Search

The laser head with fixed focus optics is commonly used for the deep penetration laser welding. In such case the geometry and position of the beam waist are defined by the focusing lens. If the laser beam incident on the focusing lens is not well collimated but divergent and its divergence can be varied by proper adaptive optical elements, then also the geometry and position of the focus will be changeable. In this way it is possible to affect the energy coupling from the laser beam to the keyhole walls and thus to control the geometry and quality of the weld. In this paper we present a theoretical and numerical study of the beam shaping by adaptive optics and its influence on the weld quality. For the CO2 laser welding machine the adaptive optics was realized by a deformable mirror and itsti’ect was tested also experimentally. For the solid-state laser welding machine we designed a laser head with changeable distance between the optical fiber and the collimating lens and we simulated its performance.

In this paper, I combine an exposition of the historical development of sociology and philosophy of science from the era of grand theories onwards, with an explication as to why the grand theories have failed. First, I trace some parallels in the history of each of the disciplines. After presenting their chronological development, I scrutinize the metatheoretical findings about the disciplines and examine the main ontological and epistemic reasons why attempts at these general theories or frameworks have not succeeded. Among them are the lack of a universal methodology and of a theoretical core, together with the impossibility of achieving a common objective view. On this basis I conclude that general theories or frameworks are not achievable in principle. As it turns out, however, some contemporary social theorists and philosophers still harbor hopes that they can be successfully formulated, or at the least do not rule out such possibility. Thus, in closing, I argue that the critical points can also be applied to these latest attempts, as the call for grand theories or frameworks has never ceased and returns regularly with each new generation of social theorists and philosophers of science. [ABSTRACT FROM AUTHOR]

Animals are faced with a range of ecological constraints that shape their behavioural decisions. Habitat features that affect resource abundance will also have an impact, especially as regards spatial distribution, which will in turn affect associations between the animals. Here we utilised a network approach, using spatial and genetic data, to describe patterns in use of space (foraging sites) by free-ranging Egyptian fruit bats (Rousettus aegyptiacus) at the Dakhla Oasis in Egypt. We observed a decrease in home range size during spring, when food availability was lowest, which was reflected by differences in space sharing networks. Our data showed that when food was abundant, space sharing networks were less connected and more related individuals shared more foraging sites. In comparison, when food was scarce the bats had few possibilities to decide where and with whom to forage. Overall, both networks had high mean degree, suggesting communal knowledge of predictable food distribution. [ABSTRACT FROM AUTHOR]

Objectivity, as one of the key attributes of science, has become an indispensable part of its ethos and a central theme of the philosophy of science. As such, it has been a subject of philosophical reflection by a number of authors. In our project - in which both philosophers of science and scientists participate - we examine the concept of objectivity in the natural sciences with the tools of experimental philosophy. We aim to identify specific operational dimensions of objectivity, those with which current scientist actually work, thus making them accessible for further theoretical analysis and research. In this text, we present results from the first, qualitative phase of our research based on in-depth interviews and focus groups with scientists working in the Czech Republic. Further, we confront this empirical data with theoretical notions of objectivity (Hacking, Crombie, Solomon, Popper, Galison, Daston, Quine, Kuhn and others). We also present other findings from the research and formulate hypotheses for the research's subsequent phases. [ABSTRACT FROM AUTHOR]

Copyright of Insurance Discourses / Pojistne Rozpravy is the property of Czech Insurance Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the early 20th century underdetermination has been one of the most contentious problems in the philosophy of science. In this article I relate the underdetermination problem to models in biology and defend two main lines of argument: First, the use of models in this discipline lends strong support to the underdetermination thesis. Second, models and theories in biology are not determined strictly by the logic of representation of the studied phenomena, but also by other constraints such as research traditions, backgrounds of the scientists, aims of the research and available technology. Convincing evidence for the existence of underdetermination in biology, where models abound, comes both from the fact that for a natural phenomenon we can create a number of candidate models but also from the fact that we do not have a universal rule that would adjudicate among them. This all makes a strong case for the general validity of the underdetermination thesis. [ABSTRACT FROM AUTHOR]

