bluuebunny/crossref_metadata_2025 huggingface dataset:
A Dynamic Response of a Module/Array Simulator Using I-V Magnifier Circuit of a PN Photo-Sensor
Authors: Nagayoshi Hiroshi
Published: January 2009

Basic characteristics and dynamic response of a 30W module/array simulator using PV I-V magnifier circuit was studied. It was confirmed that each gain of voltage and current was independently adjustable using feedback control of current signal. Simulator circuit output power is controlled by LED irradiation light which works as an irradiation of sun light to real PV modules. Maximum power of the circuit depends on maximum power of the power amplifier used in the circuit. A photo-current of pn photo-sensor was some micro ampere hence the current gain of the simulator needed more than 50dB. The voltage gain was not more than 3dB because a multi junction pn photo-sensor was used. To control the simulator circuit by personal computer, an LED driver circuit was added. A fill factor was also easily changeable by change of shunt resistor connected with pn photo-sensor in parallel. A dynamic response of short circuit current was measured and confirmed that the circuit has enough response ability to apply the MPPT evaluation. A grand line of each module is isolated, hence any topology of connections is available. This circuit simplifies the control system and makes it easy to handle multi simulator units by one personal computer. This system is suitable for the evaluation of multi inverter system.
Reducing the Cost of Energy From Parabolic Trough Solar Power Plants
Authors: Price Henry , Kearney David
Published: January 2009

Parabolic trough solar technology is the most proven and lowest cost large-scale solar power technology available today, primarily because of the nine large commercial-scale solar power plants that are operating in the California Mojave Desert. However, no new plants have been built during the past ten years because the cost of power from these plants is more expensive than power from conventional fossil fuel power plants. This paper reviews the current cost of energy and the potential for reducing the cost of energy from parabolic trough solar power plant technology based on the latest technological advancements and projected improvements from industry and sponsored R&D. The paper also looks at the impact of project financing and incentives on the cost of energy.
Improved Alignment Technique for Dish Concentrators
Authors: Andraka Charles E. , Diver Richard B. , Rawlinson K. Scott
Published: January 2009

Parabolic dish concentrators have shown significant promise of generating competitive electric energy for grid and off-grid applications. The efficiency of a dish-electric system is strongly affected by the quality of the concentrator optics. Most parabolic systems consist of a number of facets mounted to a support structure in an approximate parabolic arrangement, where the individual facets have spherical or parabolic optical shapes. The individual facets must be accurately aligned because improper alignment can compromise performance or create hot spots that can reduce receiver life. A number of techniques have been used over the years to align concentrator facets. In the Advanced Dish Development System (ADDS) project, a color look-back alignment approach that accurately aligns facets (mirror panels) and in addition indicates quantitative information about the focal length was developed. Key factors influencing the alignment, some of which had very large effects on the quality of the alignment, were also identified. The influence of some of the key factors was characterized with a flux mapping system on the second-generation ADDS concentrator. Some of these factors also affect other alignment approaches. The approach was also successfully applied to two other concentrators with differing facet arrangements. Finally, we have extended the method to a 2-f approach that eliminates the need for a distant line-of-sight to the dish and permits alignment at near vertical dish attitudes. In this paper, we outline the color look-back alignment approach, discuss the key alignment factors and their effect on flux distribution, and discuss extensions to non-gore dishes. A companion paper discusses the 2-f color alignment approach in detail.
Thermal Management of the Polymethylmethacrylate (PMMA) Core Optical Fiber for Use in Hybrid Solar Lighting
Authors: Tekelioglu Murat , Wood Byard D.
Published: January 2009

This work is part of a team effort to develop a hybrid solar lighting (HSL) system that transports day light from a paraboloidal dish concentrator to a luminaire via a large core polymer fiber optic. For example, the luminaire can be a device to distribute sunlight into a space or it can be a device that is a combination of day lighting and florescent lighting. In this project, the sunlight is collected using a one-meter paraboloidal concentrator dish with two-axis tracking. The secondary mirror consists of eight planar-segmented mirrors that direct the visible part of the spectrum to eight fibers (receiver) and subsequently to eight luminaires. This results in about 8,200 lumens incident at each fiber tip. This paper is concerned with predicting the radial and axial temperature distribution in the entrance region of the fiber in light transmission. Thermal management is especially important because when PMA-core optical fibers are used in light transmitting systems, the core of the optical fiber is prone to thermal degradation due to the heating effect of the infrared spectrum. Thermal degradation of the fiber core can cause fiber aging, reduce the life-time of the fiber from years to months, increase the attenuation in the short visible region (in the 400 ∼ 470 nm) and can soften the PMA core making it susceptable to damage. In order to ensure the thermal degradation free operation of plastic optical fibers, an economical and viable solution has to be found. The solution should keep the light loss at minimum at the expense of its implementation. Several filtering techniques have been investigated to minimize the effect of IR portion of the solar spectrum at the fiber entrance tip surface as well as the whole-spectrum absorption of solar energy inside the fiber. According to the analysis results, the use of fused quartz glass attachment was proven to be cheaper, more cost effective and feasible among other proposed solutions. Depending on the mirror/filter specifications, the first 8 mm of the fiber was found to be critical based on 5 m/s air speed across the lateral surface of fiber. Modes of heat transfer taken into account included thermal conduction, convection and radiation on the first 5 cm of the polymethylmethacrylate (PMMA) core and Teflon-FEP cladding fiber. A case-basis comparison was made with the experimental result.
Operating Strategy of a Stand-Alone Photovoltaic/Diesel/Battery Power System
Authors: Ismail Yusuf , Kemmoku Yoshishige , Takikawa Hirofumi , Sakakibara Tateki
Published: January 2009

