Tidal Constraints Research Articles

Simulation Modeling of Super-Large Ships Traffic: Insights from Ningbo-Zhoushan Port for Coastal Port Management

With the expansion of coastal ports, the number of super-large berths is on the rise. It has become imperative to accurately assess the operational impact of these berths, optimize berth utilization, and minimize ship delays. In this study, a detailed simulation model of super-large ship arrivals and departures was developed, focusing on the Ningbo-Zhoushan Port. The model accounts for various special navigation constraints, including berthing and departure time windows, safety separations, tidal constraints, and interference from neighboring berths. The simulation results highlight a significant disparity in waiting times between arriving and departing ships, with daytime restrictions and berth time windows emerging as the primary factors influencing wait times. Consequently, several improvement measures are proposed. These include implementing priority rules based on time windows, establishing additional inner anchorages, and reducing safety separations. Among these, reducing safety separations offers the best cost-effectiveness due to its low application cost and effective results. Although these measures may lead to varying waiting times among berths, they collectively contribute to a substantial 25.6% reduction in overall waiting time. This study offers valuable insights and practical guidance for the planning, construction, and operation of super-large berths in coastal ports.

Retraction of: Self-consistent models of Earth's mantle and core from long-period seismic and tidal constraints

Retraction of: Self-consistent models of Earth's mantle and core from long-period seismic and tidal constraints

Retracted: Self-consistent models of Earth’s mantle and core from long-period seismic and tidal constraints

SUMMARYIn this study, we inverted a large set of normal-mode centre-frequencies and quality (attenuation) factors, including astronomic-geodetic data (mass, moment of inertia and tidal response), using self-consistently built models of the radial elastic and anelastic seismic structure of the Earth. The mantle models are constructed using petrologic phase equilibria in combination with a laboratory-based viscoelastic model that connects dissipation from seismic to tidal periods, whereas seismic properties for a well-mixed and homogeneous core are computed using equations-of-state. Relative to the preliminary seismic reference model (PREM), we find that for the models to fit the observations, mantle P- and S-wave velocities have to be slightly faster and slower, respectively, while outer-core P-wave velocity is slower on account of a different velocity gradient, whereas inner-core velocity structure is similar, within the uncertainties of the inferred model parameters. In terms of density, we find that the lower mantle is less dense and the outer core more dense than PREM, while the inner core is similar to PREM. To study the impact of the inferred mantle seismic velocity structure, we computed P- and S-wave traveltimes and compared these to the observations of globally-averaged P- and S-wave traveltimes from the reprocessed ISC catalogue that resulted in an excellent match. In an attempt to further refine the seismic P-wave velocity structure of the outer core, we also considered multiple core–mantle-boundary underside-reflected body wave traveltime data. Although the match to the underside reflections clearly improves as a result of a steeper velocity gradient in the outer core relative to the normal-modes- and astronomic-geodetic-data-only case, subtle differences nevertheless persist that appear to support a change in velocity gradient in the outermost core, evocative of a stably-stratified layer. The laboratory-based viscoelastic model considered here resolves the anelastic response of Earth’s mantle from long-period seismic (∼100 s) to tidal (18.6 yr) periods, accounting for both normal-mode and tidal dissipation measurements. Finally, as a potential means of refining core composition, we considered the density contrast across the inner-core boundary (ICB) based on our inverted models. The most probable ICB density difference found here is 0.3–0.45 g cm−3, which is in the lower range of earlier body-wave- and normal-mode-based predictions. This suggests that the compositional heterogeneity associated with light-element partitioning, which is considered the principal driving mechanism for the compositional convection that powers the geodynamo, may be less effective than previously thought, calling for exsolution of solids from the liquid outer core as a possible additional source of energy. This would also help address the problem of a young inner core.