In this article we describe prototype designs and tests for low-cost rotational medium- and strong-motion seismometers using three types of proof mass (two liquid and one solid) and a number of transducer configurations. This article describes the third set of designs and tests in our development program. The details of our results for most of these are in the E electronic supplement to this article, whereas here we concentrate on three of the most promising and representative design combinations. Most of our results pertain to sensors with water or silicon oil as the proof mass, though we also tested a torsion-bar design with a solid proof mass. We find that most mass-transducer combinations lead to output proportional to rotational acceleration, with varying degrees of fidelity. Most combinations we tested can be dismissed from further development for reasons of performance or inconvenience during analysis of acceleration response (compare with E electronic supplement). In this article, we describe three of the more promising combinations, one each for the three types of response functions we measured. Of these three, one mass-transducer combination in particular (a hinged sensing element and capacitive transduction) has output voltage closely proportional to rotational displacement (angle) over a wide frequency range; such displacement proportionality obviates two of the integration steps normally required to solve for continuum single-point motions or correct for tilt-induced errors in horizontal translational sensors. Thus, although we illustrate two other designs of some promise, we propose a new design that follows this displacement-proportional path while increasing the device's sensitivity to on-axis rotations, improving its manufacturing ease and lowering its sensitivity to translational motions. [ABSTRACT FROM AUTHOR]

Radiotracking is an important and often the only possible method to explore specific habits and the behaviour of animals, but it has proven to be very demanding and time-consuming, especially when frequent positioning of a large group is required. Our aim was to address this issue by making the process partially automated, to mitigate the demands and related costs. This paper presents a novel automated tracking system that consists of a network of automated tracking stations deployed within the target area. Each station reads the signals from telemetry transmitters, estimates the bearing and distance of the tagged animals and records their position. The station is capable of tracking a theoretically unlimited number of transmitters on different frequency channels with the period of 5–15 seconds per single channel. An ordinary transmitter that fits within the supported frequency band might be used with BAARA (Biological AutomAted RAdiotracking); an extra option is the use of a custom-programmable transmitter with configurable operational parameters, such as the precise frequency channel or the transmission parameters. This new approach to a tracking system was tested for its applicability in a series of field and laboratory tests. BAARA has been tested within fieldwork explorations of Rousettus aegyptiacus during field trips to Dakhla oasis in Egypt. The results illustrate the novel perspective which automated radiotracking opens for the study of spatial behaviour, particularly in addressing topics in the domain of population ecology. [ABSTRACT FROM AUTHOR]

On 21 April 2011, an adult male of the Schreibers' bat (Miniopterus schreibersii) was caught in the Hranická propast (Hranická Chasm, 49° 32' N, 17° 45' E, 315 m a. s. l., Hranice na Moravě, Přerov District), from a crevice of the chasm wall above a pond. This record represents the first evidence of this bat species as well as a new family in the Czech Republic. It documents the affinity of marginal populations of the species to warmer cave systems. [ABSTRACT FROM AUTHOR]

We present a stabilized semiconductor laser system designed to operate as a fiber-optic front-end master oscillator of a pulsed high-power iodine laser Prague Asterix Laser System (PALS). The replacement of the PALS master oscillator is a part of a broader effort to rebuild PALS into a laser generating shorter pulses with higher pulse power by the technique of optical parametric chirped pulse amplification. With an operating wavelength of 1315.15 nm the stabilized laser master oscillator is based on a telecommunication single-frequency distributed feedback diode. The frequency stabilization is derived from transitions in thermally dissociated iodine. Locking to the selected transition is fully automatic and the control system employs a unique combination of control loops derived from temperature and absorption to overcome the problem of narrow locking range of a single absorption line. [ABSTRACT FROM AUTHOR]

We present a current controller which satisfies the highest protection criteria of semiconductor lasers notorious for their great sensitivity to damage caused by induced electromagnetic interference. The core current source is supplied by linear isolating converter providing ripple free voltage. It is galvanically isolated, double shielded and current sense as well as current modulation are coupled via linear optocouplers. The current controller in this configuration makes safe operation of semiconductor lasers in laboratory conditions possible. [ABSTRACT FROM AUTHOR]