Martin Bichler

An experimental analysis of multi-attribute auctions

Abstract Auctions are a fundamental mechanism to automating negotiations in electronic commerce. We investigate multi-attribute auctions, an economic mechanism, which automates negotiation on multiple attributes of a deal. In this approach, we combine decision analysis techniques and single-sided auction mechanisms in order to procure goods and services. The paper describes an experimental analysis of multi-attribute auctions. First, we will provide an overview of the preliminary game-theoretical and simulation results. Then we will introduce a Web-based implementation of the mechanism and describe the design and the results of an experiment analyzing the economic behavior of multi-attribute auction formats. In the experiment, the utility scores achieved in multi-attribute auctions were significantly higher than those of single-attribute auctions. The efficiency was similar in single-attribute and multi-attribute auctions, and we did not find evidence for revenue equivalence between the multi-attribute auction formats.

Identification of influencers - Measuring influence in customer networks

Viral marketing refers to marketing techniques that use social networks to produce increases in brand awareness through self-replicating viral diffusion of messages, analogous to the spread of pathological and computer viruses. The idea has successfully been used by marketers to reach a large number of customers rapidly. If data about the customer network is available, centrality measures provide a structural measure that can be used in decision support systems to select influencers and spread viral marketing campaigns in a customer network. Usage stimulation and churn management are examples of DSS applications, where centrality of customers does play a role. The literature on network theory describes a large number of such centrality measures. A critical question is which of these measures is best to select an initial set of customers for a marketing campaign, in order to achieve a maximum dissemination of messages. In this paper, we present the results of computational experiments based on call data from a telecom company to compare different centrality measures for the diffusion of marketing messages. We found a significant lift when using central customers in message diffusion, but also found differences in the various centrality measures depending on the underlying network topology and diffusion process.

A Mathematical Programming Approach for Server Consolidation Problems in Virtualized Data Centers

Todays data centers offer IT services mostly hosted on dedicated physical servers. Server virtualization provides a technical means for server consolidation. Thus, multiple virtual servers can be hosted on a single server. Server consolidation describes the process of combining the workloads of several different servers on a set of target servers. We focus on server consolidation with dozens or hundreds of servers, which can be regularly found in enterprise data centers. Cost saving is among the key drivers for such projects. This paper presents decision models to optimally allocate source servers to physical target servers while considering real-world constraints. Our central model is proven to be an NP-hard problem. Therefore, besides an exact solution method, a heuristic is presented to address large-scale server consolidation projects. In addition, a preprocessing method for server load data is introduced allowing for the consideration of quality-of-service levels. Extensive experiments were conducted based on a large set of server load data from a data center provider focusing on managerial concerns over what types of problems can be solved. Results show that, on average, server savings of 31 percent can be achieved only by taking cycles in the server workload into account.

Towards a Structured Design of Electronic Negotiations

Global communication networks and advances in information technology enable the design of information systems facilitating effective formulation and efficient resolution of negotiation problems. Increasingly, these systems guide negotiators in clarifying the relevant issues, provide media for offer formulation and exchange, and help in achieving an agreement. In practice, the task of analysing, modelling, designing and implementing electronic negotiation media demands a systematic, traceable and reproducible approach. An engineering approach to media specification and construction has these characteristics. In this paper, we provide a rationale for the engineering approach that allows pragmatic adoption of economic and social sciences perspectives on negotiated decisions for the purpose of supporting and undertaking electronic negotiations. Similarities and differences of different theories that underlie on-going studies of electronic negotiations are identified. This provides a basis for integration of different theories and approaches for the specific purpose of the design of effective electronic negotiations. Drawing on diverse streams of literature in different fields such as economics, management, computer, and behavioural sciences, we present an example of an integration of three significant streams of theoretical and applied research involving negotiations, traditional auctions and on-line auctions.

Direct observation of controlled coupling in an individual quantum dot molecule.

We report the direct observation of quantum coupling in individual quantum dot molecules and its manipulation using static electric fields. A pronounced anticrossing of different excitonic transitions is observed as the electric field is tuned. A comparison of our experimental results with theory shows that the observed anticrossing occurs between excitons with predominant spatially direct and indirect character and reveals a field driven transition of the nature of the molecular ground state exciton wave function. Finally, the interdot quantum coupling strength is deduced optically and its dependence on the interdot separation is calculated.

