bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of IgE turnover in non‐sensitized and sensitized rats
Authors: Hanashiro Kazuhiko , Tokeshi Yoshihiro , Nakasone Toshiyuki , Sunagawa Masanori , Nakamura Mariko , Kosugi Tadayoshi
Published: November 2003

Background: Although the levels of immunoglobulin E (IgE) in the circulating blood are often elevated in patients with allergic diseases, such levels cannot always be considered as pathognomonic signs of allergy. The induction of allergic reactions in the tissue was inferred to be related to the amount of IgE passing through the vascular wall.

Aims: We attempted to clarify which compartment, the intravascular or extravascular, plays an important role in the regulation of the turnover of rat IgE.

Methods: The level of DNP‐specific rat IgE in the serum was estimated by IgE‐capture enzyme‐linked immunosorbent assay, and the turnover of IgE was analyzed from its pharmacokinetic parameters.

Results: The transfer rate constants from the central to tissue compartment
(Kct) were larger than those from the tissue to central compartment
(Ktc) irrespective of the sensitized state. The value of the distribution volume of the tissue compartment
(Vt) was larger than that of the distribution volume of the central compartment
(Vc) irrespective of the sensitized state.

Conclusions: These findings suggest that the short half‐life of rat IgE in the circulation could be attributable to the distribution of IgE from the intravascular to the extravascular compartment.
Tumor necrosis factor‐α/interleukin‐10 balance in normal and cystic fibrosis children
Authors: Shmarina Galina V. , Pukhalsky Alexander L. , Kokarovtseva Svetlana N. , Pukhalskaya Daria A. , Shabalova Lidia A. , Kapranov Nikolai I. , Kashirskaja Natalia J.
Published: November 2003

Background: The balance between tumor necrosis factor‐α (TNF‐α) and interleukin‐10 (IL‐10) is important for immune homeostasis maintenance. Exuberant production of TNF‐α contributes to overwhelming inflammatory response and tissue damage. But, commonly, increase in TNF‐α is counterbalanced by simultaneous synthesis of an anti‐inflammatory cytokine IL‐10, which suppresses production of many activating and regulatory mediators.

Aims: In the present study, the relationships between TNF‐α and IL‐10 in the plasma of healthy schoolchildren and cystic fibrosis (CF) patients have been investigated.

Methods: Blood samples were obtained from 12 CF patients with chronic pulmonary disease and 18 healthy schoolchildren vaccinated with live attenuated rubella vaccine. IL‐10 and TNF‐α were determined in the plasma samples using commercially available enzyme‐linked immunosorbent assay kits.

Results: Before vaccination, most healthy children (13 of 18) demonstrated superiority of pro‐inflammatory TNF‐α over anti‐inflammatory IL‐10 (TNF‐α/IL‐10 Â 1). In these subjects, a significant positive linear association between the cytokine values has been found. Vaccine challenge resulted in a marked reduction of TNF‐α/IL‐10 ratios. In addition, a disappearance of correlation between the cytokine values was observed. Such disturbance was related to exuberant elevation of the IL‐10 levels after inoculation. On the contrary, in CF individuals, plasma cytokine values remained in strong linear association independently of TNF‐α or IL‐10 predominance. No spikes in the plasma levels of IL‐10 in CF patients during a 6‐month observation period have been revealed.

Conclusions: There were no fundamental differences between CF and healthy children in the regulation of TNF‐α and IL‐10 secretion. Thus, immune quiescence seemed to be associated with the predominance of TNF‐α, whereas immune disturbance was characterized by IL‐10 superiority. The only abnormality that was found in CF patients consisted of their inability to produce unlimitedly IL‐10 in response to antigen stimuli.
Inflammatory cell distribution in guinea pig airways and its relationship to airway reactivity
Authors: Westerhof Fiona , Timens Wim , van Oosten Annemiek , Zuidhof Annet B. , Nauta Nathalie , Schuiling Martin , Vos Johannes T. W. M. , Zaagsma Johan , Meurs Herman , Coers Wilko
Published: November 2003

Although airway inflammation and airway hyperreactivity are observed after allergen inhalation both in allergic humans and animals, little is known about the mechanisms by which inflammatory cells can contribute to allergen‐induced airway hyperreactivity. To understand how inflammatory cell infiltration can contribute to airway hyperreactivity, the location of these cells within the airways may be crucial.

Using a guinea pig model of acute allergic asthma, we investigated the inflammatory cell infiltration in different airway compartments at 6 and 24 h (i.e. after the early and the late asthmatic reaction, respectively) after allergen or saline challenge in relation to changes in airway reactivity (AR) to histamine.

At 6 h after allergen challenge, a threefold (p < 0.01) increase in the AR to histamine was observed. At 24 h after challenge, the AR to histamine was lower, but still significantly enhanced (1.6‐fold, p < 0.05).