A new method for operating a stand-alone photovoltaic/diesel/battery system is presented in this paper. The diesel generator is controlled so that the state of charge (SOC) of the battery may be maintained at a certain specified charge level in daily time. The battery is discharged when the SOC is higher than the specified charge level and charged when lower. A simulation is carried out over one year using the hourly data of electric load, insolation intensity, and atmospheric temperature on Kamishima Island, Japan in 1996. The minimum specified level is pursued in every day so that the fuel consumption is minimum. This method is compared with other operating methods: a conventional operating method maintaining the battery charge level at the full level (FCL), and Dynamic Programming (DP) operating method. The results show that for diesel generator fuel consumption, this method is superior than FCL, although not to the DP.
Sensitivity Factors in Building Integrated Photovoltaic (BIPV) System Cost
Authors: Sozer Hatice , Elnimeiri Mahjoub
Published: January 2009

Even though PV technology is new and expensive for the building industry today, and regardless of market development and technology advancement, a BIPV system cost can actually be reduced and its application can spread further into the building industry as this paper will manage to show. However, PV systems still have not been accepted by the building industry and consumers yet. According to the results of a survey by the workshop of Building Integrated Photovoltaic for Design Professionals which was sponsored by the National Energy Laboratory (NREL) and the American Institute of Architects (AIA), “a major barrier to analyzing renewable energy systems is assembling and presenting the technical and financial data to persuade a client that a BIPV would make economic sense.” [Wenger and Eiffert, 1996] This paper uses Life Cycle Cost Analysis (LCCA) for identifying BIPV system cost components and makes the connection between the findings of LCCA and the design process. It identifies specific quantifiable measures/variables that will be compared with a non-PV integrated building or different PV system applications by using the LCCA method that confirms cost related issues. Calculations of payback period as a result of LCCA gauge the sensitivity of these variables and show how some of them are significantly more important than others in reducing the pay back period. Offering an efficient approach for integration of PV into curtain wall also meets the long-term objective of the satisfaction of the building user.
Certification for Photovoltaic Power Systems: Premature, Timely or Too Late?
Authors: Bower Ward , Parker Wendy
Published: January 2009

Photovoltaic power systems of all types are being installed in the United States. Grid-connected installations have seen a tremendous jump in their numbers and sizes of installations but there is no complete photovoltaic product (component or system) or installer certification program in effect today in the United States. Standards for utility interconnect, listing for safety, and qualification of hardware are written and listing and qualification programs are available, but practitioner and hardware certifications are not yet in place. This paper addresses the timeliness, framework, and progress of hardware and practitioner certification efforts currently under way in the United States.
The eco/Tech Sludge Recycling System: New Waste Streams, New Revenues
Authors: Beaumont E. Larry
Published: January 2009

The eco/Technologies Sludge Recycling System (eco/Tech SRS) is an important new patented and commercially proven technology that provides resource recovery facilities with a new revenue source and the potential for reduced oxides of nitrogen emissions. The eco/Tech SRS offers an environmentally sound, cost-effective disposal option for sludge producers, while ensuring significant increased net revenue potential for municipal waste combustor facilities. As the wastewater treatment industry faces increasing regulatory scrutiny that will result in more expensive sludge disposal practices, the resource recovery industry, which has already met the regulatory challenge and has taken the lead in compliance and corporate citizenship, can provide the answer.
Water Gauge, Flue Plate Stiffeners, and Insulation Systems Design Considerations
Authors: Bases Gary J.
Published: January 2009