Configurable offers and winner determination in multi-attribute auctions

Abstract The theory of procurement auctions traditionally assumes that the offered quantity and quality is fixed prior to source selection. Multi-attribute reverse auctions allow negotiation over price and qualitative attributes such as color, weight, or delivery time. They promise higher market efficiency through a more effective information exchange of buyer’s preferences and supplier’s offerings. This paper focuses on a number of winner determination problems in multi-attribute auctions. Previous work assumes that multi-attribute bids are described as attribute value pairs and that the entire demand is purchased from a single supplier. Our contribution is twofold: First, we will analyze the winner determination problem in case of multiple sourcing. Second, we will extend the concept of multi-attribute auctions to allow for configurable offers. Configurable offers enable suppliers to specify multiple values and price markups for each attribute. In addition, suppliers can define configuration and discount rules in form of propositional logic statements. These extensions provide suppliers with more flexibility in the specification of their bids and allow for an efficient information exchange among market participants. We will present MIP formulations for the resulting allocation problems and an implementation.

Knowledge representation concepts for automated SLA management

Outsourcing of complex IT infrastructure to IT service providers has increased substantially during the past years. IT service providers must be able to fulfil their service-quality commitments based upon predefined Service Level Agreements (SLAs) with the service customer. They need to manage, execute and maintain thousands of SLAs for different customers and different types of services, which needs new levels of flexibility and automation not available with the current technology. The complexity of contractual logic in SLAs requires new forms of knowledge representation to automatically draw inferences and execute contractual agreemen ts. A logic-based approach provides several advantages including automated rule chaining allowing for compact knowledge representation as well as flexibility to adapt to rapidly changing business requirements. We suggest logical formalisms for the representation and enforcement of SLA rules and describe a proof-of-concept implementation. The article describes selected formalisms of the ContractLog KR and their adequacy for automated SLA management and presents results of experiments and examples from common industry use cases to demonstrate the expressiveness of the language and the scalability of the approach.

Applications of flexible pricing in business-to-business electronic commerce

The increasingly dynamic nature of business-to-business electronic commerce has produced a recent shift away from fixed pricing and toward flexible pricing. Flexible pricing, as defined here, includes both differential pricing, in which different buyers may receive different prices based on expected valuations, and dynamic-pricing mechanisms, such as auctions, where prices and conditions are based on bids by market participants. In this paper we survey ongoing work in flexible pricing in the context of the supply chain, including revenue management, procurement, and supply-chain coordination. We review negotiation mechanisms for procurement, including optimization approaches to the evaluation of complex, multidimensional bids. We also discuss several applications of flexible pricing on the sell side, including pricing strategies for response to requests for quotes, dynamic pricing in a reverse logistics application, and pricing in the emerging area of hosted applications services. We conclude with a discussion of future research directions in this rapidly growing area.

Observation of extremely slow hole spin relaxation in self-assembled quantum dots

We report the measurement of extremely slow hole spin relaxation dynamics in small ensembles of self-assembled InGaAs quantum dots. Individual spin oriented holes are optically created in the lowest orbital state of each dot and read out after a defined storage time using spin memory devices. The resulting luminescence signal exhibits a pronounced polarization memory effect that vanishes for long storage times. The hole spin relaxation dynamics are measured as a function of external magnetic field and lattice temperature. We show that hole spin relaxation can occur over remarkably long time scales in strongly confined quantum dots (up to similar to 270 mu s), as predicted by recent theory. Our findings are supported by calculations that reproduce both the observed magnetic field and temperature dependencies. The results suggest that hole spin relaxation in strongly confined quantum dots is due to spin-orbit-mediated phonon scattering between Zeeman levels, in marked contrast to higher-dimensional nanostructures where it is limited by valence band mixing.

Growth kinetics in position-controlled and catalyst-free InAs nanowire arrays on Si"111… grown by selective area molecular beam epitaxy

We investigated the interwire distance dependence on the growth kinetics of vertical, high-yield InAs nanowire arrays on Si(111) grown by catalyst-free selective area molecular beam epitaxy (MBE). Utilizing lithographically defined SiO2 nanomasks on Si(111) with regular hole patterns, catalyst-free and site-selective growth of vertically (111)-oriented InAs nanowires was achieved with very high yields of ∼90 percent. Interestingly, the yield of vertically ordered nanowires was independent of the interwire distance and the initial growth stages. Significant size variation in the nanowires was found to depend critically on the interwire distance and growth time. Two growth regimes were identified—(i) a competitive growth regime with shorter and thinner nanowires for narrow interwire distances and (ii) a diffusion-limited growth regime for wider distances, providing good estimates for the surface diffusion lengths. Surprisingly, despite these size-dependent effects the nanowire geometries remained unaltered ...