bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for an Inorganic Carbon-Concentrating Mechanism in the Symbiotic DinoflagellateSymbiodiniumsp.
Authors: Leggat William , Badger Murray R. , Yellowlees David
Published: July 2002

The presence of a carbon-concentrating mechanism in the symbiotic dinoflagellateSymbiodinium sp. was investigated. Its existence was postulated to explain how these algae fix inorganic carbon (Ci) efficiently despite the presence of a form II Rubisco. When the dinoflagellates were isolated from their host, the giant clam (Tridacna gigas), CO2 uptake was found to support the majority of net photosynthesis (45%–80%) at pH 8.0; however, 2 d after isolation this decreased to 5% to 65%, with HCO3  − uptake supporting 35% to 95% of net photosynthesis. Measurements of intracellular Ciconcentrations showed that levels inside the cell were between two and seven times what would be expected from passive diffusion of Ci into the cell. Symbiodinium also exhibits a distinct light-activated intracellular carbonic anhydrase activity. This, coupled with elevated intracellular Ci and the ability to utilize both CO2 and HCO3  − from the medium, suggests thatSymbiodinium sp. does possess a carbon-concentrating mechanism. However, intracellular Ci levels are not as large as might be expected of an alga utilizing a form II Rubisco with a poor affinity for CO2.
Increases in Water Potential Gradient Reduce Xylem Conductivity in Whole Plants. Evidence from a Low-Pressure Conductivity Method
Authors: Brodribb Tim J. , Hill Robert S.
Published: July 2002

A new method using hydrostatic suctions (less than 0.02 MPa) was used to measure whole-root conductivity (K  r) in saplings of two angiosperm pioneer trees (Eucalyptus regnans and Toona australis) and two rainforest conifers (Dacrycarpus dacrydioides and Nageia fleurii). The resultant K  r was combined with measurements of stem and leaf hydraulic conductivity to calculate whole-plant conductivity and to predict leaf water potential (Ψl) during transpiration. At normal soil temperatures there was good agreement between measured and predicted Ψl during transpiration in all species. Changes in the soil-to-leaf water potential gradient were produced by root chilling, and in three of the four species, changes in Ψlcorresponded to those expected by the effect of increased water viscosity on K  r. In one species, however, root chilling produced severe plant wilting and a decline in Ψl significantly below the predicted value. In this species Ψl decreased to a value close to, or below, the Ψl at 50% xylem cavitation. It is concluded that decreased whole-plant conductivity in T. australisresulted from a decrease in xylem conductivity due to stress-induced cavitation.
Changes in Photosynthetic Carbon Flow in Transgenic Rice Plants That Express C4-Type Phosphoenolpyruvate Carboxykinase from Urochloa panicoides
Authors: Suzuki Shoichi , Murai Nobuhiko , Burnell James N. , Arai Masao
Published: July 2002

A cDNA encoding phosphoenolpyruvate carboxykinase (PCK) of Urochloa panicoides (a PCK-type C4 plant) was expressed in rice (Oryza sativa cv Tsukinohikari) plants under the control of the promoter of a maize (Zea mays) gene for phosphoenolpyruvate carboxylase or pyruvate, orthophosphate dikinase with the transit peptide of the small subunit of Rubisco. Crude extracts prepared from the green leaves of transgenic plants had high PCK activity and the newly expressed PCK was localized in chloroplasts. In labeling experiments with 14CO2 up to 20% of the radioactivity was incorporated into 4C compounds (malate, oxaloacetate, and aspartate) in excised leaves of transgenic plants, as compared with about 1% in excised leaves of control plants. There was a positive correlation between PCK activity and the extent of labeling of 4C compounds. When l-[4-14C]malate was fed to excised leaves the extent of incorporation of radioactivity into sucrose was 3-fold greater in transgenic plants than in control plants and the level of radiolabeled aspartate was significantly lower in transgenic plants. These results indicate that the ectopic expression of PCK in rice chloroplasts was able partially to change the carbon flow in mesophyll cells into a C4-like photosynthetic pathway. Such a strategy appears to provide a possible method for enhancing the photosynthetic capacity of C3 plants.
Expression and Processing of a Hormonally Regulated β-Expansin from Soybean
Authors: Downes Brian P. , Steinbaker C. Ryan , Crowell Dring N.
Published: July 2002

Expansin proteins are essential components of acid-induced cell wall loosening in plants. β-Expansins, which constitute a subfamily of related expansin proteins, include the group I grass pollen allergens. To provide a better description of β-expansin expression, we have characterized a cytokinin-inducible β-expansin from soybean (Glycine max cv Mandarin) called Cim1. Our results demonstrate that the hormones cytokinin and auxin act synergistically to induce the accumulation and proteolytic processing of Cim1. Carboxyl terminal truncation of a 35-kD form of Cim1 is predicted to remove the putative cellulose binding domain from the amino terminal cysteine-rich domain, resulting in a 20-kD form of the protein. Furthermore, the identical amino termini of the 35- and 20-kD forms of Cim1 correspond to a position 11 amino acids downstream of the predicted signal sequence cleavage site, suggesting proteolysis of a short amino terminal propeptide after removal of the signal peptide. This propeptide fragment contains a consensus site for N-glycosylation and our data suggest that it is glycosylated by a tunicamycin-sensitive mechanism in cultured soybean cells. The onset of Cim1 expression correlates with increased growth of soybean cultures. Ultimately, Cim1 is rapidly and specifically proteolyzed as soybean cultures reach stationary phase. These findings are consistent with the hypothesis that β-expansin proteins are extensively modified by post-translational N-glycosylation and proteolysis.
Inhibition of corrosion of mild steel in acidic solutions by quarternary salts of pyridinium bases
Authors: Vasudevan T. , Muralidharan B. , Muralidharan S. , Venkatakrishna Iyer S.
Published: July 2002