Tremendous money is wasted due to the lack of attention to the water gauge and flue plate stiffeners, and their impact on the insulation and lagging design. The design and installation of an insulation and lagging system will depend heavily upon the flue or duct stiffener arrangement. The stiffener arrangement is determined by many factors including the water gauge of the flue or duct plate design. The stiffener pattern and size is the first thing you consider when designing an insulation and lagging system. Therefore, it is imperative to understand how the size, shape and pattern of the external stiffeners are developed. The stiffener sizing of yesterday was based on a much lower water gauge pressure and allowed the insulation to be placed between the stiffeners without having to cut-to-fit. The stiffeners being designed today are quite large and much farther apart. This is due in part to the water gauge number being used in the design calculations and because they have not considered the required insulation thickness and application. A well designed and installed insulation and lagging system will save money and energy at a rate that is essential for an efficient plant operation. This is especially true when adding a selective catalytic reduction system (SCR) or a selective non catalytic reduction system (SNCR) to the back end of a steam-generating unit. The insulation and lagging system is critical for these air pollution systems to operate correctly.
Potential Concerns and Impacts of CCA-Treated Wood for the Waste-to-Energy Industry
Authors: Townsend Timothy , Solo-Gabriele Helena
Published: January 2009

An issue that has received much attention in the U.S. in recent years, especially in Florida, is the impact of CCA-treated wood on human health and the environment (Decker et al. 2002; Gordon et al. 2002) , including risks faced as a result of discarded CCA-treated wood in the solid waste stream (Townsend et al. 2001; Townsend et al. 2003). CCA-treated wood is preserved with copper, chromium and arsenic. All of the metals have toxic impacts at high exposures; it is arsenic however, which has raised the greatest concern (it is more hazardous at lower concentrations than the other CCA constituents). CCA-treated wood often becomes mixed with other wood from construction and demolition (C&D) debris (Tolaymat et al. 2000). Mixed C&D debris wood is either landfilled along with the rest of the C&D debris stream (e.g. concrete, gypsum drywall) or it is separated and processed for a variety of recycling markets.
Comprehensive Power Engineer Training Increases Safety, Production and Plant Peformance at Montenay Inc., British Columbia, Canada: A Case Study
Authors: Asada Vicki
Published: January 2009

Disastrous boiler and pressure vessel incidents result in loss of property and life. Most accidents are due to individual or human error, not equipment. It is important for plant supervisors and management to know how training has been implemented in a plant that has not had any accidents, and has also increased production and overall plant performance.
FEA Models to Identify Possible Fatigue Failures on a Large Diameter Turbine, Installed on a Floating Platform
Authors: Obeyesekera Ranjith K.
Published: January 2009

The paper discusses the influence of body loads and dynamic loads on the surface of a large diameter turbine. In this study the corrosion fatigues due to the sea environment are not considered. The study shows that increasing the body loads decrease the endurance limits of the turbine. The computational FEA study reveals that endurance is significantly effected the gyroscopic loads at lower speeds of the turbine. In this study the floating platform is a large hollowed floating chamber, both sides of which are rigidly fixed to the two parabolic walls and floats as a single unit. The turbine is installed on the deck of the floating device and the endurance stresses of which are influenced by the dynamic loads. Dynamic loads are classified as fluctuating loads and repeated loads. In this study fluctuating loads mainly depend on the variable pitch determined by the sea waves. These are also known as gyroscopic loads. The repeated loads are derived from the body loads. The magnitude of the gyroscopic load depends on sea wave characteristics, mechanical characteristics of the floating device, and the kinematics of the turbine. The FEA model study shows that an increase of the body loads lowers the factor of safety. The study compares the gyroscopic loads and the body loads of the turbine against the endurance stresses. Computational analysis shows that modifying the body loads within the gyroscopic stress environment influences the area of low fatigues.
Evaluating the Stress Intensity Modification Factor in Offshore Tubular T Joints Using Artificial Neural Networks
Authors: Fathi Ali , Aghakouchak A. A. , Montazer Gh. A.
Published: January 2009

Linear Elastic Fracture Mechanics (LEFM) and Stress Intensity Factor (SIF) are applicable tools to evaluate growth rate of existing fatigue cracks in offshore tubular joints. This is because the plastic zone around the fatigue crack tips is satisfactorily small. Several approaches based on LEFM have been proposed in this regard. Each of them uses different methods for estimating Stress Intensity Modification Factor (Y). In this research two types of Artificial Neural Networks (ANN) are trained for predicting the Y factor: Radial Basis Function (RBF) and Multi Layer Perceptron (MLP) networks. These networks are capable of estimating the Y factor at deepest point of a fatigue crack, located in tubular T joints under axial loading, when the crack depth is more than 20% of chord wall thickness. The required input data consist of the crack shape and the percent of the crack growth through thickness. Experimental data from NDE center in University College London are used for training and testing the networks. This data has been gathered by applying constant amplitude axial load to the brace of six full-scaled T joints. The results of this research are compared with different empirical and semi-empirical solutions, used in previous research works. The Y factors obtained from networks show better agreement with actual ones when compared to those obtained from previously established methods.
A Novel Application of Constrained NewWave Theory for Floatover Deck Installations
Authors: O’Neill Lee A. , Fakas Emmanuel , Cassidy Mark
Published: January 2009

