bluuebunny/crossref_metadata_2025 huggingface dataset:
The Involvement of a Cysteine Proteinase in the Nodule Development in Chinese Milk Vetch Infected with Mesorhizobium huakuii subsp. rengei
Authors: Naito Yuki , Fujie Makoto , Usami Shoji , Murooka Yoshikatsu , Yamada Takashi
Published: July 2002

Cys proteinases play important roles in plant cell development and senescence. A cDNA, AsNODf32, obtained by differential screening of a nodule cDNA library of the leguminous plant Chinese milk vetch (Astragalus sinicus), represents a nodule-specific Cys proteinase similar to that reported for the actinorhizal Alnus glutinosa-Flankia symbiosis. A characteristic feature of this proteinase is the presence of a putative vacuolar targetting signal, LQDA, within its propeptide. Expression of the AsNODf32 gene, which was studied on northern blots and in situ hybridization, showed good correlation with the onset of nodule senescence. In situ hybridization studies revealed thatAsNODf32 was expressed in senescent-infected tissue at the base of the nodule, as well as in interzone II-III of the infected nodules. In addition to degrading old nodule tissues and bacteroids, AsNODf32 protein may be required as a component of tissue remodeling during nodule development.
Diversity of appraisal and performance‐related pay practices in higher education
Authors: Shelley Steve
Published: July 2002

This paper discusses the use of appraisal and performance‐related pay practices for academic staff in higher education in the UK. This discussion is based on the reports of heads of personnel in universities, with the aim of portraying the pattern of such practices across the sector as a whole, and of investigating the extent to which these activities parallel institutional characteristics and are part of a strategic approach to employment management. It finds some evidence for a continued binary divide in practice between pre‐1992 and post‐1992 universities, but also a great diversity of practice which can support a convergence thesis for the sector. The paper concludes that such diversity may have a place within the requirements of the higher education system, but it may need to be managed in a more proactive and strategic way in the future.
Robots for the dangerous tasks
Authors: Hollingum Jack
Published: July 2002

Last December a meeting of the SILVER Robotics Special Interest Group was held at the Land Systems Section of DERA at Chertsey, UK, and addressed the subject of robotics in military and explosive ordnance disposal (EOD) applications. Presentations speculated on the future of intelligent vehicles; battlefield engineering and robotics; the RAVEN explosive ordnance disposal system; stereo vision and virtual reality for robotics; and three papers on explosive ordnance disposal. During the lunch break there was a demonstration of some of the systems reviewed at the meeting.
Combating humidity ‐ the hidden enemy in manufacturing
Authors: Bracken Ernest
Published: July 2002

Explains the problems, often unrecognized by engineers, which can be caused by excessive humidity in manufacturing, and identifies the confusion surrounding the measurement of humidity, which may account for the low level of recognition. Reports on the measures being taken to eliminate that confusion and some of the instruments currently available to measure humidity. Outlines the main technologies available to correct excess humidity and their qualities.
Reform of UK local government domestic property taxes
Authors: Plimmer Frances , McCluskey W.J. , Connellan Owen
Published: July 2002

The importance of local government within the UK has never been stronger, and this has direct implications as to the most appropriate method of financing this level of government. The council tax in Great Britain and traditional domestic rates in Northern Ireland represent the two primary sources of local government finance based on domestic property, which currently require significant reform. Weaknesses of the existing systems include the lack of buoyancy due to infrequent revaluations, horizontal and vertical inequities and the need to ensure that domestic property tax systems are seen to be fair. The paper makes a number of important recommendations which would enhance the acceptability and ultimately improve the operation of these forms of ad valorem taxation.
An implementation of mixed enhanced finite elements with strains assumed in Cartesian and natural element coordinates using sparse B (overline)‐matrices
Authors: Piltner R.
Published: July 2002

The use of enhanced strains leads to an improved performance of low order finite elements. A modified Hu‐Washizu variational formulation with orthogonal stress and strain functions is considered. The use of orthogonal functions leads to a formulation with B (overline) ‐strain matrices which avoids numerical inversion of matrices. Depending on the choice of the stress and strain functions in Cartesian or natural element coordinates one can recover, for example, the hybrid stress element P‐S of Pian‐Sumihara or the Trefftz‐type element QE2 of Piltner and Taylor. With the mixed formulation discussed in this paper a simple extension of the high precision elements P‐S and QE2 to general non‐linear problems is possible, since the final computer implementation of the mixed element is very similar to the implementation of a displacement element. Instead of sparse B‐matrices, sparse B (overline) ‐matrices are used and the typical matrix inversions of hybrid and mixed methods can be avoided. The two most efficient four‐node B (overline) ‐elements for plane strain and plane stress in this study are denoted B (overline)(x, y)‐QE4 and B (overline)(ξ, η)‐QE4.
Object oriented programming via Fortran 90
Authors: Akin J.E.
Published: July 2002

