bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring the life cycle of cirrus clouds using Meteosat‐4 data during ICE‐1989
Authors: Szantai André , Désalmand Françoise , Desbois Michel
Published: July 2002

During the International Cirrus Experiment (ICE), cirrus cloud properties over the North Sea were observed from local surface‐based and aircraft instruments. In order to place these measurements in the context of the general space‐time evolution of the cirrus systems and smaller cloud elements, Meteosat images were used to study the evolution of the clouds along their trajectories. The trajectories were established with techniques derived from those used to compute cloud motion winds from geostationary satellite images. Thermal infrared (IR) and water vapour (WV) channel tracking was performed to take advantage of the properties of each channel: better contrast of the clouds over the surface in the IR, and better discrimination of upper layers in the WV channel. Although long tracks, up to 60 hours, could be observed, they did not correspond to the same cirrus elements, or even the same system along the track. The evolution of the brightness temperatures along the tracked elements showed periodic fluctuations. The representativeness of these fluctuations in terms of cloud life cycle is discussed, as it may be related to the quality of the tracking. Copyright © 2001 Royal Meteorological Society
Comparison of measured and modelled uv indices for the assessment of health risks
Authors: De Backer Hugo , Koepke Peter , Bais Alkiviadis , de Cabo Xavier , Frei Thomas , Gillotay Didier , Haite Christine , Heikkilä Anu , Kazantzidis Andreas , Koskela Tapani , Kyrö Esko , Lapeta Bozena , Lorente Jeronimo , Masson Kaisa , Mayer Bernhard , Plets Hans , Redondas Alberto , Renaud Anne , Schauberger Gunther , Schmalwieser Alois , Schwander Harry , Vanicek Karel
Published: July 2002

The World Health Organisation (WHO) and the World Meteorological Organisation (WMO) have jointly recommended that the UV Index (UVI) should be used to inform the public about possible health risks due to overexposure to solar radiation, especially skin damage. To test the current operational status of measuring and modelling techniques used in providing the public with UVI information, this article compares cloudless sky UVIs (measured using five instruments at four locations with different latitudes and climate) with the results of 13 models used in UVI forecasting schemes. For the models, only location, total ozone and solar zenith angle were provided as input parameters. In many cases the agreement is acceptable, i.e. less than 0.5 UVI. Larger differences may originate from instrumental errors and shortcomings in the models and their input parameters. A possible explanation for the differences between models is the treatment of the unknown input parameters, especially aerosols. Copyright © 2001 Royal Meteorological Society
A case study using Doppler radar to identify a dry‐air intrusion in frontal cyclogenesis
Authors: Hardaker P J , Collier C G
Published: July 2002

A sequence of Doppler radar observations obtained during the PADRE project is used to identify a region of dry‐air intrusion in a frontal system approaching the Alps. The study demonstrates the potential of Doppler radar to provide additional information to forecasters on fine spatial and temporal characteristics of frontal cyclogenesis. Copyright © 1997 Royal Meteorological Society
Utilising a farm‐level decision model to help prioritise future climate prediction research needs
Authors: Mjelde James W , Thompson Troy N , Nixon Clair J , Lamb Peter J
Published: July 2002

A whole‐farm‐level decision model is used to examine the impact of the type of decisions producers make on the value of seasonal climate forecasts. Results suggest that precipitation forecasts directed towards crop mix and applied nitrogen level decisions would have the largest economic value. Further, the results show that the economic value of climate forecasts cannot be obtained by examining only a small set of decision types. Rather, all decision types must be modelled to value seasonal precipitation forecasts correctly. This occurs because in response to seasonal climate forecasts changes in one type of decision may override the need to change other decision types. Finally, forecasts of precipitation during the crop tasselling and grain filling stages may be more valuable than precipitation forecasts for earlier crop growth periods. Copyright © 1997 Royal Meteorological Society
Observations of sea clutter using an S‐band weather radar
Authors: Collier C G
Published: July 2002

In this paper we review work undertaken on sea clutter illustrated by previously unpublished observations made with an S‐band radar during a research project in South Wales carried out during the winter of 1976/77. The implications for detection with C‐band Doppler radar are considered. Copyright © 1998 Royal Meteorological Society
A fast method for statistical grammar induction
Authors: HOGENHOUT WIDE R. , MATSUMOTO YUJI
Published: July 2002

The statistical induction of stochastic context free grammars
from bracketed corpora with the
Inside Outside Algorithm is an appealing method for grammar learning, but
the computational
complexity of this algorithm has made it impossible to generate a large
scale grammar.
Researchers from natural language processing and speech recognition have
suggested various
methods to reduce the computational complexity and, at the same time, guide
the learning
algorithm towards a solution by, for example, placing constraints on the
grammar. We suggest
a method that strongly reduces that computational cost of the algorithm
without placing
constraints on the grammar. This method can in principle be combined with
any of the
constraints on grammars that have been suggested in earlier studies. We
show that it is
feasible to achieve results equivalent to earlier research, but with much
lower computational
effort. After creating a small grammar, the grammar is incrementally increased
while rules
that have become obsolete are removed at the same time. We explain the
modifications to
the algorithm, give results of experiments and compare these to results
reported in other
publications.
SENSE: an analogy-based Word Sense Disambiguation system
Authors: FEDERICI STEFANO , MONTEMAGNI SIMONETTA , PIRRELLI VITO
Published: July 2002

