Changes In Arrival Time Research Articles

Shared e-scooters: A last-minute mode?

In this paper we assess whether shared e-scooters are being used in hurried situations to avoid arriving late, making trips we define as last-minute trips. We identify trip characteristics for last-minute trips using data from shared e-scooters in Stockholm. Trip arrival time patterns, distances, durations, and speeds are analyzed in relation to desired arrival times. We observe a peak in the number of trips ending before the full hour and a smaller peak of trips ending before the half hour of weekday mornings. These trips have lower average trip durations and higher average speeds, indicating a larger share of last-minute trips. Arrival patterns shift when the assumed preferred arrival time changes, and when the risk associated with arriving late increases. Furthermore, there is an increased share of trips that started close to public transportation around the full hour, indicating that a portion of last-minute trips may also be last-mile trips. Our results show that while last-minute trips are infrequent per user, they do make up a relatively large share of weekday morning trips. These results highlight an important market segment for shared e-scooter services and may also explain why some research reports e-scooter usage replacing walking.

Controlling Aircraft Inter-Arrival Time to Reduce Arrival Traffic Delay via a Queue-Based Integer Programming Approach

Despite the importance of controlling the inter-arrival times of flights to propose strategies for efficient arrival management by the Arrival Manager (AMAN), the specific guidelines of such adjustments and their effect on reducing delays have not been explicitly considered. Accordingly, this paper proposes a novel approach, which integrates the Gt/GI/st+GI time-varying fluid model and nonlinear integer programming to flatten the arrival rate at terminal gates. This, in turn, is achieved by minimizing the variance in inter-arrival times by penalizing any excessive change in arrival time, considering operational constraints. The results for Tokyo International Airport show potential to significantly reduce arrival traffic delays by minimizing said variance. This study may also spawn subsequent work, which builds a queuing network comprising upstream and terminal airspace and demonstrates the scope to reduce delays in the terminal airspace by controlling inter-arrival times at the upstream airspace.

Supply chain visibility for improving inbound logistics: a design science approach

ABSTRACT Supply chain visibility (SCV) has been gaining recognition in recent years as a key factor for achieving analytical capabilities and improving supply chain performance. However, levels of SCV implementation lag behind current technological advances. This research was motivated by the lack of visibility in inbound logistics, which limits the possibility of managing deviation, in particular concerning changes in arrival time of incoming goods, in large industrial firms. We addressed this problem by adopting a design science approach. In particular, we followed context–intervention–mechanism–outcome (CIMO) logic to map and analyse material and information flows. The problems areas were successively translated via business and functional requirements into technological solutions. We evaluated alternative technologies using controlled experiments that mimicked real-life situations. This study provides guidance for manufacturing companies aiming to enhance deviation management and predictive capabilities by improving visibility in their inbound logistics and potentially extending visibility to other areas, such as internal and outbound flows.

Characterization of membrane wetting phenomenon by ionic liquid via ultrasonic time-domain reflectometry (UTDR)

Ionic liquids (ILs) are becoming attractive solvents or catalysts in many industries, thus energy-efficient membrane-based technologies for the purification and concentration of ILs are gaining attention. Membrane wetting by ILs is recognised as the major challenge in membrane processes, but limited information is available. In this study, the dynamics of wetting of commercial hydrophobic polytetrafluoroethylene (PTFE) membranes by a water-immiscible IL, trihexyl(tetradecyl)phosphonium (THTDP), was characterized by an online and non-destructive technique – ultrasonic time-domain reflectometry (UTDR). In the UTDR analysis, information such as resistance of membrane to IL penetration, duration and rate of wetting process can be deduced from the changes in arrival time and amplitude of reflected peak from the IL/pore-air interface, i.e., pores in pristine hydrophobic membrane are completely-filled with air until IL penetration that displaces the pore-air. The UTDR analysis was further supported by offline and destructive methods typically used to characterize membrane such as Fourier-transform infrared spectroscopy (FTIR), contact angle (CA), liquid entry pressure (LEP) and field emission scanning electron microscopy (FESEM). Through the abovementioned analyses, it was concluded that the commercial hydrophobic PTFE membranes exhibited poor anti-wetting properties against concentrated THTDP IL due to chemical affinity between IL and membrane.

