Efficient generic calibration method for general cameras with single centre of projection

Generic camera calibration is a non-parametric calibration technique that is applicable to any type of vision sensor. However, the standard generic calibration method was developed with the goal of generality and it is therefore sub-optimal for the common case of cameras with a single centre of projection (e.g. pinhole, fisheye, hyperboloidal catadioptric). This paper proposes novel improvements to the standard generic calibration method for central cameras that reduce its complexity, and improve its accuracy and robustness. Improvements are achieved by taking advantage of the geometric constraints resulting from a single centre of projection. Input data for the algorithm is acquired using active grids, the performance of which is characterised. A new linear estimation stage to the generic algorithm is proposed incorporating classical pinhole calibration techniques, and it is shown to be significantly more accurate than the linear estimation stage of the standard method. A linear method for pose estimation is also proposed and evaluated against the existing polynomial method. Distortion correction and motion reconstruction experiments are conducted with real data for a hyperboloidal catadioptric sensor for both the standard and proposed methods. Results show the accuracy and robustness of the proposed method to be superior to those of the standard method

Towards dynamic camera calibration for constrained flexible mirror imaging

Flexible mirror imaging systems consisting of a perspective camera viewing a scene reflected in a flexible mirror can provide direct control over image field-of-view and resolution. However, calibration of such systems is difficult due to the vast range of possible mirror shapes and the flexible nature of the system. This paper proposes the fundamentals of a dynamic calibration approach for flexible mirror imaging systems by examining the constrained case of single dimensional flexing. The calibration process consists of an initial primary calibration stage followed by in-service dynamic calibration. Dynamic calibration uses a linear approximation to initialise a non-linear minimisation step, the result of which is the estimate of the mirror surface shape. The method is easier to implement than existing calibration methods for flexible mirror imagers, requiring only two images of a calibration grid for each dynamic calibration update. Experimental results with both simulated and real data are presented that demonstrate the capabilities of the proposed approach

A manual on macroeconomic fundamentals for conflict-affected states

Increasingly, peace agreements and economic development programs reference the centrality of sound economic policy and a stable macroeconomic framework in state-building efforts. But few practitioners have the background to know what this means and to understand the relationship between their areas of responsibility and the policies needed to attain macroeconomic stability. Even fewer feel able to contribute meaningfully to designing and implementing strategies to attain and maintain this fundamental end state. This manual aims to serves as an introductory guide to and reference document on macroeconomics. It is intended for noneconomists who may be involved in peace negotiations and would benefit from a clearer understanding of the underlying macroeconomic issues

A comparison of new generic camera calibration with the standard parametric approach

This paper deals with a recently proposed nonparametric approach to camera calibration, which is applicable to any type of sensor design. Currently, no relative quantitative performance data is available for this method. This paper addresses this issue, by providing a comprehensive evaluation with respect to the standard planar calibration technique in the literature. Experiments are conducted on simulated and real data, with the firm conclusion that the generic calibration method has the capability to outperform the standard parametric approach for imaging systems with significant distortion. The results provide important practical information for the vision community at large

Determining military expenditures: Arms races and spill-over effects in cross-section and panel data

This paper considers the determinants of military spending, building on an emerging literature that estimates military expenditure demand functions in cross-section and panel data, incorporating ‘arms-race’ type effects. It updates Dunne and Perlo-Freeman (2003b) using the SIPRI military expenditure database for the period 1988-2003, finding broadly similar results. It also shows differences in results across panel methods, particularly the within and between estimates and illustrates the importance of recognising and modelling dynamic processes within panel data.Heterogeneity is also found to be an important issue and when countries are broken up into groups on the basis of per capita income there is no obvious systematic pattern in the results. This is seen to imply that the demand for military spending, even between two mutually hostile powers,may depend on the whole nature of the relationship between them (and other countries and events in the region), and not simply Richardsonian action-reaction patterns

Military Expenditure, Endogeneity and Economic Growth

The debate over the economic effects of military spending continues to develop, with no consensus, but a deepening understanding of the issues and limitations of previous work. A recent survey has suggested that the inclusion of post Cold War data has tended to make finding a negative effect more common, but issues remain (Dunne and Tian, 2013). One particularly important issue that has not been adequately dealt with, is the possible endogeneity of military spending in the growth equation, mainly because of the difficulty of finding any variables that would make adequate instruments. This paper considers the likely importance of endogeneity, using conflict onset as an instrument for military spending in an endogenous growth model for a panel of African countries 1989-2010. Following a brief review of the literature the theoretical and empirical models are outlined and the use of conflict onset as an instrumental variable for military spending in the panel estimates is justified. The empirical analysis suggests that endogeneity is likely to be an important issue and using IV estimation provides a larger significant negative effect for military spending on growth than OLS. It also identifies a further potential bias in the same direction in studies not including non-military spending in the growth equation. These results imply that the damaging effects of military spending on growth in Africa are being underestimated in most studies. While it is clear that conflict onset is a suitable and successful instrument in this analysis, the results are not directly generalisable. Conflict onset is unlikely to be applicable to a larger and more diverse panel of countries. What is of general concern is the finding that endogeneity is important and is likely to be influencing the results of studies of military spending and growth. It is important that future research tries to deal with endogeneity and the search for reasonable instruments is one that needs to engage researchers

