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The paper describes the development and testing of a comprehensive finite element model of a mobile arctic caisson which has been used for offshore drilling in the Canadian Arctic, and which has been exposed to significant dynamic ice forces. The specific structure, the Molikpaq, is owned by Gulf Canada. The structure consists of an eight-sided annular steel caisson, whose overall width is 110m. The caisson is set down on a berm such that the effective water depth is approximately 19m. The central core is then filled with sand to provide the overall stability and to increase the resistance to lateral loads. The system is designed for year-round drilling, and therefore must be capable of resisting loads from impacts from thick multi-year ice floes. The model described in this paper consists of a finite element representation of the caisson which is developed using macro-elements to model the complex structural steel arrangement of bulkheads and stiffened steel plates in the caisson. These macro-elements are then combined with a brick element representation of the core, and various alternative models for the berm. The static and dynamic behaviour of the model are tested, and the results compared to the behaviour of the prototype.

The authors report on measurements of the chirp factor versus modulation frequency and bias for 1.55 mu m distributed feedback lasers. A scanning Michelson interferometer is used to measure the phase response of the optical field under small-signal modulation of the injection current. The magnitude of the phase response is then quantified in terms of an effective chirp factor corresponding to the well known alpha -parameter. The authors find this factor to increase monotonically and nearly double as the modulation frequency increases from below to above the resonance frequency of the relaxation oscillation. The results contradict the commonly held view of alpha as a constant parameter for a given laser structure. >

The phenomenon of intensity-phase coupling in semiconductor lasers is studied in the linear regime in terms of an effective linewidth enhancement factor. The circumstances under which the longitudinal laser structure of a distributed feedback laser may influence this coupling are determined. For the case of uniform gain and carrier density no effect is expected from a periodic or quasi-periodic corrugation. However, when the gain layer is corrugated or a periodic gain is otherwise implemented, the influence may be considerable. It is shown that the degree of gain coupling between right- and left-travelling waves and the specific mechanism by which variations in the carrier density influence this coupling are of key importance. It is found that depending on the degree and nature of the gain coupling the effective linewidth enhancement factor may be considerably reduced or enhanced. >

Using non-linear coupled-mode equations and a Bloch-wave approach, we show that the nonlinear propagation of femtosecond pulses and supercontinuum light inside fiber grating can be modeled by nonlinear Schrodinger equation with modified dispersion profile.

NCSX [National Compact Stellarator Experiment] is the first of a new class of stellarators called compact stellarators which hold the promise of retaining the steady state feature of the stellarator but at a much lower aspect ratio and using a quasi-axisymmetric magnetic field to obtain tokamak-like performance. Although much of NCSX is conventional in design and construction, the vacuum vessel and modular coils provide significant engineering challenges due to their complex shapes, need for high dimensional accuracy, and the high current density required in the modular coils due space constraints. Consequently, a three-phase development program has been undertaken. In the first phase, laboratory/industrial studies were performed during the development of the conceptual design to permit advances in manufacturing technology to be incorporated into NCSX's plans. In the second phase, full-scale prototype modular coil winding forms, compacted cable conductors, and 20 degree sectors of the vacuum vessel were fabricated in industry. In parallel, the NCSX project team undertook R&D studies that focused on the windings. The third (production) phase began in September 2004. First plasma is scheduled for January 2008.

The TPX configuration was designed to meet the physics objectives and subsystem requirements in an arrangement that allowed access for remote maintenance. The steady state operations of TPX favored the use of superconducting magnets for both the toroidal and poloidal field systems. The desire to react the TF centering and overturning forces in a simplified wedged system lead to a TF case concept incorporating "two-coil" TF modules in a 90/spl deg/ four-coil quadrant arrangement. Low ripple and tangential plasma access to accommodate TFTR neutral beams were leading factors in determining the size and number of TF coils. The need for a large amount of space for the divertor and first wall component coolant services further influenced the shaping of the vacuum vessel. Additional configuration influences included: low activation considerations, divertor pumping, remote maintenance requirements, service access and compatibility with the existing TFTR text cell facility. The TPX configuration development and integration process has evolved through the conceptual design period and is now ready to enter the Preliminary Design Phase of the project. This paper describes the status of the configuration development and integration of the major TPX tokamak subsystems components.