Tidal Constraints on the Martian Interior

AbstractWe compare several recent Martian interior models and evaluate how these are impacted by the tidal constraints provided by the Love number k2 and the secular acceleration in longitude s of its main moon, Phobos. The expression of the latter is developed up to harmonic degree 5 to match the accuracy of the current observations. We match a number of current interior structure models to the recent measurements of the tidal parameters and derive estimations of the possible core radius, temperature profile, and attenuation in the Martian interior. Our estimation of the core radius is 1,820 ± 80 km, consistent with recent seismic measurements. The attenuation profiles in the Martian interior at the main tidal period of Phobos are similar between the considered models, giving a range for the degree‐2 bulk tidal attenuation Q2 = 93.0 ± 8.40 but diverge at seismic frequencies. At seismic frequencies, model shear attenuation Qμ ranges between 100 and 4,000 in the lower mantle, so that a measurement of seismic shear attenuation could be used as an effective means for distinguishing between the models considered. Other constraints such as elastic lithosphere thickness and Chandler Wobble period favor a thicker elastic lithosphere and models with a frequency dependence α of the shear attenuation between 0.15 and 0.4. Improved constraints on the Martian interior should be possible with additional seismic and radio observations from the InSight mission.

Tidal Constraints for Wide Binaries in Pleiades

Tidal Constraints for Wide Binaries in Pleiades

Traversable wormhole on the brane with non-exotic matter: a broader view

In this article, the possibility of construction of a traversable wormhole on the Randall–Sundrum braneworld with non-exotic matter employing the Kuchowicz potential has been studied. We have obtained the solution for the shape function of the wormhole and studied its properties along with validity of null energy condition. The junction conditions at the surface of the wormhole are used to evaluate the model parameters. We also evaluate the surface density and surface pressure for the wormhole. We study the geometrical nature of the wormhole and consider the radial and tangential tidal constraints on a traveller trying to traverse the wormhole. Besides, a linearized stability analysis is performed to obtain the region of stability for the wormhole. Our analysis, besides giving an estimate for the bulk equation of state (EoS) parameter, imposes restrictions on the brane tension, which is a very essential parameter in braneworld physics, and very interestingly the restrictions imposed by our physically plausible and traversable wormhole model are in conformity with those imposed by other braneworld geometries which are not associated with a wormhole solution. Besides, it is important to study such constraints imposed by geometrical objects such as wormholes on any gravity theory operating at high-energy scales like braneworld, as wormholes are believed to have been formed from massive compact objects of high energy densities. Also, we go on to justify that the possible detection of a wormhole may well indicate that we live on a three-brane universe.

Exact and heuristic methods for the berth allocation problem with multiple continuous quays in tidal bulk terminals

The Berth Allocation Problem (BAP) is a primary seaside operations planning problem in bulk terminals. It consists of allocating quayside space to incoming vessels. In this article, the BAP for multiple continuous quays and dynamic arrivals is considered. The formulation considers the tidal constraints typical to exporting bulk terminals and restrictions regarding each vessel's possible quays. To solve the problem, a mixed-integer linear model is first presented. As the complexity of the problem grows exponentially with the size of the instances, an Iterated Local Search (ILS) approach is proposed to solve industrial-sized instances. The ILS approach works on sequences of vessels that are decoded using a bottom-left constructive heuristic. The initial sequences are obtained using a greedy scheduling heuristic that provides suitable starting solutions, especially for congested terminals. Extensive numerical experiments are carried on randomly generated instances for tidal bulk terminals and reported benchmark sets in literature. The results prove that the proposed ILS can provide good-quality solutions.

Tidal constraints on the low-viscosity zone of the Moon

In this paper, the effect on the tidal response of the low-viscosity zone in the deep interior of the Moon is investigated based on hypothetical temperature profiles. The tidal parameters are computed numerically to demonstrate their dependence on the low-viscosity zone and frequency. One of the calculated parameters is the tidal quality factor, to which energy dissipation is inversely proportional. The other parameters are the tidal Love numbers, which are normalized magnitudes of displacement and potential perturbation of tidal deformation. Unlike earlier considerations, the viscosity structure of the low-viscosity zone is no longer assumed to be fully uniform but linked with several temperature profiles such as a thermal boundary layer model or a convective layer model. The calculations show that the latest observational ranges of the frequency-dependent quality factors can be satisfied only by the convective layer model with some viscosity value for the middle layer but not by the thermal boundary layer model for any structure. The approximate viscosity solution is estimated to be 3 × 1016 Pa s. If considering also the observational ranges of the Love numbers together with those of the quality factors, the solution of the outer radius of the low-viscosity zone is approximately either 560 or 580 km. These solutions are almost identical to those based on the previous model where the low-viscosity zone has uniform viscosity. It is concluded that the thermal state of the bottom layer of the lunar mantle is predicted to be mainly controlled by local convection, and possibly maintained by the energy balance between convective cooling and tidal heating, as previously suggested.

