bluuebunny/crossref_metadata_2025 huggingface dataset:
Dendritic cells: biology of the skin
Authors: Toebak Mascha J. , Gibbs Susan , Bruynzeel Derk P. , Scheper Rik J. , Rustemeyer Thomas
Published: January 2009

Allergic contact dermatitis results from a T‐cell‐mediated, delayed‐type hypersensitivity immune response induced by allergens. Skin dendritic cells (DCs) play a central role in the initiation of allergic skin responses. Following encounter with an allergen, DCs become activated and undergo maturation and differentiate into immunostimulatory DCs and are able to present antigens effectively to T cells. The frequency of allergic skin disorders has increased in the past decades. Therefore, the identification of potential sensitizing chemicals is important for skin safety. Traditionally, predictive testing for allergenicity has been conducted in animal models. For regulatory reasons, animal use for sensitization testing of compounds for cosmetic purposes is shortly to be prohibited in Europe. Therefore, new non‐animal‐based test methods need to be developed. Several DC‐based assays have been described to discriminate allergens from irritants. Unfortunately, current in vitro methods are not sufficiently resilient to identify allergens and therefore need refinement. Here, we review the immunobiology of skin DCs (Langerhans’ cells and dermal dendritic cells) and their role in allergic and irritant contact dermatitis and then explore the possible use of DC‐based models for discriminating between allergens and irritants.
α‐Adrenergic signalling activates protein kinase D and causes nuclear efflux of the transcriptional repressor HDAC5 in cultured adult mouse soleus skeletal muscle fibres
Authors: Liu Yewei , Contreras Minerva , Shen Tiansheng , Randall William R. , Schneider Martin F.
Published: January 2009

The protein kinase PKD1 has recently been linked to slow fibre‐type gene expression in fast skeletal muscle through phosphorylation of class II histone deacetylase (HDAC) molecules, resulting in nuclear efflux of HDAC and consequent activation of the transcription factor MEF2. However, possible upstream activators of PKD, and the time course and signalling pathway of downstream effectors have not been determined in skeletal muscle. Using fluorescent fusion proteins HDAC5–green fluorescent protein (GFP) and PKD1–mPlum expressed in fibres isolated from predominantly slow soleus muscle and maintained for 4 days in culture, we now show that α‐adrenergic receptor activation by phenylephrine causes a transient, PKD‐dependent HDAC5–GFP nuclear efflux. Concurrent to this response, PKD1–mPlum transiently redistributes from cytoplasm to plasma membrane and nuclei, and back, during 2 h exposure to phenylephrine. The recovery may reflect α‐receptor desensitization. In contrast, the phorbol ester PMA (phorbol‐12‐myristate‐13‐acetate, a pharmacological mimic of the downstream mediator diacylglycerol in α‐adrenergic signalling), caused continuous PKD‐dependent HDAC5–GFP nuclear efflux and maintained PKD1–mPlum redistribution. In the absence of expressed HDAC, PMA increased histone H3 acetylation and increased MEF2 reporter activity in a PKD‐dependent manner, consistent with PKD phosphorylation of endogenous HDAC(s) and reduced nuclear HDAC activity due to HDAC nuclear efflux. HDAC5–GFP did not respond to PMA in fibres from predominantly fast flexor digitorum brevis (FDB) muscle, but did in FDB fibres expressing exogenous PKD1. Our results demonstrate that a PKD‐mediated signalling pathway for HDAC nuclear efflux is activated in slow skeletal muscle through adrenergic input, which is typically active in parallel with motor neurone input during muscular activity.
Brain‐derived neurotrophic factor drives the changes in excitatory synaptic transmission in the rat superficial dorsal horn that follow sciatic nerve injury
Authors: Lu Van B. , Biggs James E. , Stebbing Martin J. , Balasubramanyan Sridhar , Todd Kathryn G. , Lai Aaron Y. , Colmers William F. , Dawbarn David , Ballanyi Klaus , Smith Peter A.
Published: January 2009

Peripheral nerve injury can promote neuropathic pain. The basis of the ‘central sensitization’ that underlies this often intractable condition was investigated using 14–20‐day chronic constriction injury (CCI) of the sciatic nerve of 20‐day‐old rats followed by electrophysiological analysis of acutely isolated spinal cord slices. In addition, defined‐medium organotypic spinal cord slice cultures were exposed for 5–6 days to brain‐derived neurotrophic factor (BDNF, 200 ng ml−1) or to medium conditioned with activated microglia (aMCM). Since microglial activation is an early consequence of CCI, the latter manipulation allowed us to model the effect of peripheral nerve injury on the dorsal horn in vitro. Using whole‐cell recording from superficial dorsal horn neurons, we found that both BDNF and CCI increased excitatory synaptic drive to putative excitatory ‘radial delay’ neurons and decreased synaptic excitation of inhibitory ‘tonic islet/central’ neurons. BDNF also attenuated synaptic excitation of putative GABAergic neurons identified by glutamic acid decarboxylase (GAD) immunoreactivity. Intrinsic neuronal properties (rheobase, input resistance and action potential discharge rates) were unaffected. Exposure of organotypic cultures to either BDNF or aMCM increased overall excitability of the dorsal horn, as seen by increased cytoplasmic Ca2+ responses to 35 mm K+ as monitored by confocal Fluo‐4AM imaging. The effect of aMCM was attenuated by the recombinant BDNF binding protein TrkBd5 and the effect of BDNF persisted when GABAergic inhibition was blocked with SR95531. These findings suggest that CCI enhances excitatory synaptic drive to excitatory neurons but decreases that to inhibitory neurons. Both effects are mediated by nerve injury‐induced release of BDNF from microglia.
A Study of Operation Performance of Circulating Fluidized Bed Combustion Boiler
Authors: Wu Zhengshun , Chen Hanping , Liu Dechang , Wang Jie , Wu Chuangzhi , Huang Haitao
Published: January 2009

