bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deep Diving From a Dynamically Positioned Drill Ship
Authors: LePage Alain , Wide Peter 
Published: October 2008

SUMMARY
When offshore drilling started, water was very shallow, but new oil fields were exploited and drilling depths rose rapidly. In shallow water, fixed platforms or jack-up barges were utilized, but when deeper drilling was necessary, drill ships with conventional anchoring were used. Conventional anchoring is possible down to about 300 m, but is not practical deeper than about 200 m. Therefore, about 1970, when the need for even deeper drilling became obvious, the system of dynamic positioning was studied and adapted with its almost unlimited depth capacity.
Diving equipment aboard drill platforms and vessels shows a similar rapid development to meet the needs for greater depths. On the first fixed platforms, only surface diving was carried out and no advanced diving equipment used. As this equipment is heavy, it had to be installed permanently on board to permit quick response of diving services when require a. Normally, the positioning of the diving bell was done by means of a guideline.
The use of dynamic positioning of the drill ships also raises the demands on diving systems on board. Such problems as increasing diving depths are, to a great extent, already solved or on the edge of being solved from the physiological point of view.
The 1972, 2,00l-ft dive at the Hyperbaric facility of COMEX, Marseille shows the human capacity. From the technical point of view, however, the dynamic positioning leads to problems until now unknown in the use of deep diving systems such as guiding and positioning the bell between the surface and the work site, handling without guide lines, supply of gas and power, safety aspects, etc.
Principally and practically, these problems have been solved and the first diving systems are already working from dynamically positioned drill ships, such as the Pelican, from which in Dec., 1972, about 50 dives had been carried out.

THE TYPE OF DIVING TO BE PERFORMED
For different water depths and work, various methods of diving have to be used and the diving systems must be able to meet the requirements as follows:Shallow water surface-to-surface diving from a to 50 m requires no advanced diving equipment.Bounce diving from 50 to 150 m, requires a diving system with decompression capacity of about 15 hours per dive and a diving bell. It is used for short duration work. The divers are compressed rapidly on every dive and are working 1 to 2 hours on the work site. After that, they are decompressed. Mixed gas is used.
Navigation Data Reduction Enhances Plot Accuracies
Authors: Kronberger Fritz P. , Keahey Ned F. 
Published: October 2008

ABSTRACT
Data reduction of navigation parameters recorded in real-time is a key phase of satellite navigation in marine geophysical operations. The positioning system operates in a statistical predictor-corrector manner and is complemented by post processing of the shipboard data to provide the most precise postplots.

INTRODUCTION
Integrated satellite navigation systems are a valuable tool in today's marine exploration efforts. Such systems have proven accuracy and reliability in real-time. However, because of larger statistical data sets, that is, data before and after any given position, the post survey data reduction can further enhance the overall accuracy. Data reduction compensates 'for systematic errors and smoothes the "saw tooth effect" (see Figure 1) of real-time statistical filtering (i.e., Kalman, minimum variance, least squares, etc.).
To perform the reduction task the following steps (see Figure 2) are required:Edit field dataAnalyze and recompute satellite fixesDetermine and remove systematic errorsAdjust random errorsCompute and plot auxiliary dataPlot preliminary mapsCheck and adjust mistiesPlot final maps

BASIC PHILOSOPHY
The basic function of the integrated satellite navigation system is to control the position of the vessel on a preplanned course or "line" during the geophysical survey (see Figure 3). Most operations are defined as "on-line" or "off-line." While "on-line" the integrated navigation system serves as a shot point counter, i.e., it determines the "on-line" course and transmits a discrete pulse, on the basis of distance traveled, to the geophysical recording system which performs the data acquisition and recording operations.
The integrated system, while computing position and maintaining vessel course, records positional information on digital magnetic tape. Computations are based on inputs to a digital computer froma satellite receiver,a Doppler sonar,a gyrocompass,an inelinometer, anda velocimeter (see Figure 4).
These inputs are sampled continuously to determine the vessel's position at one-half second intervals. Onboard data is filtered in a predictor-corrector (Kalman) manner to obtain optimum real-time results. It is this data recorded on magnetic tape and its post processing that is the subject of the discussion below.

