Damping-Antidamping Effect on Comets Motion

We make an observation about Galilean transformation on a 1-D mass variable systems which leads us to the right way to deal with mass variable systems. Then using this observation, we study two-bodies gravitational problem where the mass of one of the bodies varies and suffers a damping-antidamping effect due to star wind during its motion. For this system, a constant of motion, a Lagrangian and a Hamiltonian are given for the radial motion, and the period of the body is studied using the constant of motion of the system. Our theoretical results are applied to Halley's comet.Comment: 19 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:0910.468

Shape Persistence in Elicited Subjective Crop Yield Probability Density Functions

The shape persistence of a crop yield probability density function (PDF) was studied by using two variants of the Visual Impact Method (VIM) to elicit subjective estimations by farmers. In one variant ten weights were used to describe the PDF and in the other variant the farmer chose the number of weights. Results were compared directly and by means of Weibull distributions fitting, with evidence being obtained in favor of methodological persistence and the equivalence of the two estimation methods.Subjective crop yield PDF elicitation, Visual impact method, Methodological persistence, Crop Production/Industries,

Elicitation of Subjective Crop Yield PDF for DSS Implementation

The aim of this research is to establish the persistence of annual crop yield point values subjective estimates, and the coherence and reliability of subjective crop yield probability density functions (PDF) elicited from a series of interviews carried out on a wide group of farmers, and then to determine whether they should be included or not in a decision support system (DSS). Three different elicitation techniques were used: a) The Two Step PDF estimation method b) Triangular distribution c) Beta distribution Although the results are noteworthy, further studies should be carried out to perfect the aforementioned techniques before crop yield PDF's are used in decision making processes.decision support systems, subjective crop yield PDF elicitation, two step PDF estimation method, triangular and beta distributions, Crop Production/Industries,

The Use of a Lock-In Amplifier to Stabilize the Frequency of a Laser Diode

We have designed, constructed, and tested a lock-in amplifier with readily available electronic components and homebuilt analog circuits. Its performance is comparable to that of a commercial unit, but it costs significantly less and is much more compact. The various components of our lock-in amplifier are discussed and the basic principles behind the function and operation of this versatile device are explained. We have also assembled a laser system and used the output signal of our lock-in amplifier in a negative feedback loop to stabilize the frequency of our laser to an atomic reference frequency