An aggregate sales model for consumer durables incorporating a time-varying mean replacement age

Forecasting category or industry sales is a vital component of a company's planning and control activities. Sales for most mature durable product categories are dominated by replacement purchases. Previous sales models which explicitly incorporate a component of sales due to replacement assume there is an age distribution for replacements of existing units which remains constant over time. However, there is evidence that changes in factors such as product reliability/durability, price, repair costs, scrapping values, styling and economic conditions will result in changes in the mean replacement age of units. This paper develops a model for such time-varying replacement behaviour and empirically tests it in the Australian automotive industry. Both longitudinal census data and the empirical analysis of the replacement sales model confirm that there has been a substantial increase in the average aggregate replacement age for motor vehicles over the past 20 years. Further, much of this variation could be explained by real price increases and a linear temporal trend. Consequently, the time-varying model significantly outperformed previous models both in terms of fitting and forecasting the sales data. Copyright (C) 2001 John Wiley & Sons, Ltd.

Database technologies for l-system simulations in virtual plant applications on bioinformatics

One of the most important advantages of database systems is that the underlying mathematics is rich enough to specify very complex operations with a small number of statements in the database language. This research covers an aspect of biological informatics that is the marriage of information technology and biology, involving the study of real-world phenomena using virtual plants derived from L-systems simulation. L-systems were introduced by Aristid Lindenmayer as a mathematical model of multicellular organisms. Not much consideration has been given to the problem of persistent storage for these simulations. Current procedures for querying data generated by L-systems for scientific experiments, simulations and measurements are also inadequate. To address these problems the research in this paper presents a generic process for data-modeling tools (L-DBM) between L-systems and database systems. This paper shows how L-system productions can be generically and automatically represented in database schemas and how a database can be populated from the L-system strings. This paper further describes the idea of pre-computing recursive structures in the data into derived attributes using compiler generation. A method to allow a correspondence between biologists' terms and compiler-generated terms in a biologist computing environment is supplied. Once the L-DBM gets any specific L-systems productions and its declarations, it can generate the specific schema for both simple correspondence terminology and also complex recursive structure data attributes and relationships.

Does gender affect visiting a world heritage site?

The city of Guimarães in Portugal is a place of strong symbolic and cultural significance, and the nomination of its historical center as a World Heritage Site in 2001 enhanced its tourism potential. This study presents the results of a survey conducted in 2010 and 2011 to capture the profile and motivations of tourists visiting Guimarães as a cultural tourism destination. The study addressed two main issues: whether males and females have similar or different preferences in choosing the city as their destination, and whether there are gender differences in the perception of the attributes of Guimarães. A better understanding of the gendered nature of the destination is a valuable cue for shaping products and services according to visitors’ preferences. The results suggest that both men and women are aware of the main elements responsible for the city’s World Heritage status. That the destination is a Heritage Site that also offers the opportunity to tour the region has a significant positive effect on male tourists’ choice of Guimarães. Regarding the perceived attributes of the city, results indicate minor gender differences with one exception: Women expressed more apprehension than men regarding the perceived security of the destination.

How does gender affect visiting a world heritage site?: the case study of Guimarães

To date few studies have been undertaken in Portugal dealing with the attitudes, motivations, and profile of tourists who visit World Heritage Sites. Also, few studies have dealt with destination image (e.g., Agapito, Mendes & Valle, 2010; Lopes, 2011). As far as it is known, none have approached the issue of gender differences in the choice of a Portuguese heritage destination. Since cultural tourism destinations need to differentiate themselves from each other, appropriate market segmentation must be based on a deep understanding of the customers’ motivations and preferences. Keeping in mind results from empirical literature (e.g., Silberberg, 1995; Beerli & Martin, 2004; Richards, 2004; Pérez, 2009; Sheng, Shen, & Chen, 2008), gender seems to be a possible approach to market segmentation, whether for Guimarães or for other cultural tourism destinations around the world. Located in the north-western region of Portugal, Guimarães is a city of strong symbolic and cultural significance, and the nomination of its historical centre as a World Heritage Site in 2001 enhanced its tourism potential. This study analyses the possible relation between gender and attitudes and motivations towards a World Heritage Site, such as Guimarães. Additionally, the empirical approach used in the study tries to capture differences in the perceived attributes of the city. Commonalities and distinctions within and between groups of tourists, by focusing on the specific characteristic of gender, were analysed. The study addressed two main questions: first, whether males and females have similar or different preferences in choosing the city as their destination; and, second, whether there are gender differences in the perception of the attributes of Guimarães. A better understanding of the gendered nature of the destination is a valuable cue for shaping products and services according to visitors’ preferences.

Does Gender Affect Visiting a World Heritage Site?

The city of Guimar˜aes in Portugal is a place of strong symbolic and cultural significance, and the nomination of its historical center as a World Heritage Site in 2001 enhanced its tourism potential. This study presents the results of a survey conducted in 2010 and 2011 to capture the profile and motivations of tourists visiting Guimar˜aes as a cultural tourism destination. The study addressed two main issues: whether males and females have similar or different preferences in choosing the city as their destination, and whether there are gender differences in the perception of the attributes of Guimar˜aes. A better understanding of the gendered nature of the destination is a valuable cue for shaping products and services according to visitors’ preferences. The results suggest that both men and women are aware of the main elements responsible for the city’s World Heritage status. That the destination is a Heritage Site that also offers the opportunity to tour the region has a significant positive effect on male tourists’ choice of Guimar˜aes. Regarding the perceived attributes of the city, results indicate minor gender differences with one exception: Women expressed more apprehension than men regarding the perceived security of the destination.