Numerical techniques are extensively used to predict vessel motions and associated contact forces for offshore operations such as lift and floatover deck installations. The accuracy of such predictions however is highly dependent on the comprehensive modelling of seastate conditions, which is often limited by computational power and time constraints. A time-efficient methodology, suitable for modelling large numbers of installation seastates, is developed to alleviate this problem. The methodology is based on the Constrained NewWave model which has been previously used to overcome similar problems. However this has only been for individual, extreme storm conditions. The accuracy, time-efficiency and practicality of the revised methodology is demonstrated by means of direct comparison of simulation results obtained for a floatover deck installation on the North West Shelf of Australia. The ability to perform large number of simulations in a time and cost efficient manner is of paramount importance in assessing the system limitations to varying installation conditions, a case that has always been challenging to designers during the development of oil and gas projects. Such flexibility improves confidence in the overall system, necessary for the accurate assessment of the commercial viability of marginal developments.
Using Motan to Measure Global Accelerations of the CCGS TERRY FOX During Bergy Bit Trials
Authors: Johnston M. , Frederking R. , Timco G. , Miles M.
Published: January 2009

The whole-ship motions of the CCGS TERRY FOX were measured for more than 150 controlled impacts with small pieces of glacial ice, or bergy bits. The impacts were conducted at speeds up to 14 kt. This paper uses global ship accelerations measured during three different impact events to demonstrate proof of concept for an inertial measurement system called MOTAN.
A Critical Review of Evaluation Methods of Ice Adhesion Strength on the Surface of Materials
Authors: Kasaai Mohammad R. , Farzaneh Masoud
Published: January 2009

Several techniques have already been proposed to determine ice adhesion strength. This study made a critical review of the existing methods and proposed three other techniques for ice/substrate systems, where the latter techniques have already been used to other adhesive/substrate systems. In this study, these methods are compared for their performance and limitations, with a selection of the most promising ones. The main conclusions are: in most techniques, test procedures required a long time while showing a low degree of reproducibility. Cohesive and adhesive failures, as well as a combination of both, were observed in the measurements. Macroscopic or microscopic/nanoscopic scale tests were used to evaluate ice adhesion strength Micro/nano scale tests using Atomic Force Microscopy (AFM) or nano indentation instrument can be used to estimate the nature and surface energy of water-repellent materials, and identify materials with low-ice adhesion. Among various methods the combination of AFM /nano-indentation technique with either lap-shear or combined lap-shear and tensile modes should be the most powerful.
CARISIMA: A Catenary Riser/Soil Interaction Model for Global Riser Analysis
Authors: Giertsen Egil , Verley Richard , Schro̸der Knut
Published: January 2009

Steel or titanium catenary type risers may provide cost effective alternatives to flexible risers, particularly for deeper water (>300 meters). Existing analysis tools for riser response have proven reliable for most types of risers. However, in the area where catenary risers are resting on the seafloor, existing models for riser/soil contact are too simplified to capture the complexity of the interaction. Some of the key findings of earlier work are that the fatigue life predictions at the touchdown area are sensitive to the FEM modelling, fatigue accumulation procedures and, in particular, the soil model. Hence, an important step forward in improving riser analysis tools is to improve the riser/soil interaction model. This issue was the key objective of the CARISIMA JIP. This paper gives an overview of the main activities in the CARISIMA project.
Simulation of Ice Accumulation on Transmission Line Cables Based on Time-Dependent Airflow and Water Droplet Trajectory Calculations
Authors: Fu Ping , Bouchard Gilles , Farzaneh Masoud
Published: January 2009

The Local Collision Efficiency (LCE) is a key parameter for ice accretion simulation, since it describes the distribution of droplet impingements on the surface of an object. In this paper, a numerical procedure is introduced to calculate airflow and water droplet trajectories, which were used to evaluate the LCE in the newly developed ice code. Also, the validity of several approaches and approximations for determining LCE in the context of atmospheric icing is examined. In the procedure proposed here, the LCE was evaluated, based on solving droplet trajectories according to its original definition, taking into account the changes in geometry and airflow field. Airflow field was modeled as a potential flow combined with boundary layer separation. The potential flow was solved by using the Boundary Element Method (BEM). The droplet trajectories were obtained by solving the equation of motion using the Runge-Kutta algorithm for a spectrum of droplets, and as a result the LCE was determined in accordance with its definition. Several specific problems were addressed within the scope of this paper, including changes in geometry during the simulation process, separation of boundary layer by bluff object, and the presence of large droplets, particularly for freezing rain precipitation. This paper also examines the influence of the droplet spectrum on the collision efficiency. Specifically, a spectrum of droplets from natural conditions and a spectrum of droplets from experimental wind tunnel conditions were compared with a monodisperse spectrum of the same Median Volume Diameter (MVD). For simplicity, numerical icing model researchers prefer to use a monodisperse spectrum, since the droplet trajectory computations are impractically time-consuming. The validity of this practice is assessed in the present paper.
Non-Linear Time Domain Analysis of Vortex Induced Vibrations for Free Spanning Pipelines
Authors: Larsen Carl M. , Passano Elizabeth , Baarholm Gro Sagli , Koushan Kamran
Published: January 2009

