bluuebunny/crossref_metadata_2025 huggingface dataset:
Flashback Propensity of Syngas Fuels
Authors: Dam Bidhan , Choudhuri Ahsan
Published: September 2010

The paper presents experimental measurements of flashback propensity of H2-CO mixtures (primary constituents of syngas fuels). Effects of H2 concentration, external excitation and swirl on the flashback propensity of H2-CO flames are discussed. The flashback behavior of H2-CO flames changes nonlinearly with the increase in H2 contents in the mixture. The critical velocity gradient (gF) values of 5%–95% and 15%–85% H2-CO mixtures somewhat agree with the scaling relation (gF = c(SL2/α)) and yield an average c value of 0.035. However, the gF values of 25%–75% H2-CO mixture show higher order variations with the SL2/α ratio (especially for SL2/α < 19,000 s−1). At a lower SL2/α ratio, burner diameters have small effects on critical velocity gradient measurements; however, the effect is significant at higher SL2/α ratio. The effect of external excitation on the flashback propensity of H2-CO flames with more than 5% H2 is not significant. Flashback through two mechanisms and their dependence on combustor parameters were also identified for swirl stabilized H2-CO flames.
Conveyor Architecture for the 21st Century
Authors: Swinderman R. Todd , Bierie Greg , Marti Andrew D. , Wheatall Barbara A.
Published: September 2010

To address issues associated with the recently updated OSHA Instruction on combustible dust hazards, this presentation will explore an innovative concept of conveyor design. The author will also examine two “leading edge” conveyor technologies and review recent projects that employed these two technologies. This presentation will first address concerns associated with the OSHA Instruction on combustible dust hazards by exploring the architecture concept for conveyor design and the new dust accumulation resistant conveyor structure. This pioneering approach to conveyor design focuses on prevention of fugitive dust accumulation and ease of maintenance. The next of these advanced technologies is “engineered-flow” chutes. Designed from material testing and flow studies, these transfer chute systems provide better material control, continuous flow at higher capacities, and dramatic reductions in material spillage and the release of airborne dust. By regulating the path of material movement, these engineered chutes improve the load placement on the belt, eliminate chute blockages, reduce safety hazards, and minimize maintenance costs. A third leading edge conveying system is air-supported belt conveyors. Rather than using rollers, these leading edge systems use a film of air rising from a troughed pan to support the belt and cargo. These totally enclosed conveyors offer a number of benefits, including improved tracking, improved control of dust and spillage, and reduced friction and power consumption. In this presentation, the author will present “project profiles” of recent installations of these systems. The author will look at the reasons these systems were selected and report on the lessons learned from system engineering, installation, and operation. These projects will include systems handling Powder River Basin (PRB) coal in mines and power plants.
Topics for On-Site Rehabilitation of a 30 MW Geothermal Turbine
Authors: Herna´ndez Rossette Alejandro , Mazur C. Zdzislaw
Published: September 2010

During a major overhaul of a 30 MW geothermal turbine for the electricity sector of Mexico, a new rotor and new diaphragms were provided to recovery the power rate of the unit. Recuperation of the horizontal joint of upper and lower casings was required, as well as the inner diameter for diaphragm lodgings in both casings. The Geothermal steam turbines in Mexico suffer of accelerate degradation due mainly to high levels of sulphidric acid in the geothermal steam flow. Corrosion and dust particles are often present in the flow path turbine components affecting the performance and maintenance. In addition, the paper includes topics for on-site rehabilitation which include complex activities and challenges that must be taken into account for a successful rehabilitation process. The mapping process for horizontal joint casing, the processes used for recovery of planarity, the post weld heat treatments used for these components, and the machining process used for recovery inner diameters of casings.
Fouling Formation in 575 MW Tangential-Fired Pulverized-Coal Boiler
Authors: Bar-Ziv E. , Berman Y. , Saveliev R. , Perelman M. , Korytnyi E. , Davidson B. , Chudnovsky B.
Published: September 2010

Over the past years we have gained experience in employing varying types of coal fired in the same boiler. Consequently, we developed evaluation criteria regarding the operation of these coals. In the present study we evaluated fouling propensity of two bituminous South African coals Billiton-Prime and Anglo-Kromdraai (AKD). From an experimental work carried out in a 50 kW test facility where we obtained emissivity and thermal resistance of the two coal ashes. We also developed a new method for evaluating fouling in full-scale utility boilers that is based on adhering of an ash particle depending on its temperature and velocity vector at the boundary layer of the water-walls. The flow and temperature fields were determined by computational fluid dynamic (CFD) simulations. We used the emissivity and thermal resistance determined from the test furnace in the CFD calculations to evaluate fouling in the combustion chamber of a 575 MW tangential-fired utility boiler when the two bituminous coals were fired. Mapping of the fouling locations that are mostly to occur were determined and this behavior fit the experience from the power station and data obtained for these two coals.
Development of Mg-Based Additive to Control Corrosion and Fouling in Heavy Crude Oil for Gas Turbine Power Plants Applications
Authors: Sandu Corina L. , Howard Lee , Kremer Lawrence N.
Published: September 2010

