Solving the vehicle routing problem with drone for delivery services using an ant colony optimization algorithm

E-commerce and logistics companies are facing important challenges to satisfy the rapid growth of customer demands. Unmanned aerial vehicles such as drones are an emerging technology that are very useful to cope with rising customer expectations of fast, flexible, and reliable delivery services. Drones work in tandem with trucks to perform parcel delivery, which have proven to reduce costs, CO2 emissions, and delivery times. This research proposes a mixed integer programming formulation to address the Vehicle Routing Problem with Drone (VRPD) by assigning customers to drone-truck pairs, determining the number of dispatching drone-truck units, and obtaining optimal service routes while the fixed and travel costs of both vehicles are minimized. Given the NP-hard nature of the VRPD, an ant colony optimization (ACO) algorithm is elaborated to solve this problem. Two novel methods are proposed to investigate the efficiency of the drone-truck combination by allowing the drones to perform additional delivery services to only one feasible customer and also multiple feasible customers while the truck waits at a customer location. Experimental results show that the proposed ACO algorithm can effectively solve the VRDP for different size instances and different customer location distributions, and is successful in providing timely solutions for small test instances within 1% of the optimal solutions. Finally, experimentation also reveals that the ACO algorithm outperforms the classical VRP by obtaining cost-savings of over 30% for large instances.     

On the Scheduling of Conflictual Deliveries in a last-mile delivery scenario with truck-carried drones

In this paper, we investigate the symbiosis between a truck and multiple drones in a last-mile package delivery scenario, introducing the Scheduling Conflictual Deliveries Problem (SCDP). From the main depot, a truck takes care of transporting a fleet of drones that will be used to deliver packages to customers. The route of the truck is predefined. Each delivery is associated with the energy cost of a drone, a reward that characterizes the priority of the delivery, and an interval between two points of the truck’s route: the point from which the drone departs (launch point) and the point at which the drone returns to the truck (rendezvous point). The objective of the SCDP is to find a scheduling for the drones that maximizes the overall reward subject to the drone’s battery capacity while ensuring that the same drone performs deliveries whose delivery intervals do not intersect. After showing that SCDP is an NP-hard problem, we devise an Integer Linear Programming (ILP) formulation for it. Furthermore, we devise a pseudo-polynomial time optimal algorithm for the single drone case and additional approximation algorithms for both the single and multiple drones case. Finally, we thoroughly compare the performances of our presented algorithms on different synthetic datasets.     

A comprehensive theoretical evaluation of the end-to-end performance of SoftCast-based linear video delivery schemes

SoftCast-based linear video delivery (LVD) schemes have been proposed as an alternative to traditional video transmission schemes in wireless error-prone environments. The end-to-end performance of SoftCast-based schemes have been evaluated in Xiong et al. (2016), where a theoretical model based on the Peak Signal-to-Noise Ratio (PSNR) metric has been proposed. The latter is limited to the use of a Zero-Forcing (ZF) estimator at the receiver side, and does not consider bandwidth restrictions. Nevertheless, bandwidth restrictions are common and necessary in practice, especially when considering the transmission of video content. It is mandatory to take this aspect into consideration as it may drastically influence the received video quality. In this paper, we provide valid and significant extensions of the initial model. In total, three models are introduced taking into account both (1) bandwidth constraints (i.e., data compression applied), (2) the use of a Linear Least Square Error (LLSE) estimator instead of the ZF one as well as (3) the use of the optimal power allocation. We show that regardless of the bandwidth reduction applied, the type of estimator as well as the power allocation used, the end-to-end video quality can be accurately modeled and predicted at the transmitter according to the video content characteristics, the type of estimator used at the receiver and the channel conditions. The validity of these three models is assessed through extensive end-to-end simulations. These new models give solid theoretical guidelines for optimizing and studying the performance of linear video delivery schemes.     

