Multiple Time Windows Research Articles

A metaheuristic based on a pool of routes for the vehicle routing problem with multiple trips and time windows

This paper studies the vehicle routing problem with multiple trips and time windows, in which vehicles are allowed to perform multiple trips during a scheduling period and each customer must be served within a given time interval. The problem is of particular importance for planning fleets of hired vehicles in common practices, such as e-grocery distributions, but this problem has received little attention in the literature. As a result of the multi-layered structure characteristic of the problem solution, we propose a pool-based metaheuristic in which various routes are first constructed to fill a pool, following which some of the routes are selected and combined to form vehicle working schedules. Finally, we conduct a series of experiments over a set of benchmark instances to evaluate and demonstrate the effectiveness of the proposed metaheuristic.

Magnetocardiac signal analysis based on multiple time windows beamformer method

A beamformer method based on multiple time windows is proposed to estimate the equivalent current sources of different strength and duration from multi-channel magnetocardiography data. This technique of visualizing cardiac electric activities will be a great help to the diagnosis of relevant heart diseases. Feasibility of this beamformer method has been proved by simulation experiments of two known sources. Source estimation results and two-dimensional excitation propagation diagrams of a complete left bundle branch block and a complete right bundle branch block patients during QRS complex are taken to be compared. The revealed characteristics of their electrophysiological phenomena are analyzed.

Two-step Solving Algorithm for Hazmat Transportation Routing and Dispatch Problem

This paper focus on the multi-objective routing and dispatch problem for a given hazardous materials shipment with multiple time windows and time varying attributes. Section 1 consists of background and purpose of the research. Section 2 proposes a mathematical model for this problem by introducing the punishing functions to convert time windows into penalty variables of model. Section 3 develops a two-step solving algorithm for model, of which the first step is to identify the non-dominated paths with specific dispatch time based on the improved dynamic programming method, and the second step is to choose the optimal alternatives from non-dominated paths by the application of the grey correlation analysis method. Section 4 carries out a case study to test the methodology proposed in the paper. The results show that the model and the two-step algorithm can effectively solve road hazardous materials transportation routing and dispatch problem.

Hybrid estimation of distribution algorithm for a multiple trips fixed fleet vehicle routing problems with time windows

In this paper, we consider a variant of vehicle routing problem with multiple trip and time windows. In this alternative problem, we think about the scheduling of trucks to a number of customers in the presence of fixed fleet and time windows constraints. This type of problem can be described as determining a number of vehicle trips minimising total travelled distance complying with the time windows and the multiple use of vehicles. We call this problem a multiple trips fixed fleet vehicle routing problems with time windows (MTFFVRPTW). To solve this variant, a new hybrid evolutionary algorithm for transport optimisation problems, called estimation of distribution algorithm with local search is used. The proposed algorithm integrates a double structure of distribution technique, which is used to introduce the variables dependency. To evaluate our approach we provide a number of experimentation to a modified Solomon's instances for the case of multiple trips. The results show that the hybrid proposed algorithm offer a good quality solution in the term of objective functions, also in the running time.

진원 깊이를 고려한 한반도 다중지연시간창 해석

The recent Multiple Lapse Time Window (MLTW) analysis of Korean Peninsula event showed that the focal depth was far greater influence factor than the velocity structure of the model, applying the analysis of the direct simulation Monte Carlo (DSMC) method. Thus, using the events with focal depth of about 10 km, this study considered 330 paths connecting 41 events and 71 stations, and re-examined uniform and depth-dependent velocity models previously studied. As a result, the residual of misfit function greatly decrease from analytic model to DSMC model, reflecting variation of the focal depth from 0 to 10 km. On the other hand, the difference of residuals for each velocity model were relatively small.

