bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of keratinocyte growth factor and its receptor in clear cell acanthoma
Authors: Kovacs Daniela , Cota Carlo , Cardinali Giorgia , Aspite Nicaela , Bolasco Giulia , Amantea Ada , Torrisi Maria Rosaria , Picardo Mauro
Published: September 2006

Abstract:  The aetiopathogenic mechanism underlying clear cell acanthoma (CCA) is not completely clear and it has been postulated that CCA and psoriasis may have a similar pathogenesis because of the common features shared by the two diseases. As it has been recently demonstrated that in psoriatic lesions the paracrine epithelial growth factors [keratinocyte growth factor (KGF)/fibroblast growth factor (FGF)‐7 and FGF‐10] are involved in promoting and sustaining the keratinocyte hyperproliferation, the aim of this study was to analyse the expression of KGF on CCA lesions and to search for a role of this growth factor in CCA pathogenesis. Immunohistochemical analysis showed an up‐modulation of KGF in CCA, although the immunostaining was variable among the different samples collected. Positive immunoreactivity for KGF was detected mainly on dermal areas where the inflammatory infiltrate was more pronounced suggesting a relationship between lymphocyte activation and KGF up‐modulation. Real‐time quantitative RT‐PCR assay performed on mRNA extracted from formalin‐fixed paraffin‐embedded CCA and normal skin (NS) samples further demonstrated the overexpression of the KGF/FGF‐7 gene in all CCA samples compared with NS. Moreover, the evaluation by immunohistochemistry of KGF receptor distribution, the high‐affinity tyrosine kinase receptor for KGF, showed a down‐modulation of this receptor, as previously reported in the presence of increased levels of KGF. Taken together these results suggest the inflammatory nature of CCA and further support the hypothesis that this disease may represent, like psoriasis, an inflammatory dermatosis in which KGF up‐modulation may be responsible for keratinocyte hyperproliferation and may represent a new common feature of both diseases.
Influence of interleukin‐1α on androgen receptor expression and cytokine secretion by cultured human dermal papilla cells
Authors: Boivin Wendy A. , Jiang Huijun , Utting Oliver B. , Hunt David W. C.
Published: September 2006

Abstract:  Dermal papilla cells (DPC) control the growth character of the hair follicle through their elaboration of mitogenic factors and extracellular matrix components. Further, the dermal papilla is a primary site of androgen action in the hair follicle. Interleukin‐1α (IL‐1α) is prominent in skin wounding and inflammatory responses although regarded as a negative hair growth regulator. We studied the effect of IL‐1α and the potent androgen 5α‐dihydrotestosterone (DHT) on the expression of the androgen receptor (AR) and various factors secreted by cultured human temporal scalp DPC. IL‐1α triggered cellular changes consistent with nuclear factor‐κB pathway activation as well as reduced AR mRNA and protein expression levels for DHT‐stimulated DPC. This cytokine also increased DPC supernatant keratinocyte growth factor (KGF), vascular endothelial growth factor (VEGF), IL‐8 and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) concentrations. IL‐1α did not influence DPC supernatant levels of transforming growth factor‐β1, a negative hair growth regulator. The stimulatory effect of IL‐1α on DPC VEGF, GM‐CSF, KGF, and IL‐8 expression was also evident at the mRNA level for these cytokines. IL‐1α also increased mRNA transcript levels of protease‐nexin‐1, a secreted serine protease inhibitor expressed in the dermal papilla of anagen‐stage hair follicles. Although DHT did not affect supernatant cytokine concentrations, the androgen altered mRNA transcript levels of several factors for DPC co‐stimulated with IL‐1α. In consideration of its in vitro activity profile, IL‐1α may be an important modifier of dermal papilla activity as well as potentially influence androgen‐regulated gene expression in DPC.
FOXM1c transactivates the human c‐myc promoter directly via the two TATA boxes P1 and P2
Authors: Wierstra Inken , Alves Jürgen
Published: September 2006

FOXM1c transactivates the c‐myc promoter via the P1 and P2 TATA boxes using a new mechanism. Whereas the P1 TATA box TATAATGC requires its sequence context to be FOXM1c responsive, the P2 TATA box TATAAAAG alone is sufficient to confer FOXM1c responsiveness to any minimal promoter. FOXM1c transactivates by binding to the TATA box as well as directly to TATA‐binding protein, transcription factor IIB and transcription factor IIA. This new transactivation mechanism is clearly distinguished from the function of FOXM1c as a conventional transcription factor. The central domain of FOXM1c functions as an essential domain for activation via the TATA box, but as an inhibitory domain (retinoblastoma protein‐independent transrepression domain and retinoblastoma protein‐recruiting negative regulatory domain) for transactivation via conventional FOXM1c‐binding sites. Each promoter with the P2 TATA box TATAAAAG is postulated to be transactivated by FOXM1c. This was demonstrated for the promoters of c‐fos, hsp70 and histone H2B/a. A database search revealed almost 300 probable FOXM1c target genes, many of which function in proliferation and tumorigenesis. Accordingly, dominant‐negative FOXM1c proteins reduced cell growth approximately threefold, demonstrating a proliferation‐stimulating function for wild‐type FOXM1c.
A novel HLA‐B allele, B*5612, identified by sequence‐based typing method
Authors: Chu C‐C. , Chang H‐L. , Chen Z‐S. , Lee H‐L. , Lin M.
Published: September 2006