The influence of pyridinium chloride (PC) and n‐hexa decyl pyridinium chloride (HDPC) on the corrosion of mild steel in 5N HCl and 5N H2SO4 has been studied using techniques such as weight loss and gasometric measurements, potentiodynamic polarisation studies, linear polarisation studies and small amplitude cyclic voltametric studies. It is found that HDPC is more inhibitive than PC and both the compounds perform better in H2SO4. Polarisation studies reveal that PC behaves as an anodic inhibitor in H2SO4 and as a mixed inhibitor in HCl. Measurements of values of polarisation resistance (Rp) and double layer capacitance (Cdl) in the presence of these compounds also reveal the better performance of HDPC in both the acids. The adsorption of PC and HDPC on a mild steel surface from both the acids is found to obey Temkin’s adsorption isotherm.
Hexadecyl trimethyl ammonium bromide as an effective inhibitor for the corrosion of steel in sulphuric acid solution
Authors: Osman M.M.
Published: July 2002

The corrosion of steel in sulphuric acid containing hexadecyl trimethyl ammonium bromide (HTABr) was studied over the temperature range 30‐60°C at different inhibitor concentrations of 0.5 × 10‐3 to 2.5 × 10‐3 M/L by the mass‐loss method. Langmuir’s adsorption isotherm fits the experimental data for the studied compound. Thermodynamic parameters for dissolution and adsorption were calculated. It is observed that HTABr can be used as an effective inhibitor.
Recognising the perceived causes of stress – a training and development perspective
Authors: Rees Christopher J. , Redfern David
Published: July 2002

Acknowledges that the subject of occupational stress has become a major workplace issue. Suggests that employers may expect training and development specialists to play an increasingly prominent role in tackling stress within the workplace. Identifies a general lack of a consensus about the nature and causes of stress. Illustrates this point by investigating perceptions of occupational stress, as outlined in information dissemination by trade unions and employers’ organisations. Uses core HR activities to provide examples of how different perspectives of occupational stress can be identified. Highlights that training and development specialists can play an important role in ensuring that a balanced and eclectic approach to occupational stress is adopted in the workplace.
Force control basics
Authors: Erlbacher Edwin A.
Published: July 2002

There are two commercially accepted methods of force control used in automated surface finishing today. The first method, “through‐the‐arm” force control, applies force using the position of all the robot axes in unison. The second method, “around‐the‐arm” force control, uses the robot for positioning motion only, and applies a controlled force through an auxiliary‐compliant end‐of‐arm tool. Discusses the theory, applicability and features of each of these two technologies.
Lasers become the acceptable face of precision welding and cutting
Authors: Rooks Brian
Published: July 2002

The current state in the application of lasers for cutting and welding is reviewed. Most cutting operations are performed on specifically developed laser machine tools such as the Trumpf Lasercell and its application in the development of trim shapes and low volume panel production at a sub‐contract toolmaker is described. Robots are mainly used with lasers for welding, particularly of vehicle body components where laser welds are found to be advantageous in reducing material weight and improving body strength. One example is the production of differing thickness panels and a robotic installation for producing car door inners is described. The benefits of the new generation of Nd:YAG power lasers are listed, including the ability to transmit the laser beam via fibre optic cables. This is particularly advantageous when robots are used to manipulate the “torch” and a new robot cell from Trumpf is described. Finally, the role of gases in laser processing is discussed.
Efficient robotic welding for shipyards ‐ virtual reality simulation holds the key
Authors: Sorenti Peter
Published: July 2002

Describes how virtual reality simulation technology is being used and developed to support the design, and programming, of large‐scale robot arc‐welding cells in two of the world’s largest and most modern shipyards. GRASP‐VRI is a shipbuilding‐specific software simulation and offline programming tool, developed as part of a highly‐productive method for rapidly creating arc‐welding programs for robots. Describes the integrated program creation concept which uses pre‐defined, parametric libraries of generic arc‐welding tasks that were created and verified prior to, and during, cell commissioning. Says that the approach is applicable to other robotics applications such as cutting, gluing and inspection.
Robot guidance with a photogrammetric 3‐D measuring system
Authors: Leikas Esa
Published: July 2002

