Oblique Motion Research Articles

A Frog-Shaped Linear Piezoelectric Actuator Using First-Order Longitudinal Vibration Mode

A frog-shaped linear piezoelectric actuator was proposed, designed, fabricated, and tested. The proposed actuator only used the first-order longitudinal vibration to generate linear motion, which made the design, optimization, and miniaturization of the actuator more flexible by abbreviating the frequency degeneration. By stimulating the first-order longitudinal vibration, alternate oblique movements are formed on the ends of two driving feet. Meanwhile, an elongating and shortening movement of the whole actuator is generated. When two parallel walls are in contact with the ends of two diving feet and a vertical preload is applied, the vertical components of the alternate oblique movements will overcome the preload, while the horizontal components of the alternate oblique movements and the elongating and shortening movements will together push the actuator into linear motion. Vibration characteristics and alternate oblique movements of the driving feet were investigated by the finite-element method. Experiment tests of vibration characteristics and mechanical output ability were then carried out. The tested resonance frequency and vibration amplitudes agreed well with the calculated ones. The prototype achieved a maximum speed and a thrust of 287 mm/s and 11.8 N, respectively.

Impact of a detector dead time in phase-resolved Doppler analysis using spectral domain optical coherence tomography.

For any oblique sample movement containing a transverse velocity component, the commonly used linear relationship between the phase shift and the axial velocity component is erroneous for spectrometer-based optical coherence tomography (spectral domain OCT, SD-OCT). We recently proposed a new Doppler model that assumes a continuous integration of the photocurrent. In this research, we extend the model for detectors with a shutter control by taking detector dead time into account. We present the new relation between phase shift and oblique sample displacement as well as the correlation of the phases of consecutive depth scans, in dependency on the detector dead times ranging from 5% to 90%, as numerically calculated universal contour plots, which are valid for any center wavelength and sample beam size. We found that detector dead time is recommended, especially for oblique sample motion. The reason for this recommendation is the achieved linear relation between the phase shift and the axial velocity component in the velocity range relevant for in vivo measurements, despite the signal damping due to shorter exposure time of the line detector. The theoretical Doppler model is verified using a 1% Intralipid flow phantom model. Because of the results of this research, we believe future measurements in Doppler SD-OCT can be more simple and more accurate by setting a shutter control for the line detector used.

Biomechanical analysis of INFINITY rehabilitation method for treatment of low back pain.

[Purpose] Low back pain is a pervasive problem in modern societies. Physical rehabilitation in treatment of low back pain should reduce pain, muscle tension and restore spine stability and balance. The INFINITY® rehabilitation method that is based on a figure of eight movement pattern was proved to be effective in low back pain treatment. The aim of the paper is to estimate the effect of a figure of eight motion on the L5/S1 load and lumbar spine muscle activation in comparison to other motion patterns. [Subjects and Methods] Three-dimensional model of lumbar spine musculoskeletal system is used to simulate effect of various load motion pattern induced by displacement of the center of gravity of the upper body. Four motion patterns were examined: lateral and oblique pendulum-like motion, elliptical motion and figure of eight motion. [Results] The simple pendulum-like and elliptical-like patterns induce harmonic muscle activation and harmonic spinal load. The figure of eight motion pattern creates high-frequency spinal loading that activates remodeling of bones and tendons. The figure of eight pattern also requires muscle activity that differs from harmonic frequency and is more demanding on muscle control and could also improve muscle coordination. [Conclusion] The results of the study indicate that complex motion pattern during INFINITY® rehabilitation might enhance the spine stability by influencing its passive, active and neural components.

