A partition‑based branch‑and‑bound algorithm for the project duration problem with partially renewable resources and general temporal constraints

The concept of partially renewable resources provides a general modeling framework that can be used for a wide range of different real-life applications. In this paper, we consider a resource-constrained project duration problem with partially renewable resources, where the temporal constraints between the activities are given by minimum and maximum time lags. We present a new branch-and-bound algorithm for this problem, which is based on a stepwise decomposition of the possible resource consumptions by the activities of the project. It is shown that the new approach results in a polynomially bounded depth of the enumeration tree, which is obtained by kind of a binary search. In a comprehensive experimental performance analysis, we compare our exact solution procedure with all branch-and-bound algorithms and state-of-the-art heuristics from the literature on different benchmark sets. The results of the performance study reveal that our branch-and-bound algorithm clearly outperforms all exact solution procedures. Furthermore, it is shown that our new approach dominates the state-of-the-art heuristics on well known benchmark instances

Assessing the suitability of ship design for human factors issues associated with evacuation and normal operations

Evaluating ship layout for human factors (HF) issues using simulation software such as maritimeEXODUS can be a long and complex process. The analysis requires the identification of relevant evaluation scenarios; encompassing evacuation and normal operations; the development of appropriate measures which can be used to gauge the performance of crew and vessel and finally; the interpretation of considerable simulation data. In this paper we present a systematic and transparent methodology for assessing the HF performance of ship design which is both discriminating and diagnostic. The methodology is demonstrated using two variants of a hypothetical naval ship

Projektplanung mit partiell erneuerbaren Ressourcen: Entwicklung und Untersuchung von Branch-and-Bound-Verfahren