The paper describes SENSE, a word sense disambiguation system which makes use of
multidimensional analogy-based proportions to infer the most likely sense of a word given
its context. Architecture and functioning of the system are illustrated in detail. Results of
different experimental settings are given, showing that the system, in spite its conservative
bias, successfully copes with the problem of training data sparseness.
They Don't Go Away When You Grow Up
Authors: Mapou Robert L.
Published: July 2002

Attention-deficit hyperactivity disorder (ADHD)
and learning disabilities (LD) are most frequently associated
with childhood. This, of course, is because a child's
job is to sit in a classroom, pay attention, and learn,
and these are disorders that interfere with completing
that job. Because these disorders are presumed due to brain
dysfunction, it should be no surprise that both LD and
ADHD continue to exert effects as children grow, go on
to postsecondary education, and enter the job market. That
is, developmental learning disorders, including LD and
ADHD, do not “go away” when one becomes an
adult. Several research groups have followed children with
LD or ADHD into adulthood and have shown the persistence
of symptoms and cognitive deficits, along with the toll
that these difficulties take on psychosocial functioning,
later academic performance, and vocational advancement.
Into the wilderness within
Authors: SHOGREN JASON F.
Published: July 2002

Levin et al. deliver a sweeping lecture on the state of nature and society. They point out that economic and ecological systems are linked, this linkage is complex, and that in the litany of environmental disasters that awaits us ‘none can be treated by traditional markets, or regulatory policies.’ Markets fail because they do not aggregate information accurately; corrective policies fail too because lobbying efforts serve to polarize rather than galvanize public debate. Policymakers, social planners, and researchers are asked to rethink their typical conduct, and instead focus on the construction of flexible and adaptive institutions that can accommodate the uncertain future in a way that maintains human welfare. Trust and intellectual guidance are the ties that bind a better world to these undefined, but resilient new institutions.
The electroacoustic community
Authors: Landy Leigh
Published: July 2002

The theme chosen for Vol. 2 No 1 of Organized Sound is one which the editors hope will become a thread for future issues. The reader may be curious why this subject has been chosen.
Children of Mothers Admitted to Psychiatric Hospital: Care Arrangements and Mothers' Perceptions
Authors: Cunningham Judi , Oyebode Femi , Vostanis Panos
Published: July 2002

This paper describes the care arrangements made for children when their
mothers are admitted to psychiatric hospital. It also describes at admission,
and at 3 months follow-up, the views and opinions of mothers and carers
with regard to the admission, its impact on the family, and the service
received. It was found that children are predominantly cared for within
their family when their mother is admitted to hospital, and that mothers
and carers are concerned about the impact of the admission and its
associated problems.
Actually, there's more to it than meets the eye
Authors: Taglicht Josef
Published: July 2002

This article presents a reanalysis of the syntax, semantics, pragmatics, and phonology of the word actually. It endeavours to show, among other things, that in addition to the distinction between Greenbaum'’s ‘disjunct’ and his ‘adjunct’, we seem to require here a distinction between two kinds of ‘disjunct’: (i) a ‘propositional modifier’ and (ii) a ‘discourse modifier’ (or ‘discourse transition marker’). An examination of constraints on the use of actually as a propositional modifier suggests the need for a feature ‘assertive/nonassertive’, not just on root sentences but on all structures that denote propositions, whatever their syntactic form.
A novel labeling technique reveals a function for histone H2A/H2B dimer tail domains in chromatin assembly in vivo
Authors: Thiriet Christophe , Hayes Jeffrey J.
Published: July 2002

During S phase in eukaryotes, assembly of chromatin on daughter strands is thought to be coupled to DNA replication. However, conflicting evidence exists concerning the role of the highly conserved core histone tail domains in this process. Here we present a novel in vivo labeling technique that was used to examine the role of the amino-terminal tails of the H2A/H2B dimer in replication-coupled assembly in live cells. Our results show that these domains are dispensable for nuclear import but at least one tail is required for replication-dependent, active assembly of H2A/H2B dimers into chromatin in vivo.
Gene Expression in the Pulp of Ripening Bananas (Two-Dimensional Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis of in Vitro Translation Products and cDNA Cloning of 25 Different Ripening-Related mRNAs)
Authors: Medina-Suarez R. , Manning K. , Fletcher J. , Aked J. , Bird C. R. , Seymour G. B.
Published: July 2002