Characterizing fluid flow paths in the Hellisheidi geothermal field using detailed fault mapping and stress-dependent permeability

The Husmuli zone of the SW-Iceland Hellisheidi geothermal field is currently being used for re-injection of geothermal fluids and geothermal CO2 for its permanent storage in the form of carbonate minerals. A fully coupled hydro-thermo-mechanical numerical model was employed to investigate the coupled impacts of these complex processes on the calibration of fluid flow paths, which can have significant implications for the long-term performance of this subsurface reservoir.Employing a combination of high-resolution fault mapping with laboratory measurements of stress dependent permeability coupled into a dual porosity field-scale model, the flow paths were calibrated using results of tracer tests performed at the site using stress-dependent permeability tensors. Although vertically extended faults are the primary fluid flow paths, fractures connecting the faults can play an important role in fluid transport. As the upward flow streamlines manifest, deep geological layers can also deviate the fluid flow towards the shallower layers provoking the vertical flow of geothermal fluids. This highlights the sweet spot for sustainable flow and heat extraction in vicinity of faults intercepting the geological layers at depth of 1100 m.It was also shown that the inclusion of the geomechanical calculations in the history matching of the tracer test could lead to changes in arrival time and peak of the tracer profiles. Results of an independent tracer test were used to validate the model and to demonstrate the predictive capability of the calibrated model. This verifies the consistency of our methodology to incorporate the stress-dependent permeability. The results of this comprehensive modelling study provide insight into the likely fluid flow paths, which can have profound impact on the evaluation of various processes such as CO2 mineralisation taking place in Hellisheidi geothermal reservoir.

HADES: A Multi-Agent Platform to Reduce Congestion Anchoring Based on Temporal Coordination of Vessel Arrivals—Application to the Multi-Client Liquid Bulk Terminal in the Port of Cartagena (Spain)

Ports are key factors in international trade, and new port terminals are quite costly and time consuming to build. Therefore, it is necessary to optimize existing infrastructure to achieve sustainability in logistics. This problem is more complex in multi-client port terminals, where quay infrastructure is shared among terminal operators who often have conflicting interests. Moreover, the berth allocation problem in liquid bulk terminals implies demanding restrictions due to the reduced flexibility in berth allocation for these types of goods. In this context, this paper presents HADES, a multi-agent platform, and the experience of its pilot use in the Port of Cartagena. HADES is a software platform where agents involved in vessel arrivals share meaningful but limited information. This is done to alleviate potential congestion in multi-client liquid bulk terminals, promoting a consensus where overall congestion anchoring is reduced. A study is presented using a mixed integer linear program (MILP) optimization model to analyze the maximum theoretical reduction in congestion anchoring, depending on the flexibility of vessel arrival time changes. Results show that 6 h of flexibility is enough to reduce congestion anchoring by half, and 24 h reduces it to negligible values. This confirms the utility of HADES, which is also briefly described.

The EXOTIME project: signals in the O–C diagrams of the rapidly pulsating subdwarfs DW Lyn, V1636 Ori, QQ Vir, and V541 Hya

Aims. We aim to investigate variations in the arrival time of coherent stellar pulsations due to the light-travel time effect to test for the presence of sub-stellar companions. Those companions are the key to one possible formation scenario of apparently single sub-dwarf B stars. Methods. We made use of an extensive set of ground-based observations of the four large amplitude p-mode pulsators DW Lyn, V1636 Ori, QQ Vir, and V541 Hya. Observations of the TESS space telescope are available on two of the targets. The timing method compares the phase of sinusoidal fits to the full multi-epoch light curves with phases from the fit of a number of subsets of the original time series. Results. Observations of the TESS mission do not sample the pulsations well enough to be useful due to the (currently) fixed two-minute cadence. From the ground-based observations, we infer evolutionary parameters from the arrival times. The residual signals show many statistically significant periodic signals, but no clear evidence for changes in arrival time induced by sub-stellar companions. The signals can be explained partly by mode beating effects. We derive upper limits on companion masses set by the observational campaign.

Quantitative evaluation of the delamination length in mechanical lap joints of high-temperature superconducting tapes using Lamb waves

A mechanical lap joint is a critical part connecting rare-earth barium copper oxide (REBCO) tapes. Until now, the delamination in joints, which causes severe heating, has not been efficiently evaluated at room temperature. This paper presents Lamb wave method to measure the delamination length in lap joints. The dispersion curves of Lamb waves in REBCO tapes and joints are calculated, and their characteristics indicate the reflected wave is more suitable for testing because of the consistency through a broadband of frequencies. Finite element simulation results show the change in arrival time of the reflected wave is larger than the transmitted wave. In the experiments, an ultrasonic probe is used to test the joints from both sides. The delamination lengths in three samples are determined by the arrival time of the reflected wave, and they are consistent with the results obtained by X-ray microtomography with a maximum difference of 2.0 mm.