High-Speed Ship Maneuverability

In this paper, the effects of changes in hull attitude and the presence of stern append- ages such as rudders, shaft brackets, bossing, and propeller shafts on the maneuver- ability of a high-speed ship are investigated. The study is conducted for a ship operating within a Froude number range of 0.6–1.0. To determine the effect of attitude changes on the hydrodynamic derivatives during maneuvering, the hydrodynamic forces acting on the ship model with/without stern appendages are measured in three conditions: an even keel with the designed draft, and the same setup including hull rise or trim. For each condition, measurements are conducted for oblique motion, steady turning, and straight motion with heel, for various ship speeds. The hydro-dynamic derivatives excluding the attitude change are obtained from the measured results, along with the changes in these derivatives due to hull rise and trim. Using the hydrodynamic derivatives, the maneuverability indexes are calculated.

Slip-partitioned surface ruptures for the Mw 7.0 16 April 2016 Kumamoto, Japan, earthquake

An ENE-trending ~30-km-long surface rupture emerged during the Mw = 7.0 16 April 2016 Kumamoto earthquake along the previously mapped Futagawa and northern Hinagu faults. This included a previously unknown 5-km-long fault within the Aso Caldera, central Kyushu. The rupture zone is mostly composed of right-lateral slip sections, with a maximum of 2-m coseismic slip. One of the noteworthy features we observed in the field are ~10-km-long segmented normal fault scarps, dipping to the northwest, along the previously mapped Idenokuchi fault, 1.2–2.0 km south of and subparallel to the Futagawa fault. The maximum amount of coseismic throw on the Idenokuchi fault is ~2 m, which is nearly equivalent to the maximum slip on the strike-slip rupture. The locations and slip motions of the 2016 rupture are also manifested as interferogram fringe offsets in InSAR images. Together with geodetic and seismic inversions of subsurface fault slip, we present a schematic structural model where oblique motion occurred on a northwest-dipping subsurface fault and the slip is partitioned at the surface into strike-slip and normal fault scarps. Our simple dislocation model demonstrates that this bifurcation into pure strike-slip and normal faults likely occurs for optimally oriented failure near the surface. The Kumamoto case, with detailed geological observations and geophysical models, would be the second significant slip-partitioned earthquake around the globe. It provides an important insight into scale- and depth-dependent stress heterogeneity and an implication to a proper estimate of seismic hazard in complex and broad multiple fault strands.

Evolution of Çamlık fissure-ridge travertines in the Başkale basin (Van, Eastern Anatolia)

Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Başkale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Başkale basin is located between the Başkale Fault Zone (BFZ) characterised by Çamlık fault and Işıklı–Ziraniş fault. It is located between dextral Yüksekova Fault Zone and southern end of dextral Guilato–Siahcheshmeh–Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Çamlık fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Çamlık fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.

Numerical simulation on planar motion mechanism of KCS ship model with a body-force propeller model

In order to solve the ship maneuvering hydrodynamic derivatives efficiently and accurately, full-appendage KCS ship model is taken in this paper as the studying object. Based on RANS equation and VOF model, a descriptive body-force model is established to represent real propellers on the star-ccm+; the influences of the free surface wave and motion attitudes change on hydrodynamic are taken into account. The oblique motion, the yaw motion, the combination of yaw and drift angle motion on Planar Motion Mechanism (PMM) are simulated, and the athwartship force Y, the yawing moment N, and the heeling moment K are also acquired. The simulation results are then compared with the actual test results: according to the dynamics equation of PMM test, the time history curves of numerical and experimental results are analyzed with least-squares fitting and Fourier integral, where the hydrodynamic derivatives of manipulation are finally obtained. The results demonstrate the feasibility of the proposed method in PMM simulation, though the errors of Y'vvv and N'vvv are slightly larger, the errors of remaining hydrodynamic derivatives are all below 15%.