The operation performance of circulating fluidized bed combustion (CFBC) boiler was studied in this paper. The experimental results indicate that the load of CFB boiler has linear relation with bed temperature and bed material height of operation. By multiple regression analysis, the relation of the load of CFB boiler with bed temperature and bed material height of operation can be expressed as a formula. The suitable temperature and the bed material height corresponding to the load of CFB boiler can be found using the formula; the problem of the boiler to be blindly operated can be reduced in practice.
Comparative Analysis of Biomass Gasifiers for Thermal and Power Applications
Authors: Kandassamy K. , Natarajan E. , Renganarayanan S.
Published: January 2009

Gasifiers are viable alternative for producing heat and power with minimal adverse impact on the environment. The gasification technology is now considered to be in an advanced stage of development. Hence there is huge expectation from the user industry for its application. For a country like India with its vast agricultural residues, there is a huge requirement for an efficient power generation system. In this regard careful studies are required to select an appropriate gasification technology to suit the available fuels. In this paper different types of gasifiers namely updraft, downdraft, bubbling fluidized bed and entrained bed are compared and their suitability for various applications are evaluated. The technological developments achieved so far and requirements of further developments are also analyzed. A systematic comparison of the performance of various gasifiers is carried out and their unique features are discussed. From the comparative study, specificity of gasifier design is brought out highlighting their merits and possible application potential. The study also brought-out the fact that a universal design concept cannot be achieved to meet the requirements of all possible applications for gasification process.
The Study of Combustion of Municipal Waste in a Fluidised Bed Combustor
Authors: Gulyurtlu I. , Crujeira T. , Abelha P. , Boavida D. , Seabra J. , Gonc¸alves R. , Sargac¸o C. , Cabrita I.
Published: January 2009

The combustion behaviour of municipal solid waste was studied in a pilot fluidised bed combustor. The waste was pelletised prior to its use. Both co-firing with coal and combustion of waste alone were under taken. The combustion studies were carried out on the pilot installation of INETI. The fluidised bed combustor is square in cross section with each side being 300 mm long. Its height is 5000 mm. There is a second air supply to the freeboard at different heights to deal with high volatile fuels. There was a continuous monitoring of the temperatures in the bed, as well as the composition of the combustion gases. The combustion gases leaving the reactor were let go through the recycling cyclone first to capture most of particulates elutriated out of the combustor. There was a second cyclone which was employed with the aim of increasing the overall efficiency of collecting solid particles. The gaseous pollutants leaving the stack were sampled under iso-kinetic conditions for particulate matter, chlorine compounds and heavy metals. The ash streams were characterised for heavy metals. The results obtained were compared with national legislation. The results obtained suggest that i) the combustion efficiency was very high, ii) there was an enrichment of ashes with heavy metals in the cyclones compared to the bed material, iii) in general, the gaseous pollutants were below the permited limits, and iv) for the compliance with the new European Directive for stricter emission limits adequate control devices, like bag filters, should be integrated with RDF combustion.
Results of Long-Term Trials First Large Scale Fluidized Bed Furnaces for Sewage Sludge Worldwide Boosted by Oxygen
Authors: Ludwig Paul , Gross Gerhard
Published: January 2009