The integration of Burning Plasma Experiment (BPX) tokamak components, peripheral equipment, service lines, and the test cell facility is being carried out to satisfy the functional requirements of all systems, maximize hands-on maintenance of peripheral equipment, and maximize access space around the machine for remote maintenance. The baseline configuration has evolved around a center cell that houses the tokamak device, has close-in North and South cells for locating peripheral equipment for hands-on maintenance, has trenches located in the test cell floor to carry away service lines to various diagnostic areas, and has equipment lines that service the device core components integrated with the cryostat and locally arranged to maximize remote maintenance access to the device and the center cell peripheral equipment. A circular pipe corridor has been located in the basement to localize floor penetrations, prevent activation of the basement, and provide support structure directly under the machine. These and other configurational design details have been developed in the process of fully integrating all BPX systems and subsystems. >

This study investigates an out-of-plane optical coupling geometry into silicon-on-insulator (SOI) technology in order to create data transmitters and receivers for optical communications wavelengths. This geometry can, in principle, provide both high switching contrasts and high speeds. The study is carried out in SOI waveguides equipped with optically-resonant periodic electrode (ORPEL) structures, developed using conventional microelectronic fabrication techniques. As a receiver, the periodic electrodes enable the device to selectively couple a narrow band of light energy into the waveguide structure. As a transmitter, data to be transmitted from the device is imposed on a reflected signal from an incident continuous-wave probe signal; modulation is controlled by electronically altering the free-carrier density and/or distribution, thus altering the effective index of refraction of the waveguide core and coupling properties of the device. Initial optical and optoelectronic test results are presented.

Many times the cost associated with minimizing the impact to the environment are burdensome to the overall project economics. There are cases when the decisions regarding these two important issues become mutually beneficial to both the environment and project economics. This paper will demonstrate an example of this situation. The Ras El Ush development lease (which is located in the southern Gulf of Suez, Egypt) was discovered in March 1995. In order to develop the reserves associated with this field in the most economical manner, many decisions where made which also impacted the environment. The environmental and economic considerations were incorporated into the decision making process. The heart of the conducted Environmental Impact Assessment for the pre-development phase was the evaluation of the possible field development alternatives including their environmental consequences in a comparative form. The first decision was to drill the wells directionally from the shore to intersect bottom-hole locations offshore in the Gulf of Suez. The cost to drill this type of well was favorable to contracting an expensive jack-up rig to drill straight hole wells in the gulf. Multiple directional wells were drilled from a single pad and utilized a common individual mud pit. This minimized land take and minimized the cost of location construction and rig moves. These techniques minimized the environmental impacts associated with the field development activities compared with offshore production options as will be presented in the paper. The next decision was to utilize the excess capacity in existing facilities nearby in order to save the cost of capital required to process and ship the oil. This also minimized the environmental impact of onshore facilities. By allowing these measures, the field was brought on line in an extra-ordinary fast schedule- first production started in January 1996, less than one year from discovery. This paper shows that the starting point of all environmental protection practices is to reduce the environmental impact at the source using typical pollution prevention mechanisms which integrate with the process of production. In the Ras El Ush field development this had economic as well as environmental benefits.

This paper describes a variety of programs specifically designed for the determination of sea ice and iceberg loads on Arctic offshore and nearshore structures. As any ice load is a function of the interaction between ice feature and structure, the design of arctic structures is very much an interactive process. Many other factors determining the overall loads and local pressures are functions jointly of ice feature and structural characteristics. For example, the ice strain rate which is a primary determinant of ice strength and failure behaviour may be determined from ice velocity and structure size.The paper details the development of a number of programs directed at the evaluation of quasi-static ice loads, dynamic ice loads, and corresponding local pressures between ice and structure. Examples are provided of the use of the various programs, including the data required and the type of outputs resulting.As a number of the programs incorporate quite extensive theoretical developments or, in one case, a large number of discrete interactions, full description of each program is beyond the scope of this paper. The reader is directed to the listed references for full developments of the various programs and algorithms. Key words: sea ice, iceberg, global ice load, local ice pressure, finite element, ice/structure interaction, probabilistic analysis, ice failure mode.