Source Model from ALOS-2 ScanSAR of the 2015 Nepal Earthquakes

Abstract The 2015 Gorkha Nepal Earthquake sequence started with a magnitude Mw 7.8 main shock and continued with several large aftershocks, particularly the second major shock of Mw 7.3. Both earthquake events were captured using ALOS-2 ScanSAR images to determine the coseismic surface deformation and the source models. In this paper, the displacement maps were produced and the corresponding modelling results were discussed. The single fault model of the main shock suggests that there was nearly 6 m of right-lateral oblique slip motion with fault struck of 292° and dipped gently Northeast at 7°, indicating that the main shock was on a thrust fault. Moreover, a single fault model for the Mw 7.3 quake with striking of 312° and dipping of 11° was derived from observed result. Both results showed the fault planes struck generally to South and dipped northeast, which depicted the risks since the main shock occurred.

The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions

The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time.The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the presence of phlogopite and the local existence of a metasomatized mantle. A carbonatite contribution is evidenced in the Nyiragongo lavas.New K-Ar ages date around 21 Ma the earliest volcanic activity made of nephelinites. A sodic alkaline volcanism took place between 13 and 9 Ma at the western side of the Virunga during the doming stage of the rift and before the formation of the rift valley. In the South-Kivu area, the first lavas were tholeiitic and dated at 11 Ma. The rift valley subsidence began around 8–7 Ma. The tholeiitic lavas were progressively replaced by alkali basaltic lavas until to 2.6 Ma. Renewal of the basaltic volcanism happened at ca. 1.7 Ma on a western step of the rift. In the Virunga area, the potassic volcanism appeared ca. 2.6 Ma along a NE-SW fault zone and then migrated both to the east and west, in jumping to oblique tension gashes.The uncommon magmatic evolution and the high diversity of volcanic rocks of the Kivu rift are explained by varying transtensional constraints during the rift history.

Advanced modeling of selection and steering data: beyond Fitts' law

Human performance in selection tasks is frequently described by Fitts' law, which states that the average time needed to move to a target and select it is linearly related to the index of difficulty for the task, which is the logarithm of the task characteristic C=A/W, where A is the target distance and W is the target width. The coefficients in this linear relationship can vary across interaction conditions, such as when using distinct interaction devices, and can for instance be used to define throughput, which is a standardized measure to compare interaction conditions. Although Fitts' law has proven very useful in the field of human-computer interaction (HCI) over the past 50 years, there are several issues with Fitts' law that argue in favor of more advanced statistical modeling of experimental data. More specifically, we propose two generalizations of Fitts' law. The first generalization is not to limit the data analysis to average movement times, but to consider the distributions of the observed times instead. The second generalization is to extend Fitts' law to a more general relationship between task characteristics and index of difficulty and to use this generalized model to come up with additional measures that can be used alongside throughput.We use data from an experiment with both selection and tracing tasks to illustrate the proposed analysis method. The primary goal of the experiment is to compare the task performance in four experimental conditions, corresponding to all combinations of interaction device (mouse or pen) and target orientation (horzizontal/vertical versus oblique movements). First, we show that non-linear transformations on the measured task completion times are indeed advised to resolve problems with the normality and homoscedasticity of the data, especially in case of the tracing task. Second, we show that in case of the selection task the data supports a linear relationship between the logarithm of the task characteristic C and the logarithm of the movement time, which corresponds to a power-law between movement time and task characteristic, an alternative to Fitts' law that has previously been proposed by several authors. In case of the tracing task, the data supports a power-law function in between a linear and a logarithmic function. We conclude by demonstrating how multiple performance measures can be used simultaneously when comparing interaction conditions. HighlightsTwo generalizations of Fitts' law: modeling data distributions and modified index of difficultyMulti-model selection is used to compare alternative models for the observed data.Advanced data modeling accomplishes closer data approximation and higher contrasts between conditions.Performance rate measure includes the form of speed-accuracy relationship.