Mathematical model for quay crane assignment problem with tidal constraints

Objetive: The operations associated with loading and unloading of container ships demand the use of quay cranes that represent one of the most expensive resources of a maritime terminal. Therefore, the assignment of cranes to ships must be optimized. This article proposes a mathematical model to optimize the decision of assignment of cranes to ships, considering the behavior of tides, which is a not commonly considered factor in the scientific literature for similar problems. Metodology: A mixed integer linear mathematical model was designed and tested for the actual case of a container terminal in Buenaventura-Colombia with satisfactory results. Results: With the available capacity the model allows to mobilize up to 2800 containers per half day, while the number of containers per ship in the real case does not exceed 2000 units. Conclusions: The consideration of tides, combined with downtime penalty cost can allow using smaller number of cranes with savings in energy cost.

A reduced VNS based approach for the dynamic continuous berth allocation problem in bulk terminals with tidal constraints

This paper deals with the problem of allocating berth positions for vessels in export bulk port terminals considering tidal constraints and was first formulated by Ernst et al., (2017). This study investigates the dynamic and continuous berth allocation problem (BAP) with respect to tidal constraints (BAP_TC), and seeks to minimize the total service time of berthed vessels. Since the BAP problem is NP-hard the BAP_TC is also NP-hard. A reduced variable neighborhood search (RVNS) based approach is developed to solve the problem. For parameters tuning a machine learning algorithm is developed and used. Problem instances are benchmarked with CPLEX and the numerical experiments proved that the proposed algorithm is capable of generating high-quality solutions in rather short time. Both small and large-scale instances in the literature are tested to evaluate the metaheuristic effectiveness using other solution approaches from the literature. The computational experiment proves that the proposed algorithm provides state of the art results.

A simulation-based approach for assessing seaside infrastructure improvement measures for large marine crude oil terminals

We develop detailed simulation models for examining how various seaside infrastructure improvement measures of a marine crude oil terminal can increase its maximum oil throughput, reduce tanker delays, and minimize the total system cost over a certain planning horizon. The models account for special navigation constraints for oil tankers, realistic tidal constraints, and practical priority rules for different tanker types at the Rizhao Shihua Oil Terminal in China. Results show that the most cost-effective measure is adding a buffer to increase the one-way channel’s tanker-handling capacity. This novel, low-cost measure thus holds much promise for real-world implementation.

Resonance in the K2-19 system is at odds with its high reported eccentricities

ABSTRACT K2-19 hosts a planetary system composed of two outer planets, b and c, with size of 7.0 ± 0.2 R⊕ and 4.1 ± 0.2 R⊕, and an inner planet, d, with a radius of 1.11 ± 0.05 R⊕. A recent analysis of Transit-Timing Variations (TTVs) suggested b and c are close to but not in 3:2 mean motion resonance (MMR) because the classical resonant angles circulate. Such an architecture challenges our understanding of planet formation. Indeed, planet migration through the protoplanetary disc should lead to a capture into the MMR. Here, we show that the planets are in fact, locked into the 3:2 resonance despite circulation of the conventional resonant angles and aligned periapses. However, we show that such an orbital configuration cannot be maintained for more than a few hundred million years due to the tidal dissipation experienced by planet d. The tidal dissipation remains efficient because of a secular forcing of the innermost planet eccentricity by planets b and c. While the observations strongly rule out an orbital solution where the three planets are on close to circular orbits, it remains possible that a fourth planet is affecting the TTVs such that the four planet system is consistent with the tidal constraints.

Ship traffic capacity model for the largest port in Latin America

Santos is the largest port in Latin America. It handles nearly 97 Million tons per year (Mtpy) of cargo, visited by approximately 6000 vessels yearly. However, given the physical constraints of the canal, there is a disagreement regarding its capacity. In this paper, the capacity of Port of Santos and the access canal to the berth considering the current demand level, and its projection which may up to go over 15,000 vessels per year were evaluated. This evaluation was realized by the use of simulation taking into consideration the arrival, maneuver, berthing, loading/unloading, unberthing, and departure. We investigated two scenarios: (1) demand of 2011; (2) expansion from 2011 to 2032. The results of the simulation have shown that current average stay time is 71 h to 6000 ships per year. For the first scenario, it was verified that up to 8700 ships the observed impact in the average stay time was the increased to 75 h. The second scenario, when the current number of ships was increased to 12,480, the average time increases from 71 to 77 h in the ship stay. Finally, the canal capacity is 17,340 ships per year, but with a prohibitive stay time (about 602 h). All such figures indicate the high detail level reached in the model built, and at the same time how the generic concept applied in this study could be used to model another port which held similar characteristics as follows: 24 h operations, terminals widely spread along a canal, limitation no only on the depth of the canal (tidal constraints), but width constraints, limiting its capacity due crossing vessels in opposite directions (inbound/outbound).