There is a widely available object oriented (OO) programming language that is usually overlooked in the OO analysis, OO design, OO programming literature. It was designed with most of the features of languages like C++, Eiffel, and Smalltalk. It has extensive and efficient numerical abilities including concise array and matrix handling, like Matlab®. In addition, it is readily extended to massively parallel machines and is backed by an international ISO and ANSI standard. The language is Fortran 90 (and Fortran 95). When the explosion of books and articles on OOP began appearing in the early 1990s many of them correctly disparaged Fortran 77 (F77) for its lack of object oriented abilities and data structures. However, then and now many authors fail to realize that the then new Fortran 90 (F90) standard established a well‐planned object oriented programming language while maintaining a full backward compatibility with the old F77 standard. F90 offers strong typing, encapsulation, inheritance, multiple inheritance, polymorphism, and other features important to object oriented programming. This paper will illustrate several of these features that are important to engineering computation using OOP.
Numerical simulation of induction hardening of steel
Authors: Fuhrmann Jürgen , Hömberg Dietmar , Uhle Manfred
Published: July 2002

We discuss a model that is capable of describing the process of induction hardening of steel: induction heating – heat transfer – solid‐solid phase transitions in steel. It consists of a reduced system of Maxwell’s equations, the heat transfer eqaution and a system of ordinary differential equations for the volume fractions of the occuring phases. The model is applied to simulate surface heat treatments, which play an important role in the manufacturing of steel. The numerical methods are implemented with tools from pdelib, a collection of modular algorithms. We present numerical simulations of surface hardening applied to the steel 42 CrMo 4.
Formulation and experiments with high‐order compact schemes for nonuniform grids
Authors: Spotz W.F.
Published: July 2002

Considers the extension of a new class of higher‐order compact methods to nonuniform grids and examines the effect of pollution that arises with differencing the associated metric coefficients. Numerical studies for the standard model convection diffusion equation in 1D and 2D are carried out to validate the convergence behaviour and demonstrate the high‐order accuracy.
Numerical study of early stages of an impulsively started unsteady laminar flow past expanded trapezoidal cylinders
Authors: Lee T.S.
Published: July 2002

Characteristics of the development of an impulsively started flow around an expanded trapezoidal cylinder were studied numerically. A stream function‐vorticity formulation in a body coordinate system was used to describe the unsteady flow field. The inflow Reynolds number considered ranges from 25 to 1,000. Pressure contours, surface pressure coefficient and drag coefficient were studied through the streamline flow field. Main‐flow and sub‐flow regimes are identified through an analysis of the evolution of the flow characteristics. Typically, for a given expanded trapezoidal cylinder, it is noted that flow starts with minimum separation at the aft end. As time advances, symmetrical standing zone of recirculation develops aft of the cylinder. The rate of growth in width, length and structure of the aft end eddies depends on the Reynolds number. As time advances and at higher Reynolds numbers, separated flow from the leading edges of the trapezoidal cylinder develops along the upper and lower inclined surfaces of the trapezoidal cylinder. The separation bubbles on the upper and lower inclined surfaces of the cylinder grow towards the downstream regions with time and eventually merge with the swelling symmetrical eddies aft of the cylinder. This merging of the flows created a complex flow regime with a disturbed tertiary flow zone near the merging junction. For the flows considered here, eventually, depending on the Reynolds number and the expanded angle of the trapezoidal cylinder, the flow field develops into a specific category of symmetrical standing recirculatory flow with its own distinct characteristics.
Academic regulation in UK higher education: part II ‐ typologies and frameworks for discourse and strategic change
Authors: Jackson Norman
Published: July 2002

The second of three linked articles which explore the dimensions of academic regulation in UK higher education. Provides a series of typologies and conceptual frameworks to aid understanding and facilitate discourse over the most appropriate strategic direction for change. Argues that the challenge is to devise a regulatory regime which is in balance with competing demands and interests in contemporary HE and which will achieve the maximum benefits, in those areas deemed to be most essential to the maintenance and improvement of the quality and standards of learning. Considers that the accountability function of the present regulatory regime has been largely accomplished through compliance with externally defined requirements and expectations. Concludes that the greatest benefits to higher education and the society it serves are to be derived from a regulatory regime which is based on the principle of partnership and which has a strong developmental focus.
New models for the management of public key infrastructure and root certification authorities
Authors: Wilson Stephen
Published: July 2002

Public key infrastructure (PKI) has been discussed for some time but has yet to command much attention from business or policy makers. The benefits of chaining certificate authorities (CA) together have not been obvious and confusion has reigned over the proper role of government. But a new PKI model emphasises control and audit, so that certificates may be issued to different user groups under their own rules, with external assurance of fitness for purpose. This type of model is supported by existing standards certification and accreditation processes. No special new authorities are needed and complex cross‐certification protocols are avoided. Other advantages of an accreditation‐based PKI include a non‐government peak authority, an opt‐in, bottom‐up growth path, easily understood business language for all the elements of the PKI, and clarification of the legal liability of all CAs, in particular the peak authority.
Issues in library development for Vietnam
Authors: Lam Vinh‐The
Published: July 2002