Temporal changes of seismic velocities in the San Jacinto Fault zone associated with the 2016Mw 5.2 Borrego Springs earthquake

SUMMARYWe study temporal changes of seismic velocities associated with the 10 June 2016 Mw 5.2 Borrego Springs earthquake in the San Jacinto fault zone, using nine component Green's function estimates reconstructed from daily cross correlations of ambient noise. The analysed data are recorded by stations in two dense linear arrays, at Dry Wash (DW) and Jackass Flat (JF), crossing the fault surface trace ∼3 km northwest and southeast of the event epicentre. The two arrays have 9 and 12 stations each with instrument spacing of 25–100 m. Relative velocity changes (δv/v) are estimated from arrival time changes in the daily correlation coda waveforms compared to a reference stack. The obtained array-average δv/v time-series exhibit changes associated with the Borrego Springs event, superposed with seasonal variations. The earthquake-related changes are characterized by a rapid coseismic velocity drop followed by a gradual recovery. This is consistently observed at both arrays using time- and frequency-domain δv/v analyses with data from different components in various frequency bands. Larger changes at lower frequencies imply that the variations are not limited to the near surface material. A decreasing coseismic velocity reduction with coda wave lapse time indicates larger coseismic structural perturbations in the fault zone and near-fault environment compared to the surrounding rock. Observed larger changes at the DW array compared to the JF array possibly reflect the northwestward rupture directivity of the Borrego Springs earthquake.

Simulation and optimisation study of the integration of distributed generation and electric vehicles in smart residential district

This paper presents an optimisation methodology for simulating the integration of distributed generation and electric vehicles (EVs) in a residential district. A model of a smart residential district is proposed. Different charging scenarios (CS) for private cars are considered for simulating different power demand distributions during the day. Four different case studies are investigated, namely the Base Case, in which no EVs are present in the district and three study cases with different CSs. A global optimisation method based on a genetic algorithm approach was applied on the model to find the total power from PV panels installed and co-generative micro gas turbines while minimising the annual energy cost in the district for the four different scenarios. In conclusion, the results showed that the use of EVs in the district introduces considerable savings with respect to the Base Case. Moreover, the impact of the chosen CS is nearly insignificant under a purely economic perspective even if it is relevant for grid management. Additionally, the optimum amounts of installed power vary in a limited range if the distance travelled by EVs, users’ departure and arrival time change broadly.

Streamline-Based Transport Tomography With Distributed Water Arrival Times

Summary Traditional history matching involves calibration of reservoir models by use of well response such as production or tracer data aggregated during multiple producing intervals. With the advent of novel tracer technologies, we now can obtain distributed water or tracer arrival-time information along the length of horizontal or vertical wellbores. This provides significantly improved flow resolution for detailed reservoir characterization through inversion of distributed water or tracer arrival times in a manner analogous to travel tomography in geophysics. In this paper, we present an efficient approach to incorporate novel tracer-surveillance data and distributed water arrival-time information during history matching of high-resolution reservoir models. Our approach relies on a streamline-based work flow that analytically computes the sensitivity of water-arrival times with respect to reservoir heterogeneity, specifically porosity and permeability variations. The sensitivities relate the changes in arrival time to small perturbations in reservoir properties and can be obtained efficiently with the streamline-based approach with a single flow simulation. This makes the approach particularly well-suited for high-resolution reservoir characterization. Finally, the sensitivities are used in conjunction with an iterative inversion algorithm to update the reservoir models with existing and proven techniques from seismic tomography. The power and utility of our proposed approach are demonstrated with both synthetic and field examples. These include the SPE benchmark Brugge field case and an offshore field in North America. Compared with traditional history-matching techniques, the proposed tomographic approach is shown to result in improved resolution of heterogeneity through matching of water-arrival time at individual completions in addition to the aggregated well-production response. This results in improved performance predictions and better identification of bypassed oil for infill targeting and enhanced-oil-recovery (EOR) applications.