Active faulting on the Wallula fault zone within the Olympic-Wallowa lineament, Washington State, USA

The Wallula fault zone is an integral feature of the Olympic-Wallowa lineament, an ∼500-km-long topographic lineament oblique to the Cascadia plate boundary, extending from Vancouver Island, British Columbia, to Walla Walla, Washington. The structure and past earthquake activity of the Wallula fault zone are important because of nearby infrastructure, and also because the fault zone defines part of the Olympic-Wallowa lineament in south-central Washington and suggests that the Olympic-Wallowa lineament may have a structural origin. We used aeromagnetic and ground magnetic data to locate the trace of the Wallula fault zone in the subsurface and map a quarry exposure of the Wallula fault zone near Finley, Washington, to investigate past earthquakes along the fault. We mapped three main packages of rocks and unconsolidated sediments in an ∼10-m-high quarry exposure. Our mapping suggests at least three late Pleistocene earthquakes with surface rupture, and an episode of liquefaction in the Holocene along the Wallula fault zone. Faint striae on the master fault surface are subhorizontal and suggest reverse dextral oblique motion for these earthquakes, consistent with dextral offset on the Wallula fault zone inferred from offset aeromagnetic anomalies associated with ca. 8.5 Ma basalt dikes. Magnetic surveys show that the Wallula fault actually lies 350 m to the southwest of the trace shown on published maps, passes directly through deformed late Pleistocene or younger deposits exposed at Finley quarry, and extends uninterrupted over 120 km.

Study of the Dynamic Properties of HTS Bulk Movers for Traveling Along Vertical Walls as a Three-Dimensional Actuator

We have been investigating three-dimensional actuators using bulk high-temperature superconductors (HTS) as transportation devices that move in free space. The large flux-pinning force of HTS allows motion without contact, even when the levitation force is not aligned against gravity, which could make them useful in clean or dangerous environments, such as clean rooms for semiconductor fabrication or in tunnels containing flammable gas. An actuator prototype, consisting of an HTS bulk with trapped magnetic field as a mover and a two-dimensional array of electromagnets as a stator, has been developed. In a previous study, the dynamic characteristics for traveling over floors were examined. In this study, horizontal, vertical, and oblique motions along vertical walls have been investigated. Movement characteristics have been studied for HTS bulks of two diameters and related to measurements of the axial components of their trapped magnetic fields. Maximum vertical displacements of 5.80 and 11.5 mm were achieved for HTS bulks of 60- and 46-mm outer diameters, respectively.

"Modified Oblique Le Fort III Osteotomy" New Concepts.

The purpose of this study is to demonstrate the surgical technique for the correction of midfacial deformities; vertical excess and posteroanterior hypoplasia. This situation obligates the need to move the whole osseous structure in an oblique posteroanterior movement that should correct both midfacial deformities. This should also correct the lip incompetence while improving the malar projection on a profile view of the patient. We also present a mathematical formula that gives the angulation needed for moving the midface complex in a simultaneous vertical and posteroanterior direction. Once given the correct angulation for the desired oblique movement, the surgeon can reproduce this angulation with custom made surgical guides over the stereolithographic model, that can then be used during surgery to achieve the desired movement accurately. This technique exemplified on this paper will give maxillofacial surgeons a new and affordable tool for the correction of midfacial deformities in an accurate and easily reproducible manner and amplifying the surgical repertoire. Patients seen in the specialty hospital "Dr. Bernardo Sepulveda" National Medical Center XXI Century, IMSS, during the period from February 2013 to November 2014 with Modified Oblique Le Fort III osteotomies, with the application of two trigonometric formulas for the accuracy of the technique. The application of the formulas give accurate results as well as the enlargement of the upper airway and esthetic results.

Oblique rifting and the Late Eocene–Oligocene demise of Laurasia with inception of Molloy Ridge: Deformation of Forlandsundet Basin, Svalbard

