Load Splitting Research Articles

Large neighborhood-based metaheuristic and branch-and-price for the pickup and delivery problem with split loads

We consider the multi-vehicle one-to-one pickup and delivery problem with split loads, a NP-hard problem linked with a variety of applications for bulk product transportation, bike-sharing systems and inventory re-balancing. This problem is notoriously difficult due to the interaction of two challenging vehicle routing attributes, “pickups and deliveries” and “split deliveries”. This possibly leads to optimal solutions of a size that grows exponentially with the instance size, containing multiple visits per customer pair, even in the same route. To solve this problem, we propose an iterated local search metaheuristic as well as a branch-and-price algorithm. The core of the metaheuristic consists of a new large neighborhood search, which reduces the problem of finding the best insertion combination of a pickup and delivery pair into a route (with possible splits) to a resource-constrained shortest path and knapsack problem. Similarly, the branch-and-price algorithm uses sophisticated labeling techniques, route relaxations, pre-processing and branching rules for an efficient resolution. Our computational experiments on classical single-vehicle instances demonstrate the excellent performance of the metaheuristic, which produces new best known solutions for 92 out of 93 test instances, and outperforms all previous algorithms. Experimental results on new multi-vehicle instances with distance constraints are also reported. The branch-and-price algorithm produces optimal solutions for instances with up to 20 pickup-and-delivery pairs, and very accurate solutions are found by the metaheuristic.

需求可分割的同时送取货车辆路径问题求解

需求可分割的同时送取货车辆路径问题求解

Experimental Analysis of Process Parameters of Robot Onboard AGVS for Material Handling in Plant Layouts with and without Split Loads

Experimental Analysis of Process Parameters of Robot Onboard AGVS for Material Handling in Plant Layouts with and without Split Loads

Performance of Anchors in Concrete Controlled by Splitting Failure under Dynamic Push-In Loadings

Anchors in concrete are widely used to transfer any given load combination into a concrete member. The dynamic behavior of post-installed rebar anchors has been experimentally investigated in this study. The attention was focused on anchors controlled by concrete splitting failure, the case that may occur with anchors and fastenings located close to an edge or to a corner. In this regard, Split Hopkinson Pressure Bar (SHPB) technique has been employed to test the anchorage systems under dynamic push-in loads. The effect of loading rates, concrete compressive strengths, and embedment depths on ultimate splitting load has been studied. The results showed the loading rates had a pronounced effect on the anchor ultimate loads and total absorbed energy by the anchors. Whereas the variation of concrete compressive strength influenced the ultimate load, the increase in embedment depth had no noticeable effect on ultimate load.

Tower of London: What Level of Planning Does it Measure?

We examined which of two levels of planning, namely action and operations planning, are involved in Tower of London (TOL). One hundred nine university students (79 females; mean age = 20.81 years) from China were assessed on measures of action planning (Crack the Code), operations planning (Planned Connections, Planned Codes, Matching Numbers), and on TOL. The results of factor analysis showed first that TOL, scored as total number of correct responses, had a split loading on action and operations planning. TOL, scored as first move time, loaded on the same action planning factor represented by Crack the Code first move time. These findings suggest that different TOL scores may capture different levels of planning. The implications of these findings especially for clinical diagnosis and rehabilitation are briefly discussed.

Fracture resistance of molar teeth with mesial-occlusal-distal (MOD) restorations

ObjectiveFilled MOD restorations show near-complete recovery of tooth strength relative to the newly prepared, unfilled state. The present study examines the underlying mechanics of this recovery by more closely quantifying the mode of splitting fracture from the cavity base. By understanding the role of specific cavity dimensions on fracture resistance, useful clinical guidelines concerning MOD morphologies are formulated. MethodsA systematic in vitro study is made of the load-bearing capacity of filled and unfilled MOD cavities by axially loading extracted molar teeth with a hard metal ball. Filled and unfilled cavities are considered as bounding cases. Focus is placed on drillings with rectangular or rounded tips, covering a range of cavity widths and depths. The failure process is monitored during loading by a video camera, enabling the entire damage evolution from first contact to ultimate failure to be recorded. SignificanceWhile respecting the widely accepted clinical practice of drilling cavities with internal widths less than one third that of the entire tooth, a stronger correlation is obtained between critical splitting load PC and ratio of cavity wall thickness h (distance between cavity wall and outer tooth surface) to cavity depth D. Imposing a conservative upper limit on PC for tooth survival, the study recommends that MOD cavities be prepared such that the ratio remains in the region h>D, regardless of the tooth size.