Extraction and analysis of multiple time window features associated with muscle fatigue conditions using sEMG signals

In this work, an attempt has been made to differentiate surface electromyography (sEMG) signals under muscle fatigue and non-fatigue conditions with multiple time window (MTW) features. sEMG signals are recorded from biceps brachii muscles of 50 volunteers. Eleven MTW features are extracted from the acquired signals using four window functions, namely rectangular windows, Hamming windows, trapezoidal windows, and Slepian windows. Prominent features are selected using genetic algorithm and information gain based ranking. Four different classification algorithms, namely naïve Bayes, support vector machines, k-nearest neighbour, and linear discriminant analysis, are used for the study. Classifier performances with the MTW features are compared with the currently used time- and frequency-domain features. The results show a reduction in mean and median frequencies of the signals under fatigue. Mean and variance of the features differ by an order of magnitude between the two cases considered. The number of features is reduced by 45% with the genetic algorithm and 36% with information gain based ranking. The k-nearest neighbour algorithm is found to be the most accurate in classifying the features, with a maximum accuracy of 93% with the features selected using information gain ranking.

The attenuation mechanism of S-waves in the source zone of the 1999 Chamoli earthquake

In the present study the attenuation mechanism of seismic wave energy in and around the source area of the Chamoli earthquake of 29th March 1999 is estimated using the aftershock data. Most of the analyzed events are from the vicinity of the Main Central Thrust (MCT), which is a well-defined tectonic discontinuity in the Himalayas. Separation of intrinsic (Qi-1) and scattering (Qs-1) attenuation coefficient is done over the frequencies 1, 2, 4, 8 and 16Hz using Multiple Lapse Time Window Analysis (MLTWA) method. It is observed that S-waves and their coda are primarily attenuated due to scattering attenuation and seismic albedo is very high at all the frequencies. A comparison of attenuation characteristics obtained using these aftershock data with those obtained using data of general seismicity of this region reveal that at lower frequencies both intrinsic and scattering attenuation for Chamoli was much higher compared to those for Garwhal-Kumaun region using general seismicity data. At higher frequencies intrinsic attenuation for Chamoli is lower than and scattering attenuation is comparable to those obtained using general seismicity data of Garwhal-Kumaun region.

A tabu search approach to the truck scheduling problem with multiple docks and time windows

While organizing the cross-docking operations, cross-dock managers are confronted with many decision problems. One of these problems is the truck scheduling problem. This paper presents a truck scheduling problem that is concerned with both inbound and outbound trucks at multiple dock doors. The objective is to minimize the total travel time and the total tardiness. The truck scheduling problem under study is described in detail and a mathematical model of the problem is provided which can be solved to optimality with a mixed integer programming solver, at the expense of a high computation time. Next, a tabu search approach is presented. Experimental results on new benchmark instances indicate that the proposed tabu search is able to find good quality results in a short time period, thus offering potential for integration in cross-docking decision support systems.

Separation of intrinsic and scattering seismic wave attenuation in Northeast India

SUMMARY We have analysed the local earthquakes (2.0 ≤ ML ≤ 5.5) occurred in northeast (NE) India recorded by a temporary seismic network of 10 stations operated by National Geophysical Research Institute (NGRI), Hyderabad to evaluate the relative contributions of scattering loss (Q −1 ) and intrinsic absorption (Q −1 ) to total attenuation (Q −1 ) using the multiple lapse time window analysis assuming multiple isotropic scattering in a medium of uniformly distributed scatterers. The results show that Q −1 is greater than Q −1 at high frequencies (f > 3Hz), while the opposite is observed at low frequencies (f < 3Hz). The observed frequency dependence of Q −1 corresponds to the scale length of lithospheric heterogeneity beneath NE India, at least comparable with the wavelength for the lowest frequencies analysed, of about 1km. The observed Q −1 for the study region obtained with single scattering theory is close to Q −1 at high frequencies, in agreement with theoretical prediction for an idealized case of uniform distribution of scatterers. However, a discrepancy exists between the two at low frequencies, which can be explained by a depth-dependent velocity and attenuation structure. High value of Q −1 is correlated with the geology and tectonic settings of the region characterized by Himalayan and Burman collision zones with a strong lateral heterogeneity. The Q −1 estimates obtained in this study can be used to infer the average temperature of the lower crust with an upper limit estimate of ∼800 ◦ C assuming a lower crustal gabbroic lithology.

