Prokrastinering är ett problematiskt beteende som tidigare forskning har visat kunna inhiberas genom närliggande deadlines. Satt i arbetspsykologiskt perspektiv var föreliggande studiens syfte att undersöka hur prokrastinering och autonomi påverkas av närliggande av deadlines på arbetsplatsen. Ett e-självskattningsformulär skickades ut till två avdelningar på en myndighet varav ena arbetade med närliggande deadlines och den andra utan. Totalt deltog 71 anställda i enkätundersökningen och en jämförelse av gruppernas medelvärden kunde inte påvisa en signifikant skillnad i arbetsprokrastinering mellan grupperna. Anställda som arbetade med närliggande deadlines upplevde emellertid signifikant högre grad av autonomi. Vikten av alternativa sätt att mäta prokrastinering på arbetsplatsen diskuteras. Studier av organisatoriska risker för prokrastinering såväl som följder av beteendet förespråkas för framtida forskning.

Efficient transmission schemes are presented for streaming scalable video over a link with limited capacity. The objective is to select a transmission sequence of data units and their transmission schedule such that the overall video quality is maximized. For video with a single spatial layer, optimal transmission schemes are obtained for two general classes of hierarchical prediction structures, which include the popular dyadic structure. Based on a new characterization of the interdependence among frames in terms of trees, structural properties of an optimal transmission schedule are derived. These properties lead to the development of a jointly optimal frame selection and scheduling algorithm, which has computational complexity that is quadratic in the number of frames. Then, using the concept of virtual deadlines, an efficient sub-optimal scheme for the transmission of video with multiple spatial layers is proposed. Simulation results show that the proposed schemes substantially outperform two existing alternatives.

Efficient transmission schemes are presented for streaming scalable video over a link with limited capacity. The objective is to select a transmission sequence of data units and their transmission schedule such that the overall video quality is maximized. For video with a single spatial layer, optimal transmission schemes are obtained for two general classes of hierarchical prediction structures, which include the popular dyadic structure. Based on a new characterization of the interdependence among frames in terms of trees, structural properties of an optimal transmission schedule are derived. These properties lead to the development of a jointly optimal frame selection and scheduling algorithm, which has computational complexity that is quadratic in the number of frames. Then, using the concept of virtual deadlines, an efficient sub-optimal scheme for the transmission of video with multiple spatial layers is proposed. Simulation results show that the proposed schemes substantially outperform two existing alternatives.

The effects of deadlines in contingency-specifying stimuli among nine 4 to 5 year old children were investigated. Each child was given verbal statements differing in the specified deadline, the delivery of the reinforcer, and the opportunity to respond. The results indicated: (a) statements not specifying deadlines or reinforcers failed to control the children's behavior reliably, (b) specifying deadlines, either immediate or delayed, and immediate reinforcers exerted reliable control over the children's behavior when the opportunity to respond was immediately available, and (c) specifying delayed deadlines or no deadlines and immediate or delayed reinforcers did not reliably control the children's behavior when the opportunity to respond was delayed.

L'influence du temps sur le droit immobilier pose plusieurs problèmes notamment quant à la qualification des termes utilisés. En effet, définir le temps, notion immatérielle par excellence, et le droit de l'immeuble, droit concret, semble paradoxal. Pourtant l'analyse de ces deux notions illustre les liens qui les unissent. Le droit immobilier utilise le temps pour créer, restreindre, voire éteindre certains droits et ce durant toutes les phases de l'immeuble : de sa construction à sa destruction. On oscille entre célérité et immobilité. Parallèlement le temps use l'immeuble, et le droit doit alors pallier les conséquences néfastes par le biais de diverses mesures. Il convient de trouver entre ces deux notions, de prime abord antinomiques, un juste équilibre qui permettra, tant dans leur approche théorique que dans leur application, au droit immobilier d'évoluer constamment et d'être le reflet d'une humanité en perpétuel mouvement. / The influence of time over property law is problematic mainly due to the qualification of the terms employed. Indeed, defining the concept of time, an ultimate immaterial notion, and property law, a very specific law, seem paradoxical. Nevertheless, the analysis of these two notions demonstrates how they are linked. Property law uses time to create, restrict, extinguish certain rights - during all the stages of the building : from its very construction to its complete destruction. We swing between quick response and immobility. In parallel, time undermines the building, and therefore the law has to respond to the harmful consequences through various measures. As such, it must be found between these two notions, at first contradictory, a balance that will allow, in their theoretical approach as well as in their application, property law to constantly evolve and be a reflection of humanity in perpetual motion.

