Mixed Schedule Research Articles

Preference pulses without reinforcers

Preference pulses are thought to represent strong, short-term effects of reinforcers on preference in concurrent schedules. However, the general shape of preference pulses is substantially determined by the distributions of responses-per-visit (visit lengths) for the two choice alternatives. In several series of simulations, we varied the means and standard deviations of distributions describing visits to two concurrently available response alternatives, arranged "reinforcers" according to concurrent variable-interval schedules, and found a range of different preference pulses. Because characteristics of these distributions describe global aspects of behavior, and the simulations assumed no local effects of reinforcement, these preference pulses derive from the visit structure alone. This strongly questions whether preference pulses should continue to be interpreted as representing local effects of reinforcement. We suggest an alternative approach whereby local effects are assessed by subtracting the artifactual part, which derives from visit structure, from the observed preference pulses. This yields "residual" preference pulses. We illustrate this method in application to published data from mixed dependent concurrent schedules, revealing evidence that the delivery of reinforcers had modest lengthening effects on the duration of the current visit, a conclusion that is quantitatively consistent with early research on short-term effects of reinforcement.

Optimisation of a mixed truck fleet schedule through a mathematical model considering a new truck-purchase option

Mining is a capital-intensive industry that requires hundreds of million-dollar investment in major equipment. In regards to surface mining operations, mine trucks are the most common pieces of equipment that are used for material haulage. Their maintenance cost, however, constitutes a significant proportion of the overall operational cost. Currently available costing methods and models do not take into account all key constraints and as a result, maintenance cost cannot be minimised. A new mixed integer programming (MIP) model is developed to minimise the maintenance cost for a heterogeneous truck fleet over a multi-year period while considering a new truck-purchase option. The proposed model is applied to truck maintenance cost data from a gold mine in Western Australia. Results indicate 21·64% and 14·76% cost savings over 10 years in comparison to the spread sheet based and original MIP models, respectively.

Behavioral functions of stimuli signaling transitions across rich and lean schedules of reinforcement

On multiple fixed-ratio schedules, pausing is extended at the start of a component ending in a small reinforcer (a lean component) but only when this component follows a component ending in a large reinforcer (a rich component). In two experiments, we assessed whether a stimulus correlated with a lean component is aversive and how its function is affected by the preceding component. In Experiment 1, pigeons responded on mixed fixed-ratio schedules ending in large or small reinforcers. Observing responses converted the mixed schedule to a multiple one by producing a stimulus correlated with the current component. Overall, the lean stimulus did not suppress observing, suggesting that it was not sufficiently aversive. In Experiment 2, an escape procedure was used, and pigeons could convert a multiple schedule to a mixed one by pecking a key to remove the discriminative stimuli. Pigeons escaped from the lean-schedule stimulus more than they did from the rich one. For two pigeons, this effect was enhanced when a rich component preceded the lean stimulus. The results indicate that a stimulus correlated with the leaner of two reinforcement schedules can acquire aversive functions, but observing and escape procedures may differ in their abilities to detect this effect.

Broadcast Scheduling with Latency and Redundancy Analysis for Cognitive Radio Networks

Cognitive radio networks (CRNs) introduce a new communication paradigm that enables unlicensed users to opportunistically access spectrum bands assigned to licensed users. Interestingly, the broadcast problem, which is one of the most fundamental operations in CRNs, has not been well studied. Existing works for the broadcast issue in CRNs are heuristic solutions either without a performance guarantee or with performance far from the optimal solution. In this paper, we study the minimum-latency broadcast scheduling (MLBS) issue for CRNs. Our contributions are threefold. First, we propose a mixed broadcast scheduling (MBS) algorithm under the unit disk graph (UDG) model, denoted by MBS-UDG. MBS-UDG finishes a broadcast task by employing mixed unicast and broadcast communication modes in two phases. We show that the latency performance of MBS-UDG is $O(\hbar+\Delta_{T})$ when $\Delta_{T}\leq \hbox{1}/p$ or $O(\hbar+\log_{1-p}(\hbox{1}/p\Delta_{T}))$ when $\Delta_{T}>\hbox{1}/p$ , where $\hbar$ and $\Delta_{T}$ are the height and the maximum number of leaf nodes connected by a second user (SU)of the broadcasting tree, respectively, and $p$ is the spectrum opportunity for a secondary communication. Furthermore, the redundancy performance of MBS-UDG is analyzed. Second, we extend MBS-UDG to a more general MBS algorithm under the protocol interference model and analyze its latency and redundancy performance. Finally, simulations are conducted to validate MBS, which indicate that MBS significantly improves existing algorithms with respect to both latency and redundancy.