The trend to use heavy crude oil in gas turbine power generation plants is the driver to develop and offer more effective chemical solutions to this particular market. Due to increased use of new heavy opportunity crude oils in these applications, there is a continuous need to improve and optimize the chemical programs implemented to minimize corrosion induced by vanadium. In addition to their anticorrosive function (to avoid the formation of V2O5 corrosive species), the additive chemistry for this application must be stable in the presence of water, acids, and a CO2 environment. Furthermore, it needs to minimize deposit formation, either organic or inorganic in nature, on the pre- and post-combustion equipment to maintain high conversion efficiencies, reduce the need for cleaning, and avoid damage. This paper presents a new chemical product that offers excellent corrosion inhibition and superior water tolerance. The new additive is designed to inhibit vanadium induced corrosion and ash fouling. The product is robust and can be applied to multiple applications and has a broad spectrum of use.
Spectroscopic Monitoring of Energy Systems (Calvin W. Rice Lecture)
Authors: Kitagawa Kuniyuki , Morita Shigeaki , Kodama Kenji , Matsumoto Kozo
Published: September 2010

A review is presented for monitoring of chemical species in flames and plasmas used for energy systems. The monitoring systems studied in our group include the followings. 1. Developments and applications of planar laser induced fluorescence spectrometry (PLIF) using isotope effect and laser-induced plasma spectrometry (LIPS) for two-dimensional combustion analyses. 2. Development of direct measurements of chemical species during combustion by coupling flames and mass spectrometers. 3. Development of in-situ monitoring of polymer electrolyte fuel cells by near infrared spectrometry (NIR).
Fluidized Bed Technologies for Biomass Combustion
Authors: Rainio Aku , Sharma Vinod , Bolha`r-Nordenkampf Markus , Brunner Christian , Lind Johannes , Crosher John
Published: September 2010

Biomass, a renewable fuel source for generating energy, is available in large quantities in the USA. Typical biomass consists of wood chips, construction and demolition wood, bark, residual logging debris, saw dust, paper rejects, and paper and sewage sludge. Composition and moisture content of biomass vary greatly and affect its heating value. There are several combustion technologies available to generate power from biomass. Fluidized bed boilers are preferred, because of their ability to burn a wide variety of biomass fuels while achieving high combustion efficiency and low emissions. This paper discusses basic design and operation features of bubbling (BFB) and circulating fluidized bed (CFB) boilers, both offering high fuel flexibility. In fluidized bed combustion, reactive biomass fuels are almost completely burned out because of close contact between the hot bed material and the fuel. In advanced BFB and CFB boilers, an open bottom design is used for ash and coarse material removal through the fluidizing air distribution system. This allows combustion of fuels containing large inert particles, such as rocks and metal pieces. If limestone is added to the bed, SO2 emissions are reduced. By using ammonia or urea in high temperature areas, NOx emissions are reduced. In order to achieve very low emissions, back-end flue gas treatment for SO2, NOx, HCl, HF, and Hg is required. To treat flue gases, several technologies can be used — such as activated carbon and sodium bicarbonate or Trona injection, Turbosorp® circulating dry scrubber, and SCR. Normally the preferred particulate matter cleaning device is a baghouse since the filter cake allows further reactions between pollutants and sorbents. Different fluidized bed designs are shown and recommended for various biomass fuels. This paper describes design, fuels, and emissions for an advanced BFB boiler producing steam at a rate of 230,000 lb/hr/930 psig/860°F (29.0 kg/s/64 barg/460°C).
Spray Technology is Critical in Helping a Plant Achieve Optimal Performance
Authors: Van Durme Robert E.
Published: September 2010

Spray nozzles are used in several locations inside a powerplant and have intimate contact with the processes in the plant. Nozzles are used for inlet fogging, humidification, Wet and Semi-Dry FGD (Flue Gas Desulphurization) applications using open spray towers, CFB (Circulating Fluidized Bed) and SDA (Spray Dry Absorber) scrubbers, NOx using SCR (Selective Catalytic Reduction) and SNCR (Selective Non-catalytic Reduction) technologies. As plants try to achieve optimum efficiency, spray nozzles need to be designed, installed, and maintained properly. In addition, operators and designers need to be aware when a spray nozzle needs to be cleaned or replaced. A defective spray nozzle will have an adverse affect on plant performance. Several factors are to be considered in selecting the proper nozzle. These include material of construction, flowrate, spray angle, operating pressure, placement, droplet size, maximum free passage, spray angle, and many more. New developments in spray nozzle technology are allowing powerplants to have better control and achieve/maintain the tighter regulations on key emissions in the plants. Examples of nozzle type, their application, and recent installations/retrofits will be discussed.
Online Combustion Dynamics Monitoring System (CDMS) for Combustion Turbines: Experience and Examples of How CDMS Supports Operations and Prevents Damages
Authors: Jansen Heino , Kraijesteijn Joop
Published: September 2010