A photogrammetric 3‐D machine vision system has been developed for industrial inspection and quality control applications. The system consists of several simultaneously operating solid‐state cameras and photogrammetric hardware and software. The same system has been adapted for robot guidance tasks, providing new possibilities and features. Two different applications have been chosen to demonstrate the accuracy, flexibility and speed of the photogrammetric systems in robotic applications. 3‐D object positioning is utilised in the measurement of car body positions for accurate seam‐sealing robot operation. A robotised propeller grinding cell uses profile and thickness measuring data to control the grinding process. Many other applications of photogrammetric systems are also possible, and their use in industrial manufacturing is predicted to increase in the future.
Tutorial Plastics welding technology for industry
Authors: Mistry Kalpana
Published: July 2002

Plastics are the engineering materials for future technological development. Advances in plastics processing and fabrication techniques have facilitated the production of novel plastics devices and components in major business sectors such as the automotive, medical and packaging industries. Reviews the current techniques available for welding plastics material and highlights their advantages, limitations and stage of development.
Organizational change: the Australian experience
Authors: Savery Lawson K. , Luks J. Alan
Published: July 2002

Organizational change is a complex phenomenon with potentially devastating consequences if not done correctly. Organizations in the global marketplace continue to experience tremendous change. This paper examines data from a survey, which examined approximately 2,000 workplaces on whether they had introduced change and the effects of these changes on the employees at the workplace. The paper considered these changes, which included such issues as downsizing, delayering and the introduction of new plant and/or technology, reason for changes and who decided to introduce the changes. It further considered the level of perceived consultation, which accompanied the change, the perceived barriers to the changes and the possible influence on productivity. Examination of the data indicates that there is no relationship between downsizing and productivity.
CCTV surveillance systems in town and city centre management
Authors: Harris Candida , Jones Peter , Hillier David , Turner David
Published: July 2002

During the 1990s, closed circuit television (CCTV) surveillance technology has been an increasingly important and visible part of crime and nuisance prevention measures in town and city centres throughout the UK. The paper outlines the principal characteristics of CCTV systems and identifies the objectives guiding their introduction. The Home Office, police forces and many local authorities have expressed support for CCTV and they often report reductions in reported crime levels and in the fear of crime following the introduction of CCTV. At the same time, there are concerns about the cost‐effectiveness of CCTV and about a number of legal, personal privacy and civil liberties issues.
Consistent gradient formulation for a stable enhanced strain method for large deformations
Authors: Korelc Joze , Wriggers Peter
Published: July 2002

Considers the problem of stability of the enhanced strain elements in the presence of large deformations. The standard orthogonality condition between the enhanced strains and constant stresses ensures satisfaction of the patch test and convergence of the method in case of linear elasticity. However, this does not hold in the case of large deformations. By analytic derivation of the element eigenvalues in large strain states additional orthogonality conditions can be derived, leading to a stable formulation, regardless of the magnitude of deformations. Proposes a new element based on a consistent formulation of the enhanced gradient with respect to new orthogonality conditions which it retains with four enhanced modes volumetric and shear locking free behaviour of the original formulation and does not exhibit hour‐glassing for large deformations.
Numerical evaluation of probabilistic fracture parameters using WSTRESS
Authors: Ruggieri Claudio , Dodds Robert H.
Published: July 2002

Describes a probabilistic methodology for fracture assessments of flawed structures constructed of ferritic steels using the research code WSTRESS. The probabilistic formulation for cleavage fracture implements a multiaxial form of the weakest link model which couples the macroscopic fracture behavior with a micromechanics model based on the statistics of microcracks. The Weibull stress, σw, emerges as a suitable near‐tip parameter to provide a connection between the microregime of failure and remote loading (J). WSTRESS builds on an iterative procedure to incorporate a 3‐D finite element description of the crack‐tip stress field and measured values of fracture toughness to calibrate the Weibull modulus, m, and the scale parameter, σu. Specific features of the code include statistical inference of Weibull parameters based on uncensored and censored models (with maximum likelihood method), construction of confidence intervals, several definitions for the near‐tip fracture process zone and other general facilities such as spatial integration of the stress field (to incorporate the random orientation of microcracks) and stochastic simulation of fracture data using the Monte Carlo method. The code also includes a convenient free‐form command language and a seamless interface with finite element results files stored in Patran binary or ASCII format.
Understanding and contending with passive‐aggressive behaviour in teams and organizations
Authors: McIlduff Edward , Coghlan David
Published: July 2002

Managers and consultants have reported that they frequently encounter situations in which individual members of an organization exude an attitude of muted hostility and non‐compliance to a change process. This obstructive behaviour can take an indirect form and be masked by a veneer of apparent co‐operation, smiles and seemingly correct behaviour. When this phenomenon is encountered it can be defined “passive‐aggressive behaviour”. In this article, we examine this type of behaviour from both the clinical and the more pragmatic/operational perspectives in order to bring more understanding and clarity to the concept. We discuss its impact in teams, organizations and in the field of organizational change. Our concluding section sets out a framework or intervention approach which the manger, consultant and trainer might find useful in dealing with this type of behaviour as well as with truculent, avoidant and hostile behaviours.
3‐D calculations of leakage field and reactance for special transformers
Authors: Zakrzewski K. , Lukaniszyn M. , Tomczuk B.
Published: July 2002