Crane scheduling for opportunistic remarshaling of containers in an automated stacking yard

Loading of containers onto a vessel can be delayed if the containers are inappropriately stacked at the yard. Remarshaling is the preparatory task of rearranging the containers ahead of loading time to minimize the delay at the time of loading. Previous works on remarshaling derive a remarshaling plan assuming that a certain amount of continuous period of time is available for the remarshaling jobs to be done in a batch; remarshaling jobs cannot be mixed together with the current main jobs in the crane schedule. In contrast, the method proposed in this paper allows remarshaling jobs to be scheduled together with the current jobs under the framework of iterative rescheduling, in which scheduling and execution of the jobs within a predetermined fixed-length look-ahead horizon are repeated in a regular interval. The remarshaling jobs selected for the mix are those that contribute the most to the reduction of future loading delay. The number of remarshaling jobs and their temporal positions within the mixed schedule for a look-ahead horizon are determined appropriately to best utilize the idle time of the automated cranes, which is enforced by an objective function to minimize the delay of the current main jobs as well as the makespan of all the jobs in the horizon.

Scheduling of high-speed rail traffic based on discrete-time movement model

In this paper, a new simulation approach for solving the mixed train scheduling problem on the high-speed double-track rail line is presented. Based on the discrete-time movement model, we propose control strategies for mixed train movement with different speeds on a high-speed double-track rail line, including braking strategy, priority rule, travelling strategy, and departing rule. A new detailed algorithm is also presented based on the proposed control strategies for mixed train movement. Moreover, we analyze the dynamic properties of rail traffic flow on a high-speed rail line. Using our proposed method, we can effectively simulate the mixed train schedule on a rail line. The numerical results demonstrate that an appropriate decrease of the departure interval can enhance the capacity, and a suitable increase of the distance between two adjacent stations can enhance the average speed. Meanwhile, the capacity and the average speed will be increased by appropriately enhancing the ratio of faster train number to slower train number from 1.

Parallel Machine Scheduling with Fuzzy due Date Using Improved Simulated Annealing in Lean Production

Tardiness scheduling problems in the lean production has received extensive attention recently, and in most tardiness scheduling problems job due dates are regarded as invariable and known in advance. The study deals with fuzzy tardiness scheduling for parallel machines with fuzzy job due dates, where the objective is to minimize the average penalty cost of jobs tardiness. To describe the tardy degree of job clearly, a novel tardiness measure index is introduced based on the possibility and necessity measures in the study. And further, the mixed integer programming scheduling model of parallel machines is constructed for jobs tardiness. Since this problem is NP-hard, an improved simulated annealing is proposed and designed to solve the model. Finally, a numerical experiment is presented to illustrate the feasibility and effectiveness of the proposed method.

A mixed-integer nonlinear program for the optimal design and dispatch of distributed generation systems

Maturing distributed generation (DG) technologies have promoted interest in alternative sources of energy for commercial building applications due to their potential to supply on-site heat and power at a lower cost and emissions rate compared to centralized generation. Accordingly, we present an optimization model that determines the mix, capacity, and operational schedule of DG technologies that minimize economic and environmental costs subject to the heat and power demands of a building and to the performance characteristics of the technologies. The technologies available to design the system include lead-acid batteries, photovoltaic cells, solid oxide fuel cells, heat exchangers, and a hot water storage tank. Modeling the acquisition and operation of discrete technologies requires integer restrictions, and modeling the variable electric efficiency of the fuel cells and the variable temperature of the tank water introduces nonlinear equality constraints. Thus, our optimization model is a nonconvex, mixed-integer nonlinear programming (MINLP) problem. Given the difficulties associated with solving large, nonconvex MINLPs to global optimality, we present convex underestimation and linearization techniques to bound and solve the problem. The solutions provided by our techniques are close to those provided by existing MINLP solvers for small problem instances. However, our methodology offers the possibility to solve large problem instances that exceed the capacity of existing solvers and that are critical to the real-world application of the model.

Research on Mechanical Automation with Analysis of Mixed Train Scheduling Problem on the High-Speed Rail Line

In this paper, we study mechanical automation with analysis of mixed train scheduling problem on the high-speed rail line and present a new simulation approach for solving the mixed train scheduling problem on a high-speed double-track rail line. Based on the discrete-time movement model, we propose control strategies for mixed train movement on a high-speed double-track rail line. Using our proposed method, we can effectively simulate the mixed train schedule on a rail line. The numerical results demonstrate that a proper decrease of the departure intervals can enhance the capacity.