Does elevation matter? Living foraminiferal distribution in a hyper tidal salt marsh (Canche Estuary, Northern France)

In the present study we investigate the ecology and distribution of living benthic foraminifera to test the effect of hyper tidal exposure and their suitability as sea level indicators. Within a salt marsh area along the Canche Estuary (northern France), four transects were sampled to see the effects of maximal tidal constraints (shore transects) and minimal tidal constraints (alongshore transects). Multivariate analyses have been performed to determine the correlations between biotic (foraminiferal absolute abundances) and abiotic factors (elevation, grain-size, TOC and total sulphur). For each of the principal benthic foraminiferal species the tolerance to subaerial exposure have been estimated as well. Two distinctive foraminiferal zones have been identified along the vertical tidal gradient: a zone I in the higher part of the salt marsh dominated by agglutinated and porcelaneous taxa, and a zone II in the lower one dominated by hyaline specimens. Hyper tidal exposure constraints the foraminiferal vertical zonation in accordance with the tidal frame. However it does not constitute a threshold parameter able by itself to explain all the faunal variations in the Canche Estuary. For sea level indicators, foraminifera should be considered relative to tidal subaerial exposure rather than to absolute altitude.

Tidal constraints on the interior of Venus

AbstractAs a prospective study for a future exploration of Venus, we compute the tidal response of Venus' interior assuming various mantle compositions and temperature profiles representative of different scenarios of Venus' formation and evolution. The mantle density and seismic velocities are modeled from thermodynamical equilibria of mantle minerals and used to predict the moment of inertia, Love numbers, and tide‐induced phase lag characterizing the signature of the internal structure in the gravity field. The viscoelasticity of the mantle is parameterized using an Andrade rheology. From the models considered here, the moment of inertia lies in the range of 0.327 to 0.342, corresponding to a core radius of 2900 to 3450 km. Viscoelasticity of the mantle strongly increases the potential Love number relative to previously published elastic models. Due to the anelasticity effects, we show that the possibility of a completely solid metal core inside Venus cannot be ruled out based on the available estimate of k2 from the Magellan mission (Konopliv and Yoder, 1996). A Love number k2 lower than 0.27 would indicate the presence of a fully solid iron core, while for larger values, solutions with an entirely or partially liquid core are possible. Precise determination of the Love numbers, k2 and h2, together with an estimate of the tidal phase lag, are required to determine the state and size of the core, as well as the composition and viscosity of the mantle.

Mathematical models for the berth allocation problem in dry bulk terminals

Port terminals processing large cargo vessels play an important role in bulk material supply chains. This paper addresses the question of how to allocate vessels to a location on a berth and the sequence in which the vessels should be processed in order to minimize delays. An important consideration in the berth allocation is the presence of tidal constraints that limit the departure of fully loaded vessels from the terminal. We show how the berth allocation problem can be modeled as an integer program and discuss a number of ways to tighten the formulation in order to make it computationally tractable. In addition, a two-phase method is developed for solving these problems. Empirical computational results demonstrate an order of magnitude improvement in performance. The two new approaches can solve significantly larger instances, producing faster solutions for small instances and much tighter bounds for large instances.

M2, overtides and compound tides generation in the Strait of Messina: the response of a non-hydrostatic, finite-element ocean model

ABSTRACT Quattrocchi, A.; Gorman, J.G., Piggott M.D. and Cucco, A., 2016. M2, overtides and compound tides generation in the Strait of Messina: the response of a non-hydrostatic, finite-element ocean model. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 657–661. Coconut Creek (Florida), ISSN 0749-0208. The nonlinear interactions between the main tidal constituents and geographical constraints are investigated using Fluidity-ICOM, a non-hydrostatic finite-element ocean model that was implemented in the region of the Strait of Messina (Mediterranean Sea). As a first crucial approach, the barotropic tidal dynamics was investigated and the model solution was interpreted in terms of tidal maps and spectra obtained by harmonic analysis of the sea surface elevation. The model domain is represented by an unstructured mesh with variable spatial resolution...