Final breakup of the Laurasian supercontinent occurred within a residual continental bridge that spanned Svalbard, Greenland and Arctic Canada from Late Cretaceous to Oligocene time, but the timing and precise kinematics of that breakup have remained obscure. Dextral oblique motion between Svalbard and northeastern Greenland initially generated the West Spitsbergen Fold-Thrust Belt (a transpressional orogen) but evolved into oblique rifting until the ultimate demise of the continental bridge with the Early Miocene formation of the Molloy Ridge. The Forlandsundet basin stands as a critical entity within the Svalbard continental margin whose fill captured the progressive transition between oblique convergence and divergence. The basin originated as a Late Eocene piggyback basin within the fold-thrust belt during deposition of the oldest unit, the marine fluvio-deltaic Sarsbukta conglomerate. Structural mapping highlights early deformation of the Sarsbukta strata expressed as (1) fractured cobbles in which fractures formed by consistent NNW–SSE stretching were injected with sandy matrix (when poorly lithified), (2) stylolites recording WSW–ENE shortening, and (3) conjugate dextral- and sinistral-normal mesoscale faults that indicate WSW–ENE shortening (P axes) and NNW–SSE extension (T axes). Between 38 and 31Ma, this episode of orogen–normal shortening with orogen–parallel extension evolved progressively into oblique divergence (NW–SE extension) recorded in the Sarsbukta strata as basin-wide strike-slip/normal faults, transtensional folds, and sub-horizontal stylolite surfaces (subvertical P axes). Thus NW–SE extension, consistent with present spreading on the Molloy Ridge, was established at least 9m.y. before the first emergence of recognized oceanic lithosphere. Deformation occurred at upper-crustal temperatures of ≤104°C based on new vitrinite reflectance data. Transtension resulted in intrabasinal exposures of the Caledonide metamorphic basement during deposition of the second unit, the ≥31Ma marine fan-deltaic Sarstangen conglomerate, in the Forlandsundet graben sensu stricto. Such oblique stretching severed the continental bridge heralding ultimate oceanic spreading at the Molloy Ridge.

The Correlation Between Pelvic Obliquity And Dynamic Alignment Of Knee During Gait.

Tsuji et al. reported that a patellofemoral joint pain was related to a sacral inclination that caused by changing of lumbar alignment, and they called this pathological concept “the knee-spine syndrome”. Tauchi et al. reported that influence of spinal imbalance on knee osteoarthritis. However, few studies reported the dynamic alignment on the frontal plane on the frontal plane to elucidate knee - spine syndrome. PURPOSE: To investigate association of the dynamic alignment of the pelvic and the knee during gait. METHODS: This study included 100 patients (58 male; 31.7±17.45ys, 168.0±6.74cm, 63.1±11.33kg and 42 female; 38.5±20.42ys, 156.5±8.71cm, 52.0±10.93kg) with pain in the lower limbs and/or low back pain. The dynamic alignment of pelvic and knee during gait was measured at our clinic using a motion analysis system which consisted of six cameras, two force plates, and 39 retro-reflective markers. The relationship between the frontal plane motion of pelvic (i.e. pelvic obliquity) and knee (i.e. knee varus-valgus) were analyzed using linear regression. Then the patients were classified into three groups by pelvic obliquity imbalance and the dynamic alignment of knee was compared among four groups. RESULTS: At the initial contact of left foot, the pelvic right obliquity angle was 3.7±1.92 (degrees; d) and the angular velocity of left knee varus was 28.3±38.26 (degree/sec; d/s), and the coefficients of correlation of them (r) was -.091 (ns). On the other hand at the initial contact of right foot, the pelvic left obliquity angle was 5.8±2.15 (d) and the angular velocity of right knee varus was 37.9±34.43 (d/s), and r was .379 (p> right obliquity) group was 40.7±7.63 (d/s), and was larger than normal balance group (24.4±4.29 (d/s), p<.05 ). CONCLUSIONS: In the landing movement, the correlation between the dynamic alignment of trunk and knee was reported. The same as the previous study, this study suggested that the correlation between pelvic obliquity and knee varus during gait. We hypothesize that the increases in pelvic obliquity motion from initial contact to foot flat was increased of frontal-plane knee movement and torques because of to transfer lateral-down forces from the trunk through the lower extremity. The findings of this study will provide clinicians with useful information for prevention overuse injuries.