mRNA was extracted from the pulp and peel of preclimacteric (d 0) bananas (Musa AAA group, cv Grand Nain) and those exposed to ethylene gas for 24 h and stored in air alone for a further 1 (d 2) and 4 d (d 5). Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of in vitro translation products from the pulp and peel of these fruits revealed significant up-regulation of numerous transcripts during ripening. The majority of the changes were initiated by d 2, with the level of these messages increasing during the remainder of the ripening period. Pulp tissue from d 2 was used for the construction of a cDNA library. This library was differentially screened for ripening-related clones using cDNA from d-0 and d-2 pulp by a novel microtiter plate method. In the primary screen 250 up- and down-regulated clones were isolated. Of these, 59 differentially expressed clones were obtained from the secondary screen. All of these cDNAs were partially sequenced and grouped into families after database searches. Twenty-five nonredundant groups of pulp clones were identified. These encoded enzymes were involved in ethylene biosynthesis, respiration, starch metabolism, cell wall degradation, and several other key metabolic events. We describe the analysis of these clones and their possible involvement in ripening.
Fatty Acid Elongation Is Independent of Acyl-Coenzyme A Synthetase Activities in Leek and Brassica napus1
Authors: Hlousek-Radojcic Alenka , Evenson Kimberly J. , Jaworski Jan G. , Post-Beittenmiller Dusty
Published: July 2002

In both animal and plant acyl elongation systems, it has been proposed that fatty acids are first activated to acyl-coenzyme A (CoA) before their elongation, and that the ATP dependence of fatty acid elongation is evidence of acyl-CoA synthetase involvement. However, because CoA is not supplied in standard fatty acid elongation assays, it is not clear if CoA-dependent acyl-CoA synthetase activity can provide levels of acyl-CoAs necessary to support typical rates of fatty acid elongation. Therefore, we examined the role of acyl-CoA synthetase in providing the primer for acyl elongation in leek (Allium porrum L.) epidermal microsomes and Brassica napus L. cv Reston oil bodies. As presented here, fatty acid elongation was independent of CoA and proceeded at maximum rates with CoA-free preparations of malonyl-CoA. We also showed that stearic acid ([1-14C]18:0)-CoA was synthesized from [1-14C]18:0 in the presence of CoA-free malonyl-CoA or acetyl-CoA, and that [1-14C]18:0-CoA synthesis under these conditions was ATP dependent. Furthermore, the appearance of [1-14C]18:0 in the acyl-CoA fraction was simultaneous with its appearance in phosphatidylcholine. These data, together with the results of a previous study (A. Hlousek-Radojcic, H. Imai, J.G. Jaworski [1995] Plant J 8: 803–809) showing that exogenous [14C]acyl-CoAs are diluted by a relatively large endogenous pool before they are elongated, strongly indicated that acyl-CoA synthetase did not play a direct role in fatty acid elongation, and that phosphatidylcholine or another glycerolipid was a more likely source of elongation primers than acyl-CoAs.
Nitrate Transport and Not Photoinhibition Limits Growth of the Freshwater Cyanobacterium Synechococcus Species PCC 6301 at Low Temperature1
Authors: Sakamoto Toshio , Bryant Donald A.
Published: July 2002

The effect of low temperature on cell growth, photosynthesis, photoinhibition, and nitrate assimilation was examined in the cyanobacterium Synechococcus sp. PCC 6301 to determine the factor that limits growth.Synechococcus sp. PCC 6301 grew exponentially between 20°C and 38°C, the growth rate decreased with decreasing temperature, and growth ceased at 15°C. The rate of photosynthetic oxygen evolution decreased more slowly with temperature than the growth rate, and more than 20% of the activity at 38°C remained at 15°C. Oxygen evolution was rapidly inactivated at high light intensity (3 mE m−2 s−1) at 15°C. Little or no loss of oxygen evolution was observed under the normal light intensity (250 μE m−2 s−1) for growth at 15°C. The decrease in the rate of nitrate consumption by cells as a function of temperature was similar to the decrease in the growth rate. Cells could not actively take up nitrate or nitrite at 15°C, although nitrate reductase and nitrite reductase were still active. These data demonstrate that growth at low temperature is not limited by a decrease in the rate of photosynthetic electron transport or by photoinhibition, but that inactivation of the nitrate/nitrite transporter limits growth at low temperature.
Characterization of Plant β-Ureidopropionase and Functional Overexpression in Escherichia coli
Authors: Walsh Terence A. , Green Susan B. , Larrinua Ignacio M. , Schmitzer Paul R.
Published: July 2002

Pyrimidine bases are rapidly catabolized in growing plant tissues. The final enzyme of the catabolic pathway, β-ureidopropionase (β-UP; EC 3.5.1.6), was partially purified from the shoots of etiolated maize (Zea mays) seedlings. The enzyme had aK  m for β-ureidopropionate (the substrate derived from uracil) of 11 μm. Only one enantiomer of racemic β-ureidoisobutyrate (derived from thymine) was processed with a K  m of 6 μm. The enzyme was inactivated by dialysis against 1,10-phenanthroline and activity could be partially restored by addition of Zn2+. Maize β-UP was very sensitive to inactivation by iodoacetamide. This could be prevented by addition of substrate, indicating the presence of an active site Cys. The enzyme was strongly inhibited by short chain aliphatic acids and aryl propionates, the most potent inhibitor of which was 2-(2, 6-dinitrophenoxy)-propionate (I  50 = 0.5 μm). A gene for Arabidopsis β-UP encodes a polypeptide of 405 amino acids and has about 55% homology with the enzymes from other eukaryotic organisms. Several highly conserved residues link the plant β-UP with a larger class of prokaryotic and eukaryotic amidohydrolases. An Arabidopsis cDNA truncated at the N terminus by 14 residues was cloned and overexpressed in Escherichia coli. The recombinant enzyme (43.7 kD) was soluble, functional, and purified to homogeneity with yields of 15 to 20 mg per 30 g fresh weight of E. coli cells. The recombinant enzyme from Arabidopsis and the native enzyme from maize had molecular masses of approximately 440 kD, indicating the enzyme is a decamer at pH 7.
Continuing wing production
Authors: Ford Terry
Published: July 2002