Two approaches to 3‐D magnetic field calculations for low‐power special transformers are presented in the paper. The application of fast calculation procedures based on the finite difference method, to direct solving of the Poisson and Laplace equations is given. The calculated example deals with the three‐phase leakage transformer. On the other hand, the iterative solution of regularized integral equations used for calculation of 3‐D field distribution and integral parameters of leakage field in current transformer is also presented. The software packages developed by the authors are useful for computer‐aided design of low‐power special transformers.
The computer subconscious
Authors: Caulfield H. John
Published: July 2002

One thing which distinguishes people from computers and from one another is variously called creativity, the right brain, or the subconscious. Computers are designed to be fast, almost‐error‐free rule followers. Artificial intelligence (AI) has been based on computers and their rule‐following skills, e.g. expert systems. Yet we do not value Mozart, Einstein, Van Gogh, etc. for their rule following skills. In order to understand our own creativity we must model our subconscious. Once we model it, we can learn more about it by building a computer subconscious. Shows how a multiple‐module Darwinistic model can account for the human subconscious and how such a system can be emulated in a computer. For a quantum computer, perhaps the only technological computer fast enough to make computer creativity interesting, the results are also unpredictable in principle. Computers will differ in personality, skill and interests just as people do even if they start off identical.
The strategies for implementing multilevel self‐ management in schools
Authors: Ming Cheung Wing , Cheong Cheng Yin
Published: July 2002

School‐based management programmes have been launched in various regions of the world to enhance education quality in schools. Presents a multilevel self‐management framework necessary for effective implementation of school‐based management. Proposes strategies for minimizing restraining forces and developing plans for effective multilevel self‐management in schools. Suggests three stages of implementation: unfreezing stage, changing stage and reinforcing stage. The time frame is critical for implementing the three levels of self‐management and, therefore, its management is discussed. Proposes seven types of skill required to work more effectively through the above stages, reduce resistance and gain support from school members.
3D numerical simulation of melt flow in the presence of a rotating magnetic field
Authors: Vizman D. , Fischer B. , Friedrich J. , Müller G.
Published: July 2002

Being extensively used in metallurgy, rotating magnetic fields are also becoming increasingly interesting for application in crystal growth, where they are intended to act by stabilizing the melt flow. For this purpose, it is important to understand the basic interactions of the magnetically induced flow and other flow components like time‐dependent buoyant convection. So a three‐dimensional finite volume method was developed in order to numerically study the effect of a rotating magnetic field on convection in a cylindrical melt volume. The equations of mass, momentum, and heat transport are solved together with the potential equations describing the electromagnetic field. The numerical computation of the Lorenz force distribution is validated by comparison with an analytical solution. The effects of magnetic field parameters on the temperature distributions and the flow patterns in the considered configurations are analysed.
Emergency response preparedness: small group training. Part I – training and learning styles
Authors: Wilson Henry C.
Published: July 2002

This is Part 1 of a multi‐part paper and examines small group training for those charged with responding in an emergency situation. To ensure both effective and efficient training it is important to understand that people learn in different ways. Their learning styles have to be taken into account for both the design and the implementation of the learning experiences. Discusses different learning styles and tools available.
Pakistani librarians as authors: a bibliometric study of citations in LISA‐PLUS
Authors: Anwar Mumtaz Ali , Saeed Hamid
Published: July 2002

This study presents quantitative analysis of 251 items contributed by 64 Pakistani LIS professionals culled from LISA‐PLUS. Volume of contribution, sources where published, periodic distribution, type of publications and topical coverage are dealt with in the analysis. Journal literature which represents 90.4 per cent of the citations is published in 43 periodicals, most of which are from the United States. However, more than half of the journal literature comes from one national journal. A wide range of topics is covered, but critical areas such as information needs, user education and collection evaluation receive very little attention.
In vivo assembly of aspartate transcarbamoylase from fragmented and circularly permuted catalytic polypeptide chains
Authors: Ni Xinhai , Schachman Howard K.
Published: July 2002

Previous studies on Escherichia coli aspartate transcarbamoylase (ATCase) demonstrated that active, stable enzyme was formed in vivo from complementing polypeptides of the catalytic (c) chain encoded by gene fragments derived from the pyrBI operon. However, the enzyme lacked the allosteric properties characteristic of wild‐type ATCase. In order to determine whether the loss of homotropic and heterotropic properties was attributable to the location of the interruption in the polypeptide chain rather than to the lack of continuity, we constructed a series of fragmented genes so that the breaks in the polypeptide chains would be dispersed in different domains and diverse regions of the structure. Also, analogous molecules containing circularly permuted c chains with altered termini were constructed for comparison with the ATCase molecules containing fragmented c chains. Studies were performed on four sets of ATCase molecules containing cleaved c chains at positions between residues 98 and 99, 121 and 122, 180 and 181, and 221 and 222; the corresponding circularly permuted chains had N termini at positions 99, 122, 181, and 222. All of the ATCase molecules containing fragmented or circularly permuted c chains exhibited the homotropic and heterotropic properties characteristic of the wild‐type enzyme. Hill coefficients (nH) and changes in them upon the addition of ATP and CTP were similar to those observed with wild‐type ATCase. In addition, the conformational changes revealed by the decrease in sedimentation coefficient upon the addition of a bisubstrate analog were virtually identical to that for the wild‐type enzyme. Differential scanning calorimetry showed that neither the breakage of the polypeptide chains nor the newly formed covalent bond between the termini in the wild‐type enzyme had a significant impact on the thermal stability of the assembled dodecamers. The studies demonstrate that continuity of the polypeptide chain within structural domains is not essential for the assembly, activity, and allosteric properties of ATCase.
Viability and Equilibrium in Securities Markets with Frictions
Authors: Jouini Elyès , Kallal Hédi
Published: July 2002

