Velocity control of a 2D dynamic walking robot

In this abstract we introduce velocity control for our 2D dynamic walking robot Dribbel [1] (figure 1) and show that, by ‘closing the loop’, this automatically leads to increased robustness

Geometric dynamics analysis of humanoids - locked inertia

The advantage of geometric dynamics analysis over most classical 3D analysis is that the equations are coordinate- neutral: as long as all quantities are expressed in the same coordinate frame, the equations are correct

Coordinate transformation as a help for controller design in walking robots

For walking robots, the robot’s absolute position must be re- flected in the state. Usually one chooses to include the pose and velocity of the torso in the state (i.e., the torso is taken as the reference body). However, sometimes it is useful to choose a different reference body; in particular the stance foot is a good choice

Control of walking robots using virtual springs

At the Control Engineering group of the University of Twente, we are conducting research on control of bipedal robots. In our search for robust and energy efficient control, we are making extensive use of simulation. In order to facil- itate the development of algorithms, we want to design con- trollers that work in a space of “meaningful variables”; i.e. we don’t control joint angles directly but we control things as “position and velocity of center of mass”, “shape of the robot’s locked inertia ellipsoid” [1] and “foot position”

The Effect of Food Supplement MalnuForte on the Quality of Life of Children who Suffered Malnutrition in the First 1000 Days of their lives: A Case Report (MalnuForte Case Study)

Objective: Malnutrition is a common worldwide problem and, for children, has a major impact on cognitive and physical development, productivity and health. The damage due to malnutrition is largest when it occurs in the first 1000 days of life. It is largely irreversible and has far-reaching consequences. There is as yet no known cure for the negative effects of malnutrition, while a cure for a large number of previously malnourished children worldwide would lead to better chances for them in life. This case study, therefore, examines the effect of a six-month treatment of MalnuForte on the quality of life of children between 5 and 11 years who suffered malnutrition in the first 1000 days of their livesMethods: The study subjects are five adopted children who suffered malnutrition in the first 1000 days of their lives and experienced problems or backlog in their quality of life. For six months, the children took one tablet of food supplement MalnuForte a day orally. To estimate the subjects' quality of life, a standardized and validated quality of life questionnaire for children was used, the PedsQL.Results: A higher quality of life after six months was found for all subjects. The mean total increase of the PedsQL scores between baseline and 6 months was 50%.Conclusion: In this case study, the intake of food supplement MalnuForte shows remarkable increases in the quality of life of five adopted children who had suffered from malnutrition during the first 1000 days of their lives

Impacts of climate change on rice production in Africa and causes of simulated yield changes

This study is the first of its kind to quantify possible effects of climate change on rice production in Africa. We simulated impacts on rice in irrigated systems (dry season and wet season) and rainfed systems (upland and lowland). We simulated the use of rice varieties with a higher temperature sum as adaptation option. We simulated rice yields for 4 RCP climate change scenarios and identified causes of yield declines. Without adaptation, shortening of the growing period due to higher temperatures had a negative impact on yields (−24% in RCP 8.5 in 2070 compared with the baseline year 2000). With varieties that have a high temperature sum, the length of the growing period would remain the same as under the baseline conditions. With this adaptation option rainfed rice yields would increase slightly (+8%) but they remain subject to water availability constraints. Irrigated rice yields in East Africa would increase (+25%) due to more favourable temperatures and due to CO2 fertilization. Wet season irrigated rice yields in West Africa were projected to change by −21% or +7% (without/with adaptation). Without adaptation irrigated rice yields in West Africa in the dry season would decrease by −45% with adaptation they would decrease significantly less (−15%). The main cause of this decline was reduced photosynthesis at extremely high temperatures. Simulated heat sterility hardly increased and was not found a major cause for yield decline. The implications for these findings are as follows. For East Africa to benefit from climate change, improved water and nutrient management will be needed to benefit fully from the more favourable temperatures and increased CO2 concentrations. For West Africa, more research is needed on photosynthesis processes at extreme temperatures and on adaptation options such as shifting sowing dates