The development of advanced premix burners in combustion turbines has paved the way for dry low NOx combustion. The very lean mixtures of air and fuel in these burners lead to lower flame temperatures, drastically reducing the thermal production of nitric oxides. Careful tuning can reduce NOx emissions to single digit levels. The downside is that the introduction of lean premix combustion has made flames more susceptible to instabilities. Excess air is added to such an extent that the mixture approaches the lean-blow-out limit. Changing ambient conditions or a deviation from the mean calorific value of the fuel can lead to acoustic oscillations or pressure pulsations, known as “humming”. Low frequency pulsations or “chugging” can also occur. Besides flame flash back, also lean blow out of the flames is possible. Acoustic oscillations of the combustion chamber can excite natural frequencies of hot gas path components leading to mechanical vibrations. The vibrations can become large enough for the safety system to trip the machine and can cause severe damages (see figure 1). The need to monitor combustion dynamics and avoid possible damages caused by high dynamics has gained increased attention over the last years. This paper will cover some background and theory on this phenomenon and will then focus on how to detect, monitor and avoid damages caused by increased combustion dynamics. More and more users install combustion dynamics monitoring systems (CDMS) to monitor the combustion dynamics on-line. Examples will be given of how users of KEMA’s combustion dynamics monitoring system FlameBeat® have changed their operations and prevented damages based on the information presented by the CDMS.
Specifying and Evaluating Steam Turbines in Combined Cycle Applications
Authors: Penna Lawrence A. Lon
Published: September 2010

The ASME Performance Test Code PTC-6.2-2004 provides for the testing of steam turbines in combined cycle applications. The acceptance criterion, called “Output Performance” is primarily a measure of efficiency. This paper presents a scenario that illustrates that efficiency alone is not always a sufficient criterion. In this case history, MW Output at the revenue meters suffered by nearly 10% and yet the PTC-6.2 efficiency criterion was satisfied.
Consumption Criteria and Energy Labeling of Wet Cooling Towers in Iran
Authors: Sajadi B. , Sayyadi P. , Saidi M. H.
Published: September 2010

Increasing concerns about global warming and environmental pollution control has pushed the relevant organizations to set regulations and to develop programs for energy saving. In addition, for many high energy using appliances, energy labeling provides the end user with important data to select energy-efficient equipments and encourage the manufacturers to enhance the performance of their productions. In this research, a new energy-saving program for wet cooling towers has been developed. Considering a thermo-hydraulic analysis, a novel Energy Index (IE) has been extracted which takes all aspects of the problem into account. The present index can be used as a proper criterion for energy consumption of wet cooling towers. The required parameters are measured using national and international standards. Based on the experimental-statistical study of a comprehensive range of products, the quantities of acceptable energy consumption criterion and energy rating have been extracted for different types of cooling towers. Administration of such program may lead to considerable energy saving in cooling systems which have major economical and environmental advantages especially in large industries.
Gas Turbine Part Load Exhaust Gas Emissions Turndown Envelope Testing Methodology
Authors: LeClair Kristen , Schmitt Thomas , Frederick Garth
Published: September 2010

Economic and regulatory requirements have transformed today’s power plant operations. High reserve margins and increased fuel costs have driven combined cycle plants that were once dispatched primarily at base-load to be cycled off during off-peak hours. For many plants, the increased cycling has contributed to shorter maintenance intervals and higher overall operating costs. Technology advancements in combustion system design and in gas turbine control systems has led to extensions in the emissions-compliant operating window of gas turbines, also known as turndown. With extended turndown capability, customers are now able to significantly reduce fuel consumption during minimum load operation at off-peak hours, while simultaneously minimizing the number of shutdowns. Extended turndown reduces operational costs by offsetting the fuel consumption costs against the costs associated with starting up and the maintenance costs associated with such starts. Along with the increased emphasis on turndown capability, there has been a rising need to develop and standardize methods by which turndown capability can be accurately measured and reported. By definition, the limiting factor for turndown is the exhaust gas emissions, primarily CO and NOx. A concurrent and accurate measurement of performance and emissions is an essential ingredient to the determination of turndown capability. Of particular challenge is the method by which turndown results that were measured at one set of ambient conditions can be accurately projected to a specific guarantee condition, or to a range of ambient conditions, for which turndown capabilities have been guaranteed. The turndown projection methodology needs to consider combustion physics, control system algorithms, and basic cycle thermodynamics. Recent advances in the integration of empirically tuned physics-based combustion models with control system models and the gas turbine thermodynamic simulation, has resulted in test procedures for use in the contractual demonstration of turndown capability. A discussion of these methods is presented, along with data showing the extent to which the methods have provided accurate and repeatable test results.
Performance of Canola Methyl Ester Biofuel in a Partial Swirl Spray Flame Combustor
Authors: Erazo Jaime A. , Gollahalli S. R. , Parthasarathy R. N.
Published: September 2010