A hybrid variable neighborhood tabu search heuristic for the vehicle routing problem with multiple time windows

This paper presents a new hybrid variable neighborhood-tabu search heuristic for the Vehicle Routing Problem with Multiple Time windows. It also proposes a minimum backward time slack algorithm applicable to a multiple time windows environment. This algorithm records the minimum waiting time and the minimum delay during route generation and adjusts the arrival and departure times backward. The implementation of the proposed heuristic is compared to an ant colony heuristic on benchmark instances involving multiple time windows. Computational results on newly generated instances are provided.

Attenuation of seismic waves in Central Egypt

Attenuation of seismic waves in central Egypt had never been studied before. The results of the research on the seismic attenuation are based upon the information collected by the seismological network from 1998 to 2011. 855 earthquakes were selected from the Egyptian seismological catalog, with their epicenter distances between 15 and 150km, their magnitudes ranging from 2 and 4.1 and focal depths reaching up to 30km. The first systematic study of attenuation derived from the P-, S- and coda wave in the frequency range 1–24Hz is presented. In the interpretation of the results both single and multiple scattering in a half space are considered. The single scattering model proposed by Sato (1977) was used. Two methods, the coda (Qc) and the Multiple Lapse Time Window (MLTW) method are used. The aim of this study is to validate these interpretations in the region and to try to identify the effects of attenuation due to intrinsic (Qi) and scattering attenuation (Qsc). The mean Qc value calculated was Qc=(39±1)f1.0±0.009. The average Qc at 1.5Hz is (53±6) and Qc=(900±195) at 24Hz with Qo ranging between 23 and 107, where η ranging between 0.9 and 1.3. The quality factor (Q) was estimated from spectra of P- and S-waves by applying a spectral ratio technique. The results show variations in Qp and QS as a function of frequency, according to the power law Q=56η1.1. The seismic albedo is 0.7 at all stations and it mean that the earthquake activity is due to tectonic origin. The attenuation and frequency dependency for different paths and the correlation of the results with the geotectonic of the region are presented. The Qc values were calculated and correlated with the geology and tectonics of the area. The relatively low Qo and the high frequency dependency agree with the values of a region characterized by a low tectonic activity and vise versa.

Model and Algorithm for Routing and Scheduling Problem in Hazardous Materials Transportation Network

To reduce the risks associated with hazardous materials transportation by optimizing routes and delivery schedules, a multiobjective routing and scheduling program with multiple time windows and time varying attributes in hazardous materials transportation network is studied. First, a mathematical model for this program is proposed and two punishing functions are introduced to the model for converting multiple time windows into the penalty variables of model. Second, a two-step solving algorithm for model is developed, and the first step of algorithm is to find the set of non-dominated paths with specific departure time from the origin based on the improved dynamic programming method, the second step is to identify the optimal alternatives from the non-dominated set by using the grey correlation analysis method. Finally, a case study is given to show that the model and algorithm can effectively solve the routing and scheduling program in hazmat transportation network, and can identify the optimal transportation paths for the decision maker.

A new VRPPD model and a hybrid heuristic solution approach for e-tailing

We analyze a business model for e-supermarkets to enable multi-product sourcing capacity through co-opetition (collaborative competition). The logistics aspect of our approach is to design and execute a network system where “premium” goods are acquired from vendors at multiple locations in the supply network and delivered to customers. Our specific goals are to: (i) investigate the role of premium product offerings in creating critical mass and profit; (ii) develop a model for the multiple-pickup single-delivery vehicle routing problem in the presence of multiple vendors; and (iii) propose a hybrid solution approach. To solve the problem introduced in this paper, we develop a hybrid metaheuristic approach that uses a Genetic Algorithm for vendor selection and allocation, and a modified savings algorithm for the capacitated VRP with multiple pickup, single delivery and time windows (CVRPMPDTW). The proposed Genetic Algorithm guides the search for optimal vendor pickup location decisions, and for each generated solution in the genetic population, a corresponding CVRPMPDTW is solved using the savings algorithm. We validate our solution approach against published VRPTW solutions and also test our algorithm with Solomon instances modified for CVRPMPDTW.