On specifying heterogeneity in knowledge production functions

Within the Geography of Innovation literature, the Knowledge Production Function approach has become a reference framework to investigate the presence of localized knowledge spillovers and spatial econometric tools have been applied to study interregional spillovers. A linear specification for the KPF is assumed linking patents to R&D expenditure. This approach however suffers of different drawbacks. First patent applications are count data in nature. Patents per inhabitants may produce an unrealistic picture of the spatial distribution of innovative activities. Secondly, spatial heterogeneity is not usually observed, producing both omitted variables bias and spatial correlation in the error structure. Third, a positive R&D-patents linkage may arise as a spurious correlation if market size is not observed, causing R&D to be endogenous. This paper uses a regional cross section model to study the spatial distribution of high tech patents across 232 European regions in the period 2005/2006 to address these issues. Two main processes drive technological change in the model: research activities and knowledge generated outside firms and in a second moment embedded through either formal or informal acquisition. Among the different knowledge sources we particularly focus on the role of firms working in Knowledge Intensive Business Services and on that of universities. In developing the empirical model we take into account that a) patents are count data; b) the exclusion of market size will cause biased and inconsistent model parameters estimates; c) estimates of interregional spillovers may be biased by the omission of heterogeneity in the model specification. Empirical results indicate that, as expected, a count data distribution best fits the data, producing less spatially autocorrelated residuals. Regional innovative activity is explained by both investments in research and localization of KIBS, but only the first generates positive interregional externalities. Scientific universities do not directly affect the production of new knowledge. However, different knowledge production processes characterize regions with and without scientific universities, with R&D driving innovation in the sooner and KIBS in the latter. Finally, most of what are assumed to be interregional spillovers reveal to be, at a more careful inquiry, effect due to unaccounted spatial heterogeneity in regional innovation.

ICT loves agglomeration The urban impacts of ICT in the Netherlands

Information and Communication Technology (ICT) has had an undeniable impact on our society. Some people argue that technology has projected us onto a new wave of social and cultural change. Nevertheless, despite the growth of technology and the social significance of its applications, we have only a poor grasp of its actual impact on the use of physical space. The key question addressed in this paper is therefore: how will ICT influence the spatial-economic patterns of business activities in the Netherlands? In offering answers to this question, the paper develops a conceptual framework that distinguishes two roles of ICT in spatial-economic development: that of a ‘motor’, enhancing productivity and encourages the development of economic sectors, and that of an ‘enabler’ (of e-work, e-commerce and e-business), which may lead households and firms to adopt a different attitude to space requirements. The paper is based on a thorough survey of the current literature on the subject, the results of a recent survey of ICT’s impact on society, and original empirical research into specific factors such as ICT companies’ location preferences and the willingness of knowledge workers to commute. The paper presents an assessment of the usefulness of these concepts in terms of the Dutch situation, both today and in the future. We conclude that Information and Communication Technology has not yet had a marked visible impact on the use of space. To the contrary, despite predictions neither Dutch companies (particularly those in the ICT sector) nor knowledge workers display any unusual degree of mobility at the local or regional s 2perfect substitute for ‘traditional’ behavioural patterns. Nevertheless, there are clear indications that the ‘spatial order’ of the Netherlands is likely to change. Although it is likely that ICT will consolidate underlying spatial patterns, on the regional aggregate changes are occurring within those patterns. While (inner) cities have traditionally been the breeding ground for new ICT companies, this function has now largely been taken over by the outlying city regions, in which multiple clusters of economic activity are emerging: a process of ‘splintering urbanism’. However, despite this regionalized pattern of deconcentration, the traditional city centres continue to fulfil a number of essential functions. These centres remain the meeting places, and the shopping and entertainment centres for businesses and households (the ‘Consumer City’). In the processes of deconcentration and multimodality, ICT should be seen to play an important facilitating and strengthening role. cale. ICT does not function as a 2perfect substitute for ‘traditional’ behavioural patterns. Nevertheless, there are clear indications that the ‘spatial order’ of the Netherlands is likely to change. Although it is likely that ICT will consolidate underlying spatial patterns, on the regional aggregate changes are occurring within those patterns. While (inner) cities have traditionally been the breeding ground for new ICT companies, this function has now largely been taken over by the outlying city regions, in which multiple clusters of economic activity are emerging: a process of ‘splintering urbanism’. However, despite this regionalized pattern of deconcentration, the traditional city centres continue to fulfil a number of essential functions. These centres remain the meeting places, and the shopping and entertainment centres for businesses and households (the ‘Consumer City’). In the processes of deconcentration and multimodality, ICT should be seen to play an important facilitating and strengthening role.