Oxygen is required in every combustion process, including the incineration of sewage sludge. When air is used to provide oxygen the nitrogen it contains is only ballast which has to be heated up in the furnace and which further increases the volume of flue gas to be purified. The process for partial oxygen combustion (POC) jointly developed and patented by Messer Griesheim and Infraserv Ho¨chst avoids this problem. In this process, oxygen is blown directly and transversally into the fluidized bed at supersonic speed. The first promising test results were already presented at the 16th International Conference on Fluidized Bed Combustion 2001 in Reno. In the meantime we have three years of experience with detailed operating results. Up to 2000 m3/h of pure oxygen is blasted into the two furnaces transversally via the supersonic nozzles built into the walling. This results in a highly turbulent flow which considerably improves the mixing and the combustion in the fluidized bed. Using the POC method it has been possible to increase the combustion capacity of the systems from 130,000 to currently 160,000 t/a. The hourly throughput of waste material suitable for fluidized bed combustion has been increased by up to 40%. At the same time the combustion air volume has been reduced by 15% and the specific natural gas consumption by 35%. This considerably reduces the specific incineration costs (€ / t waste material). Alongside industrial and residential sewage sludges with calorific values of 500 to 11,000 KJ/kg (depending on the original substance) and dry-substance contents between 22 and 60%, other solid and liquid waste material suitable for fluidized bed combustion can also be processed, including bone meal, screenings, plastics granulate, spent active carbon, building timber, contaminated packaging material, organic solvents and urea waste. Calorific values can here fluctuate between 1,500 and 42,000 KJ/kg (depending on the original substance) and the dry-substance content between 5 and 100%. The specific emissions, e.g. carbon dioxide and nitrogen oxides per ton of incinerated waste material are reduced. Thus the POC process gives Infraserv a third virtual furnace at low investment cost, enabling it to respond to the demands of the market. With this technology, the status of “Best Available Technology” (BAT) was conferred upon the sewage sludge incineration plant operated by Infraserv Ho¨chst by the German Ministry for the Environment.
Experimental Investigation on Atomization Properties of Coal-Water Paste Fired Into Pressurized Fluidized Bed Combustor
Authors: Lu Ping , Zhang Mingyao
Published: January 2009

According to the properties of coal-water paste (CWP), a series of experimental devices were constructed to study the atomizing characteristics of the CWP nozzle deeply. The particle size and its distribution of several types of atomizing nozzle of CWP in the spray are measured by PIV measurement and newly developed image processing software. The influences of every factor on the atomizing properties are analyzed. The atomizing experimental results show that atomizing quality of CWP was found to correlate with the characteristics of CWP, air to CWP mass ratio, atomizing air motion, coal particle size distribution and the structure of atomizer etc. mass median diameter (MMD) of atomizing particle decrease with the increase of gas to CWP mass ratio, and the proper type of nozzle and proper parameters for engineering are suggested.
Modeling of NH3 and HCN Emissions From Biomass CFB Gasifiers
Authors: Liu Hao , Gibbs Bernard M.
Published: January 2009

A circulating fluidized bed (CFB) biomass gasification model is developed in the present study. The model consists of sub-models for devolatilization, tar cracking and a chemical reaction network of main gasification reactions and nitrogen chemistry. Unlike the most of the previous biomass gasification models, devolatilization of biomass particles is modeled with a limited rate, which is selected from the literature based on woody biomass fuels. To predict the tar content of the gasification gaseous products, kinetics for tar evolution and cracking is adopted from literature and included in the model. All model parameters are chosen for a typical woody biomass — pinewood chips. The partition of fuel nitrogen between volatiles and char is also specifically chosen for pinewood based on the available experimental data from literature. Volatile nitrogen is assumed to consist of NH3, HCN and N2 with the distribution between three species as input parameters to the model. A total of forty global chemical reactions are included in the model, of which twenty-eight reactions belong to fuel-nitrogen reaction network. Individual reaction rates are selected from the literature, wherever possible, based on studies of woody biomass fuels. Modeling of the hydrodynamics of the riser is simplified by using solids concentration profile along the riser as an input to the model. Both gaseous phase and solids phase are assumed to be in plug flow. Modeling results are compared with the experimental results published in the literature. Predicted effects of bed temperature and equivalence ratio on main gaseous composition, tar content and NH3, HCN emissions generally agree with the literature data.
Advanced Fluidized-Bed Combustor Firing Waste Coal: A Case Study
Authors: Goldstein Harvey N. , Brown Wayne , Tursi Vincent J. , Kenney Charles W.
Published: January 2009

This paper describes the integration of an advanced fluidized-bed combustor with other technologies into a complete system that will fire waste coal blended with purchased coal to produce steam, electricity, and structural building products. The integrated system provides remediation of a waste coal pile, meets stringent environmental standards, and is economically viable.
Investigation of Transport Phenomena in Micro Flow Channels for Miniature Fuel Cells
Authors: Cha S. W. , Lee S. J. , Park Y. I. , Prinz F. B.
Published: January 2009

This paper presents a study on the transport phenomena related to gas flow through fuel cell micro-channels, specifically the impact of dimensional scale on the order of 100 microns and below. Especially critical is the ability to experimentally verify model predictions, and this is made efficiently possible by the use of structural photopolymer (SU-8) to directly fabricate functional fuel cell micro-channels. The design and analysis components of this investigation apply 3-D multi-physics modeling to predict cell performance under micro-channel conditions. Interestingly, the model predicts that very small channels (specifically 100 microns and below) result in a significantly higher peak power density than larger counterparts. SU-8 micro-channels with different feature sizes have been integrated into fuel cell prototypes and tested for comparison against model predictions. The results not only demonstrate that the SU-8 channels with metal current collector show quite appreciable performance, but also provide experimental verification of the merits of channel miniaturization. As predicted, the performance in terms of peak power density increases as the feature size of the channel decreases, even though the pressure drop is higher in the more narrow channels. So it has been observed both theoretically and experimentally that cell performance shows an improving trend with micro-channels, and design optimization for miniature fuel cell provides a powerful method for increasing power density.
Modeling of Reformers for Fuel Cell Applications
Authors: Rogers William A. , Shi Shaoping , Berry David A. , Gardner Todd H. , Shekhawat Dushyant
Published: January 2009

