Volcanic rifting environments, such as in Iceland, are challenging for conventional seismic reflection methods using active surface seismic sources. This study demonstrates the potential of a novel technique, called Virtual Reflection Seismic Profiling (VRSP) for imaging reflections in geothermal regions, like Hverahlíð, where a dense seismic array recorded a number of local microearthquakes for cross-correlation. Uppsala University, in collaboration with Reykjavik Energy, recorded seismicity in Hverahlíð using both seismometers and geophones. Acquired data were processed using the VRSP method, which applies seismic interferometry only to selected events, in this thesis local microearthquakes. Cross-correlation of the signal from a microearthquake recorded at one of the stations, which acts as a virtual source, with a ghost reflection recorded by the remaining receivers, produces a virtual shot gather. Stacking each station’s result, for all available events, and following a conventional multichannel processing sequence resulted in two stacked seismic images. Potential reflections observed in the obtained sections could be associated with major feed zones identified in the area by the borehole measurements. Eight dynamite explosions were processed with a conventional seismic reflection method, as a complementary source to the microearthquakes. In the produced stacked seismic section two potential reflections could be observed. Results from both passive and active datasets were 3D visualised to verify whether the reflections correspond to each other between sections. Two horizons were traced throughout all three stacked sections. One more interface appeared on two images obtained from processing the passive data. This study shows promising results for using natural sources to image the subsurface in a challenging environment.

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This Ph.D. dissertation focuses on a comprehensive study of seismic waveform similarity aiming at two themes: (1) reliable identification of repeating earthquakes (repeaters) and (2) investigation of the detailed source process of induced seismicity through the three-dimensional spatiotemporal evolution of mainly neighbouring earthquakes. Theme 1: Reliable identification of repeaters. Repeaters, occurring repeatedly on the same fault patch with nearly identical waveforms, are usually identified with the match-filtering (MF) method which essentially measures the degree of waveform similarity between an earthquake pair through the corresponding cross-correlation coefficient (CC). However, the performance of the MF method can be severely affected by the length of the cross‐correlation window, the frequency band of the applied digital filter, and the presence of a large‐amplitude wave train. To optimize the performance of MF, I first examine the effects of different operational parameters and determine generic rules for selecting the window length and the optimal frequency passband. To minimize the impact of a large‐amplitude wave train, I then develop a new method, named the match-filtering with multisegment cross-correlation (MFMC) method. By equally incorporating the contributions from various segments of the waveforms, the new method is much more effective in capturing the minor waveform discrepancy between an event pair due to location difference and hence is more reliable in detecting potential repeaters and discriminating non-repeaters with large inter-event separation. With both synthetic and borehole array waveform data, I further reveal that waveform similarity is controlled by not only the inter-event separation but also many other factors, including station azimuth, epicentral distance, velocity structure, etc. Therefore, in contrast to the traditional view, the results indicate that waveform similarity alone is insufficient to unambiguously identify true repeaters. For reliable repeater identification, we should rely on a physics-based approach considering both the overlapped source area and magnitude difference. Specifically, I define an event pair to be true repeaters if their inter-event separation is smaller than the rupture radius of the larger event and their magnitude difference is no more than 1. For the precise estimation of inter-event distance in cases of limited data, I develop the differential traveltime double-difference (DTDD) method which relies on the relative S-P differential traveltime. The findings of this study imply that previously identified repeaters and their interpretations/hypotheses potentially can be biased and hence may need a systematic reexamination. Theme 2: Investigation of the detailed source process of induced seismicity. Earthquakes induced by hydraulic fracturing (HF), especially those with large magnitudes, are often observed to have occurred near/after well completion. The delayed triggering of induced seismicity with respect to injection commencement poses serious challenges for risk mitigation and hazard assessment. By performing waveform cross-correlation and hierarchical clustering analysis, I reveal a high-resolution three-dimensional source migration process with mainshock delayed triggering that is probably controlled by local hydrogeological conditions. The results suggest that poroelastic effects might contribute to induced seismicity but are likely insufficient to activate a non-critically stressed fault of sufficient size. My analysis shows that the rapid pore-pressure build-up from HF can be very localized and capable of producing large, felt earthquakes on non-critically stressed fault segments. I further infer that the number of critically stressed, large intraplate faults should be very limited, and that reactivation of such faults may require sufficient pore-pressure accumulation. The findings of this study may also explain why so few fluid injections are seismogenic. / Graduate

This thesis investigates the development of a low-cost passive acoustic system for localizing moving vessels to monitor areas where human activities such as fishing, snorkeling and poaching are restricted. The system uses several off-the-shelf sensors with unsynchronized clocks where the Time Difference of Arrival (TDOA) or time delay is extracted by cross-correlation of the signal between paired sensors. The cross-correlation function uses phase correlation or Phase Transform (PHAT) which whitens the cross-spectrum in order to de-emphasize dominant frequency components. Using the locations of pairs of sensors as foci, hyperbolic equations can be defined using the time delay between them. With three or more sensors, multiple hyperbolic functions can be calculated which intersect at a unique point: the boat's location. It is also found that increasing separation distances between sensors decreased the correlation between the signals. However larger separation distances have better localization capability than with small distances. Experimental results from the Columbia and Willamette Rivers are presented to demonstrate performance.