Agglomeration economies and the location of new information and communication technology (ICT) firms in the Netherlands

In 2000, the world wide, rapid employment growth in the ICT-sector came to an end. Knowledge-intensive ICT-firms and -sectors in the Netherlands confirmed to this negative development trend as well. The life-cycle of the ICT-sector appears to reach a new phase of development, dominated by saturation of demand and enforced competition. This might affect the localised growth in the ICT-sector as well. According to evolutionary interpretations of agglomeration theory, one expects that new ICT firms start up in knowledge intensive, urban setting in order to gain from localised knowledge spillovers. The recent empirical literature is not unambiguous clear upon the role of intra- and intersectoral (specialisation or sectoral diversity based) agglomeration circumstances that determine firm formation, growth and survival patterns. In later stages of sectoral development, three kinds of spatial developments are expected from the geographical growth literature: (1) a cummulative causation based process of growth within the preliminary urban settings; (2) a dispersion process towards suburban and adjacent rural regions based on physical network and proximity conceptualisations, (3) spatial growth transmittance and firm dispersion based on functional network spatial relationships which are predominantly non-contiguous in character. For the latter category of spatial economic dynamics, the degree of urbanisation, accessibility, regional labour market- and national zoning spatial regimes are assumed to be leading spatial conceptualisations. A favourable macro-economic growth perspective, as present in the Netherlands during our research period, is assumed to speed up (and condition) spatial economic dispersal patterns. To test these spatial growth transmittance and firm dispersal hypotheses we analyse the components of growth (new firm formation, survival and growth in incumbent firms) of a large dataset of in total 36,000 ICT firms in the Netherlands for the period 1996-2000. The papers empirically distinguishes in-situ urban growth, contiguous relations in growth patterns (starting on an initially low, intra-urban spatial scale) and heterogeneous (non-contiguous) spatial research designs. Conclusions are drawn in relation to the recent agglomeration and economic growth literature.

The knowledge economy and Dutch cities

How can cities and metropolitan regions remain prosperous and competitive in a rapidly changing economy? In our paper we argue that ‘the knowledge economy’ offers perspectives for growth and added value creation. The paper clarifies what elements the knowledge economy actually consists of, how it can be measured in statistical indicators, in which regions and cities in the Netherlands the knowledge economy has its most significant imprints and what statistical association there is between these regions and cities and relatively good economic performance of firms. We test two contrasting hypotheses often heard in the international literature. The current embedding of knowledge externalities in endogenous economic growth theory have led to important contributions that stress the urban character knowledge transmission in particular. The reasoning is that if knowledge spillovers and –externalities are important to growth and innovation, they should be more easily identified in cities where many people are concentrated into a relatively small geographic space so that knowledge can be transmitted between them more easily. Much recent research indeed finds a limited extent of spatial spillovers and a large degree of local clustering. Alternatively, a large body of literature on Western spatial configurations of innovation and high-technology firms predominantly stresses the supposed ‘urban field’ character of firm performance: location and agglomeration aspects do not seem to have a systematic impact on the distribution of innovative and growth inducing activities over space. We test the urban hypothesis using spatial econometric modeling techniques. On the one hand, the fact that a distance squared distance weight matrix in spatial lag estimations fits the performance data best in relation to knowledge economy factors indicates that spatial relations are limited and urban fixed. On the other hand, the significance of several spatial regimes though (especially those of the Randstad core region, the so-called intermediate zone and medium-sized cities) indicates that the urban structure related to the knowledge economy and economic performance is not straightforward hierarchical (largest cities are not the relatively most attached to the knowledge economy). Both hypotheses (urban and non-urban) are too extreme to fit the Dutch situation. We also conclude that the locational attributes of the factor ‘knowledge workers’ are much more significantly related to economic growth and added value (in practically all specifications over regimes and spatial lag estimations) than the R&D-based innovation input factor. This questions Dutch policy initiatives that mainly focus on R&D as stimulator of the ‘knowledge economy’.