantitative tool in the majority of past studies, which only allows for the measurement of airborne noise and is influenced by the distance from the sound source. In addition to airborne noise, intuitively, bone conduction noise during the ear surgery appears to be more likely to cause iatrogenic hearing loss. The difficulty of bone conduction noise measurement is that there is no standard instrument like a sound level meter that can directly measure the noise value. In prior limited investigations of bone conduction noise, a compromised way was employed, which involved establishing a correlation between bone-conducted sound pressure at the specific frequency and acceleration around the ear. The former was exerted by the bone transducer of the audiometer, while the latter was logged by the accelerometer. Thus, by measuring the acceleration, it is possible to indirectly infer the bone-conducted sound level. Following the same train of thought, our research team developed a measurement system for bone-conducted noise in previous study which consisted of an accelerometer, a piezoshaker and a force sensor, the combination of latter two can be regarded as equivalent to the bone transducer of audiometer. Through this device, compared to an audiometer, we can sample this corresponding relationship across a wider range of frequencies and calculate the superposition of sound levels with different phase at each frequency. In this study, the relationship curve (FRF) between force and acceleration has been further optimized to reduce the influence of abnormally high values. Additionally, a calibration coefficient obtained from a group of temporal bone experiments has been introduced to more accurately reflect bone-conducted noise when drilling at the round window niche. All of those enhancements were applied to quantify the drilling-induced bone conduction noise in a batch of 25 cochlear implantation procedures, which constitutes the most extensive study cohort in this field thus far. According to the measurement results, the maximum values of sound pressure level with A-weighting and Fast-time-weighting (LAF) were recorded between 111dB to 122dB. LAF most frequently occurred around 95 dB. Daily noise dose reflecting the total amount of noise in the surgery varied from 15.8% to 494.8% with a mean of 138.4%. Despite the addition of correction value which obtained from temporal bone experiment, the implant bed preparation still had the highest noise dose and noise density (dose/time) among 4 divided drilling steps: implant bed, mastoidectomy, typampotomy and cochleotomy (drilling at the round window niche). Based on the above data and according to the NIOSH noise protection standards, the noise exposure caused by drilling during CI procedure is not deemed highly hazardous and as long as the burr does not touch the inner membrane, removing the round window niche by drilling is a relatively safe procedure for preserving residual hearing. It is worth noting that all kinds of noise protection standards are based on measurements with sound level meter which directly gauges the sound pressure in the air. However, in the industry of bone conduction device, e.g., bone conduction headphone, the parameter corresponding to sound pressure in this context is the force exerted by transducer. Given the fact that lack the researches and protection standards regarding the damage that overload force can cause to our hearing, ISO 389-3 standard in terms of audiometer is employed to indirectly convert the force to the sound level in this study. Hence, all sound pressure values are inferred from force values. Meanwhile, all force values are deduced from acceleration values by the established frequency response function. In the future, any efforts aimed at reducing the number of steps involved in this conversion process or improving conversion precision would help enhance the accuracy of bone conduction noise measurements. It is also expected to carry out the correlation study between the logged noise level and post-operative bone conduction hearing level in the patients who has practical hearing.:1. Introduction 2. Theoretical Basis 2.1. Sound Energy 2.2. Fourier transform of signals and parameter settings 2.2.1. Conversion between time-domain signals and frequency-domain signals 2.2.2. Transform velocity to acceleration or displacement in frequency domain 2.3. Frequency response function 2.4. Reflection and Transmission of sound wave 2.5. Loudness simulation: ISO 389-3:2016 and A-weighting 2.6. Sound level meter: Fast, Slow and Impulse time weighting 3. Method 3.1. Overall road map 3.2. Calibration 3.2.1. General layout 3.2.2. Signal configuration and parameters 3.2.3. Optimization of calibration curve 3.3. Acquisition of correction coefficient by temporal bone experiment. 