As a South‐East Asian country developing a market economy, Vietnam needs a solid information infrastructure. Library developments will play an important part in this regard. This paper discusses issues relating to library infrastructure development. First, standardisation is recommended in the organisation of information. Then courses are suggested for Vietnamese library schools to adopt in their curricula. Finally the role of a proposed Vietnamese Library Association is discussed.
Talking their language
Authors: Ryder‐Smith Jocelyn
Published: July 2002

Good communication is crucial for effective team working. A failure to understand and value personal differences in style and approach often blocks good communication and leads to unnecessary team conflict. The article outlines key elements of a framework for understanding different personalities and priorities in a way which enables team members to recognise profound difference and its value and to “talk each other’s language” to unblock sticking points and conflict. The article recognises we all use all the ways of working but have preferences among them. It describes first those who prefer to work with logic and practicality; second, those primarily interested in relationships and practicalities; third, those focusing first on logical options, and fourth, people who care most about vision and values for people. Understanding and working with these differences enables better communication and better decisions.
Using rapid prototyping to produce electrical discharge machining electrodes
Authors: Arthur Alan , Dickens Phillip Michael , Cobb Richard Charles
Published: July 2002

Presents the background to and efforts being made to find a direct production route using rapid prototype (RP) parts as the electrodes for electrical discharge machining (EDM). It would have the double effect of unlocking the potential of the EDM die sinking process and expanding the role of RP in the production environment. Thin coated stereolithography (SL) models have been used to erode hardened tool steel to a depth of 4mm. Machining efficiency of these copper coated RP models is not comparable to that of conventional machined solid copper electrodes. Parametric optimization has been applied, achieving substantial improvements in machining efficiency. At present these electrodes are suitable for semi‐roughing or finishing cuts in EDM die sinking. Electroforming copper into SL cavities shows potential for manufacture of electrodes with comparable performance to that of solid copper.
Roles of dimerization in folding and stability of ketosteroid isomerase from Pseudomonas putida biotype B
Authors: Kim Do‐Hyung , Nam Gyu Hyun , Jang Do Soo , Yun Sunggoo , Choi Gildon , Lee Hee Cheon , Choi Kwan Yong
Published: July 2002

Equilibrium and kinetic analyses have been performed to elucidate the roles of dimerization in folding and stability of KSI from Pseudomonas putida biotype B. Folding was reversible in secondary and tertiary structures as well as in activity. Equilibrium unfolding transition, as monitored by fluorescence and ellipticity measurements, could be modeled by a two‐state mechanism without thermodynamically stable intermediates. Consistent with the two‐state model, one dimensional (1D) NMR spectra and gel‐filtration chromatography analysis did not show any evidence for a folded monomeric intermediate. Interestingly enough, Cys 81 located at the dimeric interface was modified by DTNB before unfolding. This inconsistent result might be explained by increased dynamic motion of the interface residues in the presence of urea to expose Cys 81 more frequently without the dimer dissociation. The refolding process, as monitored by fluorescence change, could best be described by five kinetic phases, in which the second phase was a bimolecular step. Because <30% of the total fluorescence change occurred during the first step, most of the native tertiary structure may be driven to form by the bimolecular step. During the refolding process, negative ellipticity at 225 nm increased very fast within 80 msec to account for >80% of the total amplitude. This result suggests that the protein folds into a monomer containing most of the α‐helical structures before dimerization. Monitoring the enzyme activity during the refolding process could estimate the activity of the monomer that is not fully active. Together, these results stress the importance of dimerization in the formation and maintenance of the functional native tertiary structure.
Stabilizing interactions in the dimer interface of α‐subunit in Escherichia coli RNA polymerase: A graph spectral and point mutation study
Authors: Kannan Natarajan , Chander Preethi , Ghosh Pallavi , Vishveshwara Saraswathi , Chatterji Dipankar
Published: July 2002

The formation of α2 dimer in Escherichia coli core RNA polymerase (RNAP) is thought to be the first step toward the assembly of the functional enzyme. A large number of evidences indicate that the α‐subunit dimerizes through its N‐terminal domain (NTD). The crystal structures of the α‐subunit NTD and that of a homologous Thermus aquaticus core RNAP are known. To identify the stabilizing interactions in the dimer interface of the α‐NTD of E. coli RNAP, we identified side‐chain clusters by using the crystal structure coordinates of E. coli α‐NTD. A graph spectral algorithm was used to identify side‐chain clusters. This algorithm considers the global nonbonded side‐chain interactions of the residues for the clustering procedure and is unique in identifying residues that make the largest number of interactions among the residues that form clusters in a very quantitative way. By using this algorithm, a nine‐residue cluster consisting of polar and hydrophobic residues was identified in the subunit interface adjacent to the hydrophobic core. The residues forming the cluster are relatively rigid regions of the interface, as measured by the thermal factors of the residues. Most of the cluster residues in the E. coli enzyme were topologically and sequentially conserved in the T. aquaticus RNAP crystal structure. Residues 35F and 46I were predicted to be important in the stability of the α‐dimer interface, with 35F forming the center of the cluster. The predictions were tested by isolating single‐point mutants α‐F35A and α‐I46S on the dimer interface, which were found to disrupt dimerization. Thus, the identified cluster at the edge of the dimer interface seems to be a vital component in stabilizing the α‐NTD.
Effect of polymorphisms on ligand binding by mouse major urinary proteins
Authors: Darwish Marie Amr , Veggerby Christina , Robertson Duncan H.L. , Gaskell Simon J. , Hubbard Simon J. , Martinsen Line , Hurst Jane L. , Beynon Robert J.
Published: July 2002