Military Expenditure, Endogeneity and Economic Growth

The debate over the economic effects of military spending continues to develop, with no consensus, but a deepening understanding of the issues and limitations of previous work. A recent survey has suggested that the inclusion of post Cold War data has tended to make finding a negative effect more common, but issues remain (Dunne and Tian, 2013). One particularly important issue that has not been adequately dealt with, is the possible endogeneity of military spending in the growth equation, mainly because of the difficulty of finding any variables that would make adequate instruments. This paper considers the likely importance of endogeneity, using conflict onset as an instrument for military spending in an endogenous growth model for a panel of African countries 1989-2010. Following a brief review of the literature the theoretical and empirical models are outlined and the use of conflict onset as an instrumental variable for military spending in the panel estimates is justified. The empirical analysis suggests that endogeneity is likely to be an important issue and using IV estimation provides a larger significant negative effect for military spending on growth than OLS. It also identifies a further potential bias in the same direction in studies not including non-military spending in the growth equation. These results imply that the damaging effects of military spending on growth in Africa are being underestimated in most studies. While it is clear that conflict onset is a suitable and successful instrument in this analysis, the results are not directly generalisable. Conflict onset is unlikely to be applicable to a larger and more diverse panel of countries. What is of general concern is the finding that endogeneity is important and is likely to be influencing the results of studies of military spending and growth. It is important that future research tries to deal with endogeneity and the search for reasonable instruments is one that needs to engage researchers

DySCo: Quantitating Associations of Membrane Proteins Using Two-Color Single-Molecule Tracking

We present a general method called dynamic single-molecule colocalization for quantitating the associations of single cell surface molecules labeled with distinct autofluorescent proteins. The chief advantages of the new quantitative approach are that, in addition to stable interactions, it is capable of measuring nonconstitutive associations, such as those induced by the cytoskeleton, and it is applicable to situations where the number of molecules is small

Association between rheumatoid arthritis disease activity, progression of functional limitation and long-term risk of orthopaedic surgery : Combined analysis of two prospective cohorts supports EULAR treat to target DAS thresholds

Objectives: To examine the association between disease activity in early rheumatoid arthritis (RA), functional limitation and long-term orthopaedic episodes. Methods: Health Assessment Questionnaire (HAQ) disability scores were collected from two longitudinal early RA inception cohorts in routine care; Early Rheumatoid Arthritis Study and Early Rheumatoid Arthritis Network from 1986 to 2012. The incidence of major and intermediate orthopaedic surgical episodes over 25 years was collected from national data sets. Disease activity was categorised by mean disease activity score (DAS28) annually between years 1 and 5; remission (RDAS≤2.6), low (LDAS>2.6-3.2), low-moderate (LMDAS≥3.2-4.19), high-moderate (HMDAS 4.2-5.1) and high (HDAS>5.1). Results: Data from 2045 patients were analysed. Patients in RDAS showed no HAQ progression over 5 years, whereas there was a significant relationship between rising DAS28 category and HAQ at 1 year, and the rate of HAQ progression between years 1 and 5. During 27 986 person-years follow-up, 392 intermediate and 591 major surgeries were observed. Compared with the RDAS category, there was a significantly increased cumulative incidence of intermediate surgery in HDAS (OR 2.59 CI 1.49 to 4.52) and HMDAS (OR 1.8 CI 1.05 to 3.11) categories, and for major surgery in HDAS (OR 2.48 CI 1.5 to 4.11), HMDAS (OR 2.16 CI 1.32 to 3.52) and LMDAS (OR 2.07 CI 1.28 to 3.33) categories. There was no significant difference in HAQ progression or orthopaedic episodes between RDAS and LDAS categories. Conclusions: There is an association between disease activity and both poor function and long-term orthopaedic episodes. This illustrates the far from benign consequences of persistent moderate disease activity, and supports European League Against Rheumatism treat to target recommendations to secure low disease activity or remission in all patients.Peer reviewedFinal Published versio