Interval Travel Times Research Articles

Interval travel times for robust synchronization in city logistics vehicle routing

We propose a consistent information flow to integrate Interval Travel Times (ITT) into a city logistics vehicle routing problem with satellites. The consistent information flow encompasses the derivation of ITT, the usage of ITT in robust shortest path computation and the integration of ITT into robust vehicle routing. Based on the results of the information flow, robust meeting times of first-tier and second-tier vehicles are created. We evaluate the approach with large real-world traffic data sets. We observe that the integration of ITT leads to first-tier routes that are reasonably efficient and robust.

Female pelvic shape: time to dispel the myth of Caldwell and Moloy classification

In this paper, we propose a city logistics vehicle routing problem in which goods are delivered from a major terminal to several satellite locations. Travel times in the planning area are uncertain. The objective is to find suitable a-priori tours that are both cost-efficient and reliable. Therefore, Interval Travel Times (ITT) and a suitable criterion for efficiency and reliability are considered within vehicle routing. The resulting delivery tours are evaluated within a case study for the city of Stuttgart. Computational experiments show that integrating ITT into the routing leads to an improved efficiency and reliability of the planned tours.

Babies born with ambiguous genitalia: exploring the midwife's role in supporting families at birth

In this paper, we propose a city logistics vehicle routing problem in which goods are delivered from a major terminal to several satellite locations. Travel times in the planning area are uncertain. The objective is to find suitable a-priori tours that are both cost-efficient and reliable. Therefore, Interval Travel Times (ITT) and a suitable criterion for efficiency and reliability are considered within vehicle routing. The resulting delivery tours are evaluated within a case study for the city of Stuttgart. Computational experiments show that integrating ITT into the routing leads to an improved efficiency and reliability of the planned tours.

Cost-Efficient and Reliable City Logistics Vehicle Routing with Satellite Locations under Travel Time Uncertainty

Abstract In this paper, we propose a city logistics vehicle routing problem in which goods are delivered from a major terminal to several satellite locations. Travel times in the planning area are uncertain. The objective is to find suitable a-priori tours that are both cost-efficient and reliable. Therefore, Interval Travel Times (ITT) and a suitable criterion for efficiency and reliability are considered within vehicle routing. The resulting delivery tours are evaluated within a case study for the city of Stuttgart. Computational experiments show that integrating ITT into the routing leads to an improved efficiency and reliability of the planned tours.

Evaluation of Alternative Paths for Reliable Routing in City Logistics

Abstract Due to varying traffic volumes and limited traffic infrastructure in urban areas, travel times are uncertain and differ during the day. In this environment, city logistics service providers (CLSP) have to fulfill deliveries in a cost-efficient and reliable manner. To ensure cost-efficient routing while satisfying promised delivery dates, information on the expected travel times between customers needs to be considered appropriately. Typically, vehicle routing is based on information from shortest paths between customers, to determine the cost-minimal sequence of customer visits. This information is usually precomputed using shortest path algorithms. Most approaches merely consider a single (shortest) path, based on a single cost value (e.g., distance or average travel time). To incorporate information on travel time variation, it might be of value to consider alternative paths and more sophisticated travel time models such as Interval Travel Times (ITT). In this work, we investigate the incorporation of alternative paths into city logistics vehicle routing. For this purpose, we compare our approach to classical shortest path approaches within a vehicle routing problem. Our approach considers a set of alternative paths and incorporates ITT. Experiments are conducted within an exemplary city logistics setting. Computational results show that the consideration of alternative paths allows to select better paths with regard to a trade-off between efficiency and reliability when travel times are varying.

Interval Travel Times for More Reliable Routing in City Logistics

Due to varying traffic volumes and limited traffic infrastructure in urban areas, travel times generally are uncertain and differ during the day. In this environment, city logistics service providers (CLSP) have to fulfill deliveries cost-efficiently and reliably. To ensure cost-efficient routing while satisfying promised delivery dates, information on expected travel times between customers needs to be exploited. If a sufficient amount of data is not available or expensive to acquire, deriving this information presents a major challenge for CLSP. Therefore, we propose the usage of interval travel times (ITT) to enable cost-efficient and reliable routing in urban areas. ITT define an expected range of travel times, which can be derived with relatively low effort by CLSP. We modify an existing approach from the domain of robust planning to the requirements of routing in urban areas. Further, we present and discuss the process of deriving ITT. An exemplary city logistics setting is developed and different routing solutions are examined. Computational experiments show that, in contrast to well-known deterministic approaches, routing considering ITT allows both cost-efficient and reliable routing.

Exploiting Travel Time Information for Reliable Routing in City Logistics

Due to varying traffic volumes and limited traffic infrastructure in urban areas, travel times generally are uncertain and differ during the day. In this environment, city logistics service providers (CLSP) have to fulfill deliveries cost-efficient and reliable. To ensure cost-efficient routing while satisfying promised delivery dates, information on expected travel times between customers needs to be exploited.If sufficient amount of data is not available or expensive to acquire, deriving this information presents a major challenge for CLSP. Therefore, we propose the usage of interval travel times (ITT) to enable cost-efficient and reliable routing in urban areas. ITT define an expected range of travel times, which can be derived with relatively low effort by CLSP. We present and discuss the process of deriving ITT. Further, we investigate an existing approach from the domain of robust planning within the scope of rout- ing in urban areas. An exemplary city logistics setting is developed and different routing solutions are examined. Computational experiments show that, in contrast to well-known deterministic approaches, routing considering ITT allows both, cost-efficient and reliable routing.