Mouse urine contains an abundance of major urinary proteins, lipocalins, whose roles include slow release of semiochemicals. These proteins are highly polymorphic, with small sequence differences between individual members. In this study, we purified to homogeneity four of these proteins from two strains of inbred mice and characterized them by mass spectrometry. This analysis has led to the discovery of another variant in this group of proteins. Three of the polymorphic variants that map to the surface have no effect on the binding of a fluorescent probe in the binding cavity, but the fourth, characterized by a Phe to Val substitution in the cavity, shows a substantially lower affinity and fluorescence yield for the probe. These results are interpreted in light of the known crystal structure of the protein and molecular modeling calculations, which rationalize the experimental findings. This work raises the possibility that the calyx‐binding site can show specificity for different ligands, the implications of which on pheromone binding and chemical communication are discussed.
Thermal and urea‐induced unfolding in T7 RNA polymerase: Calorimetry, circular dichroism and fluorescence study
Authors: Griko Yuri , Sreerama Narasimha , Osumi‐Davis Patricia , Woody Robert W. , Woody A‐Young Moon
Published: July 2002

Structural changes in T7 RNA polymerase (T7RNAP) induced by temperature and urea have been studied over a wide range of conditions to obtain information about the structural organization and the stability of the enzyme. T7RNAP is a large monomeric enzyme (99 kD). Calorimetric studies of the thermal transitions in T7RNAP show that the enzyme consists of three cooperative units that may be regarded as structural domains. Interactions between these structural domains and their stability strongly depend on solvent conditions. The unfolding of T7RNAP under different solvent conditions induces a highly stable intermediate state that lacks specific tertiary interactions, contains a significant amount of residual secondary structure, and undergoes further cooperative unfolding at high urea concentrations. Circular dichroism (CD) studies show that thermal unfolding leads to an intermediate state that has increased β‐sheet and reduced α‐helix content relative to the native state. Urea‐induced unfolding at 25°C reveals a two‐step process. The first transition centered near 3 M urea leads to a plateau from 3.5 to 5.0 M urea, followed by a second transition centered near 6.5 M urea. The CD spectrum of the enzyme in the plateau region, which is similar to that of the enzyme thermally unfolded in the absence of urea, shows little temperature dependence from 15° to 60°C. The second transition leads to a mixture of poly(Pro)II and unordered conformations. As the temperature increases, the ellipticity at 222 nm becomes more negative because of conversion of poly(Pro)II to the unordered conformation. Near‐ultraviolet CD spectra at 25°C at varying concentrations of urea are consistent with this picture. Both thermal and urea denaturation are irreversible, presumably because of processes that follow unfolding.
Volatility Estimation with Price Quanta
Authors: Rogers L. C. G.
Published: July 2002

Volatility estimators based on high, low, opening and closing prices have been developed, and perform well on simulated data, but on real data they frequently give lower values for volatility than the simple open–close estimator. This may be due to the fact that for real data, the maximum (or minimum) price is often at the beginning or end of the day. While this could not happen if the observed process was log Brownian, it could happen if the observed process were log Brownian, but observed only to the nearest penny. We develop the theory of such approximations to derive the corrected versions of the basic estimators.
Differential ontogeny of GABABreceptor‐mediated pre‐ and postsynaptic modulation of GABA and glycine transmission in respiratory rhythm‐generating network in mouse
Authors: Zhang W. , Barnbrock A. , Gajic S. , Pfeiffer A. , Ritter B.
Published: July 2002

Rhythm generation in mature respiratory networks is influenced strongly by synaptic inhibition. In early neonates, GABAA‐receptor‐ and glycine‐receptor‐mediated inhibition is not present, thus the question arises as to whether GABAB‐receptor‐mediated inhibition plays an important role. Using brainstem slices of neonatal mice (postnatal day, P0‐P15), we analysed the role of GABAB‐mediated modulation of GABA and glycine synaptic transmission in the respiratory network. Blockade of GABA uptake by nipecotic acid (0.25–2 mm) reduced the respiratory frequency. This reduction was prevented by the selective GABAB receptor antagonist CGP55845A (CGP) alone at P0‐P3, but by bicuculline as well as CGP at P7‐P15. Blockade of GABAB receptors by CGP increased the respiratory frequency at P0‐P3, whereas it caused a reduction of frequency in older animals. The effect of CGP on respiratory frequency was diminished in the presence of bicuculline and strychnine in older but not in younger animals. The relative contribution of GABAB‐receptor‐mediated pre‐ and postsynaptic modulation was examined by analysing the effect of GABAB receptors on spontaneous and miniature IPSCs. In younger animals (P0‐P3), the GABAB receptor agonist baclofen had no detectable effect on IPSC frequency, but caused a significant decrease in the amplitude. In older animals (P7‐P15), baclofen decreased both the frequency and amplitude of spontaneous and miniature IPSCs. These results demonstrate that GABAB‐receptor‐mediated postsynaptic modulation plays an important role in the respiratory network from P0 on. GABAB‐receptor‐mediated presynaptic modulation develops with a longer postnatal latency, and becomes predominant within the first postnatal week.
Central regulation of cerebellar climbing fibre input during motor learning
Authors: Apps Richard , Lee Stephen
Published: July 2002