本論文は，われわれの感情が表情として表出されるとき, 通常の顕在化した表出に先行して，刺激に対する無意識，かつ"真"の感情を反映すると考えられる"premier expressions"の存在を探ることを目的として行われたものである。本論文では，感情喚起刺激による表情表出過程を，刺激に対しまず現れる反応と，第1反応に続く，誇張や，抑制など様々な心理的調整を反映した第2の反応に分けてとらえている。この最初の反応を"premier expressions"と呼ぶ。この語は本論文提出者の造語である。"premier expressions"の理論的根拠はTomkins(1961)の感情理論の中に見られるが，これまでその存在を実証したものはない。本論文が研究対象としている"premier expressions"はこのTomkins のいう最初に生じる反応，あるいはそれに類似した反応と考えられる。 / This research consists of three experiments aiming to determine the existence of the premier expression and its features. We defined the premier expression as a primitive, reflex-like, automatic facial response to evoked emotion that cannot be modified by one's conscious or unconscious effort because of its initiating timing and speed. However, a facial response develops after the premier expression that corresponds to a generally recognized facial expression, which is easily concealed or modified by display rules or social context. The premier expression is regarded as the first response to induced emotion, and might not even be visible to the naked eye because of its speed and subtlety. This postulation is based on Darwin’s first principle of expression (1872/2009) and Tomkins' (1962) hypothesis that the face is the primary site of affect and has priority over the outer skeletal and inner visceral behaviors (i.e., blood pressure, heart rate, skin conductance) for the expression of emotion, since it is a faster, more precise and visible display. / 博士(心理学) / Doctor of Philosophy in Psychology / 同志社大学 / Doshisha University

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Physical implementations of cryptographic algorithmscan leak sensitive information through different kindsof side-channels. This information can potentially be used forrecovering the secret key used in the algorithms. Recently, sidechannelattacks on CPU implementations of Advanced EncryptionStandard (AES) has been presented. Some of these attacksuse far-field electromagnetic radiation.In this thesis, we investigate if cross correlation can be used tolocate the part of the signal corresponding to the execution of theAES-encryption. We gather side-channel signal data containingencryption activity to create and test multiple templates forcorrelation. By evaluating the performance of the templates indifferent scenarios, we conclude that the method is useful andrelatively easy to implement compared to previous methods.Furthermore, our extraction method has a low execution timewhich gives it potential to be used in real-time attacks. / Fysiska implementationer av krypteringsalgoritmerkan läcka känslig information genom olika typer avsidokanaler. Informationen kan potentiellt användas för att återskapa algoritmernas hemliga krypteringsnycklar. Senastetiden har sidokanalsattacker mot CPU-implementationer av AdvancedEncryption Standard (AES) presenterats. Vissa av dessaattacker nyttjar utstrålande elektromagnetiska fjärrfält. I denna rapport undersöker vi om korskorrelation kananvändas för att hitta tidpunkten i signalen då AES-krypteringengenomfördes. Vi samlar in signaldata från sidokanalen sominnehåller krypteringsaktivitet, detta för att skapa och testa olikakorrelationsmallar. Genom att utvärdera mallarnas prestanda iolika scenarion kan vi sluta oss till att denna metod är användbarsamt lätt att implementera jämfört med tidigare metoder. Därtillvisar vår metods korta körtid att den har potential att användasi en realtidsattack. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Naiqian Zhang / Suspended sediment concentration (SSC) in water is one of the most important parameters to evaluate water quality. Monitoring SSC provides important information on determining sediment transport for soil erosion research and soil/water conservation practices. Sediment mass transported at a given time can be assessed by simultaneous SSC and water flow velocity measurements. Fouling, including bio-fouling, has damaging impact on optical SSC measurements over the long term. In this study, an inexpensive, real-time, self-cleaning, optical sediment and flow velocity sensor was developed. Laboratory experiments were conducted on a previously designed SSC sensor. A light modulation algorithm was designed to reduce the influence of ambient light, especially sunlight, on measurement accuracy. Statistical models to predict SSC based on measured light intensities were established and compared with neural network models. The statistical analysis showed that soil texture played an important role in SSC measurement accuracy while the designed sensor was capable of reducing the effect of water color on sensor performance. Neural-network models can further remove the influence of soil texture type on SSC measurement. The sensor design was simplified based on a stepwise selection analysis. Long-term field experiments were conducted in Kansas and Georgia to evaluate the sensor performance, the effect of fouling, including bio-fouling, on sensor lenses, and the effect of temperature on the measurement. Methods of removing the fouling effect through data correction were developed. Results indicated that the designed optical SSC sensor was capable of providing rapid response to SSC fluctuations in water flow. Temperature of the water body has an insignificant impact on SSC measurement. In order to reduce fouling, an air-blast cleaning mechanism was integrated into the optical sediment sensor. Laboratory experiments in a manually created fouling environment were conducted to observe the fouling process on sensor cases made of different materials, and to verify the effectiveness of air-blast cleaning in reducing fouling. Results indicated that air-blast cleaning mechanism was capable of reducing clay/silt fouling on sensor signals. The duration and frequency of air-blast cleaning can be determined and adjusted depending on actual field conditions. An air pressure drop test was conducted on the hose carrying pressurized air. Results showed negligible pressure drop.A flow velocity measurement function based on the cross-correlation principle was integrated into the optical sediment sensor. An experiment was conducted in laboratory to examine the sensor performance on velocity measurement using a closed circulation system. A solution of blue colorant, Brilliant Blue FCF, was used as an artificial source to absorb light emitted by LEDs in the sensor and the signal variation patterns were measured. The results indicated that the cross-correlation-based velocity sensor was capable of measuring water flow velocity within in a certain velocity range using the dye injection method.