Adventitial eosinophil and neutrophil numbers in both bronchi and bronchioli were significantly increased at 6 h post‐allergen provocation as compared with saline (p < 0.01 for all), while there was a strong tendency to enhanced eosinophils in the bronchial submucosa at this time point
(p = 0.08). At 24 h after allergen challenge, the eosinophilic and neutrophilic cell infiltration was reduced. CD3+ T lymphocytes were increased in the adventitial compartment of the large airways (p < 0.05) and in the parenchyma (p < 0.05) at 24h post‐allergen, while numbers of CD8+ cells did not differ from saline treatment at any time point post‐provocation.

The results indicate that, after allergen provocation, inflammatory cell numbers in the airways are mainly elevated in the adventitial compartment. The adventitial inflammation could be important for the development of allergen‐induced airway hyperreactivity.
The expression of COX‐2 in VEGF‐treated endothelial cells is mediated through protein tyrosine kinase
Authors: Akarasereenont Pravit , Techatraisak Kitirat , Thaworn Athiwat , Chotewuttakorn Sirikul
Published: November 2003

Cyclooxygenase (COX), existing as the COX‐1 and COX‐2 isoforms, converts arachidonic acid to prostaglandin H2, which is then further metabolized to various prostaglandins. Vascular endothelial growth factor (VEGF) has been shown to play important roles in inflammation and is upregulated by the prostaglandin E series through COX‐2 in several cell types. Here, we have investigated the effects of VEGF on the COX isoform expressed in human umbilical vein endothelial cells (HUVEC). The signalling mechanism of the COX isoform expressed in endothelial cells activated with VEGF will be also investigated using the tyrosine kinase inhibitor, genistein, and protein kinase C inhibitor, staurosporine. The activity of COX2 was assessed by measuring the production of 6‐keto‐prostaglandin F1α in the presence of exogenous arachidonic acids (10 μM, 10 min) by enzyme immunoassay. The expression of COX isoform protein was detected by immunoblot using specific antibodies. Untreated HUVEC contained no COX‐2 protein. In HUVEC treated with VEGF (0.01‐50 ng/ml), COX‐2 protein, but not COX‐1, and COX activity were increased in a dose‐dependent manner. Interestingly, the increased COX‐2 protein and activity in response to VEGF (10 ng/ml) was inhibited by the tyrosine kinase inhibitor, genistein (0.05‐5 μg/ml), but not by the protein kinase C inhibitor, staurosporine (0.1‐10 ng/ml). Thus, the induction of COX‐2 by VEGF in endothelial cells was mediated through protein tyrosine kinase, and the uses of specific COX‐2 inhibitors in these conditions, in which VEGF
was involved, might have a role.
An upper and lower solution approach for a generalizedThomas–Fermi theory of neutral atoms
Authors: Agarwal Ravi P. , O′Regan Donal
Published: November 2003

This paper presents an upper and lower solution theory for boundary value problems modelled from the Thomas–Fermi equation subject to a boundary condition corresponding to the neutral atom with Bohr radius.
Steady‐state solution of the PTC thermistor problem using aquadratic spline finite element method
Authors: Bahadir A. R.
Published: November 2003

The problem of heat transfer in a Positive Temperature Coefficient (PTC) thermistor, which may form one element of an electric circuit, is solved numerically by a finite element method. The approach used is based on Galerkin finite element using quadratic splines as shape functions. The resulting system of ordinary differential equations is solved by the finite difference method. Comparison is made with numerical and analytical solutions and the accuracy of the computed solutions indicates that the method is well suited for the solution of the PTC thermistor problem.
On potential energies and constraints in the dynamics of rigidbodies and particles
Authors: O′reilly Oliver M. , Srinivasa Arun R.
Published: November 2003

A new treatment of kinematical constraints and potential energies arising in the dynamics of systems of rigid bodies and particles is presented which is suited to Newtonian and Lagrangian formulations. Its novel feature is the imposing of invariance requirements on the constraint functions and potential energy functions. These requirements are extensively used in continuum mechanics and, in the present context, one finds certain generalizations of Newton′s third law of motion and an elucidation of the nature of constraint forces and moments. One motivation for such a treatment can be found by considering approaches where invariance
requirements are ignored. In contrast to the treatment presented in this paper, it is shown that this may lead to a difficulty in formulating the equations governing the motion of the system.
Direct Cloning of a Target Gene from a Pool of Homologous Sequences: Complete cDNA Sequence of a Weak Neurotoxin from Cobra Naja kaouthia
Authors: Oustitch TL , Peters L‐E. , Utkin Yu , Tsetlin VI
Published: November 2003