In this paper we study some foundational issues in the theory of asset pricing with market frictions. We model market frictions by letting the set of marketed contingent claims (the opportunity set) be a convex set, and the pricing rule at which these claims are available be convex. This is the reduced form of multiperiod securities price models incorporating a large class of market frictions. It is said to be viable as a model of economic equilibrium if there exist price‐taking maximizing agents who are happy with their initial endowment, given the opportunity set, and hence for whom supply equals demand. This is equivalent to the existence of a positive lineaar pricing rule on the entirespace of contingent claims—an underlying frictionless linear pricing rule—that lies below the convex pricing rule on the set of marketed claims. This is also equivalent to the absence of asymptotic free lunches—a generalization of opportunities of arbitrage. When a market for a nonmarketed contingent claim opens, a bid‐ask price pair for this claim is said to be consistent if it is a bid‐ask price pair in at least a viable economy with this extended opportunity set. If the set of marketed contingent claims is a convex cone and the pricing rule is convex and sublinear, we show that the set of consistent prices of a claim is a closed interval and is equal (up to its boundary) to the set of its prices for all the underlying frictionless pricing rules. We also show that there exists a unique extended consistent sublinear pricing rule—the supremum of the underlying frictionless linear pricing rules—for which the original equilibrium does not collapse when a new market opens, regardless of preferences and endowments. If the opportunity set is the reduced form of a multiperiod securities market model, we study the closedness of the interval of prices of a contingent claim for the underlying frictionless pricing rules.
Effects of prior contractions on muscle microvascular oxygen pressure at onset of subsequent contractions
Authors: Behnke Brad J. , Kindig Casey A. , Musch Timothy I. , Sexton William L. , Poole David C.
Published: July 2002

In humans, pulmonary oxygen uptake (V̇O2) kinetics may be speeded by prior exercise in the heavy domain. This ‘speeding’ arises potentially as the result of an increased muscle O2 delivery (Q̇O2) and/or a more rapid elevation of oxidative phosphorylation. We adapted phosphorescence quenching techniques to determine the QO2‐to‐O2 utilization (Q̇O2/V̇O2) characteristics via microvascular O2 pressure (PO2,m) measurements across sequential bouts of contractions in rat spinotrapezius muscle. Spinotrapezius muscles from female Sprague‐Dawley rats (n= 6) were electrically stimulated (1 Hz twitch, 3–5 V) for two 3 min bouts (ST1 and ST2) separated by 10 min rest. PO2,m responses were analysed using an exponential + time delay (TD) model. There was no significant difference in baseline and ΔPO2,m between ST1 and ST2 (28.5 ± 2.6 vs. 27.9 ± 2.4 mmHg, and 13.9 ± 1.8 vs. 14.1 ± 1.3 mmHg, respectively). The TD was reduced significantly in the second contraction bout (ST1, 12.2 ± 1.9; ST2, 5.7 ± 2.2 s, P < 0.05), whereas the time constant of the exponential PO2,m decrease was unchanged (ST1, 16.3 ± 2.6; ST2, 17.6 ± 2.7 s, P > 0.1). The shortened TD found in ST2 led to a reduced time to reach 63 % of the final response of ST2 compared to ST1 (ST1, 28.3 ± 3.0; ST2, 20.2 ± 1.8 s, P < 0.05). The speeding of the overall response in the absence of an elevated PO2,m baseline (which had it occurred would indicate an elevated QO2/V̇O2) or muscle blood flow suggests that some intracellular process(es) (e.g. more rapid increase in oxidative phosphorylation) may be responsible for the increased speed of PO2,m kinetics after prior contractions under these conditions.
Inverse Determination of Temperature-Dependent Thermal Conductivity Using Steady Surface Data on Arbitrary Objects
Authors: Martin T. J. , Dulikravich G. S.
Published: July 2002

An inverse computational method has been developed for the nonintrusive and nondestructive evaluation of the temperature-dependence of thermal conductivity. The methodology is based on an inverse computational procedure that can be used in conjunction with an experiment. Given steady-state heat flux measurements or convection heat transfer coefficients on the surface of the specimen, in addition to a finite number of steady-state surface temperature measurements, the algorithm can predict the variation of thermal conductivity over the entire range of measured temperatures. Thus, this method requires only one temperature probe and one heat flux probe. The thermal conductivity dependence on temperature (k-T curve) can be completely arbitrary, although a priori knowledge of the general form of the k-T curve substantially improves the accuracy of the algorithm. The influence of errors of measured surface temperatures and heat fluxes on the predicted thermal conductivity has been evaluated. It was found that measurement errors of temperature up to five percent standard deviation were not magnified by this inverse procedure, while the effect of errors in measured heat fluxes were even lower. The method is applicable to two-dimensional and three-dimensional solids of arbitrary shape and size. [S0022-1481(00)01703-5]
Stoichiometric Operation of a Gas Engine Utilizing Synthesis Gas and EGR for NOx Control
Authors: Smith Jack A. , Bartley Gordon J. J.
Published: July 2002