Spectroscopic orbital elements and/or related parameters have been determined for eight binary systems, using radial-velocity measurements that have a typical precision of about 15 ms⁻¹. The orbital periods of these systems range from about 10 days to 26 years, with a median of about 6 years. Orbital solutions were determined for the seven systems with shorter periods. The measurement of the mass ratio of the longest-period system, HD217166, demonstrates that this important astrophysical quantity can be estimated in a model-free manner with less than 10% of the orbital cycle observed spectroscopically.\\ Single-lined orbital solutions have been derived for five of the binaries. Two of these systems are astrometric binaries: β Ret and ν Oct. The other SB1 systems were 94 Aqr A, θ Ant, and the 10-day system, HD159656. The preliminary spectroscopic solution for θ Ant (P~18 years), is the first one derived for this system. The improvement to the precision achieved for the elements of the other four systems was typically between 1--2 orders of magnitude. The very high precision with which the spectroscopic solution for HD159656 has been measured should allow an investigation into possible apsidal motion in the near future. In addition to the variable radial velocity owing to its orbital motion, the K-giant, ν Oct, has been found to have an additional long-term irregular periodicity, attributed, for the time being, to the rotation of a large surface feature.\\ Double-lined solutions were obtained for HD206804 (K7V+K7V), which previously had two competing astrometric solutions but no spectroscopic solution, and a newly discovered seventh-magnitude system, HD181958 (F6V+F7V). This latter system has the distinction of having components and orbital characteristics whose study should be possible with present ground-based interferometers. All eight of the binary systems have had their mass ratio and the masses of their components estimated.\\ The following comments summarize the motivation for getting these results, and the manner in which the research was carried out. \\ The majority of stars exist in binary systems rather than singly as does the Sun. These systems provide astronomers with the most reliable and proven means to determine many of the fundamental properties of stars. One of these properties is the stellar mass, which is regarded as being the most important of all, since most other stellar characteristics are very sensitive to the mass. Therefore, empirical masses, combined with measurements of other stellar properties, such as radii and luminosities, are an excellent test for competing models of stellar structure and evolution.\\ Binary stars also provide opportunities to observe and investigate many extraordinary astrophysical processes that do not occur in isolated stars. These processes often arise as a result of direct and indirect interactions between the components, when they are sufficiently close to each other. Some of the interactions are relatively passive, such as the circularization of the mutual orbits, whilst others result from much more active processes, such as mass exchange leading to intense radiation emissions. \\ A complete understanding of a binary system's orbital characteristics, as well as the measurement of the all-important stellar masses, is almost always only achieved after the binary system has been studied using two or more complementary observing techniques. Two of the suitable techniques are astrometry and spectroscopy. In favourable circumstances, astrometry can deduce the angular dimensions of the orbit, the total mass of the system, and sometimes, its distance from us. Spectroscopy, on the other hand, can determine the linear scale of the orbit and the ratio of the stellar masses, based on the changing radial velocities of both stars. When a resolved astrometric orbital solution is also available, the velocities of both stars can allow the binary system's parallax to be determined, and the velocities of one star can provide a measure of the system mass ratio.\\ Unfortunately, relatively few binary systems are suited to these complementary studies. Underlying this difficulty are the facts that, typically, astrometrically-determined orbits favour those with periods of years or decades, whereas spectroscopic orbital solutions are more often measured for systems with periods of days to months. With the development of high-resolution astrometric and spectroscopic techniques in recent years, it is hoped that many more binary systems will be amenable to these complementary strategies.\\ Several months after this thesis began, a high-resolution spectrograph, HERCULES, commenced operations at the Mt John University Observatory, to be used in conjuction with the 1-metre McLellan telescope. For late-type stars, the anticipated velocity precision was ≲10 ms⁻¹. The primary goals of this thesis were: 1.~to assess the performance of HERCULES and the related reduction software that subsequently followed, 2.~to carry out an observational programme of 20 or so binary systems, and 3.~to determine the orbital and stellar parameters which characterize some of these systems. The particular focus was on those binaries that have resolved or unresolved astrometric orbital solutions, which therefore may be suited to complementary investigations.\\ HERCULES was used to acquire spectra of the programme stars, usually every few weeks, over a timespan of about three years. High-resolution spectra were acquired for the purpose of measuring precise radial velocities of the stars. When possible, orbital solutions were derived from these velocities, using the method of differential corrections.