Selective cloning of the cDNA coding for a weak neurotoxin (WTX) from cobra N. kaouthia including the 5'‐ and 3'‐non‐translated regions (NTR) is described. The known amino acid sequence of WTX was used together with the nucleotide sequence of a weak neurotoxin NNAM2 from cobra Naja atra, to design WTX‐specific primers for direct amplification of an internal WTX cDNA fragment by RT‐PCR. The sequence of the complete WTX cDNA was determined in sequencing runs on internal PCR products, cloned 3'‐ and 5'‐RACE‐fragments and several full‐length cDNA clones. The cDNA coding sequence is in excellent agreement with the previously determined WTX amino acid sequence, has a high homology with other known weak toxin cDNAs, whereas even higher homology (up to 96%) with several classes of 3‐finger toxins was detected in the 59 bp 3'‐NTR consensus sequence. A possible function of the highly conserved nucleotide sequence elements is discussed. IUBMB Life, 55: 43‐47, 2003
Effectory Site in Escherichia coli Inorganic Pyrophosphatase is Revealed Upon Mutation at the Intertrimeric Interface
Authors: Sitnik Tatyana , Vainonen Julia , Rodina Elena , Nazarova Tatyana , Kurilova Svetlana , Vorobyeva Natalya , Avaeva Svetlana
Published: November 2003

Escherichia coli inorganic pyrophosphatase (E‐PPase) is a homohexamer formed from two trimers related by a two‐fold axis. The residue Asp26 participates in intertrimeric contacts. Kinetics of MgPPi hydrolysis by a mutant Asp26Ala E‐PPase is found to not obey Michaelis‐Menten equation but can be described within the scheme of activation of hydrolysis by a free PPi binding at an effectory subsite. Existence of such a subsite is confirmed by the finding that the free form of methylenediphosphonate activates MgPPi hydrolysis though its magnesium complex is a competitive inhibitor. The Asp26Ala variant is the first example of hexameric E‐PPase demonstrated to have an activatory subsite. IUBMB Life, 55: 37‐41, 2003
Structural and biochemical analyses of DNA and RNA binding by a bifunctional homing endonuclease and group I intron splicing factor
Authors: Bolduc Jill M. , Spiegel P. Clint , Chatterjee Piyali , Brady Kristina L. , Downing Maureen E. , Caprara Mark G. , Waring Richard B. , Stoddard Barry L.
Published: November 2003

We determined the crystal structure of a bifunctional group I intron splicing factor and homing endonuclease, termed the I-AniI maturase, in complex with its DNA target at 2.6 Å resolution. The structure demonstrates the remarkable structural conservation of the β-sheet DNA-binding motif between highly divergent enzyme subfamilies. DNA recognition by I-AniI was further studied using nucleoside deletion and DMS modification interference analyses. Correlation of these results with the crystal structure provides information on the relative importance of individual nucleotide contacts for DNA recognition. Alignment and modeling of two homologous maturases reveals conserved basic surface residues, distant from the DNA-binding surface, that might be involved in RNA binding. A point mutation that introduces a single negative charge in this region uncouples the maturase and endonuclease functions of the protein, inhibiting RNA binding and splicing while maintaining DNA binding and cleavage.
From consumer insight to advertising strategy: the account planner’s integrative role in creative advertising development
Authors: Hackley Chris
Published: November 2003

In commercial applications the somewhat passive notion of marketing research is increasingly being superseded by the more active idea of consumer insight. In advertising this subtle change of emphasis is captured in the evolution of the account planning role and the associated “philosophy” of creative advertising development. The account planner is ostensibly responsible not only for commissioning and/or conducting advertising and consumer research, she or he is also responsible for integrating the resulting consumer insights into the creative advertising development process. Account planners deploy their consumer insights to act as “midwives” to creativity in the sense that they are responsible for persuading creative staff to take research‐derived consumer insights on board. This paper draws on recent depth interviews with advertising professionals and previously published research to explore the process of integrating research‐based insights into creative advertising development. The overall aim is to further elaborate the tasks and effectiveness of the account planner.
A lack of true believers in the account‐planning discipline in Australia?
Authors: Butcher Ken , McCulloch Rod
Published: November 2003

In Australia, advertising agencies have partially embraced the UK‐originated account planning philosophy. In an exploratory study, six senior account planning directors were interviewed to gain insights into account planning in Australia. It appears that the scale and nature of the Australian advertising industry militates against full acceptance of the UK model. Indeed, the UK model has met resistance from several areas. It was further found that the expectations of the planners’ role probably exceed the individual’s capacity to deliver on that role. Hence, the outlook for planning other than for a small group of “true blues”, to use the Australian argot, may have limited success in Australia.
Effects of high‐intensity intermittent training on potassium kinetics and performance in human skeletal muscle
Authors: Nielsen Jens Jung , Mohr Magni , Klarskov Christina , Kristensen Michael , Krustrup Peter , Juel Carsten , Bangsbo Jens
Published: November 2003