HLA‐B*5612, found in Taiwan using sequence‐based typing method, was identical to HLA‐B*5502 in exon 2 but differed in exon 3 by 10 nucleotide substitutions at positions 353–420 leading to five amino acid change at codon 94, 95, 97, 103 and 116. As this sequence motif was not found in the Asian population, it is likely that HLA‐B*5612 is the product of a complex mechanism of implying a dual gene conversion event.
Increase in interleukin‐6 following arterial injury is related to insulin resistance, the −174G→C polymorphism and complex plaque morphology
Authors: Marso S. P. , House J. A. , Hopkins P. J.
Published: September 2006

Interleukin‐6 (IL‐6) is associated with many disease states in humans. We prospectively sought to determine whether IL‐6 levels increased following percutaneous coronary intervention (PCI) in the absence of myonecrosis. Additionally, we systematically assessed other clinical and anatomic factors associated with IL‐6 levels in a population of patients with coronary atherosclerosis undergoing PCI. Blood samples were collected from 117 patients at baseline, 8 and 16 h following PCI. Samples were assayed for IL‐6, creatine kinase‐myocardial band (CK‐MB), troponin‐I (Tn‐I), high sensitivity C‐reactive protein, glucose, haemoglobin A1c, and a lipid profile. Genotyping of the −174G→C polymorphism of the IL‐6 gene was performed. IL‐6 levels increased following PCI among the study group (slope = 0.4 pg/mL/h, P = 0.001). IL‐6 levels increased to a similar degree in the absence of myonecrosis. Patients with the XC genotype (either having the GC or the CC allele) had higher IL‐6‐values at baseline compared to GG genotype patients (4.9 ± 6.4 vs. 2.6 ± 1.8 pg/mL, P = 0.02). Multivariable predictors of detectable baseline IL‐6 levels included XC genotype (odds ratio [OR]: 4.14, 95% CI 1.58–10.82, P = 0.004), ACC/AHA type C lesion classification (OR: 4.08, 95% CI 1.54–10.84, P = 0.005), elevated baseline Tn‐I (OR: 3.31, 95% CI 1.16–9.43, P = 0.025), diabetes (OR: 3.00, 95% CI 1.11–8.09, P = 0.030), and waist circumference (OR: 1.49, 95% CI 1.08–2.06, P = 0.015). Predictors of peak IL‐6 following PCI included the XC genotype (estimate 1.4, 95% CI 1.06–1.87, P = 0.019), homeostasis model assessment (estimate 0.99, 95% 0.982–0.999, P = 0.042) and baseline Tn‐I > upper limit of normal (estimate 0.7, 95% CI 0.50–0.96, P = 0.039). Lastly, IL‐6 increased following PCI even in the absence of myonecrosis as measured by Tn‐I elevation. IL‐6 levels are also related to the −174G→C polymorphism, arterial injury, lesion complexity, and insulin resistance.
A novel HLA‐B*2730 allele found in a Slovene patient affected with IgA nephropathy
Authors: Vidan‐Jeras B. , Kunilo S. , Fae I. , Kandus A. , Fischer G. F.
Published: September 2006

A novel allele HLA‐B*2730 and the haplotype HLA‐A*03‐B*2730‐Cw*02‐DRB1*16‐DRB5 have been found in a Slovene patient and his mother. The exon 2 sequence is identical to that of HLA‐B*2702, and the exon 3 sequence is identical to that of HLA‐B*2719. A possible mechanism for the generation of B*2730 is a gene conversion event.
A New Multiaxial Fatigue Testing Method for Variable-Amplitude Loading and Stress Ratio
Authors: George Tommy J. , Shen M.-H. Herman , Nicholas Theodore , Cross Charles J.
Published: September 2006

