De Viti de Marco vs. Ricardo on public debt: self-extinction or default?

The most prominent Italian theorist of the late 19th and early 20th centuries, Antonio de Viti de Marco, accepted David Ricardo’s proposition that an extraordinary tax and a public loan are equivalent. Despite this common point of analytical departure, their theories of public debt diverged sharply. In this divergence, moreover, lies a fundamental gulf between two distinct analytical schemes for connecting the micro and macro levels of analysis. Ricardo treated macro aggregates as analytical primitives, with individual action being induced from those aggregates. In sharp contrast, de Viti took individual variables as primitive, with aggregate conditions being induced from interaction among those individual variables. Within de Viti’s framework of a fully cooperative state, public debt would be self-extinguishing. De Viti also recognized that democracies were never exclusively cooperative, as continuing competition among elites striving for power would enable politically dominant groups to pass cost onto the remainder of society, thereby operating as a de facto form of default

Climate Change and Violent Conflict in Europe over the Last Millennium

We investigate the relationship between a thousand-year history of violent conflict in Europe and various reconstructions of temperature and precipitation. We find that conflict was more intense during colder periods. This relationship is weakening over time, and is not robust to the details of the climate reconstruction or to the sample period. We thus confirm Zhang et al. (2006, Climatic Change, 76, 459-477) that, at least in temperate climates, global warming would, if anything, lead to reduced violent conflict.history, violent conflict, Europe, climate change

Performance of laminar-flow leading-edge test articles in cloud encounters

An extensive data bank of concurrent measurements of laminar flow (LF), particle concentration, and aircraft charging state was gathered for the first time. From this data bank, 13 flights in the simulated airline service (SAS) portion were analyzed to date. A total of 6.86 hours of data at one-second resolution were analyzed. An extensive statistical analysis, for both leading-edge test articles, shows that there is a significant effect of cloud and haze particles on the extent of laminar flow obtained. Approximately 93 percent of data points simulating LFC flight were obtained in clear air conditions; approximately 7 percent were obtained in cloud and haze. These percentages are consistent with earlier USAF and NASA estimates and results. The Hall laminar flow loss criteria was verified qualitatively. Larger particles and higher particle concentrations have a more marked effect on LF than do small particles. A particle spectrometer of a charging patch are both acceptable as diagnostic indicators of the presence of particles detrimental to laminar flow

Deformation and fracture of thin sheet aluminum-lithium alloys: The effect of cryogenic temperatures

The objective is to characterize the fracture behavior and to define the fracture mechanisms for new Al-Li-Cu alloys, with emphasis on the role of indium additions and cryogenic temperatures. Three alloys were investigated in rolled product form: 2090 baseline and 2090 + indium produced by Reynolds Metals, and commercial AA 2090-T81 produced by Alcoa. The experimental 2090 + In alloy exhibited increases in hardness and ultimate strength, but no change in tensile yield strength, compared to the baseline 2090 composition in the unstretched T6 condition. The reason for this behavior is not understood. Based on hardness and preliminary Kahn Tear fracture experiments, a nominally peak-aged condition was employed for detailed fracture studies. Crack initiation and growth fracture toughness were examined as a function of stress state and microstructure using J(delta a) methods applied to precracked compact tension specimens in the LT orientation. To date, J(delta a) experiments have been limited to 23 C. Alcoa 2090-T81 exhibited the highest toughness regardless of stress state. Fracture was accompanied by extensive delamination associated with high angle grain boundaries normal to the fatigue precrack surface and progressed microscopically by a transgranular shear mechanism. In contrast the two peak-aged Reynolds alloys had lower toughness and fracture was intersubgranular without substantial delamination. The influences of cryogenic temperature, microstructure, boundary precipitate structure, and deformation mode in governing the competing fracture mechanisms will be determined in future experiments. Results contribute to the development of predictive micromechanical models for fracture modes in Al-Li alloys, and to fracture resistant materials

Operational considerations for laminar flow aircraft

Considerable progress has been made in the development of laminar flow technology for commercial transports during the NASA Aircraft Energy Efficiency (ACEE) laminar flow program. Practical, operational laminar flow control (LFC) systems have been designed, fabricated, and are undergoing flight testing. New materials, fabrication methods, analysis techniques, and design concepts were developed and show much promise. The laminar flow control systems now being flight tested on the NASA Jetstar aircraft are complemented by natural laminar flow flight tests to be accomplished with the F-14 variable-sweep transition flight experiment. An overview of some operational aspects of this exciting program is given

The effects of management education upon strategic practice and performance: the case of the German SME machinery and equipment sector

This thesis is concerned with understanding the nature and impact of strategic management education upon management behaviour and performance. Previous research findings are limited, with continuing research being proposed. The aim of this research is to fill respective gaps. The research is carried out in the German machinery and equipment industry sector. This sector was selected because it is of strategic importance for Germany’s economy and it is faced with imminent and ongoing challenges. The research concentrates on small and medium sized companies as these companies dominate this sector. The desk research consists of a comprehensive literature review on the subjects: strategic management, SME community and research sector, previous empirical research results and management education. The field research adopts a quantitative methodology with a survey questionnaire in a cross sectional time horizon. The field research is complemented by six “micro case studies” using qualitative data from the questionnaire and publicly available information. Findings suggest that management education and, in particular, strategic management does not play an important role in German universities. Engineering faculties generally neglect strategic management education in their curricula. Evidence suggests that executives with engineering background have less knowledge in strategic management and generate a lower return on sales than those with business economic background or MBA qualified. From the research findings it can be concluded that German SMEs in the machinery and equipment sector profit from the implementation of strategic management. This thesis closes with recommendations to policy makers regarding management education in Germany and proposals for further research

Safety verification of a fault tolerant reconfigurable autonomous goal-based robotic control system

Fault tolerance and safety verification of control systems are essential for the success of autonomous robotic systems. A control architecture called Mission Data System (MDS), developed at the Jet Propulsion Laboratory, takes a goal-based control approach. In this paper, a method for converting goal network control programs into linear hybrid systems is developed. The linear hybrid system can then be verified for safety in the presence of failures using existing symbolic model checkers. An example task is simulated in MDS and successfully verified using HyTech, a symbolic model checking software for linear hybrid systems