SATELLITE FIX COMPUTATION
To compute optimum post survey positions, all navigation data, that is, satellite message data and other sensor information are recorded on magnetic tape. The first step is to edit the field reel verifying all recorded data and checking for data "drop out" (missing data, gaps in recording, loss due to parity errors) and to merge auxiliary data from external navigation aids.
The most reliable data obtained by integrated satellite navigation systems are satellite fixes. Although fixes are not absolutely correct, in a stationary position accuracies of 150 feet RMS may be expected (see Table 1).
Computer Analysis of Oblique Acoustic Reflection For Ocean Sediment Identification
Authors: Newman Anthony K. 
Published: October 2008

Abstract
Remote sensing of ocean sediments via acoustic sounding is usually attempted via simple signal processing of normal-incidence acoustic reflection from ocean sediments. Computer analysis of the acoustic-field-theoretic Green's function for a spherically spreading sound wave from a ball transducer over a semi-infinite visco elastic Voigt model of the ocean sediment has obtained a substantial improvement in the technology of remote acoustic sediment identification.
The Green's function integral, containing the complete description of the acoustic return signal as a function of all the water and sediment parameters involved, is too complex to be integrated in closed-form.
Therefore, IBM 360-50 digital computer subroutines were prepared in Fortran IV (G-level) to compute the value of the integral as various parameters were varied, to obtain the information and insight needed for the optimum system design for remote acoustic sensing of the ocean sediments.
The preliminary investigations of the many possibilities made available by this approach have been quite inspiring. For example at 5000 HZ, the ratio of the 0° (normal incidence) acoustic reflections from coarse sand over those from fine sand (Hamilton's data (1).) is 1.085 : 1. At a geometric equivalent angle of incidence of 60° this ratio is improved to 1.328 : 1. Further improvements are possible if the system is designed to allow multi-frequency and multi-angle operation using advanced signal processing.
Unforseen capabilities have surfaced from computer-experiments designed to test the limits of such improvements. Two different sediments having identical acoustic impedances, (acoustic impedance = Density × Compressional Wave Velocity) with one sediment having 1.1 greater wave velocity and 1/1.1 less density, have identical acoustical return energy at 0° or normal incidence; were computed to have acoustic returns in a nearly 2 : 1 ratio at a geometric equivalent angle of incidence of 60° at 5000 Hz.
Further computer analysis is presented showing increased improvement in remote differential sediment identification via improved system design. The range of possibilities is illustrated by an appendix of computer drawn graphs.

Introduction
The literature contains many accounts of efforts to use the acoustic return from the ocean floor to determine soil classifications and engineering properties of the ocean sediments. Examination of this literature reveals that most investigators have employed the return signals at normal incidence (0°). [See Figure I.] The geometric angle of incidence will be shortened to angle of incidence hereafter. In reference to Figure I it should be mentioned that there are in reality an infinite number of different paths from the transmitter to the receiver, as well as the direct path and path 2 shown, and the net received signal is the superposition of all of them. The angle of incidence merely refers to the angular placement of the transducers.
A New Shear Wave Velocity Measurement Technique in Ocean Bottom Soil Samples
Authors: Celikkol Barbaros , Vogel P.M. 
Published: October 2008

ABSTRACT
The shear wave velocity together with the longitudinal wave velocity and the density of the soil completely describe the first order dynamic elastic properties of the soil. This paper deals with an improved and convenient method of obtaining the shear wave velocity by using inexpensive, portable, and durable equipment. Necessary theory for proper interpretation of data (the experimental technique and data obtained using the system are presented.

INTRODUCTION
The recovery of the essential engineering data necessary for the efficient utilization of the sea floor is tedious and expensive. A low cost, effective, surface-borne acoustic soil assessment system is attractive concept; however, it is not yet fully developed. Preliminary site information that is often necessary for underwater engineering projects is usually obtained by physical tests performed on sediment core samples. Recently, the value of acoustic testing of soil samples has been recognized. Acoustic tests on core samples or reconstituted ocean soils serve two basic purposes. First of all, they provide the dynamical soil constants thus making tedious laboratory measurements unnecessary. Secondly, they provide compressional and shear wave velocity and attenuation information which in turn is necessary data for remote acoustic surveys. Also, any dynamical modeling of soils requires sound velocity and attenuation information.
Historically the most common acoustic measurement on soils has been the determination of longitudinal sound velocity. The longitudinal wave speed through soil samples is relatively easy to obtain and a great deal of information is available in the literature. Determinations of longitudinal sound speed have been made in situ (1, 2, 3, 4) as well as on laboratory sedimented (5), laboratory disturbed (6) and on cored (7) marine soils samples. However, comparatively little information is available on the transverse wave speed, although this parameter is just as important as the longitudinal wave speed. In situ measurements of the Stonely wave velocity (from which the shear wave velocity can be computed) have been made for the top layers of marine soil by Davis (8), Bucher, et al (9) and Hamilton et al (10). The dynamic rigidity of artificially sedimented clays has been determined in the laboratory by using a torsional-oscillator-resonance technique by Hutchins (11), Cohen (12) and Hardin (13) and Humphries (14). Also, a two-hole method has been used to obtain transverse wavespeed in marine (15) and terrestial soils (16).
The purpose of this paper is to describe the theory and the operation of a system that is capable of directly measuring shear wave velocity and attenuation. Here, a shear wave velocimeter for laboratory use is described which is low in cost, portable (hand held) and easy and fast to use.
Sea-Floor Electrical Resistivity Measurement Using a Diver-Operated System
Authors: Corwin R.F. 
Published: October 2008

