Open-Loop Woofer-Tweeter Control on the LAO Multi-Conjugate Adaptive Optics Testbed

Advances in micro deformable mirror (DM) technologies such as MEMs, have stimulated interest in the characteristics of systems that include a high stroke mirror in series with a high actuator count mirror. This arrangement is referred to as a woofer-tweeter system. In certain situations it may be desirable or necessary to operate the woofer DM in open-loop. We present a simple method for controlling a woofer DM in open loop provided the device behaves in an approximately linear fashion. We have tested a mirror that we believe meets our criterion, the ALPAO DM52 mirror. Using our open-loop method we fit several test Kolmogorov wavefronts with the mirror and have achieved an accuracy of approximately 25 nm rms surface deviation over the whole clear aperture, and 20 nm rms over 90% of the aperture. We have also flattened the mirror in open loop to approximately 11 nm rms residual.Comment: 5 pages, 3 figures, to be published in proceedings of The 6th International Workshop on Adaptive Optics for Industry and Medicin

Stroke saturation on a MEMS deformable mirror for woofer-tweeter adaptive optics

High-contrast imaging of extrasolar planet candidates around a main-sequence star has recently been realized from the ground using current adaptive optics (AO) systems. Advancing such observations will be a task for the Gemini Planet Imager, an upcoming "extreme" AO instrument. High-order "tweeter" and low-order "woofer" deformable mirrors (DMs) will supply a >90%-Strehl correction, a specialized coronagraph will suppress the stellar flux, and any planets can then be imaged in the "dark hole" region. Residual wavefront error scatters light into the DM-controlled dark hole, making planets difficult to image above the noise. It is crucial in this regard that the high-density tweeter, a micro-electrical mechanical systems (MEMS) DM, have sufficient stroke to deform to the shapes required by atmospheric turbulence. Laboratory experiments were conducted to determine the rate and circumstance of saturation, i.e. stroke insufficiency. A 1024-actuator 1.5-um-stroke MEMS device was empirically tested with software Kolmogorov-turbulence screens of r_0=10-15cm. The MEMS when solitary suffered saturation ~4% of the time. Simulating a woofer DM with ~5-10 actuators across a 5-m primary mitigated MEMS saturation occurrence to a fraction of a percent. While no adjacent actuators were saturated at opposing positions, mid-to-high-spatial-frequency stroke did saturate more frequently than expected, implying that correlations through the influence functions are important. Analytical models underpredict the stroke requirements, so empirical studies are important.Comment: 16 pages, 10 figure

A propos de l' ü souletin

Hay dos tesis sobre el origen de la ü suletina: viene del dialecto del Béarn o es una evolución espontánea. En el texto se estudian algunos ejemplos de palabras que contienen la üThere are two thesis on the origin of the "ü" from the Soule: either it comes from the dialect from the Béarn or it is a spontaneous evolution. Some words that contain this "ü" are studied in the tex

Le basque et les langues caucasiques: (à propos d' un ouvrage de M. Winkler)

Crítica a un artículo de Winkler en el que intenta probar que el euskera está relacionado con las lenguas caucásicas. Gavel considera que desde el punto de vista de Winkler hay analogías entre estas lenguas, pero solamente desde sus ideas sobre la construcción del euskera. Sin embargo, reconoce su ignorancia sobre las lenguas caucásicas, aunque considera que hay que descubrir y formular unas reglas precisas para poder demostrar esta relaciónCriticism on an article by Winkler in which he strives to prove that the Basque language is related to Caucasic languages. Gavel considers that, from Winkler's point of view, there are analogies between these languages, but only as refers to his ideas on the construction of the Basque language. However, he recognises his ignorance on the caucasic, although he considers that it is necessary to discover and formulate some precise rules to be able to demonstrate such a relationshi

L'accent tonique dans les formes gasconnes des noms propres basques

Estudio sobre el lugar del acento tónico en las formas gasconas de los nombres propios vascos. En su inmensa mayoría, los nombres de lugares de las tres provincias vascas continentales y los apellidos son no tanto galicizaciones como gasconizacionesde los nombres euskaldunes.Euskal izen berezien forma gaskoietan azentu tonikoak hartzen duen tokiari buruzko ikerlana. Gehienetan, Iparraldeko hiru euskal probintzietako toki izenak eta abizenak gaskoiturik ageri dira frantsesturik baino areago.Etude de la place de l'accent tonique dans les formes gasconnes des noms propres basques. Dans leur immense majorité, les noms de lieux des trois provinces basques continentales ainsi que les noms de famille sont en réalité non pas des francisations mais des gasconisations de noms euskariens.Study on the place of the tonic accent in the Gascoigne forms of Basque proper nouns. In their immense majority, the names of places of the three continental Basque provinces and the surnames are not so much gallicisations as gascoignisations of Basque names

Towards optimization of pulsed sodium laser guide stars

Pulsed sodium laser guide stars (LGS) are useful because they allow for Rayleigh blanking and fratricide avoidance in multiple-LGS systems. Bloch-equation simulations of sodium-light interactions show that these may be able to achieve photon returns nearly equal to, and in some cases greater than, what is seen from continuous-wave (CW) excitation. In this work, we study the time-dependent characteristics of sodium fluorescence, and investigate the optimal format for the new fiber laser LGS that will be part of the upgraded adaptive optics (AO) system on the Shane telescope at Mt. Hamilton. Results of this analysis are examined in the context of their general applicability to other LGS systems and the potential benefits of uplink correction are considered. Comparisons of simulation predictions with measurements from existing LGS are also presented and discussed.Comment: 9 pages, 7 figures, accepted by JOSA

More Than Mere Synonyms: Examining The Differences Between Criminogenic Thinking And Criminogenic Attitudes

More than 75% of prison inmates are arrested for a new crime within five years of being released from prison. Known as recidivism, this trend of repeated criminal activity accounts for more than half of annual prison admissions, and rehabilitative programs demonstrate varying degrees of success in reducing recidivism. Andrews, Bonta, and Hoge (1990) demonstrated that offenders are less likely to recidivate when they receive services that match their assessed level of risk factors (e.g., history of violence), intervention needs (e.g., mental health diagnosis), and responsivity (e.g., ideal learning environment). Criminogenic cognition, mental events (e.g., thoughts, attitudes, and beliefs) often exhibited by criminal offenders and thought to promote antisocial behavior, are among the greatest needs that must be addressed to decrease recidivism; however, the distinction between thought content and thought process is not sufficiently clear in the literature. The current study aimed to distinguish these two domains of criminogenic cognition and examine their relationship to one another. Specifically, four common measures of criminogenic thinking and attitudes were compared. Correlational analyses provided support for the prediction that the two constructs are related yet quantitatively distinct. Problems with the data prevented the successful completion of the primary data analysis, leading to inconclusive results. Possible explanations for these results and suggestions for future research are discussed

Evaluation of Sprinkler Systems in Northern Utah

Sprinkling as a method of irrigation has been expanding rapidly in the United States, with acreages irrigated by this method increasing every year. One of the major reasons for the expansion is the great improvements that have been made in sprinkler irrigation equipment. Lightweight aluminum pipe, with quick couplers, improved pump and motor efficiencies have all made sprinkler irrigation more desirable. High efficiency of water application, labor requirements, and favorable plant response have also favored the expansion