This paper presents the results from an internal research study conducted at the Southwest Research Institute (SwRI) on the effects of stoichiometric mixtures of natural gas and synthesis gas with exhaust gas recirculation (EGR) on engine performance and exhaust emissions. Constant load performance and emissions tests were conducted on a modified, single-cylinder, Caterpillar 1Y540 research engine at 11.0 bar (160 psi) bmep. Engine performance and emissions comparisons between natural gas with EGR, and natural gas with syngas and EGR are presented. In addition, the performance characteristics of the fuel reforming catalyst are presented. Results show that thermal efficiency increases with increasing EGR for both natural gas operation and natural gas with syngas operation at constant load. The use of syngas with natural gas extended the EGR tolerance by 44.4 percent on a mass basis compared to natural gas only, leading to a 77 percent reduction in raw NOx emissions over the lowest natural gas with EGR NOx emissions. [S0742-4795(00)00504-4]
Continuous Monitoring of Binary Gas Mixture Concentration With Application to Turbine Blade Cooling Experiments
Authors: Strilka Tomas , Sajben Miklos , Nagy Peter
Published: July 2002

Turbine blade cooling experiments often use mixtures of air and a heavy gas CO2,SF6 to simulate coolant/mainstream density ratios. If the mixing of the mainstream with the coolant ejected from the blade is of interest, then it may be necessary to determine the spatial distribution of the heavy gas concentration in the flowfield. Commercial analyzers are too slow and have other disadvantages when used for this purpose. To meet this special need, a device has been developed to monitor the heavy gas concentration continuously in a small sample stream by determining the speed of sound in the sample. Together with the temperature of the sample, the information is sufficient to determine the concentration. The device measures the time of propagation for an ultrasonic burst transverse to the stream. The temperature of the gas contained in the device is controlled and measured. Calibration with several gas mixtures (air and CO2,SF6, He) has shown an uncertainty Cmeas−Ctrue of 2 percent over the full concentration range of 0–100 percent for CO2 and SF6. The device is operable in the pressure range from −50 to 100 kPa gage and in the temperature range from 0°C to 40°C. The instrument is rugged and will survive in noisy, turbulent environments. [S0889-504X(00)01202-2]
A Strip Element Method for Analyzing Wave Scattering by a Crack in an Axisymmetric Cross-Ply Laminated Composite Cylinder
Authors: Xi Z. C. , Liu G. R. , Lam K. Y. , Shang H. M.
Published: July 2002

A strip element method is presented for analyzing waves scattered by a crack in an axisymmetric cross-ply laminated composite cylinder. The cylinder is at the outset discretized as axisymmetric strip elements through the radial direction. The application of the Hamilton variational principle develops a set of governing ordinary differential equations. The particular solutions to the resulting equations are found using a modal analysis approach in conjunction with the Fourier transform technique. The complementary solutions are formulated by the superposition of eigenvectors, the unknown coefficients of which are determined from axial stress boundary conditions at the tips of the crack. The summation of the particular and complementary solutions gives the general solutions. Numerical examples are given for cross-ply laminated composite cylinders with radial cracks. The results show that the present method is effective and efficient. [S0021-8936(00)00202-6]
Low-Gravity Sloshing in an Axisymmetrical Container Excited in the Axial Direction
Authors: Utsumi M.
Published: July 2002

The response of low-gravity propellant sloshing is analyzed for the case where an axisymmetrical container is exposed to axial excitation. Spherical coordinates are used to analytically derive the characteristic functions for an arbitrary axisymmetrical convex container, for which time-consuming and expensive numerical methods have been used in the past. Numerical results show that neglecting the surface tension results in the underestimation of the magnitude of the liquid surface oscillation. The reason for this is explained by the influences of the Bond number and the liquid filling level on the critical value of the coefficient of the excitation term in the modal equation, above which the oscillation is destabilized, and on the characteristic root of the destabilized system. [S0021-8936(00)01502-6]
Analytical Method of Response of Piping System With Nonlinear Support
Authors: Aoki Shigeru , Watanabe Takeshi
Published: July 2002

This paper deals with steady-state response of the piping system with nonlinear support having hysteresis damping characteristics. Considering the energy loss for contact with a support, an analytical method of approximate solution for the beam, a one-span model of the piping system, with quadrilateral hysteresis loop characteristics is presented. Some numerical results of the approximate solution for the response curves and the mode shapes are shown. [S0094-9930(00)00204-3]
Increased Wear Resistance of Roller Bearings Using Me-C: H Coated Rollers
Authors: Olofsson Ulf , Sjo¨stro¨m Hans , Sjo¨din Ulf
Published: July 2002