The lack of an existing hydrogen infrastructure makes fuel processing of hydrocarbon fuels a critical component of fuel cell systems. The reformer is the principle reactor in the fuel processing subsystem and converts various hydrocarbon fuels into hydrogen, carbon monoxide, and other products that can then be utilized in the fuel cell. To help understand and quantify diesel fuel reforming by partial oxidation, a computational fluid dynamic model was developed that included the following sub-processes: liquid fuel atomization, fuel drop evaporation, fuel drop boiling and vaporization, and gas-phase chemical reaction. This work focused on n-heptane as a representative diesel fuel and reduced reaction mechanisms from the literature for fuel rich oxidation of n-heptane were used to analyze reactions in the partial oxidation reformer. Turbulent chemistry was modeled using the eddy dissipation concept. Reactor performance and parametric analysis based on model simulations are presented and discussed.
Regulations Governing Transportation of Portable Fuel Cell Devices and Systems in Aircrafts
Authors: Ubong Etim U. , Berry K. J.
Published: January 2009

The revolutionary advancements of electrical fuel cell power within the past decade has drawn public awareness and criticism to the hazardous nature of hydrogen and other fuels used in fuel cell powered devices and systems. Although these fuels are regulated, their fuel storage devices (cartridges) are not, hence, requiring various governmental agencies approval such as the Department of Transportation, which typically applies its regulations for transportation of hazardous materials. As the development of these devices grow, issues regarding transportation of hazardous materials, components in mass transportation systems: e.g. passenger aircrafts, ships, trains, and buses, USPS, will come under intense legal scrutiny. The United States and other nations, including international bodies such as the United Nations have national and international laws regulating transit of hazardous/toxic materials across state/national and international boundaries. These different regulations often conflict and are serious barriers to the transportation of fuel cell powered consumer electronic devices such as laptop computers, cell phones, camcorders, calculators and even portable CD Players in commerce. This report addresses the regulatory framework regarding transportation of fuel cell hazardous-material – containing devices by aircrafts and suggests solutions to obtaining approval from various governmental agencies.
RIE-Texturing of Industrial Multicrystalline Silicon Solar Cells
Authors: Ruby Douglas S. , Zaidi Saleem , Narayanan S. , Yamanaka Satoshi , Balanga Ruben
Published: January 2009

We developed a maskless plasma texturing technique for multicrystalline Si (mc-Si) cells using Reactive Ion Etching (RIE) that results in higher cell performance than that of standard untextured cells. Elimination of plasma damage has been achieved while keeping front reflectance to low levels. Internal quantum efficiencies higher than those on planar and wet-textured cells have been obtained, boosting cell currents and efficiencies by up to 6% on tricrystalline Si cells.
Life-Cycle CO2 Emissions in Public Welfare Facilities Equipped With a PV/Solar Heat/Cogeneration System
Authors: Oke Shinichiro , Kemmoku Yoshishige , Takikawa Hirofumi , Sakakibara Tateki
Published: January 2009

The reduction effects of life-cycle CO2 emissions are examined when introducing a PV/solar heat/cogeneration system into public welfare facilities (hotel and hospital). Life-cycle CO2 emissions are calculated as the sum of the operating and manufacturing processes. The system is operated by the dynamic programming method into which hourly data of electric and heat loads, solar insolation, and atmospheric temperature during a year are input. The proposed system is compared with a conventional system and a cogeneration system. The life-cycle CO2 emissions of the PV/solar heat/cogeneration system are lower than those of the conventional system by 33 points in the hotel and 30 points in the hospital.
Fabrication and Characteristics of Recyclable PV Modules
Authors: Doi Takuya , Tsuda Izumi , Sakuta Koichi , Matsui Goichi
Published: January 2009

Since the life of crystalline silicon PV modules is mainly determined by that of the encapsulations and not of the cells, it is possible to reuse the cells, except when the cells are physically damaged. By reusing the cells, we can save the significant amount of energy consumed in the manufacture of PV cells, and reduce the total cost of PV modules as a consequence. PV cells are resources, and they should be recycled. However, it has not been easy to remove cells from modules without damaging them because of the very strong adhesiveness of EVA, the most common encapsulant resin. We propose a new PV module with a double encapsulation module (DEM) structure, in which both surfaces of the PV cells are wrapped with non-adhesive transparent films. Here, the concept of DEM is explained and detailed results from the fabrication of single-cell modules are presented. The results of PV cell recovery experiments and weather resistance tests are also shown.
Air Pollution Control System Retrofit Experience at Wasatch Energy Systems
Authors: Tsui Tien-I , Rich Nathan B.
Published: January 2009