The performance of canola methyl ester (CME) biofuel in a partial swirl spray flame combustor is compared to that of No. 2 diesel fuel in this paper. The spray flame was enclosed in an optically accessible combustor and operated at atmospheric pressure with a co-flow of heated air. Fuel was delivered through a swirl-type air-blast atomizer with an injector diameter of 300 microns. A two-component phase Doppler particle analyzer was used to measure the spray droplet size, axial and radial velocity distributions. Radial and axial concentration measurements of NO, CO, CO2 and O2 were made in the flame environment. Axial and radial flame temperature measurements were made using a Type R thermocouple. The volumetric flow rates of fuel, atomization air and co-flow air were kept constant for both fuels. The droplet SMD at the nozzle exit for CME biofuel are smaller than the No. 2 diesel fuel implying faster vaporization rates for the CME biofuel. Flame temperature decreases more rapidly for the CME biofuel than for the No. 2 diesel fuel in both axial and radial directions. CME biofuel produced lower in-flame NO and CO peak concentrations than No. 2 diesel fuel.
The Experimental Study and Numerical Simulation of Turbulent Flow in Pumping Forebay
Authors: Liu Chao , Zhou Jiren , Cheng Li
Published: September 2010

The experiment study was made to optimize the design of a pumping forebay. The Combined-sills were made in the forebay to eliminate the circulation and vortices of the diffusing flow successfully. The Numerical simulation of three-dimensional turbulent flow is applied on the complicate fore-and-aft flow of sills. The computational results are compared with the measurement results of physical model. The calculated results are in good agreement with the experimental data. The flow pattern is obviously improved. The study results have been applied in the project which gives a uniform approach flow to the pumping sump.
Performance Monitoring of Coal-Fired Units in Real-Time
Authors: Munukutla Sastry S. , Craven Robert P. M. , Coffey Michael R.
Published: September 2010

Power plant performance monitoring can be accomplished in real-time using the data already available on the plant computer in the control room. Because of this, plant operators can be provided with quantitative real-time feedback on the impact of any operational change on plant efficiency and economics. With funding from several major U.S. Utilities and the Electric Power Research Institute (EPRI) the Center for Energy Systems Research (CESR) at Tennessee Technological University (TTU) has developed a Real-Time Performance Monitoring System for evaluating plant operations continuously. The calculations are based on the output/loss method. Coal analysis in real-time is obtained by using information on flue gas composition. This is a unique technology developed at CESR. The steady-state thermodynamic model includes on the fire-side the FD and ID fans, the air preheater, the coal pulverizers and the boiler. It includes flow rate, pressure and temperature of the feedwater, main steam, cold reheat steam and the hot reheat steam on the steam-side of the calculations. The model performs calculations and displays results every minute (or whatever averaging time is chosen) by reading relevant data from the plant computer. One of the primary advantages of this method is that it can be customized to a given unit with given instrumentation. The Real-Time Performance Model has been successfully installed in 10 coal fired units in the U.S.A., four 200 MW units in New Zealand, one 200 MW unit in India and one 900 MW unit in China. In this paper the output/loss method will be introduced. The thermodynamic model with which calculations are performed will be described in detail. Field results from several units around the world will be presented. Examples of strategies for performance enhancement based on real-time performance monitoring will be discussed.
Microbiologically Influenced Corrosion of Condenser and Heat Exchanger Tubing
Authors: Horn Kenneth W.
Published: September 2010

Damage from Microbiologically Influenced Corrosion in the United States has been estimated to cost in excess of $250 billion annually. The industries most affected include oil production, water distribution, and power generation. For this reason, Microbiologically Influenced Corrosion, commonly referred to as MIC, has been the subject of many papers. Since the majority of papers are written from the viewpoint of the microbiologist, it is the intent of this paper to explain MIC in the context of classical corrosion theory, with the ultimate goal being to provide the power plant engineer with guidance on heat exchanger tube materials and how to prevent MIC in heat exchanger tubing.
Small Size Turbo-Machines for HTR Plants
Authors: El-Genk Mohamed S. , Tournier Jean-Michel P.
Published: September 2010

This paper investigated the effects of working fluid, turbine inlet temperature and shaft rotation speed on the size, number of stages and performance of turbo-machines for high temperature reactor (HTR) plants with indirect Closed Brayton Cycles (CBCs). Working fluids considered are He and 15 g/mole He-Xe and He-N2 binary mixtures. Analysis increased the shaft speed from 3000 to 9000 rpm and the turbine inlet temperature from 923 K to 1173 K. The number of compression and turbine stages for He-Xe and He-N2 are significantly lower than for He. Increasing the shaft speed from 3000 to 5400 rpm decreases the number of compression stages for He by ∼ 44% to 47%, by ∼ 40% to 46% for He-N2 and ∼ 40% to 43% for He-Xe over the range of inlet turbine temperatures considered. For He, the number of turbine stages decreases by ∼ 22% to 30%, but those for He-Xe and He-N2 turbines either stay the same or decrease by one or two stages. For a shaft speed of 3000 rpm and turbine inlet temperature of 923 K, the number of compression and turbine stages for He are 27 and 9, while those for He-Xe are 7 and 2 stages, respectively. Increasing the turbine inlet temperature to 1173 K increases the number of compression stages for He-Xe to 10 (compared to 34 for He) and the number of turbine stages to 4 (compared to 13 for He). Even though He-Xe and He-N2 have the same molecular weight, the latter requires more compression and turbine stages, though still considerably less than for He.
Temperature Measurement Applications in Power Plants
Authors: Jethra Ravi
Published: September 2010