Shallow vertical seismic profiling experiments with a surface impact source and a cemented 3-C geophone string; Perth Basin, Western Australia.

Analysis of first arrivals recorded by a total of 24 cemented geophone from a surface source provides insight into the propagation of acoustic waves. A set of surface to hole experiments have been carried out to measure variations of transit times, frequency content and amplitudes of the downgoing (transmitted) compressional waves. The geology of the test site is tightly constrained by wire-line and geological logs from more than 20 close spaced drill holes. One experiment consisted of 274 repeat blows from a surface impact source 25 m away from a vertical string of 3-C geophones cemented in a drill hole. The geophones spanned a depth range from 74 to 284 m. A detailed comparison of total travel time and interval travel times demonstrate a surprisingly high level of repeatability across 274 repeated shots at the same position. Experiments with repeat radially symmetric source positions located around the cemented 3-C geophone string were also carried out. These experiments indicated that even a slight change in source location or condition can significantly change the shape of the waveform generated at the surface. This was likely the result on slight variations at the source ground interface.

Estimation of interval anisotropy parameters using velocity-independent layer stripping

Moveout analysis of long-spread P-wave data is widely used to estimate the key time-processing parameter [Formula: see text] in layered transversely isotropic media with a vertical symmetry axis (VTI). Inversion for interval [Formula: see text] values, however, suffers from instability caused by the trade-off between the effective moveout parameters and by subsequent error amplification during Dix-type layer stripping. We propose an alternative approach to nonhyperbolic moveout inversion based on the velocity-independent layer-stripping (VILS) method of Dewangan and Tsvankin. Also, we develop the 3D version of VILS and apply it to interval parameter estimation in orthorhombic media using wide-azimuth, long-spread data. If the overburden is laterally homogeneous and has a horizontal symmetry plane, VILS produces the exact interval traveltime-offset function in the target layer without knowledgeof the velocity field. Hence, Dix-type differentiation of moveout parameters used in existing techniques is replaced by the much more stable layer stripping of reflection traveltimes. The interval traveltimes are then inverted for the moveout parameters using the single-layer nonhyperbolic moveout equation. The superior accuracy and stability of the algorithm are illustrated on ray-traced synthetic data for typical VTI and orthorhombic models. Even small correlated noise in reflection traveltimes causes substantial distortions in the interval [Formula: see text] values computed by conventional Dix-type differentiation. In contrast, the output of VILS is insensitive to mild correlated traveltime errors. The algorithm is also tested on wide-azimuth P-wave reflection data recorded above a fractured reservoir at Rulison field in Colorado. The interval moveout parameters estimated by VILS in the shale layer above the reservoir are more plausible and less influenced by noise than those obtained by the Dix-type method.

Velocity-independent layer stripping of PP and PS reflection traveltimes

Building accurate interval velocity models is critically important for seismic imaging and AVO (amplitude variation with offset) analysis. Here, we adapt the [Formula: see text] method to develop an exact technique for constructing the interval traveltime-offset function in a target zone beneath a horizontally layered overburden. All layers in the model can be anisotropic, with an essential assumption that the overburden has a horizontal symmetry plane (i.e., up-down symmetry). Our layer-stripping algorithm is entirely data-driven and, in contrast to the generalized Dix equations, does not require knowledge of the velocity field anywhere in the medium. Important advantages of our approach compared to the Dix-style formalism also include the ability to handle mode-converted waves, long-offset data, and laterally heterogeneous target layers with multiple, curved reflectors. Numerical tests confirm the high accuracy of the algorithm in computing the interval traveltimes of both PP- and PS-waves in a dipping, transversely isotropic layer with a tilted symmetry axis (TTI medium) beneath an anisotropic overburden. In combination with the inversion techniques developed for homogeneous TTI models, the proposed layer stripping of PP and PS data can be used to estimate the interval parameters of TTI formations in such important exploration areas as the Canadian Foothills. Potential applications of this methodology also include the dip-moveout inversion for the P-wave time-processing parameter [Formula: see text] and stable computation of the interval long-spread (nonhyperbolic) moveout for purposes of anisotropic velocity analysis.

Method and apparatus for determining the magnitude of components of measurements made from inside a borehole

First Page

The Interpretation of Seismic Reflection Data from the Western Platform Region of Taranaki Basin

The western-most region of Taranaki Basin, the Western Platform, has a stratigraphy which permits subdivision into major seismic units. The reflectors separating these units are easily identifiable. Each of the units and reflectors has typical reflection characteristics which are often correlatable with the lithology of the unit. Lateral velocity variations, caused by lateral deposition and compaction variations in prograding sequences, area major problem in developing depth conversion models for this region. Analysis of travel time data from wells shows that velocity variations in both the Oligocene-Miocene and Pliocene-Pleistocene sequences are predictable from the thickness variations of the units (and hence from interval travel times). The imerval velocity variations of the Paleocene-Eocene transgressive sequence are dependent on the overburden history and lithology of the unit.