Wasatch Energy Systems owns and operates two (2) mass burn incinerators each rated at 210 tons/day in Layton, Utah. Each incinerator was equipped with a three field Electrostatic Precipitator (ESP) to control the particulate emissions. Dry sorbent (trona) was injected just upstream of the economizer to control acid gas emissions. The performance of the dry sorbent injection system was marginal. In anticipation of the upcoming EPA emission guidelines, 40 CFR Part 60, Subpart BBBB, Emission Guidelines for existing small municipal waste combustion units, Wasatch Energy Systems decided to update the existing APC systems several years ahead of the schedule. A request for proposal was released in October 1999 and eight proposals were received by the facility. AirPol Inc. of Parsippany, NJ was awarded a turnkey contract in June 2000 to add a dedicated Gas Suspension Absorber (FLS miljo Inc GSA) upstream of each existing ESP. A common lime slurry storage and preparation system, carbon storage and delivery system, ash conveying system, MCC, and control system were also provided under the contract. The new APC system was commissioned and put into service in September, 2001. Initial stack testing was conducted in October 2001 to evaluate system performance. Compliance stack testing was conducted for the Utah Division of Air Quality in November 2001. Results of testing demonstrate that particulate, metals, acid gas and dioxin/furan emissions from the retrofit facility are substantially lower than required under, now final, 40 CFR Part 60, Subpart BBBB – Class 1 Emission Limits for Existing Small Municipal Waste Combustion Units. This paper discusses the retrofit system design and performance.
Comparison of Superheater Metal Wastage Rates Utilizing Various Boiler Tube Alloys in a Waste-to-Energy Facility
Authors: Turner Mark , Hanson Eric
Published: January 2009

The SEMASS Resource Recovery Facility (SEMASS) is a processed refuse fuel (PRF) waste-to-energy plant serving Southeastern Massachusetts. The plant consists of three 1000 ton per day boilers that generate steam at 765 F and 650 psig for use in a steam turbine/generator set. Over the past several years, metal wastage rates due to fire side corrosion of pressure containing components, have increased significantly in all three boilers. In an attempt to reduce overall maintenance costs and unscheduled down time due to tube failures, a test of various alloy tube materials was undertaken in the primary superheater section of boiler #1. The materials tested were SA213-T22 (original spec.), SA213-TP310H, SB-423 Incoloy 825, and Inconel 625 spiral weld overlay of SA213-T22 base material. This paper will discuss the results of the test after 9 months of service and any conclusions developed on the economic justification for upgrading tube materials in the remaining two boilers.
Application of Unifuse Overlay Tubes in the Convection Section of Waste-to-Energy Boilers
Authors: Amador Pedro , Lai George
Published: January 2009

The modern weld overlay applied by automatic gas-metal-arc welding (GMAW) process using Ni-Cr-Mo-Nb alloy 625 has been extremely successful in providing corrosion and erosion/corrosion protection for the waterwalls of waste-to-energy (WTE) boilers for over a decade. Without alloy 625 weld overlay protection, the carbon steel waterwall of a waste-to-energy boiler would be corroded through in a matter of months. The overlaid waterwalls for numerous WTE boilers have shown excellent performance results with services up to 10 years or more. Welding Services Inc. has developed a patented process for manufacturing weld overlay bimetallic tubes involving GMAW/GTAW process. Unifuse® 625 overlay tubing with carbon steel substrate has been successfully used as screen tubes, superheater tubes and generating banks in the convection section. The overlay tubes have successfully replaced such corrosion protection methods as stainless steel tube shields and refractories.
A Novel Passive Riser Tensioning System for a Dry Tree Spread Moored Barge
Authors: Katarya Amit
Published: January 2009

Dry tree risers on floating systems are presently supported either by TLPs or SPARs, both of which have limited payload capacity and no storage. A spread-moored barge having dry trees, storage and integrated drilling facilities has been developed. Model tests were performed for the riser tensioning system used on such a barge for offshore West Africa conditions. The risers are attached to a rectangular platform in a moon pool of the barge. This platform is supported by means of an articulated Rocker Arm System (RAS) located on the vessel main deck. The RAS has built-in counter weights hinged on pedestals fixed to the barge deck. In this arrangement gravity is used to tension the risers and when the barge heaves, the counterweights in the rocker arm system essentially decouple the barge vertical motion from the riser platform. This system provides a heave-restrained platform for dry trees with minimal dynamic loading of the risers. The model tests confirmed the feasibility of the new design. The paper describes the basic components of the gravity tensioning system. The model test set up and results from the model test are shown. Comparison of model test results with a fully coupled analytic model consisting of the barge and articulated tensioning system is also presented.
Dissolution of CO2 From CO2 Drops in Simulating Experiments of CO2 Ocean Storage
Authors: Nakajima Yasuharu , Shirota Hideyuki , Kojima Ryuji , Yamane Kenji , Aya Izuo , Namie Sadahiro
Published: January 2009

