Effects of Control Stick Parameters on Human Controller Response

A fixed base laboratory tracking study was conducted to determine the effects of stick displacement and stick force characteristics on human tracking performance. Three different levels of control stick force/displacement characteristics and stick electrical gain were varied to observe their influence on RMS (Root Mean Square) tracking error and RMS control activity (stick output). The results indicated that both RMS tracking error and RMS control activity were influenced by the three different levels of control stick force/displacement characteristics and stick electrical gain. The human neuromotor time constant was affected by the electrical control gain of the stick while the spring stiffness of the stick influenced the time delay characteristics of the human response behavior

Nonlinear inverse problem by T-matrix completion. I. Theory

We propose a conceptually new method for solving nonlinear inverse scattering problems (ISPs) such as are commonly encountered in tomographic ultrasound imaging, seismology and other applications. The method is inspired by the theory of nonlocality of physical interactions and utilizes the relevant formalism. We formulate the ISP as a problem whose goal is to determine an unknown interaction potential $V$ from external scattering data. Although we seek a local (diagonally-dominated) $V$ as the solution to the posed problem, we allow $V$ to be nonlocal at the intermediate stages of iterations. This allows us to utilize the one-to-one correspondence between $V$ and the T-matrix of the problem, $T$. Here it is important to realize that not every $T$ corresponds to a diagonal $V$ and we, therefore, relax the usual condition of strict diagonality (locality) of $V$. An iterative algorithm is proposed in which we seek $T$ that is (i) compatible with the measured scattering data and (ii) corresponds to an interaction potential $V$ that is as diagonally-dominated as possible. We refer to this algorithm as to the data-compatible T-matrix completion (DCTMC). This paper is Part I in a two-part series and contains theory only. Numerical examples of image reconstruction in a strongly nonlinear regime are given in Part II. The method described in this paper is particularly well suited for very large data sets that become increasingly available with the use of modern measurement techniques and instrumentation.Comment: This is Part I of a paper series containing theory only. Part II contains simulations and is available as arXiv:1505.06777 [math-ph]. Accepted in this form to Phys. Rev.

Solution of the inverse scattering problem by T-matrix completion. II. Simulations

This is Part II of the paper series on data-compatible T-matrix completion (DCTMC), which is a method for solving nonlinear inverse problems. Part I of the series contains theory and here we present simulations for inverse scattering of scalar waves. The underlying mathematical model is the scalar wave equation and the object function that is reconstructed is the medium susceptibility. The simulations are relevant to ultrasound tomographic imaging and seismic tomography. It is shown that DCTMC is a viable method for solving strongly nonlinear inverse problems with large data sets. It provides not only the overall shape of the object but the quantitative contrast, which can correspond, for instance, to the variable speed of sound in the imaged medium.Comment: This is Part II of a paper series. Part I contains theory and is available at arXiv:1401.3319 [math-ph]. Accepted in this form to Phys. Rev.

The Contours of a Very Special Border

Perhaps the best place to begin is with two brief conversations that took place after one of my classes. In the first, a student told me that his family recently sold a part of their portion. Here in the Rio Grande Valley of Texas and México, the term “portion” refers to a grant of land of at least 4,428 acres given to the Spanish settlers who first came to this Valley during the 1750s and 1760s. 1 So this student, barely into his twenties, formed part of a link extending back for more than a quarter of millennium and which crossed five national histories.2 The second young man conveyed a grimmer message; his mother’s deportation hearing would be taking place on Thursday morning and so he would not be able to attend class. She had entered the United States without federal authorization decades ago and now was to be separated from her family. Together, these two conversations tell us much about this valley, which remains a unique juncture of the United States, México, and Texas. Perhaps the best way to understand this saga is to begin at the beginning

STRESS-DEPENDENT INTERACTIONS BETWEEN CESIUM AND OTHER MATERIALS. Summary Report, February 15, 1962-February 15, 1963

Metals and alloys germane to thermionic energy converter usage were screened for embrittlement by liquid cesium. Techniques are described for more detailed studies of ceramics and susceptible metals. Definite reductions in tensile ductility were observed for 302 stainless steel and molybdenum. Bend ductility was lowered in titanium, titanium-8 aluminum-4 vanadium alloy, niobium, tantalum, and silver-- copper eutectic solder. Some difficulty in reproducibly wetting samples was evident. Slightly contaminating the cesium with oxygen (or water) was observed to increase cesium wettability. (auth

The Other Constitutional Convention: Border Delegates at the Mexican Constitutional Convention of 1916-1917

The article offers information on the Mexican Constitutional Convention of 1916-1917 and addresses the Mexicans living in states bordering the U.S. Topics discussed include dispossession of Mexicans by land seizure during the reign of Porfirio Diaz, attitude of convention delegates from the Border States and defeat of the army of Mexico President Porfirio Diaz in the Mexican Revolution

Transient Emission From Dissipative Fronts in Magnetized, Relativistic Outflows. II. Synchrotron Flares

The time dependent synchrotron emission from relativistic jets, and the relation between the synchrotron and ERC emission is considered within the framework of the radiative front model. The timescale and profile of the optically thin emission are shown to be determined, in this model, by the shock formation radius, the thickness of expelled fluid slab and the variation of the front's parameters due to its transverse expansion. For a range of reasonable conditions, a variety of flare shapes can be produced, varying from roughly symmetric with exponential rises and decays, as often seen in blazars, to highly asymmetric with a fast rise and a much slower, power law decay, as seen in GRB afterglows. The onset, duration, and fluence of low-frequency (below the initial turnover frequency) and hard gamma-ray (above the initial gamma-spheric energy) outbursts are limited by opacity effects; the emission at these energies is quite generally delayed and, in the case of sufficiently short length outbursts, severely attenuated. The observational consequences are discussed. One distinctive prediction of this model is that in a single, powerful source, the upper cutoff of the gamma-ray spectrum should be correlated with the timescale of the outburst and with the amplitude of variations at long wavelengths (typically radio to millimeter).Comment: AAS LaTex, 14 pgs, accepted to A

Mexico\u27s 2018 election

On July 1, 2018, Mexico held elections for the presidency, for all seats in the federal Chamber of Deputies, and for one third of the seats in the federal Senate

Mexican Revolution at age 100

For many, the Mexican Revolution that began in 1910 was the most important event in Mexican history. Although the immediate causes of that revolution were the conditions brought about by the 1876 to 1910 dictatorship of Porfirio Diaz causes far older that those need to be considered. So, I’ll spend the next five minutes on a quick review of early Mexican history