Temperature is one of the most widely measured parameters in a power plant. Temperature is monitored and also used for control in some areas. The paper covers some of the basics of Temperature measurement, and leads into some of the technical advances that impart higher a degree of safety and reliability to power plant operation. These advances are based on some of the latest and innovative technologies that are being implemented in process instrumentation. Irrespective of the type of power plant (coal-fired, Oil or gas based), temperature measurement remains high on the list for operational excellence throughout the plant. Implementation of some of the new technologies results in improved Safety and lower installation and maintenance costs. Incorrect measurement information due to temperature effects, non linearity or stability can result in major equipment getting damaged. Ensuring instruments that have minimal downtime from a maintenance standpoint, not just devices that have been evaluated to provide Safety Integrity Level service in Safety Instrumented Systems, is crucial for daily operations in a power plant.
Ceramic Sensors Perform Well in Tough Applications
Authors: Van Nostrand John , Jethra Ravi
Published: September 2010

The purpose of this paper is to: facilitate the advantages of selecting ceramic pressure measuring cells in applications where plant operations and maintenance personnel may realize optimum process performance and stability through the use of ceramic pressure sensors. Identify and demonstrate the inherent problems of using metal diaphragm pressure cells particularly in vacuum and chemical service. Bring awareness of enhanced performance and stability in pressure measurement to plant maintenance, quality assurance and operations personnel in order to improve their operation and the bottom line.
From Commissioning to First Year Operation of a Modern Coal Fired 242 MW Plant Facility
Authors: Mutama Kuda R. , Duperron Norm , Seeliger John
Published: September 2010

In this paper lessons learned during the period from commissioning the TS Power Plant to first year of commercial operations are discussed. It is hoped that the experience at TS Power Plant will be valuable to other new plants during the post-commissioning phase. In June 2008 the TS Power Plant commenced commercial operations. The plant is designed for a gross power output of 242 MW. Combustion takes place in a sub-critical B&W radiant boiler, which uses PRB coal for fuel to generate 1,491,000 lb/hr superheated steam at a design pressure and temperature of 2650 psi and 1055 °F respectively. The steam is used to drive a Toshiba reheat steam turbine generator set. To date the plant performance is better than expected. Actual HP turbine throttle pressures at desired load are less than design with a lower heat rate than expected. The plant has state of the art technology and follows strict emission removal standards in accordance with its air permit for the reduction of CO, NOx, SO2, mercury and particulate matter. Plant personnel addressed problems ranging from mechanical, instrumentation and control, to freezing weather issues during the first year of operations. On several occasions the plant experienced forced outages and personnel had to troubleshoot in order to identify the root cause of the problems. The critical problems developed with the DCS, coal handling system, fans and air dampers, boiler combustion systems, steam turbine auxiliaries, selective catalytic reduction system, spray dry absorber, and water treatment. A significant number of the problems were carried over from facility commissioning and new ones developed during normal operations. Plant personnel had to work through these problems on a daily basis. The operating staff had gained significant experience during the plant commissioning phase by participating in loop shooting and equipment commissioning. It is also important to note that operations staff completed a General Physics training program designed specifically around the TS Power plant systems during construction. The plant was running relatively smoothly with an average availability of 99.84% for the last three months of 2008.
Relation of Air-to-Fuel and Hydrogen-to-Carbon Ratios to Flue Gases in Common Power Generation Systems
Authors: Costarell Michael D.
Published: September 2010

For traditional power generation fuels, the flue gas components can be viewed as continuums based on the air-to-fuel (A:F) and hydrogen-to-carbon (H:C) ratios. This paper defines those continuums for common hydrocarbon fuels (coal, natural gas and oil), in the three most common combustion systems (boilers, reciprocating engines, and gas turbines). Plotted vs. A:F in two dimensions, and then plotted vs. A:F and H:C in three dimensions, overall trends are developed for flue gas carbon dioxide and oxygen. The discussion then compares the calculation of A:F ratios in natural gas combined cycle plants with those in integrated gasification combined cycle plants. Hydrocarbon fuels with no entrained oxygen trend well in both two- and three-dimensional plots, while pure hydrogen and syngas processes do not.
Ocean Thermal Energy Conversion (OTEC): Choosing a Working Fluid
Authors: Anderson James H.
Published: September 2010

Ocean thermal energy plants are thermal power plants that use warm ocean surface water as a source of heat and cold seawater from the deep ocean as a heat sink. A historical perspective along with the development of the technology will be presented. A short description describing the subtle differences between OTEC and fossil and nuclear plants will be presented. Open cycle OTEC and closed cycle OTEC will be described with a focus on the influence of choice of working fluid on the design of a plant. Various working fluids could be selected for use in closed cycle OTEC plants. A review and comparison of potential working fluids will address the advantages and disadvantages of the individual fluids. Their characteristics along with a comparison to water as a working fluid in open cycle OTEC will be explained.
Non-Linear Numerical Techniques for the Analysis of Turbomachinery Components
Authors: Franco-Nava Jose´ Manuel , Dorantes-Go´mez Oscar
Published: September 2010