Reviews the evolution of British Aerospace’s wing production facilities at Chester and Filton in the UK and on the design of the wings for the Airbus series of aircraft, from the first set of wings designed for the A300 in 1971 through to the A340‐500 and 600 and the A3XX. Reports on the design of the completely new wing for the A320 which was the first to incorporate fly‐by‐wire and other technologies. Discusses the design of load alleviation for defined manoeuvre and gust cases and the impact of a change in the airworthiness design case requirements on the design of the wing for the A321 and subsequent aircraft. Finally, the article examines the fully automated parts store at the British Aerospace Wing Centre at Filton.
Analysis of protective film formed on surface of mild steel immersed in Chloride ‐ HEDP‐molybdate ‐ Zn2+ environment
Authors: Rajendran S. , Apparao B.V. , Palaniswamy N.
Published: July 2002

The inhibition efficiency of the formulation consisting of 1‐hydroxyethane‐1, 1‐diphosphonic acid (HEDP), molybdate and Zn2+ in controlling the corrosion of mild steel in neutral aqueous environment containing 60ppm Cl‐ has been evaluated by the weight‐loss method. The formulation consisting of 50ppm HEDP, 300ppm molybdate and 10ppm Zn2+ has 97 per cent inhibition efficiency. The nature of the protective film has been analysed by using x‐ray diffraction (XRD), FTIR and fluorescence spectra. The protective film is found to be fluorescent and to consist of Fe2+‐HEDP complex, Fe2(MoO4)3 complex and Zn(OH)2. A suitable mechanism of corrosion inhibition is proposed based on the results obtained from the weight‐loss method, polarisation study, XRD, FTIR, fluorescence and atomic absorption spectra.
First impressions: the power of personal style
Authors: Sampson Eleri
Published: July 2002

Discusses how to replace negative perceptions of librarians with
positive ones. Asks key questions about personal style at work: how do I
come across? How do I behave? How do I sound? What is my image profile?
Who is my audience? Presents a checklist of what is an appropriate image
for a professional and what to avoid. Discusses the five linked elements
of personal perceptions – appearance, body language, communication
style, presence and reputation – and proposes ways to promote a
positive image.
Defect inspection in transparent materials
Authors: Pratt Vanessa , Warner Jay
Published: July 2002

Describes a machine vision system which can be used for the detection of defects in glass ribbon and plastic sheets. Uses a system of multiple line scan CCD cameras and scanned LED light sources to detect and measure defects both along and across the web.
Quick response – ten years later
Authors: Hunter N.A. , Valentino P.
Published: July 2002

In the ten years since its formulation, quick response has made only limited progress despite its well‐demonstrated benefits to the apparel pipeline. Explores the reasons for the delays in implementation and the current state of the art. Examines the steps necessary for further progress in light of likely developments in technology and consumer‐driven retail strategies.
From rationality to reasonableness in environmental administration
Authors: Bartlett Robert V. , Baber Walter F.
Published: July 2002

The administrative state is situated in a physical and ecological context that requires a conceptualisation of rationality broader than the instrumental rationality that characterizes most administrative theorising. Various scholars have contributed to clarifying some aspects of the needed broader conceptualisation, particularly with respect to focuses (system, substance, procedure) and form (social, legal, political, and ecological). But unlike the classical Aristotelian conception of rationality, the goal‐blindness of contemporary rationality still distinguishes it from reasonableness. Rawls and Habermas suggest the recoupling of reasonableness and rationality through political discourse and pursuit of social action that requires reasoning about ends as well as means. The opportunities for deliberative democracy and for furthering environmental justice provided by environmental impact assessment illustrate how rationality, justice, and ecological sustainability can be integrated by breaking down distinctions between decision‐making processes and the substance of decisions. Administration can thus move beyond proverbs to proceed on the realization that the only ecologically rational organization is a broadly reasonable one.
Efficient slicing for layered manufacturing
Authors: Tata Kamesh , Fadel Georges , Bagchi Amit , Aziz Nadim
Published: July 2002