A rise in extracellular potassium concentration in human skeletal muscle may play an important role in development of fatigue during intense exercise. The aim of the present study was to examine the effect of intense intermittent training on muscle interstitial potassium kinetics and its relationship to the density of Na+,K+‐ATPase subunits and KATP channels, as well as exercise performance, in human skeletal muscle. Six male subjects performed intense one‐legged knee‐extensor training for 7 weeks. On separate days the trained leg (TL) and the control leg (CL) performed a 30 min exercise period of 30 W and an incremental test to exhaustion. At frequent intervals during the exercise periods interstitial potassium ([K+]I) was determined by microdialysis, femoral arterial and venous blood samples were drawn and thigh blood flow was measured. Time to fatigue for TL was 28% longer (P < 0.05) than for CL (10.6 ± 0.7 (mean ±s.e.m.) versus 8.2 ± 0.7 min). The amounts of Na+,K+‐ATPase α1 and α2 subunits were, respectively, 29.0 ± 8.4 and 15.1 ± 2.7% higher (P < 0.05) in TL than in CL, while the amounts of β1 subunits and ATP‐dependent K+ (KATP) channels were the same. In CL [K+]I increased more rapidly and was higher (P < 0.05) throughout the 30 W exercise bout, as well at 60 and 70 W, compared to TL, whereas [K+]I was similar at the point of fatigue (9.9 ± 0.7 and 9.1 ± 0.5 mmol l−1, respectively). During the 30 W exercise bouts and at 70 W during the incremental exercise femoral venous potassium concentration ([K+]v) was higher (P < 0.05) in CL than in TL, but identical at exhaustion (6.2 ± 0.2 mmol l−1). Release of potassium to the blood was not different in the two legs. The present data demonstrated that intense intermittent training reduce accumulation of potassium in human skeletal muscle interstitium during exercise, probably through a larger re‐uptake of potassium due to greater activity of the muscle Na+,K+‐ATPase pumps. The lower accumulation of potassium in muscle interstitium in the trained leg was associated with delayed fatigue during intense exercise, supporting the hypothesis that interstitial potassium accumulation is involved in the development of fatigue.
Fuzzy Fuel Flow Selection Logic for a Real Time Embedded Full Authority Digital Engine Control
Authors: Martucci A. , Volponi A. J.
Published: November 2003

The control logic of the modern full authority digital engine control is comprised of many control loops, each of which has a specific purpose. Typical control loops include (but are not limited to) a high or low rotor speed governor, an acceleration and deceleration loop, and various limiting loops for temperature, speed, fuel flow, and rate of change of fuel flow. The logic that determines which of these loops is “in control” at any particular time has a history of being very simplistic. This selection logic is usually nothing more that a cascade of minimum and maximum selection logic gates. Since this logic is so simplistic, the control engineer often has to “fine-tune” the compensator design for each loop, in order to achieve proper performance.
Imbalance Response of a Rotor Supported on Flexure Pivot Tilting Pad Journal Bearings in Series With Integral Squeeze Film Dampers
Authors: San Andre´s L. , De Santiago O.
Published: November 2003

Measurements of the imbalance responses of a massive 45 kg rotor supported on series (flexure pivot) tilting pad bearings and integral squeeze film dampers (SFDs) are presented. The rotor-bearing configuration is of interest in compressor applications where often oil lubricated dampers are introduced in series with fluid film bearings to relocate critical speeds, enhance the overall system damping, and reduce the risks of rotordynamic instabilities due to seals and impellers, for example. Coast-down experiments from 9000 rpm are conducted for increasing levels of rotor imbalance, and equivalent system damping coefficients identified from the peak amplitude of rotor response while traversing cylindrical mode critical speeds. The tests performed with locked (inactive) and active SFDs demonstrate the effectiveness of the flexible damped support in reducing the system critical speed and improving the overall rotor response with reduced transmitted forces to ground. The SFDs allow safe rotor operation with values of imbalance twice as large as the maximum sustained by the rotor supported on tilting pad bearings alone. The experiments reveal a linear relationship between the peak amplitude of vibration at the critical speeds and the imbalance displacement, even for rotor motions larger than 50% of the tilting pad bearing and damper clearances. The tests also show little cross-coupling effects with the shaft centerline moving along a nearly vertical path. The rotor-bearing system remained stable in the entire range of operation and without the appearance of subsynchronous vibration or nonlinear damper jump response.
Turbulent Plane Couette Flow and Scalar Transport at Low Reynolds
Number
Authors: Liu Chun-Ho
Published: November 2003

The turbulence structure and passive scalar (heat) transport in plane Couette flow at Reynolds number equal to 3000 (based on the relative speed and distance between the walls) are studied using direct numerical simulation (DNS). The numerical model is a three-dimensional trilinear Galerkin finite element code. It is found that the structures of the mean velocity and temperature in plane Couette flow are similar to those in forced channel flow, but the empirical coefficients are different. The total (turbulent and viscous) shear stress and total (turbulent and conductive) heat flux are constant throughout the channel. The locations of maximum root-mean-square streamwise velocity and temperature fluctuations are close to the walls, while the location of maximum root-mean-square spanwise and vertical velocity fluctuations are at the channel center. The correlation coefficients between velocities and temperature are fairly constant in the center core of the channel. In particular, the streamwise velocity is highly correlated with temperature (correlation coefficient ≈−0.9). At the channel center, the turbulence production is unable to counterbalance the dissipation, in which the diffusion terms (both turbulent and viscous) bring turbulent kinetic energy from the near-wall regions toward the channel center. The snapshots of the DNS database help explain the nature of the correlation coefficients. The elongated wall streaks for both streamwise velocity and temperature in the viscous sublayer are well simulated. Moreover, the current DNS shows organized large-scale eddies (secondary rotations) perpendicular to the direction of mean flow at the channel center.
Computation of the Optimal Normal Load of a Friction Damper Under Different Types of Excitation
Authors: Cha D. , Sinha A.
Published: November 2003