INTRODUCTION AND PREVIOUS WORK
The electrical resistivity of a geologic material is related to the porosity of the material,1 with low resistivity implying high porosity. Resistivity (p) is numerically equal to the electrical resistance between opposite faces of a cube of the material of unit dimensions and usually is measured in ohm centimeters (ohm-cm) or ohm-meters (ohm-m). 8 As porosity is related to sediment composition and engineering properties, in-situ measurement of the vertical variation of the electrical resistivity of marine sediments can provide information about sea-floor structure and composition.
Resistivity techniques are well established on land, and increasing use is being made of them in the off shore environment. Several investigators3–5,7,9 'r, have measured the resistivity and porosity of sea-floor sediments and their results indicate that, except for some highly conductive clays, the formation factor of a marine sediment predicts the porosity of the sediment to within 5 or 10 percent. (Formation factor, F, is defined by the equation,(Mathematical equation available in full paper)
Measurement of the vertical resistivity distribution of the sea floor, therefore, provides a method of determining subbottom porosity and, thus, geologic and engineering properties.
Resistivity is measured on land by borehole logging or by the use of an expanding horizontal surface array. In boreholes, a small probe lowered into the hole provides a continuous record of the resistivity of the material surrounding the probe. 15 This method has been adapted successfully to marine use by forcing a thin probe into the sea-floor sediments, as shown schematically in Fig. 2. The use of a logging probe in marine sediments gives a relatively precise determination of resistivity as a function of depth, but does offer some drawbacks. The depth of measurement is limited to the depth to which the probe can be inserted into the sea floor, which may be small where sediment porosity is low. The volume of bottom material sampled is relatively small for a single insertion of the probe, so interpretation errors may result if the sampled point is not representative of the surrounding area.
Surface-deployed horizontal arrays also are used to measure vertical resistivity profiles on land. S,13 As shown in Fig. 3, this method employs two current electrodes to feed low-frequency, commutated direct current into the ground, and two (or more) potential electrodes to measure the potential difference generated at the surface of the earth by the impressed current flow". The potential difference is a function of the electrode configuration and spacing, and of the subsurface resistivity distribution.
For the equispaced Wenner array shown in Fig. 3, the "apparent, resistivity", Pa, of the earth is given by the formula:(Mathematical equation available in fullpaper)
By expanding the array, the current is forced to flow more deeply into the earth, and the apparent resistivity at larger electrode spacings is indicative of the material-at greater depth.
Sea Bed Geology from Sparker Profiles,Vermilion Block 321, offshore louisiana
Authors: King V.L. 
Published: October 2008

ABSTRACT
A diverse pattern of sands, silts and clays occurs below a thin mantle of young seabottom muds at Vermilion Block 321. The shallow layers are clearly recorded on a network of high resolution sparker lines that traverse the 2,500-acre tract in north-south and east-west directions. These lines provide data for possible platform sites and help document a wide variety of geologic features in the near surface interval. The area, located 90 miles offshore in 200 ft of water, lies within the present-day middle continental shelf province. A series of worldwide Pleistocene glaciation and deglaciation episodes directly influenced sedimentation patterns within the study area. Analysis of the sparker profiles suggests the sediments were deposited at or near an ancient shoreline during a period of sea level lowering. The strata represent a typical deltaic rock sequence. Of particular interest is a southward-oriented distributary channel recorded in both strike and dip profiles. A small, circular salt dome causing noticeable sea-bottom relief over a ½-mile circular area also is shown on the profiles.

INTRODUCTION
A diverse pattern of sands, silts and clays occurs below a mantle of young sea-bottom muds at Vermilion Block 321. The shallow layers are clearly recorded on a network of high resolution sparker lines that traverse the lease in north-south and east-west directions. This paper reviews the near surface geology of the area to a depth of about 200 ft based on an analysis of these sparker profiles. The study has three objectives: to document a variety of geologic features in the near surface interval; to demonstrate the usefulness of sparker surveys in geologic studies; and to provide supporting data for possible platform installation sites.
Vermilion Block 321 is a 2,500-acre block located about 90 miles offshore in 200 ft of water (Fig. 1). Shell acquired the lease at the Dec., 1970, general lease sale. Following acquisition, a dense grid of sparker lines (Fig. 2) was recorded to insure proper selection of sites for delineation wells and platforms. Layers to a depth of about 200 ft can be identified on the sparker records, but bottom multiples hide most events below that level.
The study area lies within the present-day middle continental shelf, an area that experienced a series of depositional cycles controlled by worldwide Pleistocene glaciation and deglaciation episodes. Several cold and warm cycles caused wide fluctuations in sea levels (Fig. 3). At low stands, deltas of the Mississippi and other rivers progressed southward across the shelf and deposited large amounts of clastics far out from the present shoreline (Bernard, 1970). The near surface sediments described in this report were deposited during the sea level lowering that created this old shoreline.
Design of a Controlled Depth, Submerged Barge and Tug System for Arctic Marine Transportation
Authors: Lewis Jack W. 
Published: October 2008