An adaptive slicing algorithm that can vary the layer thickness in relation to local geometry is presented. The algorithm is based on three fundamental concepts: choice of criterion for accommodating complexities of surfaces, recognition of key characteristics and features of the object, and development of a grouping methodology for facets used to represent the object. Four criteria, cusp height, maximum deviation, chord length and volumetric error per unit length, are identified and the layer thickness is adjusted such that one of the four is met. Next, key characteristics of the object, such as horizontal and vertical surfaces, pointed edges and ends, are identified based on the local changes in surface complexity, and slice based feature recognition is introduced to identify the nature of a feature, protrusion or depression, by studying the slice data. Note that the present approach uses information only from the tessellated model, and thus is different from current implementations. Finally, the concept of grouping of the facets based on their vertex coordinates is developed to minimize the number of searches for possible intersection of the facets with a slice plane. The slicing algorithm is interfaced with adaptive laminated machining and the stereolithography process through a CNC post processor and a hatching algorithm respectively. A comparison of the estimated surface quality and build time indicates that adaptive slicing produces superior parts in a shorter build time. The implementation of this work is protected under US Patent laws (Patent # 5,596,504, January 1997).
Bootstrap and Asymptotic Tests of Long‐run Relationships in Cointegrated Systems
Authors: Fachin Stefano
Published: July 2002

Hypothesis testing on cointegrating vectors based on the asymptotic distributions of the test statistics are known to suffer from severe small sample size distortion. In this paper an alternative bootstrap procedure is proposed and evaluated through a Monte Carlo experiment, finding that the Type I errors are close to the nominal signficance levels but power might be not entirely adequate. It is then shown that a combined test based on the outcomes of both the asymptotic and the bootstrap tests will have both correct size and low Type II error, therefore improving the currently available procedures.
Inward rectifier K+ current under physiological cytoplasmic conditions in guinea‐pig cardiac ventricular cells
Authors: Ishihara Keiko , Yan Ding‐Hong , Yamamoto Shintaro , Ehara Tsuguhisa
Published: July 2002

The outward current that flows through the strong inward rectifier K+ (KIR) channel generates IK1, one of the major repolarizing currents of the cardiac action potential. The amplitude and the time dependence of the outward current that flows through KIR channels is determined by its blockage by cytoplasmic cations such as polyamines and Mg2+. Using the conventional whole‐cell recording technique, we recently showed that the outward IK1 can show a time dependence during repolarization due to competition of cytoplasmic particles for blocking KIR channels. We used the amphotericin B perforated patch‐clamp technique to measure the physiological amplitude and time dependence of IK1 during the membrane repolarization of guinea‐pig cardiac ventricular myocytes. In 5.4 mm K+ Tyrode solution, the density of the current consisting mostly of the sustained component of the outward IK1 was about 3.1 A F−1 at around −60 mV. The outward IK1 showed an instantaneous increase followed by a time‐dependent decay (outward IK1 transient) on repolarization to −60 to −20 mV subsequent to a 200 ms depolarizing pulse at +37 mV (a double‐pulse protocol). The amplitudes of the transients were large when a hyperpolarizing pre‐pulse was applied before the double‐pulse protocol, whereas they were small when a depolarizing pre‐pulse was applied. The peak amplitudes of the transients elicited using a hyperpolarizing pre‐pulse were 0.36, 0.63 and 1.01 A F−1, and the decay time constants were 44, 14 and 6 ms, at −24, −35 and −45 mV, respectively. In the current‐clamp experiments, a phase‐plane analysis revealed that application of pre‐pulses changed the current density at the repolarization phase to the extents expected from the changes of the IK1 transient. Our study provides the first evidence that an outward IK1 transient flows during cardiac action potentials.
Closure to “Discussion of ‘The Influence of Technical Surface Roughness Caused by Precision Forging on the Flow Around a Highly Loaded Compressor Cascade’ ” [ASME J. Turbomach., 122, No. 3, p. 424 (2000)]
Authors: Leipold, Robert , Boese, and Matthias , Fottner Leonhard
Published: July 2002

[S0889-504X(00)02103-6]
Chain Reaction From Impact on Coaxial Multibody Systems
Authors: Stronge W. J.
Published: July 2002

In a mechanism or system of “rigid” bodies that are joined or connected by compliant points of contact, an external impact at one point in the system generates a pulse of reaction force that propagates outward successively through neighboring joints or connections. At each point of contact between adjacent bodies, this wave of reaction force is just sufficient to change the relative velocities so that interpenetration of the bodies is prevented; i.e., the reactions enforce the displacement constraints. Each connection has a local wave speed that depends on the contact compliance and the mass of the adjacent bodies. Where the local wave speed is decreasing with “distance” from the external impact, the reaction impulses at neighboring contacts occur sequentially whereas if the local wave speed is increasing substantially with distance, the impulses at neighboring contacts occur simultaneously. Between these limits, the dynamics of impact of multibody systems with compliant contacts depends on coupling between time-dependent contact forces rather than some assumed timing of the resultant impulses. [S0021-8936(00)00903-X]
Creep Relaxation Behavior of High-Energy Piping
Authors: Yee Raymond K. , Cohn Marvin J.
Published: July 2002