The dissolution of Carbon Dioxide (CO2) from CO2 drops covered with CO2 hydrate films under the conditions simulating the deep-sea environment was investigated with a large high-pressure tank. The lowering of pH due to CO2 dissolution was measured for two temperature regions. In the same temperature region, pH lowering at higher position above the bottom of the tank was much smaller than that at lower position. It implies that while the dissolved CO2 is diffused through water in the tank, the difference in CO2 concentration occurs between both measuring points. On the other hand, pH lowering in the lower temperatures was smaller than that in the higher temperatures at the same measuring point. The difference in pH change between both temperature regions agreed with the temperature dependency in the solubility of CO2 hydrate and the dissolution rate of a CO2 droplet with a CO2 hydrate film.
Behaviour of Minimum Structure Platforms Under Ship Impact
Authors: Lee M. M. K. , Grewal G. S.
Published: January 2009

This paper presents the findings of a numerical investigation into the strength of minimum structure platforms subject to a ship impact. The study has identified important design issues that should be addressed in order to improve the survivability and continued serviceability of minimum structures after a ship impact. It was found that, due to a lack of research effort, design guidelines governing ship impact on minimum structures are lacking in comparison with conventional jacket platforms. In particular, requirements governing the minimum amount of plastic energy absorption in minimum structures are not clearly defined. Ship impact analyses were therefore carried out in order to compare their structural integrity with that for a jacket under ship collision conditions and to evaluate the effects on their ultimate strength. The study not only established any degradation of system strength, but has also determined the amount of plastic energy absorption under various impact scenarios.
Wave Loads on a Perforated Circular Caisson and Suction Pipe of a Sea Water Intake Structure
Authors: Vijayalakshmi K. , Neelamani S. , Sundaravadivelu R.
Published: January 2009

The wave force on a seawater intake well model consisting of a perforated circular caisson (500mm diameter) encircling a vertical suction pipe (50mm dia) is measured experimentally. The effect of porosity of the caisson wall, incident wave height and wave period on the in-line forces on the caisson and suction pipe is investigated. The porosity of the caisson was varied from 4.54% to 19.15%. Waves of wide ranges of heights and periods were used. The wave forces on the outer caisson & inner cylinder, water surface fluctuations in the interior & exterior of the caisson and wave run-up on the outer caisson & inner cylinder are studied. The present paper includes the wave forces on the outer perforated circular caisson and inner circular cylinder due to regular waves only.
Parallel Simulation of a Marine Riser Using MPI
Authors: Flatschart Ricardo Becht , Meneghini Julio Romano , Ferrari Jose´ Alfredo
Published: January 2009

In this paper the dynamic response of a marine riser due to vortex shedding is numerically investigated. The riser is divided in two-dimensional sections along the riser length. The Discrete Vortex Method is employed for the assessment of the hydrodynamic forces acting on these two-dimensional sections. The hydrodynamic sections are solved independently, and the coupling among the sections is taken into account by the solution of the structure in the time domain by the Finite Element Method. Parallel processing is employed to improve the performance of the method. The simulations are carried out in a cluster of Pentium IV computers running the Linux operating system. A master-slave approach via MPI — Message Passing Interface — is used to exploit the parallelism of the present code. The riser sections are equally divided among the nodes of the cluster. Each node solves the hydrodynamic sections assigned to it. The forces acting on the sections are then passed to the master processor, which is responsible for the calculation of the displacement of the whole structure. Scalability of the algorithm is shown and discussed.
The Application of a Simulation Tool for the Analysis of Offloading Operations in FPSO Units
Authors: De Pinho Alho Alexandre Teixeira , Papera Douglas
Published: January 2009

The cargo system of FPSO units is of particular interest due to its rigorous operational requirements. In addition to structural and static stability requirements, the offloading operation of FPSO units should satisfy rigorous requirements related to the dynamic behavior of the vessel. In this sense, the cargo offloading process of FPSO units represents a critical aspect related to its design and operation. Unfortunately, due to the great computation effort usually required to analyze complex pipe networks, it is not a common practice to perform the analysis of the cargo system functioning at the design stage. This paper presents the analysis of the offloading operation of a typical FPSO unit. The analysis comprehends the simulation of the operation of the cargo system during the offloading process. The author adopted a new method to the analysis of pipe networks that seems to be more adequate for the analysis of fully branched systems. The results obtained indicate that the simulation of the cargo system operation is a useful tool for the analysis of the offloading process of FPSO units both at the design stage and during site operation.
Interaction of a Second-Order Solitary Wave With a Vertical Permeable Plane Breakwater
Authors: Basmat A.
Published: January 2009

The purpose of this paper is to develop mathematical models to investigate the interaction between long non-linear water waves and dissipative/absorbing coastal structures. The diffraction of a plane second-order solitary wave at a vertical permeable plane barrier standing in front of an impermeable wall, with calculation of the second-order wave loading is investigated. An incident plane second-order solitary wave is the Laitone solution of Boussinesq equations. The analytical solution is obtained by means of a small parameter development and Fourier transformation techniques. Computational results were performed using the software MATHEMATICA version 4.0.1.0.
Deep Penetration of Spudcan Foundation Into NC Clay
Authors: Hossain M. S. , Myhreyar Z. , Hu Y. , Randolph M. F.
Published: January 2009