The purpose of this study was to investigate the effects of three deadline conditions (i.e., frequent-instructor-set-deadline condition, flexible-instructor-set-deadline condition, and self-imposed-deadline condition) on students of different academic procrastination levels (high, medium, and low) in terms of their perceived learning, academic performance, and course satisfaction in an online course. A 3 x 3 factorial quasi-experimental design was adopted for this study. One hundred and seventy three students from three classes of different majors voluntarily participated in the study with 50 students majoring in Agriculture, 61 in International Trading, and 62 in Food Manufacturing. The three classes were randomly assigned to three deadline conditions. Data were collected through an online survey and a final exam. This study found that there were significant differences in perceived learning and course satisfaction among high, medium, and low procrastinators, but there was no significant difference in academic performance among students at different procrastination levels. Low and medium procrastinators had significantly higher perceived learning and were significantly more satisfied with the course than high procrastinators. Among the three deadline condition groups, there were no significant differences in perceived learning and course satisfaction, however, the difference in academic performance was significant. The flexible deadline group achieved the best academic performance followed by the frequent and the self-imposed deadline groups. There was no interaction effect between procrastination and deadline conditions on any of the dependent variables. Limitations of the present study, recommendations for future research, and implications for practice are discussed.

[EN] Automated temporal planning deals with the construction of plans for problems specified with durative actions of possibly different duration. The goal of temporal planning is to select and schedule the actions so as to achieve the problem goals, and the optimality criteria is the plan makespan. However, many real-word application define goals with time constraints which may not be satisfied with the plan of optimal makespan. The 2006 International Planning Competition introduced the PDDL3.0 language and organized the first and only track in planning with state trajectory constraints, including time restrictions, soft constraints and preferences. Particularly, four domains that feature deadline constraints were tested at the IPC and two planners participated in such competition although no one exhibited a good performance or fully-correction in the fulfillment of deadlines. An early detection of unsolvability in temporal planning problems, specifically those with strict deadlines, is crucial for avoiding an unfruitful exploration of the search space. And this is precisely the objective of this PhD dissertation. This work contributes with a temporal landmark-based model embedded into a temporal planner that allows for a rapid and eficient identification of unsolvable problems with deadline constraints. Our model incorporates the basic model operators of PDDL3.0 for defining temporal constraints and extends the STRIPS landmark concept to a temporal context. A temporal landmark is associated to three intervals that denote the time frame of the generation, validity and necessity of the landmark in the plan, respectively. The set of temporal landmarks of a problem along with their ordering relations and temporal restrictions define a temporal landmark graph which comprises the relationships that must exist between the literals of a solution plan and, therefore, between the corresponding actions. As long as new data is incorporated in the graph, the landmarks intervals are updated and propagated accordingly, thus reflecting a more accurate picture of a solution plan. The temporal landmark model is integrated in a domain-independent temporal planner named TempLM. During the search process, TempLM uses the temporal landmark graph to prune those partial plans of the search tree that are not compliant with the information of the graph. Additionally, we present a further improvement by which a feedback routine between the landmarks graph and the plan of a node tree is established. This process is used to refine the information of the graph and likewise narrow the search. In the experimental evaluation, we show the effectiveness of the proposed approach for detecting unsolvability and solving temporal planning problems with tight deadline constraints. / [ES] El objetivo de la planificación temporal automática es la construcción de planes con acciones de diferente duración que necesitan ser programadas adecuadamente con el fin de conseguir los objetivos del problema. En planificación temporal, la optimalidad se mide como la duración del plan más corto. Sin embargo, en muchos problemas del mundo real es necesario gestionar restricciones temporales asociadas a los objetivos del problema que pueden no satisfacerse con el plan de menor duración. En la Competición Internacional de Planificación del año 2006 se presentó el lenguaje PDDL3.0 y se realizó la primera y única competición de planificadores con gestión de restricciones de trayectorias de estado y preferencias. Concretamente, en esta IPC se probaron cuatro dominios con restricciones temporales donde los objetivos deben satisfacerse dentro de un límite de tiempo establecido o deadline. Dos planificadores participaron en esta competición aunque ninguno presentó un buen comportamiento respecto al cumplimiento de los deadlines. En este tipo de problemas, especialmente cuando se trata de problemas altamente restringidos, es crucial detectar la irresolubilidad de los mismos lo antes posible, y en este punto es donde se establece nuestro objetivo. Este trabajo de tesis presenta un modelo de landmarks temporales que permite identificar rápida y eficientemente la irresolubilidad de problemas de planificación con restricciones. Nuestro modelo incorpora las restricciones temporales del lenguaje PDDL3.0 y extiende el concepto de landmark STRIPS al contexto temporal. A cada landmark temporal se le asocian tres tipos de intervalos que se actualizan y propagan de acuerdo a las relaciones de orden y restricciones temporales entre ellos. Los landmarks temporales junto con sus relaciones de orden y restricciones temporales forman un grafo de landmarks temporales