3.3.1. General 3.3.2. Anatomy approach and equipment layout 3.3.3. Signal configuration and parameters 3.4. Loudness stimulation, Sound level meter stimulation and Noise value evaluation 3.5. Measurements in the cochlear implantation operation 3.5.1. Patients 3.5.2. Cochlear Implantation 3.5.3. Burrs 4. Results 4.1. Correction of LAF derived from cochleotomy 4.2. General condition 4.3. Maximum LAF 4.4. Time distribution of LAF above 85dB. 4.5. Drilling-induced noise production by different surgeons 4.6. Noise comparison between different drilling location 4.7. Noise comparison between different burrs 5. Discussion 5.1. Error analysis 5.1.1. The error from calibration 5.1.2. The error from correction coefficient 5.1.3. The error from ISO389-3 and A-weighting 5.1.4. The error from the standard of NIOSH 5.2. In comparison with other bone-conducted noise measurements 5.2.1. Method comparison 5.2.2. Results comparison 5.2.3. In comparison with air-conducted noise measurements 5.2.4. Can this level of noise exposure cause hearing impairment? 5.2.5. Drilling at the round window niche 5.2.6. Factors affecting drilling-induced noise 6. Summary/Zusammenfassung References Supplementary calculation code for this project Acknowledgments Anlage 1: Erklärungen zur Eröffnung des Promotionsverfahrens Anlage 2: Bestätigung über Einhaltung der aktuellen gesetzlichen Vorgaben

NASCION-type lithium-aluminum-germanium-phosphate (LAGP) glass-ceramic is one of the most promising solid electrolyte (SEs) material for the next generation Li-ion battery. Based on the crystallization of glass-ceramic material, the two-step heat treatment was designed to control the crystallization of Li-ion conducting crystal in the glass matrix. The results show that the LAGP crystal is preferred to internally crystalize, Tg + 60%∆T is the nucleation temperature that provides the highest ion conductivity. The compositional investigation also found that, pure LAGP crystal phase can be synthesized by lowering the amount of GeO2. To fill gap of atomic structure in LAGP glass-ceramic, molecular dynamic (MD) simulation was used to build the crystal, glass, and interfacial structure LAGP. The aliovalent ion substitution induced an simultaneously redistribution of Li to the 36f interstitial site, and the rapid cooperative motion between the Li-ions at 36f can drop the activation energy of LAGP crystal by decreasing the relaxation energy; furthermore, an energy model was built based on the time-based analysis of Li-ion diffusion to articulate the behavior. The glass and interfacial structure show and accumulation of AlO4, GeO4 and Li at the interface, which explains the Li-trapping on the intergranular glass phase. An in-situ synchrotron X-ray study found that, by using two-step heat treatment, the nucleation of Li-ion conducting crystal in the glass-matrix induced large strain from interfacial tension, which can also promote the incorporation of aliovalent ion substitution in the NASICON crystal and enhances the ion conductivity.

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si electrodes with high current efficiency and durability through a fundamental understanding of the ionic and electronic conduction in Si and its SEI. Multi-scale physical and chemical processes occur in the electrode during charging and discharging. This thesis, thus, focuses on multi-scale modeling, including developing new methods, to help understand these coupled physical and chemical processes. For example, we developed a new method based on ab initio molecular dynamics to study the effects of stress/strain on Li ion transport in amorphous lithiated Si electrodes. This method not only quantitatively shows the effect of stress on ionic transport in amorphous materials, but also uncovers the underlying atomistic mechanisms. However, the origin of ionic conduction in the inorganic components in SEI is different from that in the amorphous Si electrode. To tackle this problem, we developed a model by separating the problem into two scales: 1) atomistic scale: defect physics and transport in individual SEI components with consideration of the environment, e.g., LiF in equilibrium with Si electrode; 2) mesoscopic scale: defect distribution near the heterogeneous interface based on a space charge model. In addition, to help design better artificial SEI, we further demonstrated a theoretical design of multicomponent SEIs by utilizing the synergetic effect found in the natural SEI. We show that the electrical conduction can be optimized by varying the grain size and volume fraction of two phases in the artificial multicomponent SEI.