Experimental study on water fracture interactions in concrete

A novel sealing device that has a minimal effect on the mechanical behaviour of concrete specimens is proposed in this paper. This device connects one side of silicon plates to a specimen using two specially designed clamps, instead of adhesive and screws the other side of the plates together to a steel plate. Several experimental wedge-splitting tests under compact tension are conducted with and without this sealing device to investigate the effect of water pressure on concrete crack propagation. The fracture experiments for concrete under different water pressures and different loading rates are carried out by wedge-splitting tests with the water pressure applied using this novel device. The water distribution is obtained based on experimental data recorded by five pressure transducers present at the tip of a notched crack, and the results show that the internal water pressure consists of a constant curve and a parabolic curve. The water within the crack has sufficient time to enter the crack when the specimen is subjected to a slow split loading, and the water front during slow loading test exceeds that of the fast loadings when reaching the same CMOD. The effect of the water interactions in concrete is severe in quasi-static conditions rather than in fast loading conditions during crack sudden opening. The loading rate plays a dominant role in the water pressure distribution and crack propagation.

Load sharing behavior analysis method of wind turbine gearbox in consideration of multiple-errors

Conducting a further analysis on loading sharing among compound planetary gear system in wind turbine gearbox, and making a meshing error analysis on the eccentricity error, gear thickness error, base pitch error, assembly error, and bearing error of wind turbine gearbox respectively. In view of the floating meshing error resulting from meshing clearance variation caused by the simultaneous floating of all gears, this paper establishes a refined mathematical model of two-stage power split loading sharing coefficient calculation in consideration of multiple errors. Also obtains the regular curves of the load sharing coefficient and floating orbits of center gears, and conducts a load sharing coefficient test experiment of compound planetary gear system to verify the research results, which can provide scientific theory evidence for proper tolerance distribution and control in design and process.

Fracture-resistant monolithic dental crowns

ObjectiveTo quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. MethodsFracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. ResultsExperimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. SignificanceThe results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity.

STEEL FIBER-REINFORCED SELF-COMPACTING CONCRETE SUBJECTED TO CONCENTRATED LOADS

To model the behavior of precast segmental tunnel linings under thrust jack loading, cylindrical concrete columns, subjected to concentrated loads, are investigated. Specifically, uniaxial compressive tests have been performed on specimens made with self-compacting concrete and reinforced with two different amounts of steel fibers (0, 30 kg/m3, respectively). In addition, to measure concrete properties, three point bending tests have been carried out in accordance with code rules. As a result, not only the fracture toughness of concrete in compression is improved, but also the ultimate and the maximum splitting loads are remarkably increased by the presence of long fibers. Accordingly, a new formulation of the classical Leonhardt’s approach is eventually proposed. Finally, based on the results of the present research, it seems reasonable to replace reinforced concrete with SFRSCC in structures subjected to high concentrated loads.

Power splitting strategy for solar hydrogen generation

A standalone solar–hydrogen power generation system employing photovoltaic array and hydrogen storage of excess energy is an attractive solution for remote and portable applications. A demonstration system has been designed and built focus on an integrated load split and maximum power point tracker to meet the load and divert surplus power to produce hydrogen for storage. Key functional requirements of a control system are defined. The dynamics of PEM electrolyser is studied through experimental testing, and its response time is presented and analysed. A demonstration system designed to perform load splitting and maximum power point tracking is proposed and its performance is evaluated experimentally. The positive results lead to constructing a control system control and self–adjust voltage output which accomplish load splitting and maximum power point tracking automatically.