Seismic geomorphology of cretaceous megaslides offshore Namibia (Orange Basin): Insights into segmentation and degradation of gravity-driven linked systems

This study applies modern seismic geomorphology techniques to deep-water collapse features in the Orange Basin (Namibian margin, Southwest Africa) in order to provide unprecedented insights into the segmentation and degradation processes of gravity-driven linked systems. The seismic analysis was carried out using a high-quality, depth-migrated 3D volume that images the Upper Cretaceous post-rift succession of the basin, where two buried collapse features with strongly contrasting seismic expression are observed. The lower Megaslide Complex is a typical margin-scale, extensional-contractional gravity-driven linked system that deformed at least 2 km of post-rift section. The complex is laterally segmented into scoop-shaped megaslides up to 20 km wide that extend downdip for distances in excess of 30 km. The megaslides comprise extensional headwall fault systems with associated 3D rollover structures and thrust imbricates at their toes. Lateral segmentation occurs along sidewall fault systems which, in the proximal part of the megaslides, exhibit oblique extensional motion and define horst structures up to 6 km wide between individual megaslides. In the toe areas, reverse slip along these same sidewall faults, creates lateral ramps with hanging wall thrust-related folds up to 2 km wide. Headwall rollover anticlines, sidewall horsts and ramp anticlines may represent novel traps for hydrocarbon exploration on the Namibian margin.The Megaslide Complex is unconformably overlain by few hundreds of metres of highly contorted strata which define an upper Slump Complex. Combined seismic attributes and detailed seismic facies analysis allowed mapping of headscarps, thrust imbrications and longitudinal shear zones within the Slump Complex that indicate a dominantly downslope movement of a number of coalesced collapse systems. Spatial and stratal relationships between these shallow failures and the underlying megaslides suggest that the Slump Complex was likely triggered by the development of topography created by the activation of the main structural elements of the lower Megaslide Complex.This study reveals that gravity-driven linked systems undergo lateral segmentation during their evolution, and that their upper section can become unstable, favouring the initiation of a number of shallow failures that produce widespread degradation of the underlying megaslide structures. Gravity-driven linked systems along other margins are likely to share similar processes of segmentation and degradation, implying that the megaslide-related, hydrocarbon trapping structures discovered in the Namibian margin may be common elsewhere, making megaslides an attractive element of deep-water exploration along other gravitationally unstable margins.

Kinematic analysis of rock flow and deformation temperature of the Sirjan thrust sheet, Zagros Orogen, Iran

AbstractMicrostructural, finite strain and vorticity analyses of quartz-rich mylonites were used in order to investigate kinematics of rock flow and deformation temperature in the Sirjan thrust sheet exposed in a structural window within the Sanandaj–Sirjan High Pressure – Low Temperature (HP–LT) metamorphic belt that forms part of the hinterland of the Zagros orogenic belt of Iran. A dominant top-to-the-SW sense of shear in the study area is indicated by several shear sense indicators such as asymmetric boudins, rotated porphyroclasts, mica fish and S/C fabrics. Quantitative analyses reveal approximately plane strain deformation conditions with Rxz values ranging from 2.5 to 4.3 and increasing towards the Sirjan thrust. Opening angles of quartz c-axis fabrics and recrystallization regimes suggest deformation temperatures vary from 430 to 625 ± 50°C in the hanging wall rocks. Oblique grain shape and quartz c-axis fabrics were used to estimate the degree of non-coaxiality during deformation. The obtained vorticity profile indicates a down-section increase in kinematic vorticity number (Wm) from 0.6 to 0.89. This range of vorticity numbers confirms contributions of both simple (41–68 %) and pure shear (32–59 %) deformation components. The structural characteristics of the study area ultimately were controlled by oblique motion of the Afro-Arabian plate relative to the Iranian plate.