In this paper, forced responses of a frictionally damped turbine blade are investigated for three different types of excitation: white noise excitation, narrowband random excitation, and deterministic sinusoidal excitation. To determine the steady-state nonlinear response, the harmonic balance method is used for sinusoidal excitation, and the equivalent linearization method is used for white noise and narrowband random excitations. Using a new set of nondimensionalized variables, the optimal value of normal load of a friction damper is found to be almost independent of the nature of excitation. The effectiveness of the damper in reducing the vibration level is also examined for the aforementioned three different types of excitation.
Disintegration of Oil Jets Emerging From Axial Passages at the Face of a Rotating Cylinder
Authors: Glahn A. , Blair M. F. , Allard K. L. , Busam S. , Scha¨fer O. , Wittig S.
Published: November 2003

A fundamental study has been performed to examine the disintegration of oil films emerging from axial passages at the face of a rotating cylinder. The investigation has been conducted in parallel to a similar study on atomization processes at rotating radial holes (Glahn, A. et al., 2001, “Disintegration of Oil Films Emerging From Radial Holes Inside a Cylinder,” ASME Paper No. 2001-GT-0202) and has used the same approaches in simulating one of the droplet generation sources in aeroengine lubrication systems. Both papers aim to contribute to the establishment of a database that can be used for the development of droplet generation models directly applicable to engine conditions. As with the parallel investigation, the near-term objectives of fundamental oil film disintegration studies are (i) to determine droplet sizes under relevant aeroengine bearing compartment operating conditions, and (ii) to measure individual droplet diameter/velocity relationships. The long-term objective is to incorporate this information into advanced design systems such as CFD-based tools. In the present study, flow visualization has been used to identify the dominant disintegration processes. Droplet diameters and velocities have been obtained for relevant engine operating conditions. Data are presented in terms of both characteristic diameters and size-class resolved droplet velocities and flow angles. A comparison of droplet sprays measured in the present study with those generated by disintegration of oil films at the rim of a rotating disk (Glahn, A. et al., 2000, “Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk,” ASME Paper No. 2000-GT-0279) has been enabled by introducing nondimensional parameters for atomization products and operating conditions.
Advanced Catalytic Pilot for Low NOx Industrial Gas Turbines
Authors: Karim H. , Lyle K. , Etemad S. , Smith L. L. , Pfefferle W. C. , Dutta P. , Smith K.
Published: November 2003

This paper describes the design and testing of a catalytically stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high-pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598 K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single-injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.
Combustion System Development for the Ramgen Engine
Authors: Kendrick D. W. , Chenevert B. C. , Trueblood B. , Tonouchi J. , Lawlor S. P. , Steele R.
Published: November 2003

The research and development of a unique combustion engine is presented. The engine converts the thrust from ramjet modules located on the rim of a disk into shaft torque, which in turn can be used for electrical power generation or mechanical drive applications. A test program was undertaken that included evaluation of the pre-prototype engine and incorporation of improvements to the thrust modules and supporting systems. Fuel mixing studies with vortex generators and bluff-body flame holders demonstrated the importance of increasing the shear-layer area and spreading angle to augment flame volume. Evaluation of flame-holding configurations (with variable fuel injection methods) concluded that the heat release zone, and therefore combustion efficiency, could be manipulated by judicious selection of bluff-body geometry, and is less influenced by fuel injection distribution. Finally, successful operation of novel fuel and cooling air delivery systems have resolved issues of gas (fuel and air) delivery to the individual rotor segments. The lessons learned from the pre-prototype engine are currently being applied to the development of a 2.8MW engine.
The Premixed Conditional Moment Closure Method Applied to Idealized Lean Premixed Gas Turbine Combustors
Authors: Martin S. M. , Kramlich J. C. , Kosa´ly G. , Riley J. J.
Published: November 2003

This paper presents the premixed conditional moment closure (CMC) method as a new tool for modeling turbulent premixed combustion with detailed chemistry. By using conditional averages the CMC method can more accurately model the affects of the turbulent fluctuations of the temperature on the reaction rates. This provides an improved means of solving a major problem with traditional turbulent reacting flow models, namely how to close the reaction rate source term. Combined with a commercial CFD code this model provides insight into the emission formation pathways with reasonable runtimes. Results using the full GRI2.11 methane kinetic mechanism are compared to experimental data for a backward-facing step burning premixed methane. This model holds promise as a design tool for lean premixed gas turbine combustors.
Liquid Fuel Placement and Mixing of Generic Aeroengine Premix Module at Different Operating Conditions
Authors: Becker J. , Hassa C.
Published: November 2003