Die Implementierung eines geeigneten und zielgerichteten Projektmanagements stellt für viele Unternehmen im Hinblick auf kürzer werdende Innovationszyklen und sich verändernde Marktanforderungen einen immer wichtigeren Erfolgsfaktor dar. Eine entscheidende Bedeutung kommt dabei vor allem der Projektplanung als Bindeglied zwischen der Vorbereitungs- und der Ausführungsphase eines Projekts zu. Insbesondere die ressourcenbeschränkte Projektplanung kann durch die Bestimmung effizienter und kostengünstiger Einsatzpläne für begrenzt verfügbare Ressourcen einen wichtigen Beitrag zur Wettbewerbsfähigkeit eines Unternehmens leisten. Die meisten Modelle der ressourcenbeschränkten Projektplanung gehen vereinfachend davon aus, dass erneuerbare Ressourcen in bestimmten Mengen in jeder Zeitperiode für die Ausführung von Vorgängen zur Verfügung stehen, die durch Vorrangbeziehungen miteinander verbunden sind. Diese einschränkenden Annahmen führen jedoch dazu, dass praxisrelevante Restriktionen wie Arbeitszeitvereinbarungen oder Vorgaben zur Höchstauslastung von Maschinen durch Modelle der ressourcenbeschränkten Projektplanung nicht abgebildet werden können. Eine Möglichkeit, um komplexere Restriktionen in die Modelle einzubinden, stellen sogenannte partiell erneuerbare Ressourcen dar, die Kapazitätsrestriktionen auch über mehrere Zeitperioden modellieren können. Durch diese Art von Ressourcen können unter anderem maximale Arbeitsstunden am Wochenende oder vorgeschriebene Pausenzeiten von Arbeitskräften modelliert werden, die durch klassische Modelle der Projektplanung nicht abgebildet werden können. Weitere praxisrelevante Restriktionen wie technologisch bedingte Zeitfenster für die Ausführung von Fertigungsprozessen können zudem durch zeitliche Mindest- und Höchstabstände bzw. durch allgemeine Zeitbeziehungen zwischen den Vorgängen eines Projekts dargestellt werden. In der vorliegenden Arbeit wird das Projektdauerminimierungsproblem mit allgemeinen Zeitbeziehungen und partiell erneuerbaren Ressourcen (RCPSP/max-π) untersucht. Ein Schwerpunkt liegt dabei auf der Entwicklung von Branch-and-Bound-Verfahren, die auf unterschiedlichen Enumerationsschemata basieren. Es werden zwei relaxationsbasierte und ein konstruktionsbasiertes Branch-and-Bound-Verfahren vorgestellt, deren Leistungsfähigkeit anhand geeigneter Testinstanzen durch eine experimentelle Performance-Analyse untersucht werden. Die Ergebnisse der Analysen zeigen, dass eines der relaxationsbasierten Verfahren, das die zeitzulässigen Startzeitpunkte der Vorgänge des Projekts schrittweise in disjunkte Mengen zerlegt, die beiden anderen Ansätze dominiert. Aus einem weiterführenden Vergleich mit dem MILP-Solver IBM CPLEX sowie den besten bislang bekannten Näherungsverfahren zur Projektdauerminimierung mit partiell erneuerbaren Ressourcen wird zudem die vorteilhafte Performance des dominanten Branch-and-Bound-Verfahrens bestätigt. In der vorliegenden Arbeit wird weiterhin gezeigt, dass der Einsatz partiell erneuerbarer Ressourcen ein weites Feld an Modellierungsmöglichkeiten eröffnet, das auch andere Konzepte der Projektplanung umfasst, die über die letzten Jahrzehnte entwickelt wurden. Basierend auf diesen Ergebnissen wird zudem gezeigt, dass exakte Verfahren für das RCPSP/max-π auch zur Lösung anderer bekannter Projektdauerminimierungsprobleme aus der Literatur eingesetzt werden können.The implementation of a suitable and targeted project management is an increasingly important success factor for many companies in view of shorter innovation cycles and changing market requirements. Project scheduling is of particular importance as the link between the preparation and execution phase of a project. In fact, resource-constrained project scheduling can make an important contribution to the competitiveness of a company by determining efficient and cost-effective deployment plans for limited resources. Most models of resource-constrained project scheduling assume, in a simplified manner, that renewable resources are available in certain quantities in each period of time for the execution of tasks that are linked by precedence relationships. However, these limiting assumptions mean that practical restrictions such as working time agreements or specifications for the maximum utilization of machines cannot be mapped by models of resource-constrained project scheduling. One way of integrating more complex restrictions into the models are so-called partially renewable resources that can model capacity restrictions over several time periods. This type of resource can be used to model, among other things, maximum working hours on weekends or prescribed break times for workers, which cannot be mapped using classic project scheduling models. Further practical restrictions such as technologically-related time windows for the execution of manufacturing processes can be represented by minimum and maximum time lags or rather by general temporal constraints between the activities of a project. In the present work the project duration problem with general temporal constraints and partially renewable resources (RCPSP/max-π) is investigated. One focus is on the development of branch-and-bound procedures that are based on different enumeration schemes. Two relaxation-based and one construction-based branch-and-bound method are presented, the performance of which is examined using suitable test instances through an experimental performance analysis. The results of the analyzes show that one of the relaxation-based methods, which gradually decomposes the time-feasible start times of the project's activities into disjoint sets, dominates the other two approaches. A further comparison with the MILP solver IBM CPLEX as well as the best known approximation methods for project duration problems with partially renewable resources also confirms the advantageous performance of the dominant branch-and-bound method. In the present work it is further shown that the use of partially renewable resources opens up a wide field of modeling possibilities that also includes other project scheduling concepts that have been developed over the past decades. Based on these results it is shown that exact solution procedures for the RCPSP/max-π can also be used to solve other known project duration problems from the literature

Factors Influencing Customer Satisfaction towards E-shopping in Malaysia

Online shopping or e-shopping has changed the world of business and quite a few people have decided to work with these features. What their primary concerns precisely and the responses from the globalisation are the competency of incorporation while doing their businesses. E-shopping has also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction while operating in the e-retailing environment. It is very important that customers are satisfied with the website, or else, they would not return. Therefore, a crucial fact to look into is that companies must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s point of view. With is in mind, this study aimed at investigating customer satisfaction towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students randomly selected from various public and private universities located within Klang valley area. Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust, design of the website, online security and e-service quality. Finally, recommendations and future study direction is provided. Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia

Federal Register

Daily publication of the U.S. Office of the Federal Register contains rules and regulations, proposed legislation and rule changes, and other notices, including "Presidential proclamations and Executive Orders, Federal agency documents having general applicability and legal effect, documents required to be published by act of Congress, and other Federal agency documents of public interest" (p. ii). Table of Contents starts on page iii