A forelimb‐withdrawal classical conditioning paradigm was used in awake cats (n= 4) to investigate changes in transmission in climbing fibre (CF) pathways during motor learning. The conditioned stimulus was an auditory tone, while the unconditioned stimulus was a low‐intensity, single or double (0.1 ms) electrical pulse applied to the ipsilateral superficial radial nerve. Microwires chronically implanted into the paravermal cerebellar cortex (lobule V) were used to record the CF field potentials evoked by nerve stimulation, and fields at 22 recording sites (9 C1, 7 C2 and 6 C3 zone sites) were monitored during the complete sequence of at least one training run (i.e. over a period of about 2‐3 weeks of conditioning). At 19 sites (86 %) conditioning led to a significant reduction in mean size of field. Similar reductions occurred at four sites studied over two successive training runs. At 10 sites (45 %) there was a statistically significant increase prior to the reduction. The three sites that failed to exhibit a significant reduction were all located in the C1 zone. Controls showed that the changes in CF transmission were dependent on the animal being conditioned. The mean size of CF field for trials in which a conditioned EMG response was present (in either the cleidobrachialis or biceps muscle) was not significantly different from the mean size for trials in which a conditioned response was absent. Similarly, on a trial‐by‐trial basis, CF pathway excitability was not correlated with the conditioned EMG activity in the flexor muscles under study. Overall, the results demonstrate that (1) the capacity of spino‐olivocerebellar pathways (SOCPs) to forward information to the cerebellar cortex can be altered by recent experience, (2) establishment of a conditioned forelimb flexor reflex to a tone reduces SOCP excitability at most but not all sites within a forelimb‐related region of the cerebellar cortex, (3) the extent of reductions differ at different sites and some are preceded by transient increases, and (4) the changes in transmission may not be related to the conditioned movement. The implications of these findings for some key theories of cerebellar cortical function are discussed.
The Osmotic Swelling Characteristics of Cardiac Valve Prostheses
Authors: Bachmann C. , Wilson M. , Kini V. , Deutsch and S. , Fontaine A. A. , Tarbell J. M.
Published: July 2002

Several types of mechanical cardiac prostheses have been constructed with Delrin occluders, a material that is subject to osmotic swelling. The leaflets are designed to expand to specific tolerances when immersed in blood. The synthetic blood analogs commonly used in vitro contain hydrophilic compounds that can alter the osmotic expansion of the Delrin occluders. A static leak test chamber was employed to illustrate the effects of various test fluids on the sustained regurgitation phase of Delrin valves. [S0148-0731(00)02104-X]
Subcooled Flow Boiling in Circumferentially Nonuniform and Uniform Heated Vertical Channels With Downward Flow
Authors: Peatiwala Q. , Boyd, R. D.
Published: July 2002

Results are presented for new experimental data for subcooled flow boiling heat transfer in circumferentially nonuniform (single-side) and uniformly heated tubes. Although the Liu-Winterton correlation had better agreement at low power levels and axial locations, Shah’s correlation had better agreement at higher power levels and at axial locations near the center of the heated length. Both correlations overpredicted the data near the exit. Therefore, additional correlational developmental work is needed for local (axial) flow boiling heat transfer in circumferentially nonuniform heated channels. [S0022-1481(00)00603-4]
Inverse Convection Problem for Determining Wall Heat Flux in Annular Duct Flow
Authors: Li H.-Y. , Yan W.-M.
Published: July 2002

An inverse problem for unsteady forced convection in an annular duct is presented. The simulated temperature data taken at the outer wall are used to estimate the time-dependent axially varying surface heat flux distribution at the inner wall of the annular passage. No prior information on the functional form of the unknown wall heat flux is needed in the inverse method. The effects of the functional form of the wall heat flux, the number of the measurement points, and the measurement errors on the accuracy of the estimation are investigated. It is shown that the reconstruction of the timewise and spatial variations of the wall heat flux is satisfactory even if the estimated function is not smooth. [S0022-1481(00)01003-3]
A Turbulent Model for Gas-Particle Jets
Authors: Garcı´a J. , Crespo A.
Published: July 2002

