Plan of advanced satellite communication experiments using ETS-6

In 1992, an Engineering Test Satellite 6 is scheduled to be launched by an H-2 rocket. The missions of ETS-6 are to establish basic technologies of inter-satellite communications using S-band, millimeter waves and optical beams and of fixed and mobile satellite communications using multibeam antenna on board the satellite. A plan of the experiments is introduced

Agricultural productivity and mortality: evidence from Kagera, Tanzania

We ask whether prime-age adult mortality due to HIV/AIDS decreases the endowment of knowledge for agricultural production in Kagera, Tanzania, reducing total factor productivity. We also quantify how much this negative effect contributes to the decrease in long-term household agricultural output growth compared to the contribution of decreased accumulation of productive assets; household members, land, and livestock. We find that prime-age adult mortality decreases the accumulation of knowledge stock as total factor productivity and the contribution of this negative effect to the decrease in agricultural output growth is larger than the contribution of decreased accumulation of each productive asset.mortality, human capital, HIV/AIDS, agriculture, total factor productivity, Tanzania

Agricultural productivity and mortality: evidence from Kagera, Tanzania

We ask whether prime-age adult mortality due to HIV/AIDS decreases the endowment of knowledge for agricultural production in Kagera, Tanzania, reducing total factor productivity. We also quantify how much this negative effect contributes to the decrease in long-term household agricultural income growth compared to the contribution of decreased accumulation of productive assets; household members, land, and livestock. We find that prime-age adult mortality decreases the accumulation of knowledge stock as total factor productivity and the contribution of this negative effect to the decrease in agricultural income growth is larger than the contribution of decreased accumulation of each productive asset.mortality, human capital, HIV/AIDS, agriculture, total factor productivity, Tanzania

Short-Term Memory Through Persistent Activity: Evolution of Self-Stopping and Self-Sustaining Activity in Spiking Neural Networks

Memories in the brain are separated in two categories: short-term and long-term memories. Long-term memories remain for a lifetime, while short-term ones exist from a few milliseconds to a few minutes. Within short-term memory studies, there is debate about what neural structure could implement it. Indeed, mechanisms responsible for long-term memories appear inadequate for the task. Instead, it has been proposed that short-term memories could be sustained by the persistent activity of a group of neurons. In this work, we explore what topology could sustain short-term memories, not by designing a model from specific hypotheses, but through Darwinian evolution in order to obtain new insights into its implementation. We evolved 10 networks capable of retaining information for a fixed duration between 2 and 11s. Our main finding has been that the evolution naturally created two functional modules in the network: one which sustains the information containing primarily excitatory neurons, while the other, which is responsible for forgetting, was composed mainly of inhibitory neurons. This demonstrates how the balance between inhibition and excitation plays an important role in cognition.Comment: 28 page

Dynamics of Internal Models in Game Players

A new approach for the study of social games and communications is proposed. Games are simulated between cognitive players who build the opponent's internal model and decide their next strategy from predictions based on the model. In this paper, internal models are constructed by the recurrent neural network (RNN), and the iterated prisoner's dilemma game is performed. The RNN allows us to express the internal model in a geometrical shape. The complicated transients of actions are observed before the stable mutually defecting equilibrium is reached. During the transients, the model shape also becomes complicated and often experiences chaotic changes. These new chaotic dynamics of internal models reflect the dynamical and high-dimensional rugged landscape of the internal model space.Comment: 19 pages, 6 figure