Designing for interaction

At present, the design of computer-supported group-based learning (CS)GBL) is often based on subjective decisions regarding tasks, pedagogy and technology, or concepts such as ‘cooperative learning’ and ‘collaborative learning’. Critical review reveals these concepts as insufficiently substantial to serve as a basis for (CS)GBL design. Furthermore, the relationship between outcome and group interaction is rarely specified a priori. Thus, there is a need for a more systematic approach to designing (CS)GBL that focuses on the elicitation of expected interaction processes. A framework for such a process-oriented methodology is proposed. Critical elements that affect interaction are identified: learning objectives, task-type, level of pre-structuring, group size and computer support. The proposed process-oriented method aims to stimulate designers to adopt a more systematic approach to (CS)GBL design according to the interaction expected, while paying attention to critical elements that affect interaction. This approach may bridge the gap between observed quality of interaction and learning outcomes and foster (CS)GBL design that focuses on the heart of the matter: interaction

On the Huffman and Alphabetic Tree Problem with General Cost Functions

We address generalized versions of the Huffman and Alphabetic Tree Problem where the cost caused by each individual leaf i, instead of being linear, depends on its depth in the tree by an arbitrary function. The objective is to minimize either the total cost or the maximum cost among all leaves. We review and extend the known results in this direction and devise a number of new algorithms and hardness proofs. It turns out that the Dynamic Programming approach for the Alphabetic Tree Problem can be extended to arbitrary cost functions, resulting in a time O(n (4)) optimal algorithm using space O(n (3)). We identify classes of cost functions where the well-known trick to reduce the runtime by a factor of n via a "monotonicity" property can be applied. For the generalized Huffman Tree Problem we show that even the k-ary version can be solved by a generalized version of the Coin Collector Algorithm of Larmore and Hirschberg (in Proc. SODA\u2790, pp. 310-318, 1990) when the cost functions are nondecreasing and convex. Furthermore, we give an O(n (2)logn) algorithm for the worst case minimization variants of both the Huffman and Alphabetic Tree Problem with nondecreasing cost functions. Investigating the limits of computational tractability, we show that the Huffman Tree Problem in its full generality is inapproximable unless P = NP, no matter if the objective function is the sum of leaf costs or their maximum. The alphabetic version becomes NP-hard when the leaf costs are interdependent

How Venture Capital Creates Externalities in the Bioeconomy: a Geographical Perspective

A stream of literature has demonstrated that venture capital generates externalities that enhance the knowledge base of a given region and accordingly assist high technology firms to improve their innovative performance. What has gone largely unexamined in this literature is the geographic extent of such externality impact. In this research we address the issue at hand. We do so by analyzing the association between the patenting rate of all life sciences firms that have won Small Business Innovation Research grants from 1983 to 2006 and the venture capital investments that have occurred at increasingly distant spatial units from those firms. Controlling for firm-specific and environmental factors as well as for endogeneity concerns, we document that life sciences firms tend to produce more patents whenever they are situated in very close proximity to where venture capital investments occur. Further, we find that improvements of the patenting rate of focal firms largely emanate from investments that reflect the expertise of venture capitalists on advancing existing prototypes closer to commercialization. We conclude the paper with a discussion on research and policy implications of our findings