Skeletal and Dental Morphological Characteristics of the Maxillary in Patients with Impacted Canines Using Cone Beam Computed Tomography: A Retrospective Clinical Study

The aim of this study is to analyze the skeletal and dentoalveolar morphological characteristics of the maxillary in subjects with a unilateral palatally impacted canine using Cone Beam Computed Tomography (CBCT). A retrospective clinical study was conducted of 100 adult patients divided into two groups: one consisting of patients with a unilaterally palatally impacted maxillary canine (GI), with the subgroups in the right and left hemiarches (GI-R and GI-L), and the second, without impacted canine, as the control group (CG). The CBCT measured skeletal variables (maxillary basal width and alveolar crest height) and dentoalveolar variables (inclination of the upper incisor, tooth lengths of incisors and canines, arch length, tooth size and bone dental discrepancy). In skeletal variables, statistically significant differences were found in alveolar crest height (ACH) in all groups and subgroups (p < 0.01). In the dentoalveolar variables, there were differences in the angle of the upper incisor (II) and lateral incisor length (LLIL) between the GI and GC and the angle of the upper incisor (II′), arch length (AL′) and arch length-tooth size discrepancy (ATD′) among the GI subgroups (p < 0.01). There are skeletal and dentoalveolar differences in patients with unilateral palatally impacted maxillary canines, with lower angular and linear measurements compared with patients without impaction.

Study on working bodies of the soil preparation machine for sowing potatoes

The purpose of the study is to substantiate the parameters of the guide knife and the loosening pointed leg of the machine. The basic principles and methods of classical mechanics, mathematical analysis and statistics were used in this study. Theoretical studies were carried out to determine the parameters of the guide knife and the loosening pointed leg of the machine. It is established that to ensure the required value of the crest height with minimal energy consumption, the height and length of the guide knife should be 8 and 15 cm, respectively, the angle of the knife blade to the horizon - 30º, the longitudinal distance from the toe of the ploughshare body of the knife toe – 13 cm. To ensure the required crumbling of the soil, the width of the pointed loosening paw should be 15 cm.

Effects of Beach Nourishment Project on Coastal Geomorphology and Mangrove Dynamics in Southern Louisiana, USA

Relative sea-level (RSL) rise associated with decreased fluvial sediment discharge and increased hurricane activity have contributed to the high rate of shoreline retreat and threatened coastal ecosystems in Port Fourchon, Louisiana, USA. This study, based on QuickBird/drone images (2004–2019) and LIDAR data (1998–2013), analyzed the impacts of shoreline dynamics on mangroves (Avicennia germinans) and marshes before and after the initiation of a beach nourishment project in 2013. The coastal barrier and dune crest migrated landward between 1998 and 2013. Meanwhile, the dune crest height increased between 1998 and 2001, then decreased in 2013, probably due to hurricane impacts. The total sediment volume along this sandy coastal barrier presented an overall trend of decline in the 1998–2013 period, resulting in a wetlands loss of ~15.6 ha along 4 km of coastline. This has led to a landward sand migration onto muddy tidal flats occupied by Avicennia germinans (1.08 ha) and Spartina (14.52 ha). However, the beach nourishment project resulted in the advancement of the beach barrier from Nov/2012 to Jan/2015, followed by a relatively stable period between Jan/2015 and Mar/2019. Additionally, both the dune crest height and sediment volume increased between 2013 and 2019. This set of factors favored the establishment and expansion of mangroves (3.2 ha) and saltmarshes (25.4 ha) along the backbarrier environments after 2013, allowing the tidal flats to keep pace with the RSL rise. However, waves and currents caused shoreline erosion following the beach nourishment project between Oct/2017 and Nov/2019, threatening wetlands by resuming the long-term process of shoreline retreat.