Reliability and structural integrity are two of the most important factors to be considered in rotating mechanical components design. Numerical techniques had shown to be necessary tools for the evaluation of mechanical components of power plants stations, and oil industry. According to the application, mechanical components are subjected to number of loads. As a consequence, relatively high stresses may occur on the component during service and its life time become limited. In this paper the non-linear numerical techniques more often used for that evaluation are presented. Two-dimensional non-linear boundary element and finite element methods are applied to obtain the stress measures for a turbomachinery component. Elastic analysis with large deformation is presented. The non-linear elastic boundary element implementation incorporates the displacement and the traction boundary integral equations as well as finite deformation stress measures. Boundary element programs, which are based on the non-linear theoretical approach has been developed. In order to evaluate the non-linear boundary element approach with domain type loading, a rotating disc case was analysed. This case study introduces a hyper-singular boundary element method which applies the sectorial symmetry concept that reduces the problem associated with the large number of boundary elements and internal cells in boundary element models of sectorially symmetric structures. Numerical results has been shown that the non-linear formulation lead to accurate solutions. Using an axisymmetric model of a low pressure steam turbine rotor of a 300 MW electric power unit a non-linear analysis was carried out. Results shown that the non-linear effect on the stress, strain and total deformation is located in the centre of the rotor near the surface of the central bore. From this, more mechanical damage can be generated after a number of cycles during the expected time life of the rotor.
Noncontact Torque Sensing for Performance Monitoring and Fault Detection
Authors: Goldfine Neil , Lovett Tim , Sheiretov Yanko , Grundy David , Dunford Todd , Zilberstein Vladimir
Published: September 2010

A conformable, highly directional eddy current sensor, the Meandering Winding Magnetometer (MWM®), and eddy current array (MWM-Array) are described along with inverse methods that use precomputed databases to rapidly convert sensor responses to material properties of interest. An arrangement of four stacked MWM sensors, oriented at 0°, 90°, +45° and −45°, forms the quadri-directional magnetic stress gage (QD-MSG™). The QD-MSG is described and an example of noncontact torque measurement in a rotating helicopter main rotor shaft is presented. Dynamic torque measurement has previously relied upon shaft mounted hardware, such as strain gages, that must receive power and transmit signal through slip rings or rotary transformers, directionally magnetized areas of the shaft or rotational position sensors separated by some distance and sensing shaft rotational deflection. The QD-MSG has the advantages of being noncontact, requiring no modifications to a steel shaft and requiring access to a small area of the shaft.
Ex situ tunnel junction process technique characterized by Coulomb blockade thermometry
Authors: Prunnila M. , Meschke M. , Gunnarsson D. , Enouz-Vedrenne S. , Kivioja J. M. , Pekola J. P.
Published: September 2010

The authors investigate a wafer scale tunnel junction fabrication method, where a plasma etched via through a dielectric layer covering bottom Al electrode defines the tunnel junction area. The ex situ tunnel barrier is formed by oxidation of the bottom electrode in the junction area. Room temperature resistance mapping over a 150 mm wafer gives local deviation values of the tunnel junction resistance that fall below 7.5% with an average of 1.3%. The deviation is further investigated by sub-1 K measurements of a device, which has one tunnel junction connected to four arrays consisting of N junctions (N=41, junction diameter 700 nm). The differential conductance is measured in single-junction and array Coulomb blockade thermometer operation modes. By fitting the experimental data to the theoretical models, the authors found an upper limit for the local tunnel junction resistance deviation of ∼5% for the array of 2N+1 junctions. This value is of the same order as the minimum detectable deviation defined by the accuracy of the authors’ experimental setup.
a
-plane GaN hydride vapor phase epitaxy on a-plane GaN templates with and without use of TiN intermediate layers
Authors: Polyakov A. Y. , Markov A. V. , Mezhennyi M. V. , Donskov A. A. , Malakhov S. S. , Govorkov A. V. , Kozlova Yu. P. , Pavlov V. F. , Smirnov N. B. , Yugova T. G. , Lee I.-H. , Han J. , Sun Q. , Pearton S. J.
Published: September 2010

Thick a-plane GaN films were grown by hydride vapor phase epitaxy on a-plane GaN templates prepared by metalorganic chemical vapor deposition (MOCVD) and also on a-plane MOCVD templates using in situ nitridized Ti underlayers. The growth on a-GaN showed improved crystalline quality with increasing hydride vapor phase epitaxy thickness, while MOCVD template quality had little effect. With 30 nm Ti films deposited on the templates and converted to TiN islands by nitridation during growth, the authors obtained thick (350 μm), freestanding a-GaN films detached from the template. Microcathodoluminescence spectra of the growth surface showed intense band edge luminescence at 3.47 eV at 90 K with no defect bands. Spectra taken from the surface turned to the substrate were dominated by stacking fault-related bands at 3.42, 3.3, and 3.0 eV, similar to the spectra of the a-GaN templates. X-ray measurements showed the freestanding a-GaN layers consisted of misoriented large grains of a-GaN with halfwidth for individual grains close to 300–400 arc sec and halfwidth anisotropy with respect to sample rotation around the [11-20] direction.
Comment on "The Origins of Sexually Transmitted HIV Among Men Who Have Sex with Men"
Authors: Heath Laura , Frenkel Lisa M. , Foley Brian T. , Mullins James I.
Published: September 2010

