Geometric continuity and compatibility conditions for 4-patch surfaces

When considering regularity of surfaces, it is its geometry that is of interest. Thus, the concept of geometric regularity or geometric continuity of a specific order is a relevant concept. In this paper we discuss necessary and sufficient conditions for a 4-patch surface to be geometrically continuous of order one and two or, in other words, being tangent plane continuous and curvature continuous respectively. The focus is on the regularity at the point where the four patches meet and the compatibility conditions that must appear in this case. In this article the compatibility conditions are proved to be independent of the patch parametrization, i.e., the compatibility conditions are universal. In the end of the paper these results are applied to a specific parametrization such as Bezier representation in order to generalize a 4-patch surface result by Sarraga.Comment: 25 pages, 6 figure

Finite-time Convergent Gossiping

Gossip algorithms are widely used in modern distributed systems, with applications ranging from sensor networks and peer-to-peer networks to mobile vehicle networks and social networks. A tremendous research effort has been devoted to analyzing and improving the asymptotic rate of convergence for gossip algorithms. In this work we study finite-time convergence of deterministic gossiping. We show that there exists a symmetric gossip algorithm that converges in finite time if and only if the number of network nodes is a power of two, while there always exists an asymmetric gossip algorithm with finite-time convergence, independent of the number of nodes. For $n=2^m$ nodes, we prove that a fastest convergence can be reached in $nm=n\log_2 n$ node updates via symmetric gossiping. On the other hand, under asymmetric gossip among $n=2^m+r$ nodes with $0\leq r<2^m$, it takes at least $mn+2r$ node updates for achieving finite-time convergence. It is also shown that the existence of finite-time convergent gossiping often imposes strong structural requirements on the underlying interaction graph. Finally, we apply our results to gossip algorithms in quantum networks, where the goal is to control the state of a quantum system via pairwise interactions. We show that finite-time convergence is never possible for such systems.Comment: IEEE/ACM Transactions on Networking, In Pres

What is the Effect of Operational Managerial Practices on Dairy Farm Efficiency? Some Results from Sweden

The article aims to investigate how operational managerial practices can contribute to improved farm level efficiency at dairy farms. Operational managerial practices are defined as animal health, breeding, and feeding practices. The main contribution of the article is that it investigates aspects that can be adjusted every day to improve farm efficiency. Aspects describing each of the considered managerial practices are regressed on farm level data envelopment efficiency scores based on farm level data from Sweden. The results show that changes in breeding and feeding practices can lead to improved efficiency. Breeding exactly the number of heifers that is needed for replacement of the dairy cows negatively affects long-run technical efficiency. On the other hand, analyzing forage positively affects long-run allocative efficiency and analyzing fodder grain positively affects short-run economic efficiency. Feeding the cows hay instead of only silage, reduces long-run economic efficiency. No significant effects of animal health practices were found. These results suggest that the farms in the sample are homogeneous in terms of animal health practices and that inefficient farms cannot become more efficient by adapting to the animal health practices of more efficient farms.allocative efficiency, dairy farms, data envelopment analysis, economic efficiency, operational managerial practices, technical efficiency, tobit regression, Sweden, Livestock Production/Industries, Productivity Analysis,

Control Problems at the European Spallation Source

A background on the Europan Spallation Source is given, and our work on three control problems important for the design of its linear accelerator are presented

A note on approximating bond returns allowing for both yield change and time passage

A number of papers through the years have addressed the price-yield relationship, the approximation of bond returns and the associated components of price sensitivity. Typically, the research has been focused around the concept of duration and convexity to explain the price sensitivity of a bond to changes in its yield. Fixed income portfolio managers, however, are also interested in what happens to bond prices over a certain investment horizon, i.e. how time passage affect bond returns together with yield changes. Chance and Jordan [1996] examines this in a very neat way by a second order Taylor series expansion around the current market yiel

A note on approximating bond returns allowing for both yield change and time passage

A number of papers through the years have addressed the price-yield relationship, the approximation of bond returns and the associated components of price sensitivity. Typically, the research has been focused around the concept of duration and convexity to explain the price sensitivity of a bond to changes in its yield. Fixed income portfolio managers, however, are also interested in what happens to bond prices over a certain investment horizon, i.e. how time passage affect bond returns together with yield changes. Chance and Jordan [1996] examines this in a very neat way by a second order Taylor series expansion around the current market yiel

Regional policy at a crossroad: Sweden and Norway on different paths?

Sweden and Norway are two relatively similar countries in many respects. At a superficial glance, this is true also for the regional policy area. At a closer look, however, there are significant differences and consequently different experiences. An important part of the analysis focuses on how regional policies in Sweden as a member of the EU, and Norway as a non-member, are influenced by European integration. Our main hypothesis is that both countries' regional policy aims and measures move towards the EU's, Sweden's faster than Norway's. The current situation seems to be that Sweden increasingly put its trust into the Structural Fund programmes, while national regional policy is allowed to gradually wither away. To Norway as a non-member of the EU this is not an option, regional policy will have to be carried out within the state framework. While the EU dimension is important for understanding differences in recent tendencies, it should not be taken for granted as the decisive factor in explaining differences. This paper tries to illuminate the regional policy experience, to what extent regional policy has a good or bad image in the two countries, as an alternative explanation to the EU dimension. The argument is that the regional policy experience has been more positive in Norway than in Sweden and that current development must be understood in this light