Characterizing the nonlinear interaction of S- and P-waves in a rock sample

The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility of using the nonlinear characterization of rocks as an imaging tool in the field. In our experiment, we study the nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a high-amplitude 50 kHz S-wave pump in a room-dry 15 × 15 × 3 cm slab of Berea sandstone. Changes in the arrival time of the P-wave probe as it passes through the perturbation created by the traveling S-wave pump were recorded. Waveforms were time gated to simulate a semi-infinite medium. The shear wave phase relative to the P-wave probe signal was varied with resultant changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. In order to estimate the strain in our sample, we also measured the particle velocity at the sample surface to scale a finite difference linear elastic simulation to estimate the complex strain field in the sample, on the order of 10−6, induced by the S-wave pump. We derived a fourth order elastic model to relate the changes in elasticity to the pump strain components. We recover quadratic and cubic nonlinear parameters: β̃=−872 and δ̃=−1.1×1010, respectively, at room-temperature and when particle motions of the pump and probe waves are aligned. Temperature fluctuations are correlated to changes in the recovered values of β̃ and δ̃, and we find that the nonlinear parameter changes when the particle motions are orthogonal. No evidence of slow dynamics was seen in our measurements. The same experimental configuration, when applied to Lucite and aluminum, produced no measurable nonlinear effects. In summary, a method of selectively determining the local nonlinear characteristics of rock quantitatively has been demonstrated using traveling sound waves.

Characterizing the nonlinear interaction of S (shear) and P (longitudinal) waves in reservoir rocks

The nonlinear elastic response of rocks is known to be caused by internal microstructure, particularly cracks and fluids. In order to quantify this nonlinearity, this paper presents a method for characterizing the interaction of two nonresonant traveling waves: a low-amplitude P-wave probe and a high-amplitude lower frequency S-wave pump with their particle motions aligned. We measure changes in the arrival time of the P-wave probe as it passes through the perturbation created by a traveling S-wave pump in a sample of room-dry Berea sandstone (15 × 15 × 3 cm). The velocity measurements are made at times too short for the shear wave to reflect back from the bottom of the sample and interfere with the measurement. The S-wave pump induces strains of 0.3—2.2 × 10−6, and we observe changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. By changing the relative time delay between the probe and pump signals, we record the measured changes in travel time of the P-wave probe to recover the nonlinear parameters β~ −102 and δ ~−109 at room-temperature. This work significantly broadens the applicability of dynamic acousto-elastic testing by utilizing both S and P traveling waves.

Changes observed in Ao mode due to rotational misalignment of air-coupled transducers in isotropic plates

Misalignments are a major concern, when air-coupled ultrasonic probes are deployed for transmission and reception of Lamb waves. Misalignments between the air-coupled probes result in reduction in amplitude and change in arrival time of the Lamb waves. This reduction in amplitude can give a false alarm in Non-destructive Testing (NDT) applications, if amplitude is the criterion for flaw or damage detection. In the present work, one of the probe’s (transmitter or receiver) position was kept fixed, and the other probe was rotated to introduce a misalignment termed ‘rotational misalignment’. This rotation had violated the co-planarity condition, resulting in reduction in amplitude of the received fundamental anti-symmetric mode (Ao) in an isotropic material plate. Interestingly, variation in amplitude of the Ao mode with the rotational misalignment angle revealed that, at certain angular locations, there exists a local maximum and local minimum resembling sync function. Subsequently, the angular location of occurrence of these is attributed to dispersion characteristics of the Ao mode.

Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations

ABSTRACTIn this paper, we examine the influence of a velocity model and microseismic source frequency on microseismic waveforms and event locations. Finite‐difference waveform synthetics are generated based on the Cotton Valley hydraulic fracture experiment, where we vary the vertical heterogeneity of the velocity models as well as the microseismic source frequencies. We find that differences between plausible velocity models lead to changes in arrival times of approximately 0.0035 seconds for P‐waves and 0.0085 seconds for S‐waves. Based on the average P‐ and S‐wave velocities, the difference in the P‐ and S‐wave traveltimes is equivalent to approximately 20 m in location difference. Significant increases in the waveform coda develop with increasing model heterogeneity and increasing source frequency. The presence of signal noise as well as other sources of error (e.g., uncertainty in geophone location) will likely lead to further increase in uncertainty in location error estimates. Thus we note that location error due to incorrect velocity models cannot be ignored.