Fuel placement and air-fuel mixing in a generic aeroengine premix module employing plain jet liquid fuel injection into a counter-swirling double-annular crossflow were investigated at different values of air inlet pressure (6 bar, 700 K and 12 bar, 700 K) and liquid-to-air momentum flux ratio, both parameters being a function of engine power. Kerosene Jet A-1 was used as liquid fuel. Measurement techniques included LDA for investigation of the airflow and Mie-scattering laser light sheets and PDA for investigation of the two-phase flow. Measurements were taken at various axial distances from the fuel nozzle equivalent to mean residence times of up to 0.47 ms. It was found that the initial fuel placement reacts very sensitively to a variation of liquid-to-air momentum flux ratio. Susceptibility of the spray to dispersion due to centrifugal forces and to turbulent mixing is primarily a function of the fuel droplet diameters, which in turn depend on operating pressure. The data are interpreted by evaluation of the corresponding Stokes numbers.
Use of an Inverse Method to Determine Natural Convection Heat
Transfer Coefficients in Unsteady State
Authors: Trombe A. , Suleiman A. , Le Maoult Y.
Published: November 2003

The purpose of this study is to evaluate the efficiency of an inverse method to determine the variation of convective heat transfer coefficients in the unsteady state inside building enclosures. The experimental system is mainly composed of a vertical, heated, flat plate where natural convection heat flow is generated and of a radiative source which can impose a known flux condition. The inverse method calculates the total heat flux by conduction along the vertical flat plate, together with surface temperatures. Subtracting the local contribution of the radiative heat flux from the total heat flux gives the average convective heat flux at different heights of the plate. For various boundary conditions, it is then possible to determine the values of the convective heat exchange coefficients. Uncertainty calculations relative to these results confirm the reliability of the inverse method developed.
A Maximum Entropy Solution for a Two-Dimensional Inverse Heat
Conduction Problem
Authors: Kim Sun Kyoung , Lee Woo Il
Published: November 2003

A solution scheme based on the maximum entropy method (MEM) for the solution of two-dimensional inverse heat conduction problems is established. MEM finds the solution which maximizes the entropy functional under the given temperature measurements. The proposed method converts the inverse problem to a nonlinear constrained optimization problem. The constraint of the optimization problem is the statistical consistency between the measured temperature and the estimated temperature. Successive quadratic programming (SQP) facilitates the numerical estimation of the maximum entropy solution. The characteristic feature of the proposed method is investigated with the sample numerical results. The presented results show considerable enhancement in resolution for stringent cases in comparison with a conventional method.
An Inverse Determination of Unsteady Heat Fluxes Using a Network
Simulation Method
Authors: Alhama F. , Zueco J. , González Fernández C. F.
Published: November 2003

This work addresses unsteady heat conduction in a plane wall subjected to a time-variable incident heat flux. Three different types of flux are studied (sinusoidal, triangular and step waveforms) and constant thermal properties are assumed for simplicity. First, the direct heat conduction problem is solved using the Network Simulation Method (NSM) and the collection of temperatures obtained at given instants is modified by introducing a random error. The resulting temperatures act as the input data for the inverse problem, which is also solved by a sequential approach using the NSM in a simple way. The solution is a continuous piece-wise function obtained step by step by minimizing the classical functional that compares the above input data with those obtained from the solution of the inverse problem. No prior information is used for the functional forms of the unknown heat flux. A piece-wise linear stretches of variable slope and length is used for each of the stretches of the solution. The sensitivity of the functional versus the slope of the line, at each step, is acceptable and the complete piece-wise solution is very close to the exact incident heat flux in all of the mentioned waveforms.
Determination of Drying Times for Irregular Two and Three-Dimensional
Objects
Authors: Sahin A. Z. , Dincer I.
Published: November 2003

This paper deals with development of a new analytical model for determining the drying times of irregular-shaped multi-dimensional objects. Geometrically irregular two and three-dimensional products are approximated by elliptical cylinder and ellipsoidal shapes, respectively. Using experimental drying parameters that are available from the literature, drying times of irregular, multi-dimensional products are determined through the present models. Geometric shape factors for the elliptic cylinder and ellipsoid are employed and based on the reference drying time for an infinite slab. In addition, the present models are verified through comparison with experimental drying times of several food products. The accuracy of the predictions using the present models is then discussed, and a considerably high agreement is obtained between the predictions and experimental data.
Turbulent Film Condensation on a Horizontal Elliptical Tube
Authors: Chen Cha'o-Kuang , Hu Hai-Ping
Published: November 2003

This is an investigation of turbulent film condensation on a horizontal elliptical tube. The high tangential velocity of the vapor flow at the boundary layer is determined from potential flow theory. The Colburn analogy is used to define the local liquid-vapor interfacial shear which occurs for high velocity vapor flow across an elliptical tube surface. The results developed in this study are compared with those generated by previous theoretical and experimental results.
A New Generalized Carbon Exergy Tax: An Effective Rule to Control Global Warming
Authors: Traverso A. , Massardo A. F. , Santarelli M. , Cali M.
Published: November 2003