Ways and Capacity in Archaeological Data Management in Serbia

Over the past year and due to the COVID-19 pandemic, the entire world has witnessed inequalities across borders and societies. They also include access to archaeological resources, both physical and digital. Both archaeological data creators and users spent a lot of time working from their homes, away from artefact collections and research data. However, this was the perfect moment to understand the importance of making data freely and openly available, both nationally and internationally. This is why the authors of this paper chose to make a selection of data bases from various institutions responsible for preservation and protection of cultural heritage, in order to understand their policies regarding accessibility and usage of the data they keep. This will be done by simple visits to various web-sites or data bases. They intend to check on the volume and content, but also importance of the offered archaeological heritage. In addition, the authors will estimate whether the heritage has adequately been classified and described and also check whether data is available in foreign languages. It needs to be seen whether it is possible to access digital objects (documents and the accompanying metadata), whether access is opened for all users or it requires a certain hierarchy access, what is the policy of usage, reusage and distribution etc. It remains to be seen whether there are public API or whether it is possible to collect data through API. In case that there is a public API, one needs to check whether datasets are interoperable or messy, requiring data cleaning. After having visited a certain number of web-sites, the authors expect to collect enough data to make a satisfactory conclusion about accessibility and usage of Serbian archaeological data web bases

Neolithic land-use in the Dutch wetlands: estimating the land-use implications of resource exploitation strategies in the Middle Swifterbant Culture (4600-3900 BCE)

The Dutch wetlands witness the gradual adoption of Neolithic novelties by foraging societies during the Swifterbant period. Recent analyses provide new insights into the subsistence palette of Middle Swifterbant societies. Small-scale livestock herding and cultivation are in evidence at this time, but their importance if unclear. Within the framework of PAGES Land-use at 6000BP project, we aim to translate the information on resource exploitation into information on land-use that can be incorporated into global climate modelling efforts, with attention for the importance of agriculture. A reconstruction of patterns of resource exploitation and their land-use dimensions is complicated by methodological issues in comparing the results of varied recent investigations. Analyses of organic residues in ceramics have attested to the cooking of aquatic foods, ruminant meat, porcine meat, as well as rare cases of dairy. In terms of vegetative matter, some ceramics exclusively yielded evidence of wild plants, while others preserve cereal remains. Elevated δ15N values of human were interpreted as demonstrating an important aquatic component of the diet well into the 4th millennium BC. Yet recent assays on livestock remains suggest grazing on salt marshes partly accounts for the human values. Finally, renewed archaeozoological investigations have shown the early presence of domestic animals to be more limited than previously thought. We discuss the relative importance of exploited resources to produce a best-fit interpretation of changing patterns of land-use during the Middle Swifterbant phase. Our review combines recent archaeological data with wider data on anthropogenic influence on the landscape. Combining the results of plant macroremains, information from pollen cores about vegetation development, the structure of faunal assemblages, and finds of arable fields and dairy residue, we suggest the most parsimonious interpretation is one of a limited land-use footprint of cultivation and livestock keeping in Dutch wetlands between 4600 and 3900 BCE.NWOVidi 276-60-004Human Origin

Taphonomy, environment or human plant exploitation strategies?: Deciphering changes in Pleistocene-Holocene plant representation at Umhlatuzana rockshelter, South Africa

The period between ~40 and 20 ka BP encompassing the Middle Stone Age (MSA) and Later Stone Age (LSA) transition has long been of interest because of the associated technological change. Understanding this transition in southern Africa is complicated by the paucity of archaeological sites that span this period. With its occupation sequence spanning the last ~70,000 years, Umhlatuzana Rock Shelter is one of the few sites that record this transition. Umhlatuzana thus offers a great opportunity to study past environmental dynamics from the Late Pleistocene (MIS 4) to the Late Holocene, and past human subsistence strategies, their social organisation, technological and symbolic innovations. Although organic preservation is poor (bones, seeds, and charcoal) at the site, silica phytoliths preserve generally well throughout the sequence. These microscopic silica particles can identify different plant types that are no longer visible at the site because of decomposition or burning to a reliable taxonomical level. Thus, to trace site occupation, plant resource use, and in turn reconstruct past vegetation, we applied phytolith analyses to sediment samples of the newly excavated Umhlatuzana sequence. We present results of the phytolith assemblage variability to determine change in plant use from the Pleistocene to the Holocene and discuss them in relation to taphonomical processes and human plant gathering strategies and activities. This study ultimately seeks to provide a palaeoenvironmental context for modes of occupation and will shed light on past human-environmental interactions in eastern South Africa.NWOVidi 276-60-004Human Origin