Ray path of head waves with irregular interfaces

Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity. However, the path that the rays travel along in media with irregular interfaces is not clear. Here we study the problem by simulation using a new approach of the spectral-element method with some overlapped elements (SEMO) that can accurately evaluate waves traveling along an irregular interface. Consequently, the head waves are separated from interface waves by a time window. Thus, their energy and arrival time changes can be analyzed independently. These analyses demonstrate that, contrary to the case for head waves propagating along a flat interface, there are two mechanisms for head waves traveling along an irregular interface: a refraction mechanism and transmission mechanism. That is, the head waves may be refracted waves propagating along the interface or transmitted waves induced by the waves propagating in the higher-velocity media. Such knowledge will be helpful in constructing a more accurate inversion method, such as head wave travel-time tomography, and in obtaining a more accurate model of subsurface structure which is very important for understanding the formation mechanism of some special areas, such as the Tibetan Plateau.

The Optimal Toll Schemes to Container Ships Queuing at the Anchorage

This paper develops the optimal non-queuing toll and optimal step toll schemes to container ships in a queue for multiple berths at a busy port. Container ships' queuing times at the anchorage will be decreased to half of the total queuing time after pricing the optimal step toll scheme. Furthermore, container ships' arrival time change decisions from the non-toll to the optimal step toll cases can be predicted before tolling a busy port. The above outcomes are helpful if the pricing policy to a queue of container ships at the anchorage is considered by the port authorities.

Measuring arterial and tissue responses to functional challenges using arterial spin labeling

The measurement of cerebral blood flow (CBF) in functional MRI studies that aim for non-invasive, quantitative and reliable measurements is a challenge. Here, we tested the feasibility of a recently developed, model-free CBF technique to study vascular dynamics upon functional challenges. Multiple inversion time-point signals were measured from arterial and tissue compartments, allowing for the calculation of CBF through a process of deconvolution. Using graded visual stimulation known to produce increasing hemodynamic responses, we recorded significant and graded ΔCBF and Δτm (microvascular arrival time change) that were highly comparable to those estimated by a standard 3-parameter fit based on the general kinetic model, though the absolute values had weaker agreement. Estimated arterial blood volumes (excluding substantial arteriolar contribution) did not show significant change with visual stimulation. Bolus arrival times in the microvascular compartment shortened more as compared to the arrival times from the arterial compartment during visual stimulation, suggesting larger involvement of the microvasculature in local neuronal response. While there are limitations, the model-free analysis method has the potential to offer useful vascular information in fMRI studies.

Sex-differentiated migration patterns, protandry and phenology in North European songbird populations

This study aims to investigate causes and mechanisms controlling protandrous migration patterns (the earlier breeding area arrival of males relative to females) and inter-sexual differences in timing of migration in relation to the recent climate-driven changes in phenology. Using standardised ringing data from a single site for eight North European migratory passerines collected throughout 22 years, we analysed sex-differentiated migration patterns, protandry and phenology of the entire populations. Our results show protandrous patterns for the first as well as later arriving individuals for all studied species. Males show more synchronous migration patterns compared to females and, hence, first arriving females followed males more closely than later arriving individuals. However, we found no inter-sexual differences in arrival trends as both sexes advance spring arrival over time with the largest change for the first arriving individuals. These findings seem in support of the “mate opportunity” hypothesis, as the arrival of males and females is strongly coupled and both sexes seem to compete for early arrival. Changes in timing of arrival in males and females as a response to climatic changes may influence subsequent mating decisions, with subsequent feedbacks on population dynamics such as reproductive success and individual fitness. However, during decades of consistent earlier spring arrival in all phases of migration we found no evidence of inter-sexual phenological differences.

Ultrasound Transmission Loss Across Transverse and Oblique Bone Fractures: An In Vitro Study

An axial transmission technique has been used to investigate the changes in the first arrival time and signal amplitude of 200 kHz ultrasonic waves travelling across different fracture geometries. Results taken from intact bovine femora were compared with those produced when a transverse and an oblique fracture were simulated. The arrival time and signal amplitude displayed a different variation with receiver position for the two geometries and a given fracture gap width. A comparison between this work and a previous study suggested that the marrow does not play a significant role in the mechanisms causing the change in arrival time and signal amplitude. Numerical modelling revealed that an oblique fracture caused a reduction in the extra time delay of the propagating wave compared with the transverse case, but a decrease in the corresponding signal amplitude, i.e., greater signal loss. The angle of the oblique fracture was investigated and results suggested that decreasing the fracture angle relative to the wave propagation direction caused a decrease in the extra time delay and an increase in signal loss. These findings are important for determining the sensitivity of systems for monitoring fracture healing using ultrasound arrival time and signal amplitude. (E-mail: spd@inorbit.com)