The excessive penetration of spudcan foundation in jackup rigs can be costly in offshore operation. Thus, the accurate prediction of load-penetration response becomes increasingly important in offshore design. The performance of spudcan foundation during installation, subjected to vertical loading on normally consolidated (NC) clay, is investigated physically and numerically. Experiments are carried out on kaolin clay in a drum centrifuge and FE analyses are performed using AFENA. During initial penetration, soil flows towards the ground surface and therefore heave occurs close to the spudcan edges. It flows back on top of the spudcan right after the heave passes the spudcan shoulder and shortly a substantial back flow causes the spudcan to be fully embedded. When penetration ratio (d/D) reaches 0.75, a deep failure mechanism achieves. Soil failure mechanisms play a key role for evaluating bearing response at various penetration depths. By comparing FE results with centrifuge test results, an identical bearing capacity factor of Nc = 10.5 is obtained for deeply embedded spudcan. The roughness of the soil-spudcan interface has shown 10% difference in bearing capacity when d/D is larger than 1.5.
The Influence of Hindcast Modeling Uncertainty on the Prediction of High Return Period Wave Conditions
Authors: Brooker Daniel C. , Cole Geoffrey K. , McConochie Jason D.
Published: January 2009

Extreme value analysis for the prediction of long return period met-ocean conditions is often based upon hindcast studies of wind and wave conditions. The random errors associated with hindcast modeling are not usually incorporated when fitting an extreme value distribution to hindcast data. In this paper, a modified probability distribution function is derived so that modeling uncertainties can be explicitly included in extreme value analysis. Maximum likelihood estimation is then used to incorporate hindcast uncertainty into return value estimates and confidence intervals. The method presented here is compared against simulation techniques for accounting for hindcast errors. The influence of random errors within modeled datasets on predicted 100 year return wave estimates is discussed.
Uncertainties in Extreme Value Analysis and Their Effect on Load Factors
Authors: Rutten J. G. , van Gelder P. H. A. J. M. , Ewans K. C. , Efthymiou M.
Published: January 2009

A method for deriving site-specific load factors for fixed offshore structures that include uncertainties in extreme values is described. The method consists of an extreme value analysis, to derive the extreme value behaviour and the uncertainties involved, and a model, based on the Load Resistance Factor Design fo the API rules, to derive site-specific load factors with or without the inclusion of uncertainties in the long term load distribution. The application of site-specific load factors could lead to a harmonised calculation of the probability of failure for platforms around the world. The extreme value analysis that is applied is a threshold based Generalized Pareto Distribution in combination with Maximum Likelihood Estimation. This is applied to a Peaks-over-Threshold data selection from hindcast studies. The Extreme Value Analysis is used to derive four extreme value characteristics (shape and scale parameter, the threshold and the number of data points,) that are used to quantify the extreme value behaviour. The North Sea, West African Coast and Gulf of Mexico are analysed. These are three ocean basins that capture the main characteristic climates around the world: extra-tropical storms, swell dominated extremes and tropical storms, respectively. The uncertainties in the extreme value analysis are dependent on the four characteristics. A simulation study is used to extract the confidence intervals of the parameters (shape, scale and significant wave height) as a function of the characteristics. The simulation of extreme value data sets gives a bias in the results, and therefore a practical method is proposed to correct for the bias and to extract confidence intervals. The bias correction is used to derive the shape and size of the confidence intervals for the extreme significant wave heights at the North Sea, West African Coast and Gulf of Mexico. The load factors are computed on the basis of the Reserve Strength Ratio requirement. Only wave loads are incorporated in the determination of the loading on fixed platform; the current and wind loading are not considered. There computation methods for load factors are investigated; a traditional approach without the implementation of uncertainties, and two new methods that include the uncertainties derived with simulation studies. The three methods show that there are regional differences in load factors and that the implementation of uncertainties leads to an increase in the factors.
Understanding the Measured VIV Data of a Steel Catenary Riser Installed at P-18 Platform in Campos Basin
Authors: Franciss Ricardo , dos Santos Cla´udia Peri
Published: January 2009

This article describes some analyses made using the raw measured data on monitoring bottles installed at P-18 SCR. The bottles used to perform the acquisition are briefly described, as the equipment used to measure the oceanographic data. A FEM program in time domain ANFLEX was used to analyze the signal to obtain the natural frequencies and mode shapes to be used in SHEAR7 program. The raw data was transformed in engineering data and these data in time domain were transformed to frequency domain. Some comparison is shown like the evaluation if the first band of frequencies is due to the waves and the second band of frequencies is due to VIV. Finally, it is shown how the damage can be obtained directly using the data measured from the SCR, giving some results.
An Efficient Technique for Derivation of the Kurtosis of Offshore Structural Response Due to Random Morison Wave Loading
Authors: Najafian G. , Burrows R. , Tickell R. G.
Published: January 2009