Pipelines from offshore petroleum fields must frequently pass over areas with uneven seafloor. In such cases the pipeline may have free spans when crossing depressions. Hence, if dynamic loads can occur, the free span may oscillate and time varying stresses may give unacceptable fatigue damage. A major source for dynamic stresses in deep water free span pipelines is vortex induced vibrations (VIV) caused by current. Two alternative strategies for calculation of VIV are seen today. Practical engineering is still based on empirical models, while use of computational fluid dynamics (CFD) is considered immature mainly because of the needed computing resources. Most empirical models are based on frequency domain dynamic solutions and linear structural models, cf. Larsen (2000). The reason for this is simply that hydrodynamic coefficients as needed in a VIV analysis are available as functions of frequency, and therefore not directly applicable in a transient time domain simulation. A free span pipeline has, however, important nonlinearities that should be taken into consideration. Both tension variation and pipe-seafloor interaction at the span shoulders will contribute to nonlinear behaviour, which means that most empirical models will have significant limitations when dealing with the free span case. The need for non-linear time domain methods is therefore obvious. This paper describes a new approach for VIV analysis of free span pipelines where both linear frequency and non-linear time domain analyses are employed. The first step is to carry out a conventional VIV analysis that will determine response frequency and hydrodynamic coefficients by use of a linear response model. This result is then used in a time domain model that can handle non-linear boundary conditions at the span shoulders. This approach is valid as long as the response amplitudes at the main part of the span are the same for both analysis methods. The significance of the new method is that displacements, and hence also stresses, in the pipe at the shoulders will be far better described by the non-linear method than what is possible from linear theory. Since fatigue damage in most cases is larger at the shoulder than within the mid section of the span, the new approach represents an important step forward for free span pipeline analysis.
A Three-Dimensional Modeling of Multidirectional Random Wave Interactions by Multiple Rectangular Submarine Pits
Authors: Lee Hong Sik , Williams A. Neil , Kim Sung Duk
Published: January 2009

A three-dimensional numerical model is presented to predict the interactions of multidirectional random surface waves with one or more rectangular submarine pits. The water depth in the fluid region exterior to the pits is taken to be uniform. The three-dimensional Green function in the boundary integral equation, obtained by Green’s second identity, has been used for the solution of the velocity potential and its derivative in fluid interface between regions, and also a form of the Fourier expansion is utilized for the solution of the velocity potential in the interior region. The incident wave conditions are specified using a discrete form of the Mitsuyasu directional spectrum. The present method is based on the cumulative superposition of linear diffraction solutions obtained by a three-dimensional boundary integral approach. The results of the present model have been compared with those of previous theoretical studies for both regular and random wave diffraction by single or multiple pits. Reasonable agreement was consistently obtained in all cases. In accordance with good agreement from these comparisons, it is concluded that the present numerical model may accurately be utilized to predict the three-dimensional wave field around multiple submarine pits or navigation channels in many practical applications.
Reliability Characteristics of a Safety Instrumented System via Markov Analysis
Authors: Di´az-Herna´dez Alejandro , Pe´rez Medina Mari´a Eloi´sa
Published: January 2009

The Markov technique for determining the Reliability Characteristics (Probability of Failure on Demand, availability, Mean time to repair and Mean time between failures) of the Safety Instrumented System (SIS) on Offshore Metering and Custody Transfer Facility in Campeche Bay Mexico is presented in this work. Two important factors were considered based on the ISA TR84.0.02, Part 4: a) Common Cause Failure and b) the diagnostics capabilities were taking into account. The Markov technique methodology employed in order to assess and determine the Reliability characteristics of SIS was compared with Fault Tree Analysis previously analyzed, Part 3 of ISA TR84.0.02; for which the hazard and risk analysis mandated a SIL 2 for the SIS with two sets of sensors where each individual sensor can shut down the operation of the facility. Aspects like voting, redundancy or diversity bring about a full Markov model of a SIS, but it usually consists of intermediates states not significant for the assessment of the reliability characteristics. The quantitative results will mostly depend on the direct transitions to the fail-safe and fail-dangerous states. As a result, in most cases it was not necessary to present a fully developed model.
Maintenance Decisions for Offshore Structures Using Real Options Theory
Authors: Heredia-Zavoni Ernesto , Santa-Cruz Sandra
Published: January 2009