Modeling Crossing Random Seas by Fully Non-Linear Numerical Simulations

Bimodal spectrum wave conditions, known as crossing seas, can produce extreme waves which are hostile to humans during oceanic activities. This study reports some new findings of the probability of extreme waves in deep crossing random seas in response to the variation of spectral bandwidth through fully non-linear numerical simulations. Two issues are addressed, namely (i) the impacts of the spectral bandwidth on the changes of extreme wave statistics, i.e., the kurtosis and crest exceedance probability, and (ii) the suitability of theoretical distribution models for accurately describing the wave crest height exceedance probability in crossing seas. The numerical results obtained by simulating a large number of crossing sea conditions on large spatial-temporal scale with a variety of spectral bandwidth indicate that the kurtosis and crest height exceedance probability will be enhanced when the bandwidth of each wave train becomes narrower, suggesting a higher probability of encountering extreme waves in narrowband crossing seas. Meanwhile, a novel empirical formula is suggested to predict the kurtosis in crossing seas provided the bandwidth is known in advance. In addition, the Rayleigh and second-order Tayfun distribution underestimate the crest height exceedance probability, while the third-order Tayfun distribution only yields satisfactory predictions for cases with relatively broader bandwidth regarding the wave conditions considered in this study. For crossing seas with narrower bandwidth, all the theoretical distribution models failed to accurately describe the crest height exceedance probability of extreme waves.

Various experimental wave statistics emerging from a single energy spectrum

&lt;p&gt;As it strongly impacts the design of offshore structures, the accurate control of experimental wave fields is of great interest for the ocean engineering community. A significant majority of sea keeping tests are based on the stochastic approach. Long duration runs of irregular design sea states are generated at model scale in numerical or experimental wavetanks. The run duration is carefully chosen to observe the emergence of extreme events. The quality of the wavefield at the domain area of interest is assessed thanks to i) the wave energy spectrum and ii) the crest height distribution. The accurate reproduction of those two quantities stands a difficult process. Numerous complex phenomena such as wave breaking or Benjamin Feir (modulational) instabilities strongly impact the wave field. The shapes of i) the wave spectrum and ii) the tail of crest height distributions significantly evolve along the tank depending i) the wave steepness, ii) the spectral width, iii) the water depth and iv) the directional spreading (for directional sea states) [1, 2, 3].&lt;/p&gt;&lt;p&gt;The vast majority of the work in this area has focused on reproducing realistic wave energy spectra at the location of interest, assuming the indirect control of wave statistics. The present study intends to question such a characterization of a sea state. We address the problem within the framework of long crested irregular deep water waves generated in an experimental wave tank. In this respect, using the Ecole Centrale de Nantes (ECN) towing tank (140m*5m*3m), a narrow banded sea state has been generated at several locations of a long domain. The shape of the spectrum is accurately controlled thanks to a procedure based on wavemaker motion iterative correction [4]. For such nonlinear wave conditions the statistics along the wave propagation in the tank are known to be enhanced by significant spatial dynamics [1, 3]. As a result, configurations characterized by strictly identical wave spectra lead to the emergence of strongly different crest distributions. The data yielded by the study provide convincing evidence that the characterization of the wave field using the sole energy spectrum is insufficient. Particular attention must be given to the spatial dynamics of the wave field in order to control the wave statistics.&lt;/p&gt;&lt;p&gt;[1] Janssen, P. A. (2003). Nonlinear four-wave interactions and freak waves. &lt;em&gt;Journal of Physical Oceanography&lt;/em&gt;, &lt;em&gt;33&lt;/em&gt;(4), 863-884.&lt;/p&gt;&lt;p&gt;[2] Shemer, L., Sergeeva, A., &amp; Liberzon, D. (2010). Effect of the initial spectrum on the spatial evolution of statistics of unidirectional nonlinear random waves. &lt;em&gt;Journal of Geophysical Research: Oceans&lt;/em&gt;, &lt;em&gt;115&lt;/em&gt;(C12).&lt;/p&gt;&lt;p&gt;[3] Onorato, M., Cavaleri, L., Fouques, S., Gramstad, O., Janssen, P. A., Monbaliu, J., ... &amp; Trulsen, K. (2009). Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin.&lt;/p&gt;&lt;p&gt;[4] Canard, M., Ducrozet, G., &amp; Bouscasse, B. (2020, August). Generation of 3-hr Long-Crested Waves of Extreme Sea States With HOS-NWT Solver. In &lt;em&gt;International Conference on Offshore Mechanics and Arctic Engineering&lt;/em&gt; (Vol. 84386, p. V06BT06A064). American Society of Mechanical Engineers.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Afsluitdijk climate resilient with XblocPlus