Virtual communities of practice: investigating motivations and constraints in the processes of knowledge creation and transfer

With accelerated market volatility, faster response times and increased globalization, business environments are going through a major transformation and firms have intensified their search for strategies which can give them competitive advantage. This requires that companies continuously innovate, to think of new ideas that can be transformed or implemented as products, processes or services, generating value for the firm. Innovative solutions and processes are usually developed by a group of people, working together. A grouping of people that share and create new knowledge can be considered as a Community of Practice (CoP). CoP’s are places which provide a sound basis for organizational learning and encourage knowledge creation and acquisition. Virtual Communities of Practice (VCoP's) can perform a central role in promoting communication and collaboration between members who are dispersed in both time and space. Nevertheless, it is known that not all CoP's and VCoP's share the same levels of performance or produce the same results. This means that there are factors that enable or constrain the process of knowledge creation. With this in mind, we developed a case study in order to identify both the motivations and the constraints that members of an organization experience when taking part in the knowledge creating processes of VCoP's. Results show that organizational culture and professional and personal development play an important role in these processes. No interviewee referred to direct financial rewards as a motivation factor for participation in VCoPs. Most identified the difficulty in aligning objectives established by the management with justification for the time spent in the VCoP. The interviewees also said that technology is not a constraint.

Virtual power producers integration into MASCEM

All over the world Distributed Generation is seen as a valuable help to get cleaner and more efficient electricity. Under this context distributed generators, owned by different decentralized players can provide a significant amount of the electricity generation. To get negotiation power and advantages of scale economy, these players can be aggregated giving place to a new concept: the Virtual Power Producer. Virtual Power Producers are multi-technology and multi-site heterogeneous entities. Virtual Power Producers should adopt organization and management methodologies so that they can make Distributed Generation a really profitable activity, able to participate in the market. In this paper we address the integration of Virtual Power Producers into an electricity market simulator –MASCEM – as a coalition of distributed producers.

Remuneration and tariffs in the context of virtual power players

Power systems have been through deep changes in recent years, namely with the operation of competitive electricity markets in the scope and the increasingly intensive use of renewable energy sources and distributed generation. This requires new business models able to cope with the new opportunities that have emerged. Virtual Power Players (VPPs) are a new player type which allows aggregating a diversity of players (Distributed Generation (DG), Storage Agents (SA), Electrical Vehicles, (V2G) and consumers), to facilitate their participation in the electricity markets and to provide a set of new services promoting generation and consumption efficiency, while improving players` benefits. A major task of VPPs is the remuneration of generation and services (maintenance, market operation costs and energy reserves), as well as charging energy consumption. This paper proposes a model to implement fair and strategic remuneration and tariff methodologies, able to allow efficient VPP operation and VPP goals accomplishment in the scope of electricity markets.

Multi-agent electricity market simulation with dynamic strategies & virtual power producers

Distributed energy resources will provide a significant amount of the electricity generation and will be a normal profitable business. In the new decentralized grid, customers will be among the many decentralized players and may even help to co-produce the required energy services such as demand-side management and load shedding. So, they will gain the opportunity to be more active market players. The aggregation of DG plants gives place to a new concept: the Virtual Power Producer (VPP). VPPs can reinforce the importance of these generation technologies making them valuable in electricity markets. In this paper we propose the improvement of MASCEM, a multi-agent simulation tool to study negotiations in electricity spot markets based on different market mechanisms and behavior strategies, in order to take account of decentralized players such as VPP.

Renewable-based generation integration in electricity markets with virtual power producers

The development of renewable energy sources and Distributed Generation (DG) of electricity is of main importance in the way towards a sustainable development. However, the management, in large scale, of these technologies is complicated because of the intermittency of primary resources (wind, sunshine, etc.) and small scale of some plants. The aggregation of DG plants gives place to a new concept: the Virtual Power Producer (VPP). VPPs can reinforce the importance of these generation technologies making them valuable in electricity markets. VPPs can ensure a secure, environmentally friendly generation and optimal management of heat, electricity and cold as well as optimal operation and maintenance of electrical equipment, including the sale of electricity in the energy market. For attaining these goals, there are important issues to deal with, such as reserve management strategies, strategies for bids formulation, the producers’ remuneration, and the producers’ characterization for coalition formation. This chapter presents the most important concepts related with renewable-based generation integration in electricity markets, using VPP paradigm. The presented case studies make use of two main computer applications:ViProd and MASCEM. ViProd simulates VPP operation, including the management of plants in operation. MASCEM is a multi-agent based electricity market simulator that supports the inclusion of VPPs in the players set.

Reasserting curriculum design through virtual learning environments : The case of MAPE

II European Conference on Curriculum Studies. "Curriculum studies: Policies, perspectives and practices”. Porto, FPCEUP, October 16th - 17th.