This document highlights the technical requirements of the key subsystems of the Reference Design for The Next Step (TNS) and presents a preliminary assessment of the adequacy of the technical capabilities available to satisfy these requirements. Additional information on the Reference Design and the FY 1978 TNS Program activities can be found in the associated technical memoranda, ORNL/TM-6720, ORNL/TM-6721, and ORNL/TM-6723 - ORNL/TM-6733.

Advanced commercial tokamak studies were performed by the Fusion Engineering Design Center (FEDC) as a participant in the Tokamak Power Systems Studies (TPSS) project coordinated by the Office of Fusion Energy. The FEDC studies addressed the issues of tokamak reactor cost, size, and complexity. A scoping study model was developed to determine the effect of beta on tokamak economics, and it was found that a competitive cost of electricity could be achieved at a beta of 10 to 15%. The implications of operating at a beta of up to 25% were also addressed. It was found that the economics of fusion, like those of fission, improve as unit size increases. However, small units were found to be competitive as elements of a multiplex plant, provided that unit cost and maintenance time reductions are realized for the small units. The modular tokamak configuration combined several new approaches to develop a less complex and lower cost reactor. The modular design combines the toroidal field coil with the reactor structure, locates the primary vacuum boundary at the reactor cell wall, and uses a vertical assembly and maintenance approach. 12 refs., 19 figs.

The FEDC Tokamak Systems Code calculates tokamak performance, cost, and configuration as a function of plasma engineering parameters. This version of the code models experimental tokamaks. It does not currently consider tokamak configurations that generate electrical power or incorporate breeding blankets. The code has a modular (or subroutine) structure to allow independent modeling for each major tokamak component or system. A primary benefit of modularization is that a component module may be updated without disturbing the remainder of the systems code as long as the imput to or output from the module remains unchanged.

This document provides a systems description of the Reference Design for The Next Step (TNS) evolved at Oak Ridge National Laboratory (ORNL) during FY 1978. The description is presented on the basis of 24 individual device and facility systems. Additional information on these systems, the Reference Design, and the FY 1978 Oak Ridge TNS activities can be found in the associated technical memoranda, ORNL/TM-6720 and ORNL/TM-6722--ORNL/TM-6733.

A status report on the Oak Ridge TNS Program has been prepared with three basic parts--a summary of the FY 1977 activities, a discussion of the current baseline design, and a statement of work tasks for FY 1978. Within the FY 1977 activities, the plasma engineering efforts were directed toward improving the economical performance of tokamak reactors and toward easing the requirements placed upon the supporting technology development programs. The FY 1977 systems modeling efforts were used to develop comprehensive systems models for cost comparison of different toroidal field (TF) coil technology options. The FY 1977 program planning tasks provided a draft program plan with both an R and D assessment and schedule considerations. On the basis of these activities, the FY 1978 effort is being directed toward initiation of preconceptual design. The current baseline design, characterized by key parameters and overall layout drawings, is being developed from the FY 1977 activities as a starting point for the FY 1978 preconceptual design study tasks. The projected performance of the baseline design as an ignited and burning primitive fusion reactor facility is being developed through self-consistent plasma engineering calculations using 0-D, 1-D, and 1-/sup 1///sub 2/-D models. A set of pertinentmore » work tasks for the FY 1978 effort has been developed from a systematic analysis of the status of each subsystem.« less

The Fusion Engineering Device (FED) Baseline design incorporates a number of features which were selected to enhance its maintainability, as well as limit cost and achieve reliable operation. An installation of ten TF coils and ten torus sectors was selected on the basis of plasma chamber segmentation studies and TF coil cost tradeoff studies, permitting removal of a torus sector with a single radial motion. The design also features a shield sector support spool which provides a plasma chamber vacuum boundary and access to the shield sectors. The vacuum seals are made at the outboard face of the torus so that they can be readily cut and rewelded. A pumped limiter provides plasma edge definition and impurity control. Ten individual blades are inserted through the shield sector in an arrangement that permits replacement without sector removal. ICRH is used for plasma bulk heating. Two EF coils, which are located inside the TF coil bore, are segmented so that they can be removed if necessary. The removal of the superconducting lower outboard EF coil, which is trapped under the TF coil assembly, presents a problem; consideration is being given to increasing its diameter and relocating it so that it can be lifted up around the TF coils.