Influence of training schedule on development of perceptual–motor control skills for construction equipment operators in a virtual training system

Abstract Virtual Training Systems have emerged as alternative tools for construction equipment operator training that may reduce costs, avoid risks, and provide flexible environments for various training purposes. However, principles for determining training-schedule design for efficient utilization of these systems are not well established. The present research compared performance of two groups, one adopting a mixed practice schedule (with high contextual interference) and the other employing a blocked practice schedule (presumably with lower contextual interference) for learning construction excavator control skills in a computer-based virtual environment. No significant difference was found with regard to achieved skill level and skill consistency. A possible reason is that the complexity of the training task created a degree of intra-task interference in the blocked practice schedule comparable to the interference created by the mixed practice schedule. This result implies a need to further assay construction equipment operation to critically isolate influences on operator skill development.

A COMPONENT ANALYSIS OF SCHEDULE THINNING DURING FUNCTIONAL COMMUNICATION TRAINING

One limitation of functional communication training (FCT) is that individuals may request reinforcement via the functional communication response (FCR) at exceedingly high rates. Multiple schedules with alternating periods of reinforcement and extinction of the FCR combined with gradually lengthening the extinction-component interval can effectively address this limitation. However, the extent to which each of these components contributes to the effectiveness of the overall approach remains uncertain. In the current investigation, we evaluated the first component by comparing rates of the FCR and problem behavior under mixed and multiple schedules and evaluated the second component by rapidly switching from dense mixed and multiple schedules to lean multiple schedules without gradually thinning the density of reinforcement. Results indicated that multiple schedules decreased the overall rate of reinforcement for the FCR and maintained the strength of the FCR and low rates of problem behavior without gradually thinning the reinforcement schedule.

Effects of practice schedules on speech motor learning

The aim of this study was to evaluate the effects of various practice schedules on learning a novel speech task. Forty healthy Cantonese speakers were asked to learn to produce a Cantonese phrase with two target utterance durations (2500 and 3500 milliseconds). They were randomly assigned to one of four learning conditions, each completing a different practice schedule, namely Blocked only, Random only, Blocked-then-Random, and Random-then-Blocked. Two retention tests (one immediate and one delayed) and a transfer test were administered. The four groups of participants showed different patterns of learning, but achieved comparable levels of performance at the end of the acquisition phase. However, participants in the Blocked only condition were less able to differentiate the two target durations than those in the Random only condition during retention. Furthermore, participants who received both blocked and random practice were less adversely affected by the secondary task during the transfer test than those who received either blocked or random practice alone. These findings suggest that mixed practice schedules are more effective than either blocked or random practice, especially in transferring the acquired speech motor skills to a cognitively demanding situation. The results have clinical implications regarding optimal practice schedules for treatment intervention.

Effects of Heterogenous Mobility on Rate Adaptation and User Scheduling in Cellular Networks With HARQ

In this paper, we investigate the effects of heterogeneous mobility on rate adaptation and user scheduling in cellular networks with hybrid automatic repeat request (HARQ). To this end, we first show the performance tradeoff between two extreme scheduling criteria: retransmission-oriented scheduling (ROS) and mixed scheduling (MS) criteria over time-correlated Rayleigh fading channels. Then, we propose an ROS-based joint rate adaptation and user scheduling (JRAUS) policy for cellular networks and compare it with the conventional and reference JRAUS policies. We also evaluate the system-level performance of the proposed ROS-based JRAUS policy in various user distribution and mobility scenarios. In particular, in an asymmetric user distribution and heterogeneous mobility scenario, which is the most general one in practice, the proposed JRUAS policy yields a throughput gain of 49% and a fairness gain of 155% over the conventional JRAUS policies. In this paper, we find that the rate adaptation is significant not only in a single point-to-point link but in multiuser systems with heterogeneous mobility as well.

Robotics in Clothes Manufacture

Process automation and intelligent manufacturing are important factors for competing successfully in today’s international economy. The survey considers the use of these tools within the clothing industry where low cost labour has especially driven the marketplace, in recent decades, toward productive break-up, with relevant drawbacks on preserving the process control uniformity. Several hints are described for the use of modern manufacturing tools in the production flow of clothing and in the management of the related operations. Emphasis is placed on maintaining a high quality product in a customised production environment. The presentation begins by exploring the automated retrieval of fabric from a warehouse; it continues with a study of the laying and cutting process exploring mixed mode schedules, combining batch and one-of-a-kind delivery; and concludes by considering the assembly and sewing aspects of the manufacturing process. For clothing manufacturers in developed countries, the automation concepts presented here offer an alternative (and perhaps the only alternative) to out-sourcing and overseas production.