Degradation and drug‐release studies of a poly(glycolide‐co‐trimethylene carbonate) copolymer (Maxon)

Poly(glycolide‐co‐trimethylene carbonate) is available commercially as a monofilament suture known as Maxon. The literature has shown that Maxon sutures possess a slow degradation rate of about 7 months and exhibit relatively high mechanical strength in comparison with other absorbable sutures. However, very few articles are available on the degradation of unoriented Maxon. This study was designed to explore the chemical and physical aspects of the degradation of unoriented Maxon and its potential as a drug‐release device. Several analytical techniques were used, including mass measurements, simultaneous small‐angle X‐ray scattering and wide‐angle X‐ray scattering, and thermoporometry. Magnetic resonance imaging and drug‐release measurements were carried out with UV spectroscopy. The results suggest that unoriented suture‐based Maxon undergoes multiple stages of hydrolytic degradation, which involve hydration, and active and postactive periods. The drug‐release mechanism is controlled by diffusion in the early degradation stages and polymer erosion in the later stages of release. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 475–486, 2005     

Stability of DL‐poly(lactic acid) in aqueous solutions

DL ‐poly(lactic acid) of molecular weight about 2500 was prepared by polycondensation of lactic acid and characterized by viscosimetry, infrared spectroscopy, light scattering, GPC, and NMR. Tablets made of the above polymer were immersed in buffer solutions at 37°C, and their swelling behavior was recorded as a function of time, in terms of weight gain. In the same experiments, the hydrolytic stability of PLA was assessed by measuring the weight loss after drying the tablets. To inhibit any degradation due to bacteria, formaldehyde was added to the solution as a biostatic factor. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 795–804, 2003     

Distribution coefficients and diffusivities in three polymers for nineteen aqueous nonvolatile solutes

Experimental results at 25°C are reported for infinite‐dilution distribution coefficients for 19 nonvolatile solutes between aqueous solution and three kinds of polymer films, and for their diffusion coefficients in the polymer matrix. The experiments were performed by coupling UV spectroscopy and gravimetric measurements with mass balances. The solutes are aromatic nonvolatile compounds that are of interest in environmental technology and may serve as model compounds for drug‐delivery systems. The polymers are ethylene‐vinyl acetate copolymers with 33 (EVAc33) and 45 (EVAc45) weight percentage vinyl acetate, and poly(vinyl acetate) (PVAc) widely used in drug‐delivery devices. For PVAc, a long time is required to reach equilibrium. Because the required time is too long for reasonable experimental studies, equilibrium distribution coefficients were calculated from finite‐time data by using a diffusion model. The contribution of surface adsorption is shown to be negligible. Infinite‐dilution distribution coefficients K_s, defined as the volume fraction of solute in the polymer divided by that in water, tend to increase with vinyl acetate content; they range from near unity to several hundred. Diffusion coefficients, determined from time‐dependent sorption data, are significantly larger in EVAc copolymers (10^?10 to 10^?8 cm²/s) than in PVAc (10^?12 cm²/s). These data may be useful for design of membrane processes, for controlled delivery of drugs, and for application in packaging and storage of food, chemicals, and pharmaceuticals. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2041–2052, 2002     

Chitosan and chitosan/β‐cyclodextrin microspheres as sustained‐release drug carriers