This work is concerned with turbulent diffusion in gas-particle flows. The cases studied correspond to dilute flows and small Stokes number, this implies that the mean velocity of the particles is very similar to that of the fluid element. The classical k-ε method is used to model the gas-phase, modified with additional terms for the k and ε equations, that takes into account the effect of particles on the carrier phase. The additional dissipation term included in the equation for k is due to the slip between phases at an intermediate scale, far from both the Kolmogorov and the integral scales. This term has a proportionality constant equal to 3/2 of Kolmogorov constant, C0. In this paper, a value of 3.0 has been used for this constant as suggested by Du et al., 1995, “Estimation of the Kolmogorov Constant C0 for the Langarian Structure Using a Second-Order Lagrangian Model of Grid Turbulence,” Phys. Fluids 7, (12), pp. 3083–3090. The additional source term for the ε equation is taken as proportional to ε/k, as is usually done. In all experiments analyzed the particles increased the dissipation of turbulent kinetic energy. A comparison is made between the results obtained with the model proposed in this work and the experiments of Shuen et al., 1985, “Structure of Particle-Laden Jets: Measurements and Predictions,” AIAA Journal, 23, No. 3, and Hishida et al., 1992, “Experiments on Particle Dispersion in a Turbulent Mixing Layer,” ASME Journal of Fluids Engineering, 119, pp. 181–194. [S0098-2202(00)02103-9]
Performance of the Incremental and Non-Incremental Finite Element Formulations in Flexible Multibody Problems
Authors: Campanelli Marcello , Berzeri Marcello , Shabana Ahmed A.
Published: July 2002

Many flexible multibody applications are characterized by high inertia forces and motion discontinuities. Because of these characteristics, problems can be encountered when large displacement finite element formulations are used in the simulation of flexible multibody systems. In this investigation, the performance of two different large displacement finite element formulations in the analysis of flexible multibody systems is investigated. These are the incremental corotational procedure proposed in an earlier article (Rankin, C. C., and Brogan, F. A., 1986, ASME J. Pressure Vessel Technol., 108, pp. 165–174) and the non-incremental absolute nodal coordinate formulation recently proposed (Shabana, A. A., 1998, Dynamics of Multibody Systems, 2nd ed., Cambridge University Press, Cambridge). It is demonstrated in this investigation that the limitation resulting from the use of the infinitesmal nodal rotations in the incremental corotational procedure can lead to simulation problems even when simple flexible multibody applications are considered. The absolute nodal coordinate formulation, on the other hand, does not employ infinitesimal or finite rotation coordinates and leads to a constant mass matrix. Despite the fact that the absolute nodal coordinate formulation leads to a non-linear expression for the elastic forces, the results presented in this study, surprisingly, demonstrate that such a formulation is efficient in static problems as compared to the incremental corotational procedure. The excellent performance of the absolute nodal coordinate formulation in static and dynamic problems can be attributed to the fact that such a formulation does not employ rotations and leads to exact representation of the rigid body motion of the finite element. [S1050-0472(00)00604-8]
The Effect of Working Fluid Inventory on the Performance of Revolving Helically Grooved Heat Pipes
Authors: Castle R. Michael , Thomas Scott K. , Yerkes Kirk L.
Published: July 2002

The results of a recently completed experimental and analytical study showed that the capillary limit of a helically-grooved heat pipe (HGHP) was increased significantly when the transverse body force field was increased. This was due to the geometry of the helical groove wick structure. The objective of the present research was to experimentally determine the performance of revolving helically-grooved heat pipes when the working fluid inventory was varied. This report describes the measurement of the geometry of the heat pipe wick structure and the construction and testing of a heat pipe filling station. In addition, an extensive analysis of the uncertainty involved in the filling procedure and working fluid inventory has been outlined. Experimental measurements include the maximum heat transport, thermal resistance and evaporative heat transfer coefficient of the revolving helically grooved heat pipe for radial accelerations of |a⃗r|=0.0, 2.0, 4.0, 6.0, 8.0, and 10.0-g and working fluid fills of G=0.5, 1.0, and 1.5. An existing capillary limit model was updated and comparisons were made to the present experimental data.
Modeling on Combustion Characteristics of Biocoalbriquettes
Authors: Kim Hee-Joon , Lu Guo-Qing , Naruse Ichiro , Yuan Jianwei , Ohtake Kazutomo
Published: July 2002

A biocoalbriquette, a new artificial solid fuel, is manufactured by a mixture of coal and biomass under a high-compression pressure. The combustion characteristics of biocoalbriquettes were investigated in this study experimentally and numerically. The combustion process of biocoalbriquettes appears in two stages: the volatile combustion stage followed by the char combustion stage. It was found that the volatile combustion happens over the whole pellet of biocoalbriquette, whereas the char combustion proceeds in a shrinking-core mode. A volume model and a shrinking-core reaction model were introduced and modified here to simulate the two stages of combustion process. The simulation results are found to be consistent with the experimental results.
Numerical Computation of Differential-Algebraic Equations for Non-Linear Dynamics of Multibody Systems Involving Contact Forces
Authors: Fox B. , Jennings L. S. , Zomaya A. Y.
Published: July 2002