Real Options methods are currently used to assess investment projects considering: (1) the decision options that one can have along the development of the project, such as to expand it, or reduce it, or to abandon it, or to differ it, and (2) the uncertainty in some financial variables for the assessment of the economic investment. In these two regards, Real Options methods are superior to the traditional Net Present Value method. The purpose of the present paper is to establish the basis for Real Options modeling for decision making on design, inspection, maintenance, and decommissioning of offshore structures. The use of Real Options theory is sought in order to account for: (1) uncertainties in the financial variables involved in risk assessment based on expected costs, such as the economic consequences due to failure of a system; and (2) uncertainties associated with the resistance and loading of the structure for reliability assessment. An application of Real Options Theory is given in the paper for decision making on maintenance for an offshore structure. Cash flow from oil revenue is modeled as a stochastic process. Preventive and corrective maintenance is analyzed as a critical situation where the decision maker has the option to pay the costs of maintenance in order to obtain a benefit. Expressions are derived for the estimation of the value of the maintenance option; they are based on the derivation of the Black-Scholes equation for the evaluation of financial options. It is shown that the value of such project is equal to the sum of the net cash flow of the project (as with a Net Present Value evaluation) plus the value of the maintenance option. Projects with one and two decision times along the life of the structure are formulated and analyzed. Closed form solutions are obtained for such cases. An example is given in order to illustrate the differences between maintenance decisions using the Net Present Value and the Real Options method.
Maneuvering Large Tankers Alongside a Floating LNG (FLNG) Facility
Authors: Onassis Jan , Hurdle David P.
Published: January 2009

The FLNG concept involves the use of a large, turret-moored floating facility that processes natural gas from local production fields and stores the products for export. The products are transferred through conventional hard arms located on side of the FLNG to tankers moored alongside. This concept requires an evaluation of the arrival and departure maneuvers of the large tankers servicing the FLNG. As this is a new concept on this scale, it is not possible to investigate this aspect in prototype. It is however possible to carry out the evaluation with the aid of computer simulations. Important aspects to incorporate in the simulations are the hydrodynamic and aerodynamic interactions between the different bodies (FLNG, tankers and tugs) and the effect of these continuously changing interactions on the actions of the ship’s pilot. The paper presents a case study in which real-time maneuvering simulations were carried out with the multi-body version of Alkyon’s simulation model SHIP-NAVIGATOR. Experienced and active pilots ran the maneuvers. Wind, waves and currents influence both the FLNG and the tankers. Furthermore, the presence of each of these facilities can influence environmental conditions experienced by the other. The paper discusses the importance of modeling these influences properly assess the feasibility of the marine operations.
Evaluation of Inherent Safety Potential in Offshore Oil and Gas Activities
Authors: Khan Faisal I. , Veitch Brian , Amyotte Paul R.
Published: January 2009

The inherent safety approach is the best option for hazard/risk management in offshore oil and gas activities. Some of the main drivers for inherent safety in the offshore industry are to reduce manning levels and provide minimum facilities installations, encourage the use of compact and simple technology, and reduce the need for operators to be present. Though this approach is comparatively mature and has been widely accepted in onshore process industries, its applications in offshore industries are still limited. A recent pilot study to assess the extent to which the concept and principles of inherent safety are being applied in the development and design of offshore oil and gas installations revealed that the term inherent safety is only just beginning to be recognized in the industry, mainly as a result of its inclusion in the Design Safety Case Guidance, and the UKOOA Fire and Explosion Hazard Management Guide. There appears to be a number of subtle but significant differences of opinion as to what inherent safety is, including ‘hazard avoidance’, ‘hazard prevention’, ‘risk minimization’, and ‘good engineering’. While all of these may form part of an inherently safer strategy, they do not encompass a full understanding of the role of inherent safety. This paper discusses inherent safety in offshore oil and gas activities and presents methods to evaluate inherent safety potential. It also highlights areas for further research.
Development of a Computer Model for Prediction of Collision Response of a Railroad Passenger Car
Authors: Kirkpatrick Steven W. , MacNeill Robert A.
Published: January 2009

The paper describes the development of a detailed finite element model that is capable of predicting the response of a rail passenger car to collision conditions. This model was developed to predict the car crush, the three-dimensional gross motions of the car, and the vertical, lateral, and longitudinal accelerations experienced by the car during collisions. The finite element model developed was for a Pioneer passenger coach car. This vehicle was used in a single car impact test. The model was then used to simulate the test and the results are compared to the test data.
Air Dryers in Railway Service: History, Performance and Present Status
Authors: Pier Jerome R.
Published: January 2009

Pneumatic systems in railway applications are vulnerable to water condensation as a result of the cooling of compressed air. This water tends to cause corrosion, degrade lubricants and freeze in cold weather, causing malfunction in brake systems and other pneumatic devices. Prevailing practice for the control of condensation until the early 70’s consisted of cooling the compressed air followed by reduction in pressure to lower the relative humidity. These methods were less than perfect and frozen systems remained a major cause of train delays in cold climates and, in all climates, water continued to corrode devices and emulsify lubricants, increasing maintenance requirements. Regenerating desiccant type air dryers offered a solution. This paper deals with the history of air dryers in railway service, the technologies involved, and the broad significance to the industry.
Multibody Simulation of a Freight Bogie With Friction Dampers
Authors: Bosso N. , Gugliotta A. , Soma` A.
Published: January 2009