Envelope Inversion Analysis for High-Frequency Seismic Energy Radiation from the 2011 Mw 9.0 Off the Pacific Coast of Tohoku Earthquake

Abstract I study S ‐wave energy radiation in higher frequencies of 1–8 Hz from the 2011 M w 9.0 Off the Pacific Coast of Tohoku, Japan, earthquake (hereafter called the Tohoku‐Oki earthquake) based on a seismogram envelope inversion method. I first evaluate two medium parameters of scattering attenuation and intrinsic absorption for S waves using spatial and temporal distributions of seismic energy from aftershock records, which are necessary for calculating Green’s functions. Next, applying the envelope inversion method to 27 near‐field strong‐motion records from the mainshock, I estimate the S ‐wave energy radiation from 40 subfaults on the fault of 500 km×250 km. Each subfault is allowed to rupture for eight consecutive source time windows. Rupture velocity and the duration of energy radiation for each time window are determined by a grid search to be 2.5 km/s and 8.0 s, respectively. Energy radiated from the entire fault is 5.8×10 16 J for 1–2 Hz, 4.5×10 16 J for 2–4 Hz, 1.5×10 16 J for 4–8 Hz, and totaling 1.2×10 17 J in the 1–8 Hz range. Strong energy emanated twice from greater depths of the off‐Miyagi region, corresponding to two peaks seen at the northern stations. And energy radiation at greater depths off the Fukushima–Ibaraki border is compatible with a single peak found at the southern stations. Strong high‐frequency radiations at greater depths strikingly contrast with large slips at shallower depths estimated in lower frequencies. This frequency‐dependent rupture may accord with structural changes along the dip direction. Online material: Snapshots of high‐frequency energy radiation from the fault plane and results of estimating scattering parameters by the multiple lapse time window analysis in 1–2 and 2–4 Hz.

Time and Space Distribution of Coseismic Slip of the 2011 Tohoku Earthquake as Inferred from Tsunami Waveform Data

A multiple time window inversion of 53 high‐sampling tsunami waveforms on ocean‐bottom pressure, Global Positioning System, coastal wave, and tide gauges shows a temporal and spatial slip distribution during the 2011 Tohoku earthquake. The fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface. A very large slip (approximately 25 m) in the deep part off Miyagi at a location similar to the previous 869 Jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the Sendai and Ishinomaki plains. A huge slip, up to 69 m, occurred in the shallow part near the trench axis 3 min after the rupture initiation. This delayed shallow rupture extended for 400 km with more than a 10‐m slip, at a location similar to the 1896 Sanriku tsunami earthquake, and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern Sanriku coast, 100 km north of the largest slip. The average slip on the entire fault was 9.5 m, and the total seismic moment was 4.2×1022 N·m ( M w 9.0). The large horizontal displacement of seafloor slope was responsible for 20%–40% of tsunami amplitudes. The 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits, indicating that the 869 Jogan earthquake source could be similar to the 2011 earthquake, at least in the deep‐plate interface. The large tsunami at the Fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip, which was not accounted for in the previous tsunami‐hazard assessments. Online Material: Table of estimated slip for all subfaults at 0.5 min invervals.

The Multiconstraint Team Orienteering Problem with Multiple Time Windows

This paper introduces the multiconstraint team orienteering problem with multiple time windows (MC-TOP-MTW). In the MC-TOP-MTW, a set of vertices is given, each with a service time, one or more time windows, and a score. The goal is to maximize the sum of the collected scores, by a fixed number of tours. The tours are limited in length and restricted by the time windows and additional constraints. Next to a mathematical formulation of the MC-TOP-MTW, the main contribution of this paper is a fast and effective algorithm for tackling this problem, by hybridizing iterated local search with a greedy randomized adaptive search procedure. On a large test set, an average run has a score gap of only 5.19% with known high quality solutions, using 1.5 seconds of computational time. For 32% of the test instances, the known high quality solution was found or improved. This solution method also performs well on test instances of the TOPTW, the selective vehicle routing problem with time windows, and the MC-TOP-TW. A sensitivity analysis shows that the performance of the algorithm is insensitive to small changes in the parameter settings.