The analysis of the elastic stresses in high-energy piping systems is a routine calculation in the power and petrochemical industries. The American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code was developed for safe design and construction of pressure piping. Postconstruction issues, such as stress relaxation effects and selection of maximum expected creep damage locations, are not addressed in the Code. It has been expensive and time consuming to evaluate creep relaxation stresses in high energy piping systems, such as main steam and hot reheat piping. After prolonged operation of high-energy piping systems at elevated temperatures, it is very difficult to evaluate the redistribution of stresses due to dead weight, pressure, external loading, and thermal loading. The evaluation of stress relaxation and redistribution is especially important when nonideal conditions, such as bottomed-out or topped-out hangers, exist in piping systems. This paper uses three-dimensional four-node quadrilateral shell elements in the ABAQUS finite element code to evaluate the time for relaxation and the nominal relaxation stress values for a portion of a typical high-energy piping system subject to an ideally loaded hanger or to an overloaded hanger. The stress relaxation results are evaluated to suggest an approximation using elastic stress analysis results. [S0094-9930(00)01304-4]
Fixturing of Compliant Parts Using a Matrix of Reconfigurable Pins
Authors: Walczyk Daniel F. , Longtin Randy S.
Published: July 2002

Commercially-available reconfigurable fixtures, used for holding compliant sheet metal, composite and plastic parts during secondary machining operations, are extremely expensive and overly-complicated devices. A computer-controlled, reconfigurable fixturing device (RFD) concept for compliant parts, based on a matrix of individually-stoppable pins lowered by a single rigid platen, has been developed as a simple and low-cost design alternative to commercially-available devices. Two different approaches to stopping and clamping individual pins have been investigated: a combination electromagnet assist and gas springs compressed with a toggle mechanism, and a pneumatic clamp. Simple mechanical models have been developed for predicting the stopping and clamping performance of both designs including pin positioning accuracy, vertical load-carrying capacity of a pin, and deflection of a pin subjected to lateral loads. An RFD prototype, consisting of a single pin actuated by a servoed platen, has been designed, built and tested. It has demonstrated the feasibility of this new RFD design. [S1087-1357(00)02204-8]
A Learning Variable Structure Controller of a Flexible One-Link Manipulator
Authors: Cao Wen-Jun , Xu Jian-Xin
Published: July 2002

In this paper, tip regulation of a flexible one-link manipulator by Learning Variable Structure Control (LVSC) is investigated. Switching surface is designed according to a selected reference model which relocates system poles to be negative real ones, hence link vibration is eliminated. The proposed LVSC incorporates a learning mechanism to improve regulation accuracy. Rigorous proof shows: the tracking error sequence converges uniformly to zero; the uniformly bounded learning control sequence converges to the equivalent control almost everywhere. For practical considerations, the learning mechanism is further conducted in frequency domain by means of Fourier series expansion, hence achieves better regulation performance. Numerical simulations confirm the effectiveness and robustness of the proposed approach. [S0022-0434(00)01804-9]
Determination of Propane and Air Maximum Mixing Times
Authors: Brasoveanu D. , Gupta A. K.
Published: July 2002

The model of gaseous fuel and air mixing, developed by the authors, is applied here to calculate maximum mixing times of propane and air. The degree of mixing is determined using the mass fraction of fuel while the rate of mixing is determined from the rate of this mass fraction. The values of both these parameters are local, i.e., measured within an infinitesimal element of fluid. A Eulerian representation is used. The model is based on the assumption that both fuel and air behave as a single chemical species. It is further assumed that pressure is low and only fuel and air are present within the fluid element. Under nonreacting conditions, the model is valid anywhere in the combustor. Under reacting conditions, the model is valid within those combustor regions where the fuel–air mixture is not flammable. The results of this analysis show that mixing times of propane and air are most reduced by high gradients of temperature and velocity, as long as these gradients provide in phase contribution. To a lesser degree, high gradients of pressure also help reduce mixing times. High initial pressure and temperature increase mixing time. Mixing with air penetration into the fuel flow is slower than with propane dispersion into the surrounding air. In general, the exact mixing time has to be determined numerically. Nevertheless, the analytical solutions included here provide maximum mixing times of propane and air under most conditions. These results provide important guidelines for the development of high intensity, high efficiency, and low emission combustors.
Linear Stability of Mixed Convection Flow of Two Immiscible Fluids in a Vertical Annulus
Authors: Chang Kai-Ti R. , Chen Kang Ping
Published: July 2002

Linear stability of two immiscible liquids driven by a constant pressure gradient through a long vertical annulus in the gravitational field is investigated. If viscosity depends on temperature, it is found that thermal conductivity stratification can induce an interfacial instability, which is different from the instability identified by Yih (1986). The effect of temperature-dependent viscosity on various unstable modes and mode competitions are studied.
Dynamic Subgrid-Scale Modeling for Large-Eddy Simulations in Complex Topologies
Authors: Jordan Stephen A.
Published: July 2002

The dynamic eddy-viscosity relationship is a suitable choice for modeling the subgrid-scales (SGS) in a large-eddy simulation (LES) of complex turbulent flows in irregular domains. This algebraic relationship is easy to implement and its dynamic coefficient will give negligible turbulent viscosity contributions in the flow regions that are irrotational or laminar. Its fine-scale turbulence predictions can be qualitatively reasonable if the local grid resolution maintains the SGS field predominantly within the equilibrium range of turbulent energy spectra. This performance is given herein by two curvilinear coordinate forms of the dynamic Smagorinsky model that are formally derived and a-priori tested using the resolved physics of the cylinder wake. The conservative form evaluates the dynamic coefficient in the computational (transformed) space whereas its non-conservative counterpart operates in the physical domain. Although both forms equally captured the real normal SGS stress reasonably well, the real shear stress and dissipation rates were severely under-predicted. Mixing the eddy-viscosity choice with a scale-similarity model can ease this latter deficiency.
Time Periodic Control of a Bladed Disk Assembly Using Shaft Based Actuation
Authors: Sza´sz and Gyo¨rgy , Flowers George T.
Published: July 2002