Freight bogies are often built using friction element instead of viscous dampers with great advantage regarding cost and manutenibility. On the other hand this technical choice leads to low performance of the vehicle. The aim of this work is to evaluate the behaviour of a Y25 freight bogie that is the most diffuse in Europe where friction dampers are used to reduce vertical and hunting vibrations. The purpose is also to improve a bi-dimensional model of friction damper and to test its numerical efficiency on a whole vehicle model in a multibody code.
A Nonimaging Receiver for Parabolic Trough Concentrating Collectors
Authors: Gee Randy , Cohen Gilbert , Winston Roland
Published: January 2009

The design of a nonimaging secondary reflector as part of a parabolic trough receiver has been developed and evaluated. A detailed optical model was used for evaluation, which offered insight into the optical performance of the secondary and showed that the design offers about a 1% net increase in optical efficiency. In addition, the secondary was estimated to reduce heat loss from a high-performance evacuated receiver by about 4%. Overall, the net performance advantage of the secondary reflector is calculated to be 1.4%, that is, the entire trough collector field would have a 1.4% greater annual thermal energy output. This performance increase is small, but the non-imaging secondary also achieves other indirect benefits such as better flux uniformity around the absorber tube, and increased tolerance of parabolic trough collectors to optical errors.
Modal and Nodal EHD Analysis for Gas Journal Bearings
Authors: Boedo S. , Booker J. F.
Published: January 2009

This paper presents a novel finite element elastohydrodynamic lubrication analysis appropriate for gas journal bearings under dynamic conditions. The method employs gas pressure as a state variable, and structural sleeve deformation is represented by a linear combination of pre-selected mode shapes obtained from a related eigenvalue problem. The method takes into account temporal variation of journal position and velocity, and second-order slip flow boundary effects are included at no additional computational cost. The formulation is subsequently applied to a particular example (flexible large-aspect ratio, high-speed, MEMS-scale journal microbearing), where it is shown that a judicious choice of structural sleeve elasticity can significantly improve bearing performance (as measured by pressure distribution and load capacity) when compared with results obtained using rigid bearing surfaces.
Slider Pitch Moment Associated With Dimple Friction
Authors: Zhu Li-Yan , Yang Chao-Hui , Fu Yen , Cha Ellis
Published: January 2009

In a magnetic recording disk file, pitch moment exerted by the flexure on the slider is usually treated as a product of flexure pitch-static-attitude (PSA) and pitch-stiffness (Kp), both measured in the absence of preload (gram-load). However in the presence of preload, pitch moment due to dimple friction must be considered. We shall show by elementary beam theory that lever-arm of the dimple friction is related to the flexure bow-height, and that to minimize uncertainty in the pitch moment, hence improving the fly height distribution, the flexure must bow toward the disk. These results will be confirmed experimentally.
Unloading of an Elastic-Plastic Loaded Spherical Contact
Authors: Kligerman Yuri , Etsion Izhak , Kadin Yuri
Published: January 2009

The process of unloading an elastic-plastic loaded sphere in contact with a rigid flat is studied by the Finite Element Method. The sphere material is assumed isotropic with elastic-linear hardening. The numerical simulations cover a wide range of loading interference deformation of various values of Young’s modulus and Poisson ratios of the sphere material. The contact loads, stresses, and deformations in the sphere during both loading and unloading, are calculated for the range of interferences. Empirical dimensionless expressions are presented for the unloading load-deformation relation, the residual axial displacement and the residual curvature of the sphere after complete unloading.
Rheological behavior of oligomeric ionomers
Authors: Weiss R. A. , Zhao Hongying
Published: December 2008

The rheological behavior of the alkali metal salts of oligomeric sulfonated polystyrene (PS) ionomers was characterized using dynamic and steady shear measurements. The starting PS had a weight average molecular weight of 4000g∕mol and a narrow molecular weight distribution (1.06). Two sulfonation levels were examined, 2.5 and 4.8mol%, which corresponded, respectively, to one and two sulfonate groups per chain on average. The ionomers exhibited nanophase separation of an ion-rich phase, and as a consequence, time-temperature superposition failed for all samples. Sulfonation increased the melt viscosity of the ionomers, as much as seven orders of magnitude. The zero shear viscosity scaled as cq∕a, where c was the concentration of the ionic groups, q was the charge of the cation, and a was the cation radius, and although the molecular weight of the parent polystyrene was much lower than the entanglement molecular weight, the ionomer melts exhibited strong elastic behavior. The flow activation energy of the ionomers was similar to that of high molecular weight PS and the calculated molecular weight between “entanglements” of the ionomers was the same as for PS.
Magnetorheology of fiber suspensions. I. Experimental
Authors: López-López Modesto T. , Kuzhir Pavel , Bossis Georges
Published: December 2008