The contact surfaces in a boundary lubricated spherical roller thrust bearing can change form due to sliding and particle generated wear. These form changes can seriously reduce the fatigue life of the bearings. An experimental test series has been performed where this effect was investigated in bearings with metal mixed amorphous carbon, Me-C: H, coated rollers that were tested against bearings with standard rollers. The experimental results show that while the bearings with standard rollers can fail due to wear, the bearings with coated rollers are at the same time almost unaffected by wear. Also the number of particles generated in the contact was significantly less when using coated rollers. There were twice as many self-generated particles when using a standard bearing compared with a coated bearing. The effect of the coating is discussed in terms of surface hardness, coefficient of friction and tribochemical phenomena. [S0742-4787(00)02004-X]
Lateral-Flow Effect on Endwall Heat Transfer and Pressure Drop in a Pin-Fin Trapezoidal Duct of Various Pin Shapes
Authors: Hwang Jenn-Jiang , Lu Chau-Ching
Published: July 2002

The effects of lateral-flow ejection 0<ε<1.0, pin shapes (square, diamond, and circular), and flow Reynolds number (6000<Re<40,000) on the endwall heat transfer and pressure drop for turbulent flow through a pin-fin trapezoidal duct are studied experimentally. A staggered pin array of five rows and five columns is inserted in the trapezoidal duct, with the same spacings between the pins in the streamwise and spanwise directions: Sx/d=Sy/d=2.5. Three different-shaped pins of length from 2.5<l/d<4.6 span the distance between two endwalls of the trapezoidal duct. Results reveal that the pin-fin trapezoidal duct with lateral-flow rate of ε=0.3-0.4 has a local minimum endwall-averaged Nusselt number and Euler number for all pin shapes investigated. The trapezoidal duct of lateral outlet flow only (ε=1.0) has the highest endwall heat transfer and pressure drop. Moreover, the square pin results in a better heat transfer enhancement than the diamond pin, and subsequently than the circular pin. Finally, taking account of the lateral-flow rate and the flow Reynolds number, the work develops correlations of the endwall-averaged heat transfer with three different pin shapes.
Reliability-Based Management of Marine Fouling
Authors: Faber Michael Havbro , Hansen Peter Friis , Jepsen Frank Drejer , Mo̸ller Henrik Holten
Published: July 2002

The present paper describes the results of a recent study on the application of methods from structural reliability to optimize management of marine fouling on jacket-type structures. In particular, the study addresses effects on the structural response by assessment and quantification of uncertainties of a set of parameters. These are the seasonal variation of marine fouling parameters, the wave loading (taking into account the seasonal variation in sea-state statistics), and the effects of spatial variations and seasonal effects of marine fouling parameters. Comparison of design values obtained by the present model taking into account seasonal effects with those inherent in the current design specifications are made and criteria are formulated for removal of marine fouling taking into account seasonal differences in marine fouling. A methodology is outlined on how to establish new and more representative marine fouling profiles for design of new structures, and finally an approach is outlined on how to include inspections of marine fouling into a risk-based inspection philosophy.
A Fiber-Optic Tip-Shroud Deflection Measurement System
Authors: Rooth R. A. , Hiemstra W.
Published: July 2002

A Dutch utility faced the fact that a second stage set of turbine blades of a gas turbine had to be replaced long before the estimated lifetime as a result of tip shroud deflection. This deflection caused the risk of loss of support between the individual tip shroud segments. The goal of this paper is to find the cause of the problem, to see how it increases with time, and to take appropriate action to prevent the problem from occurring again. A fiber-optic tip-shroud deflection monitor has been developed and tested on a gas turbine to study this phenomenon in real time. The optical system is based on astigmatism to derive distance information from the measured optical signals. Characteristic features from the system are the good spatial resolution of about 1 mm, the distance resolution of about 0.1 mm and the distance from the probe tip to the target of about 20 mm. These specifications are difficult to achieve with, for example, capacitive sensors. The probe tip can with stand temperatures of about 500°C. The system can be calibrated in situ, given a stable operation of the gas turbine. This is accomplished by stepping the probe tip over some distance and recording the signals corresponding to a certain point on the tip shroud. The instrument has been used to monitor the tip-shroud deflection in a gas turbine at various loads and over a time span of several months. The results indicate that the deflection can be divided in a part depending on the load and a part that is a permanent deflection. Based on the results, it can be judged whether blades need to be rejected because of a too large deflection.
A Study on Turbulent Boundary Layers on a Smooth Flat Plate in an Open Channel
Authors: Balachandar Ram , Blakely D. , Tachie M. , Putz G.
Published: July 2002

An experimental study was undertaken to investigate the characteristics of turbulent boundary layers developing on smooth flat plate in an open channel flow at moderately high Froude numbers (0.25<Fr<1.1) and low momentum thickness Reynolds numbers 800<Reθ<2900. The low range of Reynolds numbers and the high Froude number range make the study important, as most other studies of this type have been conducted at high Reynolds numbers and lower Froude numbers (∼0.1). Velocity measurements were carried out using a laser-Doppler anemometer equipped with a beam expansion device to enable measurements close to the wall region. The shear velocities were computed using the near-wall measurements in the viscous subregion. The variables of interest include the longitudinal mean velocity, the turbulence intensity, and the velocity skewness and flatness distributions across the boundary layer. The applicability of a constant Coles’ wake parameter (Π=0.55) to open channel flows has been discounted. The effect of the Froude number on the above parameters was also examined.
Bubble Analogy and Stabilization of Core-Annular Flow
Authors: Bannwart Antonio C.
Published: July 2002