Unexpected diversity of HIV strains in infected patients reported by Butler
et al
. indicates that there are problems with the validity of the analysis and, therefore, the conclusion that seminal plasma is the main source of infecting virus.
Gold cluster chemistry with the tin nucleophile stanna-closo-dodecaborate
Authors: Schubert Hartmut , Küchle Fritz-Robert , Wesemann Lars
Published: September 2010

The tin nucleophile [SnB11H11]2– reacts with the gold cluster [Au9(PPh3)8][NO3]3 under formation of the tin–gold complex [Au8(PPh3)7(SnB11H11)] (1). In reaction with four equivalents of the heteroborate a mixed valence tetrahedral gold cluster [Au4(PPh3)4(SnB11H11)2]2– with two edge bridging tin ligands was isolated. The reaction products were characterized by elemental analysis, NMR spectroscopy and single crystal X-ray crystallography.
Evolutionary significance of physiological relationships among yeast communities associated with trees
Authors: Lachance Marc-André , Starmer William T.
Published: September 2010

The physiological attributes of yeast communities associated with trees from one gymnosperm and nine angiosperm families were examined in comparison with contemporary classifications of the tree taxa. While the relationships between yeasts found in five coniferous genera (Pinaceae) did not show much congruence with chemotaxonomic or immunological classifications, a physiological classification of yeast communities from 19 genera of Angisoperms showed some compatibility with their respective assignments to families. Clustering of trees as yeast habitats at the family and higher levels indicated that the physiological profiles of yeast communities are to some degree correlated with the taxonomic position of the tree taxa as viewed by some authors. The yeast communities associated with certain tree families appeared nutritionally specialized as compared to others. This evolutionary specialization most likely operates by selection of physiologically limited yeasts, rather than by reduction of the number of yeast species in each community.
The effect of abscisic acid and cytokinins on the cold hardiness of winter wheat
Authors: Gusta L. V. , Fowler D. B. , Tyler N. J.
Published: September 2010

The effect of abscisic acid (ABA) and the cytokinins benzyladenine (BA) and kinetin on the cold hardiness of winter wheat (Triticum aestivum L.) was investigated by controlled freeze tests. ABA or BA applied as a foliar spray to nonacclimated plants or to plants acclimated for 1 week had no measurable effect on crown cold hardiness. The crown water content of winter wheat plants grown in nutrient solution supplemented with BA or kinetin decreased by twofold but cold hardiness was not increased. Thus, a reduction in water content alone does not necessarily result in increased cold hardiness. After 7 days of hardening ABA added with BA increased cold hardiness of crowns 3 to 4 °C depending upon the treatment.
Quelques espèces nouvelles de Laboulbéniales (Ascomycetes) parasites de Carabiques
Authors: Rossi Walter , Rossi M. Graziella Cesari
Published: September 2010

Three new Laboulbeniales occurring on Carabidae (ground beetles) are described: Laboulbenia sciakyi, parasitic on Planetes elegans Nietner (Galeritinae, Planetini) from Sri Lanka, Rhachomyces basilewskyi, parasitic on Eunostus burgeoni Alluaud (Galeritinae, Galeritini) from Zaire, and Rhachomyces leleupidiae, parasitic on Leleupidia kahuziana Basilewsky (Zuphiinae, Leleupidiini) from Zaïre.
Plants for man: their potential in human health
Authors: Lewis Walter H.
Published: September 2010

Botanists pay too little attention to the importance of plants to mankind, including the relation of plants to human health. Many plant products available to the public are capable of causing serious harm to consumers. These include products which can produce allergic reactions in previously sensitized individuals, preparations which cause gastroenteritis but which are dispensed as herb teas, expectorants, or cathartics, abortifacients, and products with cardiovascular involvements. A further problem arises from the misidentification of plant products and from the contamination of harmless or beneficial plant material with toxic species. On the other hand, there are excellent possibilities for the discovery of new beneficial plant derivatives as illustrated by the recent development of vincristine and vinblastine from periwinkle for the treatment of leukemia and lymphoma.
Diploids of Armillaria mellea: synthesis, stability, and mating behavior
Authors: Anderson James B. , Ullrich Robert C.
Published: September 2010

In nature, the vegetative cells of most species of Hymenomycetes are dikaryotic. The only species of this group thought to have a persistent vegetative diploid phase in nature is Armillaria mellea. Mating in this fungus is determined by bifactorial heterothallism, a two-locus (A and B) multiallelic system occurring commonly in the Hymenomycetes. Compatible matings of auxotrophic haploids of A. mellea, however, routinely yield prototrophic diploids. No selective system is needed to recover diploids in compatible matings. In this study, prototrophs were also recovered from hemicompatible (A ≠ B = and A = B ≠) and fully incompatible (A = B =) pairings of auxotrophs, but only when nutritional selection was applied to these pairings. The prototrophic cells recovered by selection were uninucleate and diploid, rather than heterokaryotic, regardless of whether the strains paired were compatible or not. All of the diploids were stable on nutritionally nonselective medium; only two somatic segregants carrying auxotrophic genotypes were detected in tests with 17 different diploid strains. Diploids were capable of mating with haploid strains and the results of diploid × haploid matings clearly indicated heterozygosity for mating-type loci in diploids originally recovered from compatible and hemicompatible pairings.
Nuclear and cytoplasmic anomalies in root tips of corn (Zea mays)
Authors: Vermeer Janet , McCully M. E.
Published: September 2010