Mixed Integer Formulations for a Short Sea Fuel Oil Distribution Problem

We consider a short sea fuel oil distribution problem occurring in the archipelago at Cape Verde. Here, an oil company is responsible for the routing and scheduling of ships between the islands such that the demand for various fuel oil products is satisfied during the planning horizon. Inventory management considerations are taken into account at the demand side but not at the supply side. The ports have restricted opening hours each day, so multiple time windows are considered. In contrast to the ships in many other studies within ship routing and scheduling, ships here spend considerable time in the ports compared to at sea. Hence, the time in port is modeled in detail by incorporating both a variable (un)loading time and a setup time for loading different products in the same ports. A mathematical model of the problem is presented and it includes a combined continuous and discrete time horizon because of the multiple time windows and a daily varying consumption rate of the various products in the different ports. We discuss several strategies to improve the proposed model, such as tightening bounds, using extended formulations, and including valid inequalities. The computational study shows that the real problem can be solved to optimality within reasonable time by the use of improved formulations based on a combination of such strategies.

Exploring prenatal outdoor air pollution, birth outcomes and neonatal health care utilization in a nationally representative sample.

The impact of air pollution on fetal growth remains controversial, in part, because studies have been limited to sub-regions of the United States with limited variability. No study has examined air pollution impacts on neonatal health care utilization. We performed descriptive, univariate and multivariable analyses on administrative hospital record data from 222,359 births in the 2000, 2003 and 2006 Kids Inpatient Database linked to air pollution data drawn from the US Environmental Protection Agency's Aerometric Information Retrieval System. In this study, air pollution exposure during the birth month was estimated based on birth hospital address. Although air pollutants were not individually associated with mean birth weight, a three-pollutant model controlling for hospital characteristics, demographics, and birth month identified 9.3% and 7.2% increases in odds of low birth weight and very low birth weight for each μg/m(3) increase in PM(2.5) (both P<0.0001). PM(2.5) and NO(2) were associated with -3.0% odds/p.p.m. and +2.5% odds/p.p.b. of preterm birth, respectively (both P<0.0001). A four-pollutant multivariable model indicated a 0.05 days/p.p.m. NO(2) decrease in length of the birth hospitalization (P=0.0061) and a 0.13 days increase/p.p.m. CO (P=0.0416). A $1166 increase in per child costs was estimated for the birth hospitalization per p.p.m. CO (P=0.0002) and $964 per unit increase in O(3) (P=0.0448). A reduction from the 75th to the 25th percentile in the highest CO quartile for births predicts annual savings of $134.7 million in direct health care costs. In a national, predominantly urban, sample, air pollutant exposures during the month of birth are associated with increased low birth weight and neonatal health care utilization. Further study of this database, with enhanced control for confounding, improved exposure assessment, examination of exposures across multiple time windows in pregnancy, and in the entire national sample, is supported by these initial investigations.

Addendum to “Heuristics for the multi-period orienteering problem with multiple time windows”

This is an addendum to the paper by Tricoire et al. on various orienteering problems [1]. We present experimental results on the orienteering problem with time windows (OPTW) and team orienteering problem with time windows (TOPTW) test instances introduced by Montemanni et al. [2].

A rich vehicle routing problem dealing with perishable food: a case study

This paper presents a successful application of operations research techniques in guiding the decision making process to achieve a superior operational efficiency in core activities. We focus on a rich vehicle routing problem faced by a Portuguese food distribution company on a daily basis. This problem can be described as a heterogeneous fleet site dependent vehicle routing problem with multiple time windows. We use the adaptative large neighbourhood search framework, which has proven to be effective to solve a variety of different vehicle routing problems. Our plans are compared against those of the company and the impact that the proposed decision support tool may have in terms of cost savings is shown. The algorithm converges quickly giving the planner considerably more time to focus on value-added tasks, rather than manually correct the routing schedule. Moreover, contrarily to the necessary adaptation time of the planner, the tool is quite flexible in following market changes, such as the introduction of new customers or new products.