For a tuned or symmetrically mistuned bladed disk assembly, several vibration modes are coupled only to the axial dynamics, which forces controllers to rely on an axial actuator. A control strategy based upon deliberately mistuning in a nonsymmetric manner, which results in a time periodic dynamical system, is developed. The method presented does not require an active thrust bearing for complete controllability of a bladed disk assembly via hub based actuators.
Effects of Prestrain on Fracture Toughness and Fatigue-Crack Growth of Line Pipe Steels
Authors: Hagiwara Naoto , Masuda Tomoki , Oguchi Noritake
Published: July 2002

Crack-tip-opening displacement (CTOD) and fatigue-crack growth tests were conducted for several line pipe steels with uniaxial tensile or compressive prestrain, εpr. Critical CTOD decreased with increasing |εpr|. The reduction of critical CTOD due to prestrain was dependent on the ductile-brittle transition temperature of the steels without prestrain. A few percent of εpr induced the ductile-brittle transition for the steels with a higher transition temperature. The compressive εpr had larger effects on both reduction of critical CTOD and strain induced ductile-brittle transition than the tensile εpr. Only the high compressive εpr accelerated both fatigue crack initiation and growth, and no obvious effect of the tensile εpr on the fatigue properties was observed.
An Investigation on Underwater Explosive Bonding Process
Authors: Iyama Hirofumi , Kira Akio , Fujita Masahiro , Kubota Shiro , Hokamoto Kazuyuki , Itoh Shigeru
Published: July 2002

In this paper, we propose a new explosive bonding method for bonding materials by using the underwater shock wave from the explosion of explosives in water. This method is especially suitable to bond the materials with thin thickness and largely dissimilar property. In bonding those materials, the shock pressure and the moving velocity of shock wave on the flyer plate should be precisely managed to achieve an optimum bonding conditions. In this method, the bonding conditions can be controlled by varying of the space distance between the explosive and the flyer plate or by inclining the explosive charge with the flyer plate. We made the experiment of this technique bond the amorphous film with the steel plate. A satisfactory result was gained. At the same time, numerical analysis was performed to investigate the bonding conditions. The calculated deformation of the flyer plate by the action of underwater shock wave was compared with the experimental recordings by high-speed camera under the same conditions. The comparison shows that the numerical analysis is of good reliability on the prediction of the experimental result. Furthermore, the numerical simulation also gives the deformations of the flyer and the base plate, and the pressure and its variation during the collision process.
Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk
Authors: Glahn A. , Busam S. , Blair M. F. , Allard K. L. , Wittig S.
Published: July 2002

A fundamental study has been performed to examine oil film disintegration mechanisms at the rim of a rotating disk. The configuration investigated is an abstraction of one of the droplet generation sources in an aeroengine bearing compartment. The paper aims to contribute to both the determination of directly applicable droplet characteristics and the establishment of a database that can be used for the development of droplet generation models. The near-term objectives of the study are (i) to identify disintegration modes relevant with respect to aeroengine bearing compartment operating conditions, (ii) to determine droplet sizes under those operating conditions, and (iii) to measure individual droplet diameter/velocity relationships. The long-term objective is to incorporate this information into advanced CFD-based design tools. The disintegration modes identified here were similar to previously reported flow regimes generated by rotary atomizers. However, slightly different transition characteristics are documented for the turbine oil considered here, indicating a transition occurring at either higher speeds or higher flow rates. Droplet diameters and velocities are presented for relevant bearing compartment conditions. In this mode, droplet diameters appear to be insensitive to the volume flow rate, but show a finer atomization for increasing rotational speeds. Eventually a speed is reached beyond which no further droplet diameter reduction is obtained. For the first time, size class resolved droplet velocities are presented. A variation of operating parameters at a constant radial location does not have a significant impact on either the normalized droplet velocity or the flow angle. Radial traverses show a decrease of the droplet velocity with increasing distance from the rim of the disk and a transition from a more tangentially oriented droplet trajectory to a more radial motion.
Model Based Damage Identification Using Output Spectral Densities
Authors: Nauerz A. , Fritzen C.-P.
Published: July 2002