Coenocytic areas are present in the meristematic regions of some of the first-formed roots of young corn plants. These areas contain apparently normal cytoplasm and numerous nuclei and include irregular wall ingrowths. Some of the nuclei are stretched and highly distorted with coalesced contents. Occasionally nuclei appear to be squeezing through opened primary pit fields between an intact cell and a coenocytic region. There is no evidence for the presence of pathogens in the abnormal roots.
Hybrids between the tetraploids of Bromus inermis and B. pumpellianus
Authors: Armstrong K. C.
Published: September 2010

Tetraploid F1 hybrids from Bromus pumpellianus ssp. dicksonii (2n = 4x = 28) × B. inermis (2n = 4x = 28) were highly sterile. Chromosome pairing was regular but a low frequency of unpaired chromosomes and multivalents at metaphase I and a low frequency of bridge and fragment configurations at anaphase were recorded. These results indicate that the chromosomes of the parents differ by one or more interchanges and one or more small inversions. The karyotype of the F1 hybrid suggested some structural difference in the satellite-bearing chromosomes of the two species but no other definite evidence of structural changes.
Geographical variation in populations of Chenopodium album resistant and susceptible to atrazine. I. Between- and within-population variation in growth and response to atrazine
Authors: Warwick S. I. , Marriage P. B.
Published: September 2010

Between- and within-population variation in growth characteristics, isoenzyme patterns, and response to atrazine were studied in individuals from four atrazine-resistant (R) and four susceptible (S) populations of Chenopodium album L. collected from sites of contrasting climate in southern Ontario. In both the R and S types, population differences in growth characteristics were correlated with geographical location and climatic differences. The more northerly R and S populations had a greater rate of development, earlier maturation, lower biomass at maturity, and greater reproductive effort compared, respectively, with the more southerly R and S populations.Estimates of within-population variation were obtained statistically for a number of growth characters and from the electrophoretic patterns of five enzyme systems (PGM, PGI, GOT, MPI, and LAP). These indicated marked homogeneity in the four R populations as compared with the more variable S populations. Populations from the two disjunct areas of resistance were different for two of the enzymes studied and would appear to represent two different genotypes. This would suggest that mutation for resistance in populations of C. album has occurred independently in the two areas. Coupled with the evidence for differential growth characteristics of these two genotypes in response to climate, we would suggest that resistance has developed in individuals already established in each of the two separate areas, rather than spreading from a single recent introduction of the R type in Ontario.As expected, distinct differences between the R and S types were obtained in response to postemergence treatments with atrazine. The four R populations either showed no effect or exhibited increased growth. S populations all showed marked decreases in growth and production of biomass. Significant between-population differences in growth features were apparent for both types in the control and were maintained in the presence of atrazine. Although small differences in relative susceptibility were obtained for the susceptible populations, statistically significant population by treatment interactions were not evident.
Probabilistic analysis of predicted and measured settlements
Authors: Krizek Raymond J. , Corotis Ross B. , El-Moursi Houssam H.
Published: September 2010

The methods of probability theory are used to develop probabilistic models for predicting the total settlement (based on either consolidation test data or the results of standard penetration tests) and the time rate of settlement for a compressible clay layer in terms of uncertain values for soil compressibility and loads. The total settlement and the time rate of settlement are well approximated by log-normal distributions. Results calculated by use of the probabilistic approach are compared with settlement values measured in a well documented case history with good supporting laboratory test data.
Application of the wave equation analysis to friction piles in sand
Authors: Tavenas F. A. , Audibert J. M. E.
Published: September 2010

Based on the information gathered during a design pile testing program and the subsequent construction of a large pile foundation in Quebec City, the potential and limitation of the wave equation method for analysing pile driving behaviour are demonstrated.The application of the wave equation method to instrumented precast concrete piles driven under well controlled conditions leads to excellent predictions both in terms of driving stresses and of ultimate bearing capacities.The same high quality of prediction is obtained for a steel H-pile and a precast concrete pile driven incrementally to a depth of 53 ft (16.2 m) in a uniform sand deposit. However, proper simulation of the joints is required for the precast concrete pile.On the contrary, a very poor correlation between computed and observed ultimate capacities is obtained for the production piles. This is attributed to the poor reliability of the blow counts used as input data in the classical wave equation method of analysis.
Cyclic loading of an Ottawa area Champlain Sea clay
Authors: Mitchell R. J. , King R. Douglas
Published: September 2010

Undrained cyclic loading of triaxial samples of a sensitive Champlain Sea clay at deviatoric stress levels in excess of 50% of the static shear strength is shown to produce large deformations and eventual shear failure. Continued deformation of the clay under repeated loadings is believed to result from a progressive destruction of the cemented soil structure. Effective stress failures result from an increase in the excess pore water pressures within the sample.