donde se sintetiza las relaciones que existen entre los literales de un plan solución y, consecuentemente, entre sus correspondientes acciones. Cuando se añade nueva información al grafo, se actualizan y propagan los intervalos de los landmarks, reflejando una imagen más precisa del plan solución. Posteriormente, el modelo de landmarks temporales se integra en un planificador temporal heurístico independiente del dominio denominado TempLM. TempLM utiliza toda la información extraída del problema para podar los planes parciales en el árbol de búsqueda que no son compatibles con la información del grafo de landmarks temporales. Además, se dispone de un proceso de retroalimentación entre el grafo de landmarks temporales y el proceso de búsqueda de un plan solución que permite enriquecer el grafo y, asimismo, acotar el espacio de búsqueda. Los resultados experimentales muestran que esta aproximación detecta rápidamente problemas irresolubles y también es muy efectiva para resolver problemas con restricciones muy ajustadas. / [CA] L'objectiu de la planificació temporal automàtica és la construcció de plans amb accions de diferent durada que necessiten ser programades adequadament amb la finalitat d'aconseguir els objectius del problema. En planificació temporal, l'optimitat es mesura com la durada del pla més curt. No obstant açò, en molts problemas del món real és necessari gestionar restriccions temporals associades als objectius del problema que poden no satisfer-se amb el pla de menor durada. En la Competició Internacional de Planificació de l'any 2006 es va presentar el llenguatge PDDL3.0 i es va realitzar la primera i única competició de planificadors amb gestió de restriccions de trajectòries d'estat i preferències. Concretament, en aquesta IPC es van provar quatre dominis amb restriccions temporals on els objectius han de satisfer-se dins d'un límit de temps establit o deadline. Dos planificadors van participar en aquesta competició encara que cap va presentar un bon comportament respecte al compliment dels deadlines. En aquest tipus de problemes, especialment quan es tracta de problemes altament restringits, és crucial detectar la irresolubilitat dels mateixos el més prompte possible, i en aquest punt és on s'estableix el nostre objectiu. Aquest treball de tesi presenta un model de landmarks temporals que permet identificar ràpida i eficientment la irresolubilitat de problemes de planificació amb restriccions. El nostre model incorpora les restriccions temporals del llenguatge PDDL3.0 i estén el concepte de landmark STRIPS al context temporal. A cada landmark temporal se li associen tres tipus d'intervals que s'actualitzen i propaguen d'acord a les relacions d'ordre i restriccions temporals entre ells. Els landmarks temporals juntament amb les seues relacions d'ordre i restriccions temporals formen un graf de landmarks temporals on se sintetitza les relacions que existeixen entre els literals d'un pla solució i, conseqüentment, entre les seues corresponents accions. Quan s'afig nova informació al graf, s'actualitzen i propaguen els intervals dels landmarks, reflectint una imatge més precisa del pla solució. Posteriorment, el model de landmarks temporals s'integra en un planificador temporal heurístic independent del domini denominat TempLM. TempLM utilitza tota la informació extreta del problema per a podar els plans parcials en l'arbre de cerca que no són compatibles amb la informació del graf de landmarks temporals. A més, es disposa d'un procés de retroalimentació entre el graf de landmarks temporals i el procés de cerca d'un pla solució que permet enriquir el graf i, així mateix, limitar l'espai de cerca. Els resultats experimentals mostren que aquesta aproximació detecta ràpidament problemes irresolubles i també és molt efectiva per a resoldre problemes amb restriccions molt ajustades. / Marzal Calatayud, EJ. (2016). Modelo de landmarks temporales para problemas de planificación temporal altamente restringidos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61460

Nous considérons un problème d'ordonnancement à une machine avec dates de fin impératives et nous cherchons caractériser l'ensemble des solutions optimales, sans les énumérer. Nous supposons que les travaux sont numérotés selon la règle EDD et que cette séquence est réalisable. La méthode consiste à utiliser le treillis des permutations et d'associer à la permutation maximale du treillis la séquence EDD. Afin de caractériser beaucoup de solutions, nous cherchons une séquence réalisable aussi loin que possible de cette séquence. La distance utilisée est le niveau de la séquence dans le treillis, qui doit être minimum (le plus bas possible). Cette nouvelle fonction objectif est étudiée. Quelques cas particuliers polynomiaux sont identifiés, mais la complexité du problème général reste ouverte. Quelques méthodes de résolution, polynomiales et exponentielles, sont proposées et évaluées. Le niveau de la séquence étant en rapport avec la position des travaux dans la séquence, de nouvelles fonctions objectifs en rapport avec les positions des travaux sont identifiées et étudiées. Le problème de la minimisation de la somme pondérée des positions des travaux est prouvé fortement NP-difficile. Quelques cas particuliers sont étudiés et des méthodes de résolution proposées et évaluées. / We consider a single machine scheduling problem with deadlines and we want to characterise the set of optimal solutions, without enumerating them. We assume that jobs are numbered in EDD order and that this sequence is feasible. The key idea is to use the lattice of permutations and to associate to the supremum permutation the EDD sequence. In order to characterize a lot of solutions, we search for a feasible sequence, as far as possible to the supremum. The distance is the level of the sequence in the lattice, which has to be minimum. This new objective function is investigated. Some polynomially particular cases are identified, but the complexity of the general case problem remains open. Some resolution methods, polynomial and exponential, are proposed and evaluated. The level of the sequence being related to the positions of jobs in the sequence, new objective functions related to the jobs positions are identified and studied. The problem of minimizing the total weighted positions of jobs is proved to be strongly NP-hard. Some particular cases are investigated, resolution methods are also proposed and evaluated.