The well known Euler-Lagrange equations of motion for constrained variational problems are derived using the principle of virtual work. These equations are used in the modelling of multibody systems and result in differential-algebraic equations of high index. Here they concern an N-link pendulum, a heavy aircraft towing truck and a heavy off-highway track vehicle. The differential-algebraic equation is cast as an ordinary differential equation through differentiation of the constraint equations. The resulting system is computed using the integration routine LSODAR, the Euler and fourth order Runge-Kutta methods. The difficulty to integrate this system is revealed to be the result of many highly oscillatory forces of large magnitude acting on many bodies simultaneously. Constraint compliance is analyzed for the three different integration methods and the drift of the constraint equations for the three different systems is shown to be influenced by nonlinear contact forces.
Numerical Investigation of Nonlinear Fluid-Structure Interaction in Vibrating Compressor Blades
Authors: Carstens Volker , Belz Joachim
Published: July 2002

The aeroelastic behavior of vibrating blade assemblies is usually investigated in the frequency domain where the determination of aeroelastic stability boundaries is separated from the computation of linearized unsteady aerodynamic forces. However, nonlinear fluid-structure interaction caused by oscillating shocks or strong flow separation may significantly influence the aerodynamic damping and hence effect a shift of stability boundaries. In order to investigate such aeroelastic phenomena, the governing equations of structural and fluid motion have to be simultaneously integrated in time. In this paper a technique is presented which analyzes the aeroelastic behavior of an oscillating compressor cascade in the time domain. The structural part of the governing aeroelastic equations is time-integrated according to the algorithm of Newmark, while the unsteady airloads are computed at every time step by an Euler upwind code. The link between the two time integrations is an automatic grid generation in which the used mesh is dynamically deformed as such that it conforms with the deflected blades at every time step. The computed time series of the aeroelastic simulation of an assembly of twenty compressor blades performing torsional vibrations in transonic flow are presented. For subsonic flow, the differences between time domain and frequency domain results are of negligible order. For transonic flow, however, where vibrating shocks and a temporarily choked flow in the blade channel dominate the unsteady flow, the energy transfer between fluid and structure is no longer comparable to that of a linear system. It is demonstrated that the application of the time domain method leads to a significantly different aeroelastic behavior of the blade assembly including a shift of the stability boundary.
Visualization and Measurement of Automotive Electrostatic Rotary-Bell Paint Spray Transfer Processes
Authors: Im Kyoung-Su , Lai Ming-Chia , Liu Yi , Sankagiri Nasy , Loch Thomas , Nivi Hossein
Published: July 2002

In order to improve the transfer efficiency and finish quality in automotive spray painting, a better understanding of the paint spray structure and transfer processes of the electrostatic rotary bell applicators is needed. This paper briefly reviews the current technological challenges and research issues, and then describes the spray atomization, visualization, droplet size, and velocity measurement results of a water-borne paint spray system under various operating parameters. The optical techniques used are copper vapor laser light sheet visualizations and the phase Doppler particle analyzer. Four main operating parameters are varied in this study: liquid flow rate (100 ml/min to 250 ml/min), shaping airflow rate (120 l/min to 180 l/min), bell rotational speed (20,000 rpm to 50,000 rpm), and high voltage setting (60 kV to 90 kV, and 0 V for comparison). For simplicity, water is used as the paint surrogate, and a flat metallic panel is used as the target surface. The results show that bell speed dominates the atomization, but high voltage and flow rate settings significantly modify the spray transport. The results of this study also provide detailed information on the paint spray structure and transfer processes, which can be used on model development and validation in future. Also, the microscopic visualization images provide qualitative information on the atomization mechanism.
Efficient Tubesheet Design Using Repeated Elastic Limit Analysis Technique
Authors: Reinhardt W. D. , Mangalaramanan S. P.
Published: July 2002

Conventional analysis of tubesheets in nuclear steam generators involves elastic analysis of a solid plate with equivalent properties. It has recently been recognized that alternate design techniques such as inelastic finite element analysis would lead to substantial cost reductions in material and manufacturing. Due to the anisotropy, arriving at yield criteria for an equivalent solid tubesheet is more complicated than for an isotropic solid. In addition, applying plastic finite element analysis in design is significantly more complex and time-consuming than elastic analysis. This paper proposes a relatively simple method to perform tubesheet collapse analysis. An anisotropic yield criterion is applied in conjunction with the classical lower-bound theorem of limit analysis and repeated elastic analyses involving elastic modulus modification. Two yield criteria are examined, namely Hill’s yield criterion and a recently suggested compressible fourth-order yield function. The collapse load predictions of the lower-bound equivalent solid methods are compared with the elastic-plastic finite element collapse load of the equivalent solid and of the actual perforated tubesheet.
A Study on the Direct Applicability of a Set of Grooves of Multi-Roll Wire Mills for Different Materials
Authors: Kuroda Kouichi , Kuboki Takashi , Akiyama Masayoshi , Hayashi Chihiro
Published: July 2002