ABSTRACT
This paper describes the feasibility design of an Arctic marine, crude oil transportation system. The system consists of a depth controlled, submerged barge towed by a powerful, surface icebreaking tug. The design of the tug, barge, towing system, and control systems are described.
Because the cargo is carried below the ice water surface, the system is capable of achieving advance speeds through a given ice field which are greater than an equivalently powered conventional surface system. This feature when combined with total system costs, can give the system an economically competitive edge over alternative marine systems.
The paper concludes that the system is technically feasible and that with a suitable development program, an operational system could be realized with present day technology.

INTRODUCTION
The Continental oil Company recently completed a feasibility study of a new marine system in for transporting crude oil from the North Slope of Alaska to the United States' east coast. The system consists of a high powered, surface ice- breaking tug towing, through a flexible cable, a depth controlled submerged barge. The system, it is believed, combines the advantages of both surface and submarine tankers while at the same time eliminating their disadvantages. The barge carries all the cargo and hence avoids the ice and the corresponding large icebreaking resistances. In addition, the barge is not manned and contains only a small amount of power for driving depth control, braking, and low speed maneuvering systems. As a consequence, the barge is, re1atively cheap to manufacture. All of the prime propelling power for the system comes from the icebreaking tug. This component of the system, no longer burdened with the cargo, is made just big enough to house the required propulsion machines Since icebreaking resistance is primarily influenced by a ship's beam, it is kept as small as possible consistent with stability and machinery space requirements.
While this concept appeared very attractive, many questions arose concerning its technical feasibility. Furthermore, even if technical feasibility could be assured, there remained the question of economic feasibility. In an overview paper presented at the TRANSPO Conference in Washington, D.C. in 1972, Sudbury [1] addressed in detail the economics of a total transportation system which used the icebreaker towed submersible barge as the basic transportation unit, but treated only lightly the technical feasibility of the system. It is the purpose of this paper to present a more detailed analysis of the technical aspects of the concept. The design and predicted performance of the icebreaker, barge, towing system and control systems are the main topics such items as ice conditions along the route, terminal design, etc. were very important in the overall study but they will not be discussed in this paper.
Ice Scour on the Northern Continental Shelf of Alaska
Authors: Brooks Larry D. 
Published: October 2008

PREFACE
The intent of this investigation was two folds first, to provide an operational, research platform in the Arctic for first class cadets (seniors) of the U. S. Coast Guard Academy to supplement their education in the engineering and ocean science fields, and second, to insure that the research be pertinent to the role of the USCG in the Arctic. As Radm. R. A. Richmond, USCG, stated, "Our role has been and will continue to be to help with the research and analysis required to develop a sensible (transportation) system, and to make recommendations for sensible regulatory policies.
Within these criteria the Coast Guard Academy has been involved in the Arctic every summer since 1969 in the following areas:West Greenland glacier survey,air cushion vehicle evaluation,oil spill effects on ice,ice thickness by shear wave techniques,ice scour on the northern continental shelf of Alaska andicebreaker instrumentation and ramming tests.

BACKGROUND
Ice islands became on interest in 1946 when three were sighted in the Arctic Basin. They were tracked by aerial observations until March, 1952, when the USAF landed a scientific party on one of the three, designated T-3. 2 Several investigators began efforts to determine the origin of these ice islands, and by 1960, it was pretty much accepted that they were calved from the Ellesmere Island ice shelf'. (With evidence that the Ellesmere Island ice shelf is waning in production, there is speculation that many of the Arctic ice islands are from Siberian ice shelves as yet unknown to Free World scientists.) Caught up in the Arctic Gyre, the ice islands drift southwest along the Canadian Archipelago and into the Beaufort Sea.
The USN sponsored three oceanographic investigations into the Chukchi and Beaufort Seas and from these Carsola, in 1954, described a complicated system of bottom micro relief between depths of 30 and 200 fathoms. In water of less than 15 fathoms micro relief was noted on fathometer traces, but of a scale smaller than that in the deeper water. Without reaching any conclusions, Carsola offered five hypotheses as to the origin:glacial deposits,grounding of sea ice and icebergs,sea ice melt deposits,surface permafrost features andmass movement.
In 1968, a large ice island grounded and broke up of Prudhoe Bay and scattered remnants over a distance of 100 miles along the 15 fathom curve. Most of these remnants were about 120 ft thick and had an average horizontal area of about 1 acre. Investigators found the underwater profile of one of these remnants to be undercut in places and protruding in others. Side slopes were generally less than 45°off the vertical.