Nonlinear wave loading leads to non-Gaussian offshore structural response so that higher-order statistical moments, such as kurtosis, are often necessary for its probabilistic description. The existing models for determination of these moments are computationally very demanding. Consequently, the distributed wave loading on the structure is idealised by a relatively small number of nodal loads, requiring care and experience in the representation of the continuous loading on (complex) structures with many structural elements. These shortcomings are successfully overcome by an approximate approach, as described herein, offering a dramatic reduction in computational effort so that the distributed loading can be idealised more realistically by a large number of nodal loads. The effectiveness of the proposed procedures, which have arisen from a UK EPSRC-sponsored project, are demonstrated by applying them to a test structure under different environmental conditions. With these improved tools, designers can now consider incorporation of more robust and precise probabilistic analysis into their evaluation procedures for structural behaviour, without facing onerous computational effort.
Non-Linear Calculation of Tailored Wave Trains for Experimental Investigation of Extreme Structure Behaviour
Authors: Clauss Gu¨nther F. , Hennig Janou , Schmittner Christian E. , Ku¨hnlein Walter L.
Published: January 2009

The experimental investigation of extreme wave/structure interaction scenarios puts high demands on wave generation and calculation. This paper presents different approaches for modelling non-linear wave propagation. Results of numerical simulations from two different numerical wave tanks are compared to models tests. A further approach uses analytical wave models which are combined with empirical terms to allow a fast and precise prediction of non-linear wave propagation for day-to-day use. All approaches can be used either separately or in combination — depending on their particular purpose. As an application, different special wave scenarios — both academic and realistic — are generated and validated by measurements. The advantages and disadvantages of the presented methods are discussed in detail with regard to their appropriate use for investigations of extreme structure behaviour.
Practical Application of Global Optimization to the Design of Offshore Structures
Authors: Birk Lothar , Clauss Gu¨nther F. , Lee June Y.
Published: January 2009

The paper presents improved methods and new results on the introduction of formal optimization strategies into the design of offshore structures. The hull design stage is singled out from the overall design process and automated by introducing parametric shape generation, numeric hydrodynamic analysis and assessment tools as well as Nonlinear Programming algorithms for process control. The investigation compares the performance of three different optimization algorithms within a shape optimization framework. The classical deterministic Sequential Quadratic Programming method competes with two so called global optimization algorithms: The popular Genetic Algorithm and the more exotic Adaptive Simulated Annealing. The applications show that significant improvements of seakeeping qualities are obtained in either case. As expected, the global methods require definitely more computation time than the deterministic algorithm. Furthermore the global methods do not always produce better results, which makes a careful choice of the optimization algorithm mandatory. Guidelines for an efficient application are given in the conclusions.
Design and Application of Real Time Monitoring System for Moored Caisson
Authors: Krishna M. Sri , Qiang Shen , Prasant P. G.
Published: January 2009

Tacoma Narrows Constructors (TNC) is building a new suspension bridge in Tacoma, close to Seattle, Washington State, USA. The new bridge will be built just south of the existing bridge mounted on two caissons, referred to as East Caisson (Tacoma side) and West Caisson (Gig Harbor side). Each caisson is about 80’ wide and 130’ long in plan. The caissons are moored in place in high currents in the Narrows by two sets of mooring lines on each of them — lower set and upper set. The target positions of the new caissons are very close to the existing pier. Therefore the motions of the caisson are very critical for the success of the project and the final touchdown position of the caisson is also of main concern. The mooring monitoring and advisory system ZenMAS has the capability of monitoring the performance of the caisson in currents by acquiring real time data from instruments. Real time line tensions and GPS data are read. The instantaneous tension in each of the mooring lines is measured, recorded and reported. Using the real time GPS data, the program reports the translations and rotations of the caissons. There are warnings when any of these are exceeded beyond allowable limits. ZenMAS also has the capability to function as a simulation tool. Future what-if scenarios can be studied using this software and any necessary corrective measures taken. The analysis capabilities of ZenMAS include static and dynamic analysis using the Motion Simulator program MOTSIM [2]. Graphical representation of instantaneous caisson position and summary and detailed output and results are available from the program. A discussion on how this system was designed, typical inputs, outputs, and comparison to actual measured values is made in this paper.
Simulation of Transient Heat Transfer of Sandwich Pipes With Active Electrical Heating
Authors: Cerqueira Djane R. , Su Jian , Estefen Segen F.
Published: January 2009

Sandwich pipes consisting of two concentric metal pipes with insulation material in the annulus have been developed to meet challenging mechanical and thermal requirements of deep and ultra deepwater oil and gas production. Passive thermal insulation is designed to meet flow assurance requirements under steady-state production conditions, but is unlikely to meet more severe conditions during transient events such as warm-up and cool-down. In this work, we present the analysis of transient heat transfer in the sandwich pipelines with active electrical heating. The mathematical model governing the heat conduction in the composite pipeline and the energy transport in the produced fluid is solved by using finite difference methods. As unplanned cool-down of the pipelines is most critical to safe and economical operation of pipelines in deep and ultra deep water conditions, it is presented here numerical results of computational simulation of cool-down for three sandwich pipeline configurations under typical production conditions. The analyses show that the sandwich pipe with active heating is a viable solution to meet severe flow assurance requirements of ultra deepwater oil production even under unplanned and prolonged cool-down conditions.