A theory for the stabilization of annular liquid-liquid flow (i.e., core-annular flow) in a horizontal pipe is proposed. Based upon the analysis of the momentum conservation equation in the cross section of the flow, including the effects of peripheral flow in the annulus and interfacial tension, an equation is obtained which describes the interface shape. Results for the height-to-width aspect ratio of the core are compared with laboratory measurements done by the author for a heavy oil-water core-annular flow. A criterion for stabilization of this interesting flow pattern is proposed.
Fully Nonlinear Multidirectional Waves by a 3-D Viscous Numerical Wave Tank
Authors: Kim M. H. , Niedzwecki J. M. , Roesset J. M. , Park J. C. , Hong S. Y. , Tavassoli A.
Published: July 2002

A finite-difference scheme and a modified marker-and-cell (MAC) method are used for numerical wave tank (NWT) simulations to investigate the characteristics of nonlinear multidirectional waves. The Navier-Stokes (NS) equations are solved for two fluid layers and the boundary values updated at each time step by a finite-difference time-marching scheme in the frame of rectangular coordinate system. The fully nonlinear kinematic free-surface condition is satisfied by the density-function technique developed for two fluid layers. The directional incident waves are generated from the inflow boundary by prescribing a snakelike motion along the wavemaker direction. The outgoing waves are numerically dissipated inside an artificial damping zone located at the end of the tank. Using the NS-MAC NWT with both solid and transparent side-wall conditions, the effects of side-wall reflections are studied. Bull’s-eye waves are also numerically generated by the phase control of neighboring wavemaker segments or the reverse process of cylindrical wavemakers. The simulation results are compared with the computations by an independently developed potential-based NWT and the experiments conducted in the Offshore Technology Research Center’s 3-D wave basin.
Thermal Deformation: From Thermodynamics to Heat Transfer
Authors: Arpacı Vedat S.
Published: July 2002

An infinitesimal change in heat flux Q is shown, in terms of entropy flux Ψ=Q/T to have two parts, dQ=TdΨ+ΨdT, the first part being the thermal displacement and the second part being the thermal deformation. Only the second part dissipates into internal energy and generates entropy. This generation is shown to be dΠ=Ψ/TdT. Thermodynamic arguments are extended to transport phenomena. It is shown that a part of local rate of entropy generation is related to local rate of thermal deformation by s′′′=−ψi/T∂T/∂xi, where ψi=qi/T,qi being the rate of heat flux.
Comparison of the Dynamic Characteristics of Smooth Annular Seals and Damping Seals
Authors: Darden J. M. , Earhart E. M. , Flowers G. T.
Published: July 2002

Annular seals are known to enhance rotordynamic stability margins and minimize vibration response levels in high-speed rotating machinery. Theoretical predictions for the rotordynamic characteristics of annular seals exist but additional experimental data is needed to properly anchor these results. NASA’s Marshall Space Flight Center (MSFC) has developed an annular seal test rig and facility to experimentally characterize axially fed annular seals. Annular seals with deliberately roughened stators (i.e., damping seals) have been shown analytically to increase stability margins of rocket engine turbomachinery by reducing the seal’s whirl frequency ratio. The capabilities of MSFC’s annular seal test rig have been enhanced to allow high fluid inlet preswirl testing that is more representative of actual turbopump seal boundary conditions. The purpose of this paper is to describe the effect of this realistic preswirl on the stabilizing capability of both damping and smooth seals. Centered seal results are presented for both a smooth annular seal and a damping seal. These results were obtained for a range of seal pressure differentials, shaft rotational speeds, and two levels of inlet fluid preswirl.
On the Number and Placement of Accelerometers for Angular Velocity and Acceleration Determination
Authors: Zappa Bruno , Legnani Giovanni , van den Bogert Anton J. , Adamini Riccardo
Published: July 2002

This paper identifies the minimum number of accelerometers necessary to measure rigid body acceleration. Notwithstanding that only 9 scalar unknowns must be identified, 12 devices compose a minimum set of transducers. This redundancy is necessary to avoid singularities in the equations. Conditions for the sensor placement are given. It is also shown that when the determination of the angular velocity is not required, a reduced set of 9 sensors can be adopted.
A Practical Technique to Estimate the Formation Thickness of a Kicking Zone
Authors: Samuel G. Robello , Engler Thomas , Miska Stefan
Published: July 2002

Characterization of formation while drilling continues to be a challenge to the engineers. When a well kicks while drilling, evaluation of pore pressure and the corresponding kill mud density is of critical importance for the safety of the drilling crew and mechanical integrity of the wellbore. Besides the estimation of these parameters, it will be beneficial to estimate the thickness of the kicking formation prior to drilling. This helps to drill safely and carefully through the potentially active kicking formation. In this paper, it is shown how to calculate the thickness of the kicking zone with the limited information available at the time of an oil/gas kick. A method of data analysis (obtained on a kicking well) to estimate the formation thickness of the kicking zone is presented. Illustrative examples including actual field cases are described and analyzed.