This work reports a detailed study on the shear magnetorheology of suspensions of magnetic microfibers. The steady-state regime was investigated using a controlled-stress rheometer for different concentrations of particles and under the presence of a broad range of applied magnetic fields (up to 512kAm−1). The results were compared with those obtained for conventional magnetorheological fluids (suspensions of magnetic microspheres). It was found that the suspensions of magnetic fibers show an enhanced magnetorheological effect. We proposed the existence of field-dependent solid friction between fibers as the main physical reason for this enhancement. In order to ascertain the relevance of the interfiber solid friction, the microscopic structure of fiber suspensions was investigated using an optical microscope. In the absence of applied field, fibers form an entangled network with approximately isotropic orientation. Upon magnetic field application, the fiber network becomes deformed and approximately aligned with the field direction. Nonetheless, interfiber solid friction hinders a complete alignment of the fibers with the field, and the fiber network remains entangled.
Magnetorheology of fiber suspensions. II. Theory
Authors: Kuzhir Pavel , López-López Modesto T. , Bossis Georges
Published: December 2008

This paper reports the first predictions of the yield stress of suspensions of non-Brownian magnetic fibers in the presence of uniform magnetic fields. The quasistatic regime of the shear deformation (before the flow onset) of the suspension is studied. Four different structures of the magnetic fiber suspensions are considered—column, zigzag, three-dimensional stochastic and near-planar stochastic structures—and the yield stress is attributed to the failure of the given structure at a critical strain. The main contributions to the yield stress are found to come from the restoring magnetic torque acting on each fiber and from the solid friction between fibers. The enhanced magnetorheological effect of magnetic fiber suspensions observed experimentally [M. T. López-López et al., J. Rheol. 53, 115–126 (2009)] is explained and quantified in terms of interfiber friction. Surprisingly, the dipolar magnetic interactions between fibers do not affect significantly the yield stress. The lowest yield stress is obtained for the zigzag structure and the highest one for the column structure. A reasonable agreement with the experiments is obtained for 5% and 7% fiber volume fractions in the frame of the more realistic model of near-planar stochastic structures.
Constitutive modeling for moderate deformations of slightly compressible rubber
Authors: Horgan Cornelius O. , Murphy Jeremiah G.
Published: December 2008

A constitutive model based on an assumption regarding the general response to hydrostatic pressure is proposed for the moderate deformations of slightly compressible (or nearly incompressible) rubber. It is shown that an excellent fit is obtained with the available experimental data for a particularly simple form of strain-energy density. The data considered are from those material characterization tests that involve only moderate deformations.
Prediction of Merozoite Surface Protein 1 and Apical Membrane Antigen 1 Vaccine Efficacies againstPlasmodium chabaudiMalaria Based on Prechallenge Antibody Responses
Authors: Lynch Michelle M. , Cernetich-Ott Amy , Weidanz William P. , Burns James M.
Published: December 2008

For the development of blood-stage malaria vaccines, there is a clear need to establish in vitro measures of the antibody-mediated and the cell-mediated immune responses that correlate with protection. In this study, we focused on establishing correlates of antibody-mediated immunity induced by immunization with apical membrane antigen 1 (AMA1) and merozoite surface protein 142(MSP142) subunit vaccines. To do so, we exploited thePlasmodium chabaudirodent model, with which we can immunize animals with both protective and nonprotective vaccine formulations and allow the parasitemia in the challenged animals to peak. Vaccine formulations were varied with regard to the antigen dose, the antigen conformation, and the adjuvant used. Prechallenge antibody responses were evaluated by enzyme-linked immunosorbent assay and were tested for a correlation with protection against nonlethalP. chabaudimalaria, as measured by a reduction in the peak level of parasitemia. The analysis showed that neither the isotype profile nor the avidity of vaccine-induced antibodies correlated with protective efficacy. However, high titers of antibodies directed against conformation-independent epitopes were associated with poor vaccine performance and may limit the effectiveness of protective antibodies that recognize conformation-dependent epitopes. We were able to predict the efficacies of theP. chabaudiAMA1 (PcAMA1) andP. chabaudiMSP142(PcMSP142) vaccines only when the prechallenge antibody titers to both refolded and reduced/alkylated antigens were considered in combination. The relative importance of these two measures of vaccine-induced responses as predictors of protection differed somewhat for the PcAMA1 and the PcMSP142vaccines, a finding confirmed in our final immunization and challenge study. A similar approach to the evaluation of vaccine-induced antibody responses may be useful during clinical trials ofPlasmodium falciparumAMA1 and MSP142vaccines.