Active Crustal Deformation in the Area of San Carlos, Baja California Sur, Mexico as Shown by Data of Local Earthquake Sequences

We analyzed earthquakes of sequences that occurred at different times near San Carlos, a town of approximately 5000 inhabitants. The seismic sequences happened during March–April 1989, October 2000–June 2001, and 5–15 February 2004 at about 200 km west of the Pacific-North America plate boundary. The strong shaking from initial earthquakes of the first two sequences prompted the installation of temporary seismic stations in the area. With data recorded by these stations, we found an earthquake distribution that is consistent with the northwest segment of the Santa Margarita fault. Both the focal depth, that seemed to increase in E–NE direction, and a composite fault-plane solution, obtained from polarity data of the small earthquakes, were also consistent with the main characteristics of that fault. We also found that our normal-faulting mechanism (east side down) was quite similar to centroid moment tensor solutions for earthquakes with Mw 5.4 and 5.3 that occurred in the area in February 2004. It is likely, then, that these larger earthquakes also occurred along the Santa Margarita Fault. To get some insight into the regional stress pattern, we compared the above mechanisms with mechanisms reported for other earthquakes of the Pacific margin of Baja California Sur and the Gulf of California regions. We observed that focal mechanisms of the two regions have T axes of stress that plunge sub horizontally in E–NE average direction. The corresponding P axes have N–NW average trend, but for the Pacific earthquakes these axes plunge at angles that are ~35° larger than those for the Gulf earthquakes. These more vertically inclined P axes of compressive stress mean substantial oblique fault motions. The mixture of oblique and strike-slip components of fault motions, as the focal mechanisms show, confirms a transtensional stress regime for the region. Before this research, we knew little about the seismicity and styles of faulting in the area. Now we know that earthquakes can occur along the coastline of Baja California, at 60 km east of the Tosco-Abreojos fault system. We conclude that transtensional deformation is taking place across a wide zone of the Pacific margin of Baja California. Finally, we point out that although the studied earthquakes were of small magnitude, they might serve as a reminder of the danger that future larger events pose to San Carlos.

CECO wave energy converter: Experimental proof of concept

This paper presents the experimental proof of concept of CECO, an innovative wave energy converter designed to convert simultaneously the kinetic and the potential energy of ocean waves into electrical energy, based on the oblique motion of two floating modules. First, the main characteristics of CECO and its work principle are briefly presented. Then, the behavior of the device is analyzed for different wave conditions and modes of operation (power take-off damping levels and device inclinations), based on results obtained with a physical model built on a geometric scale of 1/20. CECO performance strongly depends on the incident wave characteristics, the device inclination angle, and the damping introduced by the power-take-off. Relative capture widths of up to 14% were reached in this initial study, confirming that CECO is a valid technology to extract energy from waves. The application of wavelets showed that CECO response occurs mainly in the frequency of incident waves during the entire test duration.

Shining a light on Harriot and Galileo: On the mechanics of reflection and projectile motion

Decades before Newton’s Principia ushered in the age of modern science, Aristotelian physics faced a serious challenge against its weakest point, in the quest to construct a new theory of projectile motion. Yet how were such new principles of motion conceived, without reference to an established theory of mechanics? This paper explores the conceptual space between the rejection of Aristotle’s physics and the appearance of Newton’s physics in which people such as Harriot and Galileo sought new ways to understand mechanical phenomena. This paper seeks to show that both Harriot and Galileo looked to the (early seventeenth-century) zeitgeist of accepting the law of reflection as a law of oblique projection-rebound for all material bodies, for their foundational (non-Aristotelian) conceptual resource. The kinematics and dynamics of light’s compound, oblique motion had been developed over centuries within optics, and constituted the ‘ideal’ resource for novel analyses of oblique projectile motion. Whereas Harriot’s inclusion of air resistance restricted the generalizability of optical principles to his simplest case, the upright parabola, Galileo’s idealized analysis of projectile motion in a vacuum represented all cases of projectile motion as upright parabolas. He was thus able to generalize these optical principles to projectile motion per se.