An instrument for promoting CO2 emission reductions, taking the Kyoto Protocol goal into account, could be the assignment to energy conversion plants of a monetary charge linked to their specific emission intensity, usually called carbon tax. There are two main problems closely connected with this approach: the estimation of the charge (that must be related to the “external” cost associated with CO2 emission) and the choice of the strategy to determine the amount of the imposed charge. In this paper an analytical procedure proposed by the authors and called carbon exergy tax (CET) for the evaluation of CO2 emission externalities is presented. It is based on the thermoeconomic analysis of energy systems, which allows second law losses to be quantified in monetary terms: the resulting cost represents the taxation that is to be applied to the energy system under examination, calculated without any arbitrary assumption. Since the complete procedure of the CET evaluation is too complex to become a feasible instrument of energy policy, hereby, after applying the procedure to some conventional and advanced power plants, gas, oil, and coal-fueled, a new generalized approach, based on the results of the complete CET procedure, is proposed. The generalized CET evaluation requires much less information about the energy system and thus a simple and effective energy policy rule to manage global warming is obtained and available.
Numerical Investigation of the Effects of Axial Cylinder Bore Profiles on Piston Ring Radial Dynamics
Authors: Piao Y. , Gulwadi S. D.
Published: November 2003

The role of cylinder bore shapes in engine performance has been the subject of several studies in recent years. In particular, the influence of bore distortion on oil consumption under high speed conditions has generated significant interest. In this paper, the effect of an axial bore profile on radial dynamics of a ring is investigated. Radial ring motions within grooves due to the axial bore profile can generate significant inertial effects and also have an impact on ring end-gap sizes and lubrication conditions at the ring-liner interfaces. The magnitude of such effects is dependent on the ring-pack configuration, engine operating conditions (speed and load) and axial bore profile details. These issues are investigated in this study due to their implication on engine oil consumption, friction and blow-by. The authors have developed an analytical expression to account for the effects of radial ring inertia due to an axial bore profile for implementation in a piston ring-pack simulation tool RINGPAK. Simulation results from a gasoline engine study are presented to illustrate the effects of engine speeds, ring tensions, and characteristics of axial bore profiles on ring radial dynamics and ring-liner lubrication. Relevant qualitative comparisons are made to experimental measurements available in the literature.
Thermodynamic Performance Analysis of New Gas Turbine Combined Cycles With No Emissions of Carbon Dioxide
Authors: Gabbrielli R. , Singh R.
Published: November 2003

In the context of the reduction of the carbon dioxide CO2 emissions as prescribed by the Kyoto protocol, this paper describes a thermodynamic performance analysis of new gas turbine combined cycles with no emissions of CO2 and nitrogen oxides. Three new similar cycles belonging to the same typology are proposed. These cycles use water/steam as working fluid, which is compressed in liquid and vapor phase, and the internal combustion process, which takes place between syngas and pure oxygen. The top Brayton cycle and the bottom Rankine cycle are integrated together. The syngas is produced by steam-natural gas reforming with internal chemical heat recovery. The CO2 produced in the combustion is captured simply by water condensation from the exhaust gas and liquefied to be stored. A simulation analysis has been performed to evaluate the net efficiency and the net specific work of the cycles. Varying the most important operative variables and using the least-square regression and 2k factorial design techniques, a very large sensitivity analysis has permitted the highlighting of performance behavior of the cycles. Including the energy penalty due to the liquefaction of CO2 and to the oxygen production and adopting standard operative conditions, the LHV-based net efficiency and the net specific work may exceed 50% and 1000 kJ/kg, respectively.
Experimental and Numerical Study of Heat Transfer in a Gas Turbine Combustor Liner
Authors: Bailey J. C. , Intile J. , Fric T. F. , Tolpadi A. K. , Nirmalan N. V. , Bunker R. S.
Published: November 2003

Experiments and numerical simulations were conducted to understand the heat transfer characteristics of a stationary gas turbine combustor liner cooled by impingement jets and cross flow between the liner and sleeve. Heat transfer was also aided by trip-strip turbulators on the outside of the liner and in the flowsleeve downstream of the jets. The study was aimed at enhancing heat transfer and prolonging the life of the combustor liner components. The combustor liner and flow sleeve were simulated using a flat-plate rig. The geometry has been scaled from actual combustion geometry except for the curvature. The jet Reynolds number and the mass-velocity ratios between the jet and cross flow in the rig were matched with the corresponding combustor conditions. A steady-state liquid crystal technique was used to measure spatially resolved heat transfer coefficients for the geometric and flow conditions mentioned above. The heat transfer was measured both in the impingement region as well as over the turbulators. A numerical model of the combustor test rig was created that included the impingement holes and the turbulators. Using CFD, the flow distribution within the flow sleeve and the heat transfer coefficients on the liner were both predicted. Calculations were made by varying the turbulence models, numerical schemes, and the geometrical mesh. The results obtained were compared to the experimental data and recommendations have been made with regard to the best modeling approach for such liner-flow sleeve configurations.
Optimization on the Performance Characteristics of a Magnetic Ericsson Refrigeration Cycle Affected by Multi-Irreversibilities
Authors: He Jizhou , Chen Jincan , Wu Chih
Published: November 2003