The relationship between shift work and body mass index among Canadian nurses

AimThe aim of this study was to examine the relationship between shift schedule and body mass index (BMI) among a sample of Canadian Nurses. BackgroundHigher BMI values have been reported for employees working non-standard shifts compared to those working a regular daytime schedule. Little is known about the pathways through which shift work is associated with higher BMI. MethodsThis study was a secondary analysis of a sample from National Survey on the Work and Health of Nurses (N=9291). ResultsWe found a small, but statistically significant, difference in BMI scores across shift schedule categories with higher BMI scores reported among female nurses working night or mixed shift schedules, compared with those working a regular daytime schedule. Adjustment for working conditions and employer supported facilities did not attenuate the association between shift work and BMI scores. ConclusionsThe potential public health importance of this relationship requires further investigation given the small, but statistically significant, differences observed in this sample.

ESTABELECIMENTO DO CONTROLE DE ESTÍMULOS E DO COMPORTAMENTO DE OBSERVAÇÃO POR DIFERENÇA DE CUSTO DE RESPOSTAS

Definindo-se comportamento de observação como aquele que produz estímulos discriminativos para outro comportamento, foi realizado um experimento em que a principal variável manipulada foi o custo relativo entre as respostas de observação e as do outro comportamento (de produção). Foram registradas as respostas nos dois comportamentos em diferentes esquemas de reforçamento. Seis pessoas adultas foram divididas em dois grupos. Os participantes do Grupo 1 foram primeiro expostos a um esquema múltiplo. Durante os componentes de reforçamento, pressões em um botão produziam pontos que eram trocados por dinheiro ao final da sessão. Após atingir um índice de discriminação de 0,9 ou mais por três ou mais sessões consecutivas, eles seriam expostos a um esquema misto, com possibilidade de emissão de respostas de observação em outro botão. Os participantes do Grupo 2 foram expostos diretamente a esta segunda condição. Os participantes do Grupo 2 atingiram índices de discriminação maiores que os do Grupo 1, principalmente após o estabelecimento de uma resposta de observação com um custo inferior ao da resposta que produzia pontos. Discute-se a relevância da análise do custo entre as respostas no estabelecimento do comportamento de observação e do controle de estímulos. Palavras-chave : comportamento de observação, resposta de observação, custo de resposta, atenção, controle de estímulos, humanos.

Immunogenicity of a Haemophilus influenzae type b–tetanus conjugate vaccine when administered separately or in combined vaccines for primary immunization in two consecutive national schedules in Turkey

In Turkey, the Haemophilus influenzae type b-tetanus toxoid conjugate vaccine (Hib) was replaced by the combined diphtheria-tetanus-acellular pertussis and inactivated polio vaccine (DTaP-IPV/Hib) in 2008. This shift to the new schedule created different cohorts of vaccinated children as a consequence of the different schedules used. We evaluated the immunogenicity of the Hib vaccine in infants vaccinated with these different schedules. Three groups of children were evaluated: group 1 comprised 145 infants vaccinated with diphtheria, tetanus, and whole cell pertussis (DTwP), oral polio vaccine (OPV), and Hib vaccines simultaneously at separate sites; group 2 comprised 204 infants vaccinated with the DTaP-IPV/Hib combined vaccine; group 3 comprised 100 infants vaccinated with a mixed schedule of DTwP, OPV, and Hib for the first one or two doses, followed by DTaP-IPV/Hib vaccine to complete the series. Anti-polyribosylribitol phosphate (anti-PRP) titers ≥0.15μg/ml were similar in groups 1, 2, and 3. However, in group 1, who received all the vaccines at separate sites, ≥ l.0μg/ml long-lasting antibody titers and anti-PRP geometric mean titers were higher (p=0.001). This study showed that even one dose administered in combination with other vaccines in a primary series decreased the level of anti-PRP.