A damage identification method utilizing an existing computational model and output spectral densities is presented. The problem covered here is the detection, localization and quantification of damage in real vibrating elastomechanical structures. The damages are localized by means of changes in the dynamic characteristics between a reference model and the actual, measured system. The main contribution is that the exact measurement of the input signals is ignored. These signals are assumed to be an ergodic random process, whose statistical properties such as mean and covariances must be estimated. Power spectral densities allow random excitations to be dealt with. The lack of measurement information is treated by means of the dynamic condensation technique and the Kalman Bucy filter technique. In the first case the size of the model matrices are reduced to the number of measured degrees of freedom (dof). In the second procedure the measured responses are expanded to the size of the model matrices. With equally sized measurement and model matrices a linear equation system for the desired parameter changes is derived by using the sensitivity approach. The equation system for this inverse problem is usually ill-conditioned and must be regularized in some way. One possibility is to reduce the subset of parameters to be in error. The algorithm is applied to a beam structure and a measured laboratory structure, a multi story frame, in which artificial damage is introduced by weakening one column between two stories. So, it is shown that the location and the size of the corresponding stiffness decrease can be detected.
Dislocation Structure and Crystallite Size Distribution in Plastically Deformed Metals Determined by Diffraction Peak Profile Analysis
Authors: Unga´r T. , Riba´rik G. , Gubicza J. , Hana´k P.
Published: July 2002

The dislocation densities and arrangement parameters and the crystallite size and size-distributions are determined in tensile or cyclically deformed polycrystalline copper specimens by X-ray diffraction peak profile analysis. The Fourier coefficients of profiles measured by a special high resolution X-ray diffractometer with negligible instrumental broadening have been fitted by the Fourier transforms of ab-initio size and strain profiles. It is found that in the fatigued samples the dislocations are mainly of edge type with strong dipole character. In the fatigued specimens the dislocation densities are found to be larger than in the tensile deformed samples when the saturation and flow stress levels are the same.
A Combined Cycle of Heating and Adsorption Refrigeration: Theory and Experiment
Authors: Wang R. Z. , Li M. , Xu Y. X. , Wu J. Y. , Shou H. B.
Published: July 2002

A combined cycle capable of heating and adsorption refrigeration is proposed, and the experimental prototype has been installed. The system consists of a heater, a water bath, an activated carbon-methanol adsorption bed and an ice box. This system has been tested with electric heating, and has been found that with 61 MJ heating, the 120 kg water in the bath can be heated from 22°C to 92°C, of while 9 kg ice at −1.5°C is made. The calculated COPsystem is 0.0591 and COPcycle is 0.41. After reconstruction to a real hybrid household water heater-refrigerator, when 55 MJ heating is added to 120 kg of 21°C water, and the condensing temperature is controlled at about 30°C, the result is the 4 kg water contained inside the methanol refrigerant evaporator was iced to −2°C, the cooling capacity of the ice and the refrigerant in the evaporator will maintain the 100 liter cold box for about three days below 5°C. The experiments show the potential of the application of the solar powered hybrid water heater and refrigerator. Theoretical simulation has been done, which is in good agreement with experimental results. This research shows that the hybrid solar water heating and ice-making is reasonable, and the combined cycle of heating and cooling is meaningful for real applications of adsorption systems.
LDA-Measurements of Transitional Flows Induced by a Square Rib
Authors: Becker S. , Stoots C. M. , Condie K. G. , Durst F. , McEligot D. M.
Published: July 2002

New fundamental measurements are presented for the transition process in flat plate boundary layers downstream of two-dimensional square ribs. By use of laser Doppler anemometry (LDA) and a large Matched-Index-of-Refraction (MIR) flow system, data for wall-normal fluctuations and Reynolds stresses were obtained in the near wall region to y+<0.1 in addition to the usual mean streamwise velocity component and its fluctuation. By varying velocity and rib height, the experiment investigated the following range of conditions: k+=5.5 to 21, 0.3<k/δ1<1,180<Rek<740,6×104<Rex,k<1.5×105,ReΘ660,−125<x−xk/k<580. Consequently, results covered boundary layers which retained their laminar characteristics through those where a turbulent boundary layer was established shortly after reattachment beyond the forcing rib. For “large” elements, evolution of turbulent statistics of the viscous layer for a turbulent boundary layer y+<∼30 was rapid even in flows where the mean velocity profile still showed laminar behavior.
Nonlinearity and Feedback Compensation Method in a Pneumatic Vibration Generator
Authors: Kuz´niewski B.
Published: July 2002

The paper presents a model of a pneumatic piston unit and analyzes dynamic processes taking place in the unit generating periodic signals. Nonlinearities and feedback occurring in flow and vibration processes are determined. A method of nonlinearity and feedback compensation by input parameters of air streams is presented. [S0022-0434(00)00201-X]
Microstructural Features Resulting From Isothermal and Thermocyclic Exposure of a Thermal Barrier Coating
Authors: Walter Mark E. , Onipede Bolarinwa , Soboyejo Wole , Mercer Chris
Published: July 2002

Thermal barrier coating (TBC) systems are receiving a great deal of attention as a result of their ability to enable higher operating temperatures without sacrificing component durability in gas turbine systems. Nonetheless, there are a number of unknowns associated with the failure of TBC systems. In particular, the initiation and propagation of damage has not been observed. In this paper, the microstructural changes in and along the thermally growth oxide layer of a TBC are presented. Specimens were studied primarily after isothermal exposure for 48, 96, 200, and 300 hours at 1100°C and also after thermocyclic exposure. Failure features are discussed and the growth of oxide is quantified. The oxide growth is placed within the context of a parabolic growth model. [S0094-4289(00)01503-6]