In-plane fracture of an ice floe: A theoretical study on the splitting failure mode

In practical offshore structure/icebreaker designs, it is critical to capture the salient failure modes of the ice feature. The dominant failure modes are influenced by the structural properties, interaction process, and characteristics of the ice features. For an ice feature of finite size with relatively small lateral confinement, splitting failure has been frequently observed during ice-structure interactions. In literature, the splitting failure of an ice floe has been studied using several different methods, ranging from strength theory to methods based on fracture mechanics. One contribution of this paper is that these various methods are compiled and evaluated collectively. Another contribution of this paper is the construction of an analytical framework to obtain solutions for the splitting process of an ice floe upon serious considerations of relevant fundamental theories. The framework developed for its calculations is presented but not limited these two base cases (i.e., rectangular and circular ice floes). Specifically, because of the complexity of the splitting failure scenario (particularly the ice floe geometry) and our pursuit of analytical solutions, within the presented framework, two different approaches have been proposed: the fracture mechanics approach and plasticity theory approach. All of the employed methods are validated against data from previous field tests or numerical results. Recommendations and discussion were presented for each of these methods’ respective application range. It was found that most of the floe sizes under engineering interests can be accurately described by linear elastic fracture mechanics. The cohesive zone method, which is one type of the nonlinear fracture mechanics based approaches, is found to be potentially applicable in extrapolating laboratory-scale measurements to the field scale. Worth mentioning, the weight function method was effectively used to calculate the fracture properties of an ice floe under various symmetric loading conditions (e.g., boundary confinement). The boundary confinement can easily prevent splitting failure or increase the ice splitting load. As one type of the lateral confinement, the inertia-induced body force, is also studied and compared with previous numerical results. Comparatively, the plasticity theory based approach (i.e., the plastic upper/lower limit theory) enables us to effectively attain a conservative estimation of the ice splitting load in an analytical form. It can serve as a supplementary tool to the fracture mechanics based approach.

Study on Split-Open Loading in V-Shaped Components Forming Process

Basised on the study of effect with different loading ways on v-shaped components forming process. Put forward a kind of split open control loading technology aiming at forming this kind of components. Studied the effect of key process parameters of split open loading on the quality of finish forging, the key process parameters scopeis given by avoid the finish forging defects. Using shunt split open loading process forming v-shaped components, make internal complex mold cavity filled full, improved the deformation uniformity, reduced the forming load.

Model and algorithm for an unpaired pickup and delivery vehicle routing problem with split loads

This paper addresses the routing problem with unpaired pickup and delivery with split loads. An interesting factor of our problem is that the quantity and place for pickup and delivery are decision variables in the network. We develop an easy-to-implement heuristic in order to gain an efficient and feasible solution quickly. Then, a local search algorithm based on the variable neighborhood search (VNS) method is developed to improve the performance of the heuristic. Computational results show that the proposed VNS method is able to obtain an optimal or near optimal solution in reasonable time for the formulated problem.

Numerical and Experimental Investigations of the Three-Dimensional-Flow Structure of Tandem Cascades in the Sidewall Region

Tandem blades can be superior to single blades, particularly when large turning angles are required. This is well documented in the open literature and many investigations have been performed on the 2D-flow of tandem cascades to date. However, much less information on the flow near the sidewalls is available. Thus, the question arises as to how the geometry of a tandem cascade should be chosen near the sidewall in order to minimize the flow losses for large turning angles. The present work examines the 3D-flow field in the region of the sidewall of two high turning tandem cascades. A large spacing ratio was chosen for the forward blade of the first tandem cascade ((t/l)1=1.92). The second tandem cascade possessed a smaller spacing ratio for the forward blades ((t/l)1=1.0). Both cascades had the same total spacing ratio of t/l=0.6. Flow phenomena, such as the corner stall of the 3D boundary layer near the sidewall, are examined using both numerical and experimental methods. The empirical correlations of Lieblein and Lei are applied. The flow topology of both tandem cascades is explained and the locations of loss onset are identified. In addition, oil pictures from experiments and streamline pictures of the numerical simulations are shown and discussed for the flow close to the sidewalls. Finally, design rules such as the aerodynamic load splitting and the spacing ratio of the forward- and aft-blades, etc. are taken into account. The examinations are performed for tandem cascades designed for flow turning of approximately 50 deg at a Reynolds number of 8×105. The tandem cascades consist of NACA65 blades with circular camber lines and an aspect ratio of b/l=1.0.

