Quality Control of Offshore Positioning Surveys

This paper discusses the need for a quality control method for offshore positioning surveys and then its actual use. It limits the discussion to radio locationing systems only, but this restriction does not imply that Satellite Navigation or Underwater Acoustic Positioning Systems do not require such quality control. The subject is divided into two parts. Firstly the calibration methods necessary to determine the zero/delay settings for the survey equipment and to establish the propagation velocity required in the survey. Secondly, the positioning of the survey vessel with the necessary, but often missing, “ simultaneous quality control” of this positioning. The methods described in this paper are compared with field results, from which can be seen the often limited value of the most commonly used, and sometimes time-consuming and expensive, calibration methods. It will be shown here that the generally accepted principle of the location offshore of vessels and structures using only two position lines not only lacks reliability but can often result in costly resurveys. The lack of data redundancy in offshore surveys stands in sharp contrast to the practice in land surveying where data redundancy in observation and control surveys is common practice. With the increasing practice of having extra positioning equipment on stand-by— especially in remote areas— and with the increase in cost of offshore surveys, Shell’s Topographic Survey Department has developed a method based on redundancy of data. This method provides a continuous quality control of the offshore positioning while surveying, and avoids unpleasant surprises after the survey vessel has left the area

Zorgen rondom IVF

De vraag naar dit onderzoek kwam vanuit de patiëntenvereniging Freya terecht bij de Wetenschapswinkel Geneeskunde en Volksgezondheid van de Rijksuniversiteit Groningen. Deze vraag is vertaald in een wetenschappelijk te beantwoorden probleemstelling. Het onderzoek dat hieruit is voort gekomen, is uitgevoerd in het kader van een afstudeeronderzoek. De probleemstelling van het onderzoek luidt: In welke opzichten en in hoeverre hebben vrouwen die kiezen voor IVF (in vitro fertilisatie), behoefte aan steun en begeleiding bij keuzen en ervaringen die zich in het behandelingstraject voordoen...

The Small-x Evolution of Unpolarized and Polarized Structure Functions

A brief overview is presented of recent developments concerning resummed small-x evolution, based upon the renormalization group equation. The non-singlet and singlet structure functions are discussed for both polarized and unpolarized deep-inelastic scattering. Quantitative results are displayed and uncertainties from uncalculated subleading terms are discussed.Comment: 9 pages with 5 EPS figures. To appear in Acta Physica Polonic

Deep-inelastic production of heavy quarks

Deep-inelastic production of heavy quarks at HERA, especially charm, is an excellent signal to measure the gluon distribution in the proton at small $x$ values. By measuring various differential distributions of the heavy quarks this reaction permits additional more incisive QCD analyses due to the many scales present. Furthermore, the relatively small mass of the charm quark, compared to the typical momentum transfer $Q$, allows one to study whether and when to treat this quark as a parton. This reaction therefore sheds light on some of the most fundamental aspects of perturbative QCD. We discuss the above issues and review the feasibility of their experimental investigation in the light of a large integrated luminosity.Comment: 10 pages, uses epsfig.sty, five ps figures included. To appear in the proceedings of the workshop Future Physics at HERA, eds. G. Ingelman, A. De Roeck and R. Klanner, DESY, Hamburg, 199