Investigations were carried out on the direct applicability of a set of grooves of multi-roll wire mills for different materials having different stress-strain curves. Special evaluation was made on the stability of the geometry among different materials when rolled under the same mill setting conditions. Influence of inter-stand tension generated by the change in roll force due to the difference in stress-strain curve was studied both numerically and experimentally. A group of three-roll and four-roll-type mills is superior to two-roll-type mill in getting rid of the time for mill setting.
At the Upper Transition of Subcritical Regime of a Circular Cylinder
Authors: Lo K. W. , Ko N. W. M.
Published: July 2002

The present study establishes the transition between the lower and upper subcritical regime of flow over a circular cylinder at 7×103<Re<2×104. Based on a new sampling technique, it is shown that the small-scale secondary vortices, especially those of high energy, play an important role in the transition. Within a primary vortex shedding period, the secondary vortices appear in groups. In a group, the streamwise velocity of secondary vortices exhibits the increase, peak, and decrease pattern associated with the formation of Strouhal vortices. In the lower subcritical regime, the Group I of singular group occurs most frequently, while in the upper subcritical regime, the Group III of three groups is the most frequent. Pairings of successive secondary vortices are found, and the paired vortices also appear in groups. The present model of transition involves the excitation of the separated shear layer at the most amplified mode by the disturbances associated with the secondary and paired vortices. Due to their mutual interference, the higher-energy small-scale vortices affect the primary vortex sheet, which in turn amplifies the former. These higher-energy vortices have enhanced pairings, which also play a dominant role in the later stage of transition.
Aspects of Finite Element Simulation of Axi-Symmetric Hydromechanical Deep Drawing
Authors: Jensen M. R. , Olovsson L. , Danckert J. , Nielsen K. B.
Published: July 2002

A new approach for the Finite Element modelling of the hydromechanical deep drawing process is evaluated. In the model a Finite Difference approximation of Reynold’s equation is solved for the fluid flow between the blank and the draw die in the flange region. The approach is implemented as a contact algorithm in an explicit Finite Element code, Exhale2D. The developed model is verified against experiments and good agreement is obtained. It is concluded that the developed model is a promising approach for simulating the hydromechanical deep drawing process using the Finite Element Method.
LDV Measurement of Confined Parallel Jet Mixing
Authors: Kunz Robert F. , D’Amico Stephen W. , Vassallo Peter F. , Zaccaria Michael A.
Published: July 2002

Laser Doppler Velocimetry (LDV) measurements were taken in a confinement, bounded by two parallel walls, into which issues a row of parallel jets. Two-component measurements were taken of two mean velocity components and three Reynolds stress components. As observed in isolated three-dimensional wall bounded jets, the transverse diffusion of the jets is quite large. The data indicate that this rapid mixing process is due to strong secondary flows, transport of large inlet intensities, and Reynolds stress anisotropy effects.
New Swash Plate Damping Model for Hydraulic Axial-Piston Pump
Authors: Zhang X. , Cho J. , Nair S. S. , Manring N. D.
Published: July 2002

A new, open-loop, reduced order model is proposed for the swash plate dynamics of an axial piston pump. The difference from previous reduced order models is the modeling of a damping mechanism not reported previously in the literature. An analytical expression for the damping mechanism is derived. The proposed reduced order model is validated by comparing with a complete nonlinear simulation of the pump dynamics over the entire range of operating conditions.
Stability Criteria of the Steady Flow of a Liquid Containing Bubbles Along a Nozzle
Authors: Crespo A. , Garcı´a J. , Jime´nez-Ferna´ndez J.
Published: July 2002

The steady cavitating flow through a converging-diverging nozzle is considered. A continuum model is assumed with the Rayleigh-Plesset equation to account for the bubble dynamics. A similar problem has been studied previously by Wang and Brennen, and they found that if the upstream gas volume fraction of the bubbles exceeds a critical value there is flashing flow instability. In the present work, a perturbation analysis is made introducing a small parameter, ε, that is the ratio of the initial bubble diameter to the length scale of the nozzle. As a result of this analysis, the critical value of the upstream void fraction is calculated as a function of the several parameters appearing in the problem, and turns out to be very small and proportional to ε3. A correlation is proposed giving explicitly the functional dependence of this critical value.
Highly Subcooled Boiling in Crossflow
Authors: Huang LiDong , Witte Larry C.
Published: July 2002

Experiments were carried out to determine the influence of fluid flow and liquid subcooling on flow boiling heat transfer of Freon-113 across horizontal tubes. The data cover wide ranges of velocity (1.5 to 6.9 m/s) and extremely high levels of liquid subcooling (29 to 100°C) at pressures ranging from 122 to 509 kPa. Thin-walled cylindrical electric resistance heaters made of Hastelloy-C with diameter of 6.35 mm were used. The azimuthal wall temperature distributions were measured with five thermocouples around the heaters. The data were compared with Chen’s two-mechanism model with modification for subcooled flow boiling. A new nucleate boiling suppression factor for cross flow was developed. The improved model could predict the present data and Yilmaz and Westwater’s (1980) data well with a mean error ratio of 1.02 and standard deviation of 0.17.