<p>The Afsluitdijk forms 32 km of the primary sea defence of the Netherlands. The Afsluitdijk was built as a closure dam in 1932 and separates the IJsselmeer from the Wadden-Sea and North Sea. Because of climate change the Afsluitdijk needs to be strengthened. A higher crest height is required to limit overtopping at higher water levels due to sea level rise. Heavier armour is required to protect the Afsluitdijk from higher wave heights. Because of the historic value of the Afsluitdijk, stringent architectural requirements are in place on the visual appearance of the dam after strengthening [1]. Therefore, a new concrete armour unit was developed to provide protection of the seaward side of the Afsluitdijk. This armour unit is called XblocPlus. The development of the armour unit is based on the breakwater armour unit Xbloc which has been applied since 2004. A saving of 56% on CO2 footprint was achieved compared to the Clients reference design.</p>

Wave Run-Up on Mortar-Grouted Riprap Revetments

The wave run-up height is a crucial design parameter that determines the crest height of a sea dike and is used for estimating the number of overtopping waves. Therefore, a reduction of the wave run-up height is generally aspired in the design of dikes, which can be achieved by mortar-grouted riprap revetments (MGRR). Although MGRRs are widely utilized revetments along the German North Sea coast, no investigations into the wave run-up height on this revetment type are available to date. Full-scale hydraulic model tests were hence conducted to investigate wave run-up heights on partially grouted and fully grouted MGRRs. The wave run-up was determined using 2D-LIDAR measurements, which were validated by video data. Partially grouted MGRRs, due to their roughness, porosity, and permeability, reduce wave run-up heights from 21% to 28%, and fully grouted MGRRs due to their roughness reduce wave run-up heights from 12% to 14% compared to smooth impermeable revetments. Influence factors have been determined for four widely used revetment configurations, which can now be used for design purposes. A comparison and subsequent discussion about the representation of the physics of wave run-up by different parameters is carried out with the results presented.

An Experimental Study of the Systematic Underestimation of Wave Crests Measured by Lagrangian Buoys, and a Retrospective Correction Method

&lt;p&gt;Wave-following buoys are used to provide measurements of free surface elevation across the oceans. The measurements they produce are widely used to derive wave-averaged parameters such as significant wave height and peak period, alongside wave-by-wave statistics such as crest height distributions. Particularly concerning the measurement of extreme wave crests, these measurements are often perceived to be less accurate. We directly assess this through a side-by-side laboratory comparison of measurements made using Eulerian wave gauges and model wave-following buoys for directionally spread waves representative of extreme conditions on deep water. Our experimental measurements are compared to exact (Herbers and Janssen 2016, J. Phys. Oceanogr, 46, 1009-1021) and new approximate expression for Lagrangian second-order theory derived herein. We derive simple closed-form expressions for the second-order contribution to crest height representative of extreme ocean waves. Our experiments confirm that the motion a wave-following buoy should not significantly affect the measurements of wave crests or spectral parameters, and that discrepancies observed for in-situ buoy data are most likely a result of filtering. This filtering occurs when accelerations that are measured by the sensors within a buoy are converted to displacements. We present an approximate means of correcting the resulting measured crest height distributions, which is shown to be effective using our experimental data.&lt;/p&gt;