The main aim of this study was to compare two microspheres, chitosan (CTS) and CTS/β‐cyclodextrin (β‐CD), made by spray‐drying, as pulmonary sustained drug‐delivery carriers. Theophylline (TH) was used as a model drug. The characteristics of the microspheres and in vitro release were studied. The yield of CTS/β‐CD microspheres was 46.1%, which was higher than that of the CTS microspheres (36.5%). The drug loads of the CTS and CTS/β‐CD microspheres were 22.7 and 21.1%, respectively, whereas the encapsulation efficiencies were 90.7 and 91.4%, respectively. The distribution of 50% [(diameter) d (0.5)] of the CTS microspheres was below 6.49 μm and that of the CTS/β‐CD microspheres was below 4.90 μm. Scanning electron microscopy showed that both microspheres yielded a spherical shape with smooth or wrinkled surfaces. Fourier transform infrared spectroscopy demonstrated that the carbonyl group of TH formed hydrogen bonds with the amide group of CTS and the hydroxyl group of β‐CD. The swelling ability of the two microspheres was more than three times their weight, and their humidity rates attained equilibrium within 24 h. The ciliary beat movement times of CTS and CTS/β‐CD microspheres were 493.00 and 512.33 min, respectively, which indicated that the two microspheres effectively reduced the ciliotoxicity and possessed better adaptability. In vitro release of TH from CTS/β‐CD microspheres was slower than that from CTS microspheres at pH 6.8 and provided a sustained release of 72.0% within 12 h. The results suggest that CTS/β‐CD microspheres are a promising carrier for sustained release for pulmonary delivery. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1183–1190, 2007     

Synthesis and properties of degradable hydrogels of konjac glucomannan grafted acrylic acid for colon-specific drug delivery

In this paper, we reported the synthesis and properties of novel hydrogel systems designed for colon targeted drug delivery. The gels were composed of konjac glucomannan (KGM), copolymerized with acrylic acid (AA) and cross-linked by N,N-methylene-bis-(acrylamide) (MBAAm). The influence of various parameters on the equilibrium swelling ratios of the hydrogels was investigated. The swelling ratio was inversely proportional to the content of MBAAm. It was possible to modulate the degree of swelling of the gels by changing cross-linking density of the polymer. The gels' swelling ratio has sensitive respondence to the environmental pH value variation. The results of degradation test show that the hydrogels retain the enzymatic degradation character of KGM and they can be degraded for 52.5% in 5 days by Cellulase E0240. In vitro release of model drug 5-aminosalicylic acid (5-ASA) was studied in the presence of Cellulase E0240 in pH 7.4 phosphate buffer at 37 °C. The accumulative release percent of 5-ASA reached 95.19% after 36 h and the drug release was controlled by the swelling and degradation of the hydrogels.     

Binding of chlorpheniramine maleate to pharmacologically important alginic acid,carboxymethylcellulose, κ‐carageenan,and ι‐carrageenan as studied by diafiltration

The binding of cationic chlorpheniramine maleate (CPM) to the anionic water‐soluble polymers (WSPs) alginic acid, carboxymethylcellulose, κ‐carageenan, and ι‐carageenan was evaluated by diafiltration at pH 7.5 and in the absence and presence of 0.13M NaCl. CPM interacted with all of the WSPs when no NaCl was present in the solution, with charge‐related formation constants of around 700 M^?1 for all of the polymers, whereas the interactions were cleaved in the presence of 0.13M NaCl, indicating interactions of an electrostatic nature screened by the single electrolyte. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 598–602, 2005     

Thermoreversible hydrogels. XIX. Synthesis and swelling behavior and drug release behavior for the N‐isopropylacrylamide/poly(ethylene glycol) methylether acrylate copolymeric hydrogels

A series of thermosensitive copolymeric hydrogels were prepared from various molar ratios of N‐isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methylether acrylate (PEGMEA_n), which was synthesized from acryloyl chloride and poly(ethylene glycol) mono methylether with three oxyethylene chain lengths. Investigation of the effect of the chain length of oxyethylene in PEGMEA_n, and the amount of the PEGMEA_n in the NIPAAm/PEGMEA_n copolymeric gels, on swelling behavior in deionized water was the main purpose of this study. Results showed that the swelling ratio for the present copolymeric gels increased with increasing chain length of oxyethylene in PEGMEA_n and also increased with increase in the amount of PEGMEA_n in the copolymeric gels. However, the gel strength and effective crosslinking density of these gels decreased with increase in swelling ratio. Some kinetic parameters were also evaluated in this study. Finally, the drug release and drug delivery behavior for these gels were also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1683–1691, 2003