When a package is shipped, the customer often requires the delivery to be made within a particular time window or by a deadline. However, meeting such time requirements is difficult, and delivery companies may not always know ahead of time which customers will need a delivery. In this thesis, we present models and solution approaches for two stochastic last-mile delivery problems in which customers have delivery time constraints and customer presence is known in advance only according to a probability distribution. Our solutions can help reduce the operational costs of delivery while improving customer service. The first problem is the probabilistic traveling salesman problem with time windows (PTSPTW). In the PTSPTW, customers have both a time window and a probability of needing a delivery on any given day. The objective is to find a pre-planned route with an expected minimum cost. We present computational results that characterize the PTSPTW solutions. We provide insights for practitioners on when solving the PTSPTW is beneficial compared to solving the deterministic analogue of the problem. The second problem is the same-day delivery problem (SDDP). The SDDP is a dynamic and stochastic pick-up and delivery problem. In the SDDP, customers make delivery requests throughout the day and vehicles are dispatched from a warehouse or brick and mortar store to serve the requests. Associated with each request is a request deadline or time window. In order to make better-informed decisions, our solution approach incorporates information about future requests into routing decisions by using a sample scenario planning approach with a consensus function. We also introduce an analytical result that identifies when it is beneficial for vehicles to wait at the depot. We present a wide range of computational experiments that demonstrate the value of our approaches.

Η διπλωµατική εργασία αποτελεί συνέχεια της µελέτης προβληµάτων χρονοπρογραµµατισµού µε αυστηρές προθεσµίες που ξεκίνησε η Αµαλία Στούµπου στην δικιά της διπλωµατική εργασία µε όνοµα "Προβλήµατα Επιτάχυνσης ∆ιεργασιών σε Grid Computing: Αλγόριθµοι και Πολυπλοκότητα". Εξετάζονται προβλήµατα δροµολόγησης διεργασιών σε περισσότερους από έναν, ίδιους µεταξύ τους, επεξεργαστές. ∆ίνονται αλγόριθµοι που λύνουν το πρόβληµα ελαχιστοποίησης του συνολικού χρόνου εκτέλεσης, µε αυστηρές προθεσµίες, αρχικά για 2 και στη συνέχεια για m επεξεργαστές. Οι αλγόριθµοι αυτοί έχουν ψευδοπολυωνυµική πολυπλοκότητα. Στη συνέχεια εξετάζονται προβλήµατα δροµολόγησης και επιτάχυνσης διεργασιών µε ίδιο χρόνο εκτέλεσης, σε περιβάλλοντα µε ίδιους µεταξύ τους επεξεργαστές και δίνονται πολυωνυµικοί αλγόριθµοι που τα λύνουν. Τέλος αναφέρονται συνοπτικά ορισµένα προβλήµατα του ευρύτερου χώρου προϐληµάτων χρονοπρογραµµατισµού που µπορούν να προσεγγιστούν ή να λυθούν µε τεχνικές που εφαρµόστηκαν για τη λύση των προηγούµενων προβληµάτων που αναφέρθηκαν. / This thesis is a continuation of the study of scheduling problems with strict deadlines that begun in the thesis "Προβλήµατα Επιτάχυνσης ∆ιεργασιών σε Grid Computing : Αλγόριθµοι και Πολυπλοκότητα" by Amalia Stoumpou. We study scheduling problems on more than one parallel processors. Algorithms are given that solve the problem of minimizing the makespan with strict deadlines, first for 2 and then for m processors. These algorithms are pseudopolynomial in complexity. We also study problems of scheduling and speedup of processes with the same execution time in parallel processor environments and we give pseudopolynomial algorithms that solve them. Finally, we mention briefly other problems that can be solved or approached using the techniques that we applied to solve the previous problems.