A Set-Partitioning-based model for the Berth Allocation Problem under Time-Dependent Limitations

This paper addresses the Berth Allocation Problem under Time-Dependent Limitations. Its goals are to allocate and schedule the available berthing positions for the container vessels arriving toward a maritime container terminal under water depth and tidal constraints. As we discuss, the only optimization model found in the literature does not guarantee the feasibility of the solutions reported in all the cases and is limited to a two-period planning horizon, i.e., one low tide and one high tide period. In this work, we propose an alternative mathematical formulation based upon the Generalized Set Partitioning Problem, which considers a multi-period planning horizon and includes constraints related to berth and vessel time windows. The performance of our optimization model is compared with that of the mathematical model reported in the related literature. In this regard, the computational experiments indicate that our model outperforms the previous one from the literature in several terms: (i) it guarantees the feasibility and optimality of the solutions reported in all the cases, (ii) reduces the computational times about 88 percent on average in the problem instances from the literature, and (iii) presents reasonable computational times in new large problem instances.

Behavioural observations of the common octopus Octopus vulgaris in Baía dos Tigres, southern Angola

Observations on the behaviour of the common octopus Octopus vulgaris were made during daytime and night-time sampling on an unexploited rocky reef habitat in Baía dos Tigres, southern Angola. The relative numerical abundance sampled was 0.47 octopus person–1 h–1 during the day and 5.33 octopus person–1 h–1 during the night, suggesting that the population under study was nocturnal. The activity patterns differed between sizes of octopus. Small octopus (<20 cm total length [TL]) were observed roaming during the night, whereas the large individuals (>20 cm TL) generally fed in their dens. This ontogenetic behavioural shift may be due to tidal constraints or could be a strategy to avoid cannibalism. Octopus inhabiting a shallow, small-boulder substratum made extensive modifications to their habitat, excavating dens of up to 1 m deep in the sand below the boulders. These dens were not visible during the day as the octopus appeared to retract the small boulders over their den entrances. This unique behavioural strategy is thought to be a means to reduce predation and reduce light intensity during the day. Octopus were not observed in the small-boulder habitat during the five hours of daytime sampling. With nocturnal activity and extensive habitat modification, it is likely that avoidance of predation may be an important driver influencing the behaviour of the octopus population under study.

Grazing dynamics in intertidal rockpools: Connectivity of microhabitats

Differences between rockpool and emergent rock communities are often attributed to their contrasting physical conditions. However, differences in grazing pressure between rockpools and open rock could also exert an important structuring role. Greater densities and/or the lack of tidal constraints on foraging may allow grazing intensity to be greater in rockpools. Here, wax discs were deployed to compare grazing intensity between rockpool and emergent rock habitats at each of three tidal heights on a moderately exposed shore in SW England. Grazing intensity was then examined in relation to herbivore density. Grazing intensity in pools was twice that on emergent rock, despite a lower density of herbivores in the rockpools. Of these herbivores, patellid limpets are the dominant grazers on rocky shores throughout the NE Atlantic and are recognised to have a major role in structuring intertidal communities. Thus, subsequent experiments focussed on the influence of limpets in determining the differences in consumer pressure between rockpools and emergent rock. Three alternative explanations were considered: (1) the effect of continuous immersion on grazing intensity in rockpools; (2) differences in limpet species abundance between the two habitats; (3) movement of limpets from emergent rock into pools to feed. The level of grazing pressure exerted by Patella ulyssiponensis (Gmelin), the predominant species living constantly immersed in rockpools, was similar to that of P. vulgata (Linnaeus) which is predominantly found on emergent rock. P. vulgata were observed moving from emergent rock into rockpools during high tide. Manipulative experiments confirmed that these foraging excursions resulted in a 2-fold increase in grazing intensity in the pools. Grazing activity of P. vulgata in rockpools was not consistent between sites and may be influenced by differences in wave exposure and/or the abundance of microbial resources. Elevated consumer pressure in rockpools may be an important factor influencing algal assemblages and probably explains the predominance of grazer resistant-species in these pools.