Client–server games and their equilibria in peer-to-peer networks

In peer-to-peer networks, each peer acts simultaneously as client and server, by issuing and satisfying content requests respectively. In this work, we use concepts from non-cooperative game theory to model the interaction of autonomous peers. The client strategy set consists of feasible request load splits towards servers, while the server strategy set is formed out of possible service disciplines on received requests. The performance metric of interest is the average retrieval delay of content requests.First, we assume preassigned fixed server policies (FIFO and priority) and study the emerging client request load splitting game. Peers are either egotistic (i.e. interested only in optimizing their own delay) or altruistic ones that also take into account delay incurred to other peers. We consider best response updates to model iterative peer interaction. For egotistic peers, we show that the sequence of best responses always converges to the unique Nash Equilibrium Point (NEP). For altruistic peers best response updates converge to one of the multiple NEPs exist, with each one being a global optimum for the FIFO case and a local optimum for any other service strategy profile. We also consider mixed swarms consisting of both egotistic and (partially-) altruistic peers and show an interesting transition from one to multiple NEPs. Next, we include service strategies in the peer strategy set. Though with its service policy a peer cannot directly affect its delay, it can affect the resulting NEP. We devise two-level game models, where, at a first level, a peer selects its favorable service rule and then peers play a client load splitting game.

Parallel Power Processing Topology for Solar PV Applications

An efficient converter topology for extracting maximum power from a photovoltaic module is presented in this paper. The proposed topology is implemented on a stand-alone battery charging system. A reversed buck-boost converter enabling parallel power processing (PPP) with a power switch referenced to the common return is the core of the charging system. Small-signal analysis of the proposed charging system is carried out to facilitate the design of a compensator for maximum power point (MPP) tracking. The simulation and experimental results confirm the validity of the model and verify the high efficient operation while tracking the MPP. The use of the PPP with split loads is also presented which would improve the converter size, efficiency, and step-down duty ratio.

Optimal Power Management of Final Load and Electrolyser in a Solar Hydrogen Power Generation System

This paper describes a control unit for a solar-hydrogen power generation system that is capable of supplying an electrical load simultaneously with diverting excess power to an electrolyser to produce hydrogen gas for storage as backup energy. The functional requirements of such a control unit are defined. The transient response time for the PEM electrolyser is studied and analyzed through experimental testing. A design of load splitting device that also performs maximum power point tracking is proposed and its performance measured experimentally. Initial results suggest that the device can accomplish both the load splitting and maximum power point tracking functions satisfactorily.

Mechanics of Kinesin-Crosslinked Microtubule Networks

We have recently shown that the mechanical properties of chemically crosslinked microtubule networks depend sensitively on the single-molecule properties of the crosslinking molecules they contain. In particular, for networks that are rigidly crosslinked by biotin-streptavidin, a small number of crosslinkers bear stress, and their force-induced detachment from the microtubule determines the time-dependent network rearrangements. Interestingly, the network retains its elastic modulus even under conditions of significant plastic flow, suggesting that crosslinker breakage is balanced by the formation of new bonds. This leads to a remarkable resilience under repeated loading, as long as a sufficient number of the original crosslinkers are preserved per loading cycle. In this current work, we have expanded our study to include compliant crosslinkers, formed by multimeric complexes of kinesin-1. A variety of biophysical approaches are used, including electron and optical microscopy to measure network architecture under different crosslinking conditions, and magnetic tweezer-based microrheology to determine the creep response of the networks under controlled loading. We find that protein compliance and filament bundling enables load splitting among adjacent crosslinkers, thereby enhancing material strength and diminishing the importance of single crosslinker unbinding in determining the mesoscopic rheology. Our results are important to understanding how network architecture and crosslinker properties influence network mechanics, and are particularly important to understanding the role of kinesin proteins in forming stress-transmitting microtubule structures, such as the mitotic spindle.

Ship Scheduling by Pure Car Carriers with Time Windows and Split Loads in Changeable Speeds

Ship Scheduling by Pure Car Carriers with Time Windows and Split Loads in Changeable Speeds