A general irreversible cycle model of a magnetic Ericsson refrigerator is established. The irreversibilities in the cycle model result from the finite-rate heat transfer between the working substance and the external heat reservoirs, the inherent regenerative loss, the additional regenerative loss due to thermal resistances, and the heat leak loss between the external heat reservoirs. The cycle model is used to optimize the performance of the magnetic Ericsson refrigeration cycle. The fundamental optimum relation between the cooling rate and the coefficient of performance of the cycle is derived. The maximum coefficient of performance, maximum cooling rate and other relevant important parameters are calculated. The optimal operating region of the cycle is determined. The results obtained here are very general and will be helpful for the optimal design and operation of the magnetic Ericsson refrigerators.
Propagation of Turbulent Natural Gas/Air Flames in Tubing With 90° Bends
Authors: Morgan Michael D. , Mehta S. A. (Raj) , Al-Himyary T. J. , Moore R. G. (Gord)
Published: November 2003

Anytime flammable gas mixtures are handled, there is a risk of combustion. This is particularly true in many industrial applications where space is limited and equipment is located near sources of ignition. Unfortunately, there is a lack of understanding of combustion phenomena within process equipment such as mufflers, rotating blowout preventers, liquid traps, and dry gas seal assemblies. These vessels have small internal volumes, complex internal geometries, and are connected using small diameter piping. This paper discusses the results of a parametric study which was carried out to establish the nature of combustion within such vessels and tubing. The test vessel had an internal volume of 7 in3 (115 ml) and the tubing had a nominal diameter of 0.5 in (1.27 mm). Flowing, turbulent, pre-mixed natural gas/air mixtures were used. The study did not attempt to increase turbulence using devices such as mesh screens or attempt to stabilize the flame. The results from a representative sample of 76 tests, from the 5,000+ tests that have been completed, are discussed herein. Typical pressure and temperature responses are presented and analyzed. It is demonstrated that flames can be remotely detected using only high speed pressure data. Turbulent flames were formed whose velocity was found to be linearly dependant on Reynolds number.
Experimental Study of Electrohydrodynamic Induction Pumping of a Dielectric Micro Liquid Film in External Horizontal Condensation Process
Authors: Brand K. , Seyed-Yagoobi J.
Published: November 2003

Electrohydrodynamic (EHD) induction pumping is based on charges induced in a dielectric liquid and delayed at a gradient or discontinuity of the electric conductivity. A traveling electric wave (AC) attracts or repels these induced charges, leading to liquid motion. EHD induction pumping of a dielectric micro condensation film, in an external horizontal configuration, is investigated experimentally. The pumping and its effect on heat transfer are explored by varying the voltage and frequency of the electric traveling wave, as well as the condensation heat flux. This study provides a fundamental understanding of induction pumping of micro liquid film and illustrates its potential for managing the flow and enhancing the heat transfer in the presence of phase change.
Study on Optimization of Transverse Thermal Conductivities of
Unidirectional Composites
Authors: Zou Mingqing , Yu Boming , Zhang Duanming , Ma Yongting
Published: November 2003

Two models, E-S and R-S unit cell models, are presented based on the thermal-electrical analogy technique. The analytical expressions for transverse thermal conductivities of unidirectional composites are derived. The dimensionless effective transverse thermal conductivities ke+ are expressed as a function of the ratio (β) of thermal conductivities of filler to matrix, filler volume fraction vf and the geometry ratio ρ=a/b of the filler. The optimization of transverse thermal conductivities of unidirectional composites is then analyzed under different filler volume fractions vf, thermal conductivity ratios β and different geometric architectures. The present analysis allows for a fairly precise evaluation of configuration performance and comparisons of different arrangements. The results show that if a composite is designed for insulation material, we should choose ρ<1, and if a composite is designed for heat dissipating purpose, we should choose ρ>1.
Thermal Resistance of Particle Laden Polymeric Thermal Interface Materials
Authors: Prasher Ravi S. , Shipley Jim , Prstic Suzana , Koning Paul , Wang Jin-lin
Published: November 2003

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research has primarily dealt with the understanding of the thermal conductivity of these types of TIMs. For thermal design, reduction of the thermal resistance is the end goal. Thermal resistance is not only dependent on the thermal conductivity, but also on the bond line thickness (BLT) of these TIMs. It is not clear which material property(s) of these particle laden TIMs affects the BLT and eventually the thermal resistance. This paper introduces a rheology based semiempirical model for the prediction of the BLT of these TIMs. BLT depends on the yield stress of the particle laden polymer and the applied pressure. The BLT model combined with the thermal conductivity model can be used for modeling the thermal resistance of these TIMs for factors such as particle volume faction, particle shape, base polymer viscosity, etc. This paper shows that there exists an optimal filler volume fraction at which thermal resistance is minimum. Finally this paper develops design rules for the optimization of thermal resistance for particle laden TIMs.