Safety and Immunogenicity of 2 Mixed Primary Infant Immunization Schedules of Pentavalent Diphtheria, Tetanus, Acellular Pertussis, Inactivated Poliomyelitis, and Haemophilus influenzae Type b Vaccines at 2, 4, and 6 Months of Age

Two pentavalent infant vaccines that contain either 5 or 3 component acellular pertussis antigens are authorized in Canada. Because of changes in vaccine use by provinces over time and movement of families across jurisdictions, it is possible that children are exposed to different combination vaccines during the primary infant immunization schedule. The safety and immunogenicity of mixed primary infant schedules is unknown. In a double-blind multicenter trial, 2-month-old healthy infants were randomized to 1 of 2 schedules at 2, 4, and 6 months of age (either Pediacel, Pediacel, Infanrix [PPI] or Infanrix, Pediacel, Pediacel [IPP]). Solicited local and systemic adverse events (AEs) were collected by parent diary on days 0 through 7; unsolicited AEs were collected for 31 days after each dose. Immune responses to polypolyribosylribitol phosphate capsular polysaccharide (PRP) (Haemophilus influenzae type b) and pertussis antigens were assessed before the first dose and 28 days after the 6 month (third) dose. In all, 127 infants were randomized to IPP and 126 to PPI. The percentage of children with anti-PRP responses ≥0.15 μg/mL after dose 3 was higher in the IPP than in the PPI group (98.3, 95% CI: 94.1, 99.8 vs. 86.1%, 95% CI: 78.6, 91.7, P < 0.001). Antipertussis toxin and anti-fimbriae 2 and 3 responses were statistically significantly higher in the IPP than in the PPI group. Higher filamentous hemagglutinin responses occurred in PPI than in IPP. No difference between groups was observed in pertactin responses.Systemic AEs were similar between the 2 vaccine schedules. Irritability (67.2 vs. 51.6, P = 0.014) and mild crying (35.2% vs. 23.0%, P = 0.037) were more common after the 6-month dose in the PPI compared with the IPP group, as were overall systemic reactions (any intensity) for the PPI group after this dose (80.0 vs. 68.0, P = 0.042). Mixed 2-, 4-, 6-month pentavalent infant vaccine schedules had different immunogenicity and reactogenicity, with a PPI schedule being more reactogenic, and less immunogenic for PRP and fimbriae 2 and 3 antigens at 7 months. It is preferable to complete the primary infant 3-dose vaccine series with the same vaccine, rather than considering infant vaccines as interchangeable.

Tidal regime dictates the cascading consumptive and nonconsumptive effects of multiple predators on a marsh plant

Prey perception of predators can dictate how prey behaviorally balance the need to avoid being eaten with the need to consume resources, and this perception and consequent behavior can be strongly influenced by physical processes. Physical factors, however, can also alter the density and diversity of predators that pursue prey. Thus, it remains uncertain to what extent variable risk perception and antipredator behavior vs. variation in predator consumption of prey underlie prey-resource dynamics and give rise to large-scale patterns in natural systems. In an experimental food web where tidal inundation of marsh controls which predators access prey, crab and conch (predators) influenced the survivorship and antipredator behavior of snails (prey) irrespective of whether tidal inundation occurred on a diurnal or mixed semidiurnal schedule. Specifically, cues of either predator caused snails to ascend marsh leaves; snail survivorship was reduced more by unrestrained crabs than by unrestrained conchs; and snail survivorship was lowest with multiple predators than with any single predator despite interference. In contrast to these tidally consistent direct consumptive and nonconsumptive effects, indirect predator effects differed with tidal regime: snail grazing of marsh leaves in the presence of predators increased in the diurnal tide but decreased in the mixed semidiurnal tidal schedule, overwhelming the differences in snail density that resulted from direct predation. In addition, results suggest that snails may increase their foraging to compensate for stress-induced metabolic demand in the presence of predator cues. Patterns from natural marshes spanning a tidal inundation gradient (from diurnal to mixed semidiurnal tides) across 400 km of coastline were consistent with experimental results: despite minimal spatial variation in densities of predators, snails, abiotic stressors, and marsh productivity, snail grazing on marsh plants increased and plant biomass decreased on shorelines exposed to a diurnal tide. Because both the field and experimental results can be explained by tidal-induced variation in risk perception and snail behavior rather than by changes in snail density, this study reinforces the importance of nonconsumptive predator effects in complex natural systems and at large spatial scales.

Heuristics and metaheuristics for mixed blocking constraints flowshop scheduling problems

Storage or buffer capacities between successive machines in flowshop problems may be unlimited, limited or null. The last two cases can lead to blocking situations. In flowshop scheduling literature, many studies have been performed about classical flowshop problems and also about some problems with only one blocking situation between all machines.This paper deals with makespan minimization in flowshop scheduling problems where mixed blocking constraints are considered. After a problem description and definitions of different blocking constraints, a mathematical model is presented and heuristics are developed to propose quick solutions to these kinds of problems. Then, metaheuristics are used to improve found solutions. A comparison between heuristics and metaheuristics is then performed.