Effects of Design Parameter on Occurrence of Snap Load and Wear of Mooring Line for Spar-Buoy With Ring-Fin Motion Stabilizer for Shallow Sea

The purpose of this study is to propose an optimal design method of the spar-buoy with ring-fin motion stabilizer for shallow sea and its mooring system, in order to avoid the occurrence of snap load. The mechanism of occurrence of snap load is investigated by model tests, and design parameters for avoiding the occurrence of snap load are investigated. From the observation of model’s motion, it has been realized that the snap load is caused by the tension of mooring line to stop the buoy’s horizontal motion, which relaxes the mooring line. Moreover, it has been confirmed that the horizontal motion is caused by the horizontal forces acting on the center pipe and float of the buoy, which relates to the acceleration component of wave excitation forces. In this paper, the effects of changing of design of the buoy (: diameter of center pipe and float, size of stabilizer, density of the buoy, length of mooring line) on avoiding or reducing snap load are investigated by using a numerical simulation (OrcaFlexver.11.0b), and the wear amounts are also estimated by using an empirical method (Takeuchi et al., 2019). From the results, it is confirmed that changing the buoy’s motion mode by shortening mooring line is effective to avoiding the occurrence of snap load, and to reduce the wear amount of the mooring line.

North American Crustal Motion and Glacial Isostatic Adjustment Model Predictions

<p>A suite of forward GIA model predictions, spanning a wide range of layered mantle viscosity and lithospheric thickness values, is compared to observed horizontal crustal motions in North America to discern optimal model parameters in order to minimize a root-mean-square (RMS) measure of the velocity residuals. To obtain the Earth model response, a combination of the full normal mode analysis and the collocation method is implemented. It provides a means to determine the surface loading response automatically and robustly to 1-dimensional (radially varying) Earth models, while retaining as much of the physics of the normal mode method as numerically feasible, given documented issues with singularities along the negative inverse-time axis in the Laplace transform domain. This method enables the exploration across a wide parameter range (for the lower mantle, transition zone, asthenosphere, and thickness of the elastic lithosphere) to find optimal combinations to explain horizontal crustal motion in North America. The analysis utilizes crustal motion rates from approximately 300 GNSS sites in central North America (Canada and United States) provided by the Nevada Geodetic Laboratory.  Preliminary results indicate that horizontal crustal motion predictions generated with a thin lithosphere, 40 – 60 km, produce horizontal motions that are strongly discrepant with the observations and have velocity residuals larger than the null model (modelled horizontal motion set to zero). As the lithospheric thickness increases, from 80 km to 240 km, the horizontal motion residuals gradually decrease with no minimum apparent for the thicknesses thus far considered. The residual velocities for the best-fitting models appear to carry a remaining signal, confirming previous inferences of limitations to spherically symmetric Earth models in modeling horizontal crustal motions in North America.</p>

Failure Mechanism of Rock Slopes under Different Seismic Excitation

In earthquake-prone areas, special attention should be paid to the study of the seismic stability of rock slope. Particularly, it becomes much more complicated for the rock slopes with weak structural surfaces. In this study, numerical simulation and the shaking table test are carried out to analyze the influence of seismic excitation and structural surface in different directions on dynamic response of rock slope. Huaping slope with bedding structural surfaces and Lijiang slope with discontinuous structural surfaces besides Jinsha River in Yunnan Province are taken as research objects. The results of numerical simulation and the model test both show that discontinuous structure surface has influence on the propagation characteristics of seismic wavefield. For Huaping slope, the seismic wavefield responses repeatedly between the bedding structural surface and slope surface lead to the increase of the amplification effect. The maximum value of seismic acceleration appears on the empty surface where terrain changes. Horizontal motion plays a leading role in slope failure, and the amplification coefficient of horizontal seismic acceleration is about twice that of vertical seismic acceleration. The failure mode is integral sliding along the bedding structural surface. For Lijiang slope, seismic acceleration field affected by complex structural surface is superimposed repeatedly in local area. The maximum value of seismic acceleration appears in the local area near slope surface. And the dynamic response of slope is controlled by vertical and horizontal motion together. Under the seismic excitation with an intense of 0.336 g in X direction and Z direction, the amplification coefficients of seismic acceleration of Lijiang slope are 3.23 and 3.18, respectively. The vertical motion leads to the cracking of the weak structural surface. Then, Lijiang slope shows the toppling failure mode under the action of horizontal motion.

Horizontal tectonics assembled unrelated crustal blocks in the Paleoarchean

Archean geodynamics and craton formation are topics of much debate for decades. Here we present evidence from field, petrography, geochronology, elements and Nd-Hf isotopes for origin of micro-blocks in different geodynamic environments and their assembly by horizontal tectonics in Paleoarchean. The cratonal core in the western Dharwar craton (southern India) formed through assembly of three genetically unrelated micro-blocks: a microcontinent with oceanic plateau remnants, oceanic arc, and a section of oceanic lithosphere. Isotopic age data of these blocks and surrounding basement gneisses indicate that most of the later is coeval to or younger than the blocks. The assembly three micro-blocks marked by intrusion of hot trondhjemite magmas which drive partial convective crustal overturn, resulting in dome-and-keel structures visible in the Archean cratons. Our study reveals horizontal motion of unrelated tectonic units during Paleoarchean, but mantle plumes driven vertical accretion contributed to major crustal growth allowing geodynamic linkage between Paleoarchean cratons.

Measuring Harmonic Tension in Post-Tonal Repertoire

Despite the large body of research that has examined tonal and atonal harmonies to our perception of tension, there is no work that describes or explores the perception of post-tonal chords, but more specifically, chords that contain both tonal and post-tonal features. This article applies the concept of calculating the total amount of voice-leading movement, to examine its relationship to our perception of tension and release. To do this, three neoclassical pieces are selected to analyze the relationship between theoretical and perceived tension. The findings suggest that in addition to calculating the horizontal motion between harmonies, physical and acoustical factors play a critical role in relating theoretical to perceived tension. This approach is adaptable to other neoclassical works and in addition, this study could have implications in other musical fields such as performance practices and analyzing formal functions in post-tonal repertoire.