A new vibration-based multiaxial fatigue testing methodology for assessing high-cycle turbine engine material fatigue strength at various stress ratios is presented. The idea is to accumulate fatigue energy on a base-excited plate specimen at high-frequency resonant modes and to complete a fatigue test in a much more efficient way at very low cost. The methodology consists of (1) a topological design procedure, incorporating a finite element model, to characterize the shape of the specimens for ensuring the required stress state/pattern, (2) a vibration feedback empirical procedure for achieving the high-cycle fatigue experiments with variable-amplitude loading, and finally (3) a yielding procedure for achieving various uniaxial stress ratios. The performance of the methodology is demonstrated by the experimental results from mild steel, 6061-T6 aluminum, and Ti-6Al-4V plate specimens subjected to fully reversed bending for both uniaxial and biaxial stress states.
Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications
Authors: Preve´y Paul S. , Ravindranath Ravi A. , Shepard Michael , Gabb Timothy
Published: September 2006

Surface enhancement technologies such as shot peening, laser shock peening, and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The x-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including the following. (1) The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing the fatigue benefit of thermal stability at engine temperatures. (2) An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. (3) Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. (4) Corrosion fatigue mitigation with LPB in Carpenter 450 steel. (5) Damage tolerance improvement in 17-4 PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine operating temperatures.
Inlet Fogging of Gas Turbine Engines: Experimental and Analytical Investigations on Impaction Pin Fog Nozzle Behavior
Authors: Chaker Mustapha A. , Meher-Homji Cyrus B. , Mee Thomas
Published: September 2006

The inlet fogging of gas turbine engines for power augmentation has seen increasing application over the past decade. This paper provides the results of extensive experimental and theoretical studies conducted on impaction pin fog nozzles. It covers the important area of the fog plume pattern of impaction pin nozzles and examines fog-plume uniformity. The subject of sprinkle (large droplet formation) from the nozzles is also examined in detail and is shown to be nonsignificant. The effect, on evaporation rate, of ambient climatic conditions and the location of the fog nozzle with respect to the gas turbine inlet duct has been analytically and experimentally analyzed. An analytical model is used to study the evaporation dynamics of fog droplets injected in the inlet ducts. The model is validated experimentally in a wind tunnel.
Jet Engine Model for Control and Real-Time Simulations
Authors: Lichtsinder Michael , Levy Yeshayahou
Published: September 2006

The main objective of this paper is development of a simple real-time transient performance model for jet engine control. A jet engine arrives to its most dangerous condition during transient operation that may be triggered by fast changes of the input fuel command signal. Thus, the control system specifications are formulated to specify the maximal variance of the fuel flow command (from idle to maximum power level) during transient maneuver. Linear and piecewise-linear techniques are not always convenient and appropriate for turbine engine controller design. An alternative quasilinear simple/fast engine model is discussed in this paper. This model has maximum accuracy for maximal variance of the fuel flow input command in accordance to the jet engine control system specifications. The fast model is obtained using the Novel Generalized Describing Function, proposed for investigation of nonlinear control systems. The paper presents the Novel Generalized Describing Function definition and then discusses the application of this technique for the development a fast turbine engine simulation suitable for control and real-time applications. Simulation results are compared between the conventional and fast models and found to provide good agreement.
Evaluation of Interstage Water Injection Effect on Compressor and Engine Performance
Authors: Roumeliotis I. , Mathioudakis K.
Published: September 2006

The present paper examines the effect of water injection at the compressor inlet or between stages, on its operation. A wet compression model coupled with an engine performance model is used. The wet compression model produces the compressor performance map when water is present and consists of a one-dimensional stage stacking model, coupled with a droplet evaporation model. The effect of water injection on overall performance and individual stage operation is examined. The map-generation procedure is embedded in an engine performance model and a study of water injection effect on overall engine performance is undertaken. The possibility to evaluate the effect on various parameters such as power, thermal efficiency, surge margin, as well as the progression of droplets through the stages is demonstrated. The results indicate that water injection causes significant stage rematching, leading the compressor toward stall and that the performance enhancement is greater as the injection point moves towards compressor inlet.
Experimental Investigation of the Effect of Exhaust Gas Recirculation on Lubricating Oil Degradation and Wear of a Compression Ignition Engine
Authors: Singh Shrawan Kumar , Agarwal Avinash Kumar , Srivastava Dhananjay Kumar , Sharma Mukesh
Published: September 2006

This experimental investigation was aimed to investigate the effect of exhaust gas recirculation (EGR) on wear of in-cylinder engine parts. EGR setup was prepared for a two-cylinder, air-cooled, constant-speed direct-injection compression-ignition engine. Test setup was run for 96hr under predetermined loading cycles in two phases; normally, operating condition (i.e., without EGR) and with a fixed EGR rate of 25%. Addition of metallic wear debris in the lubricating oil samples drawn after regular interval from both engine operating phases was investigated. Relatively higher concentrations of all wear metals were found in the lubricating oil of the EGR-operated engine, which indicates higher wear of various engine parts. Weight loss of piston rings used in both phases was compared to quantify the amount of wear of piston rings. To quantify the amount of cylinder wear surface roughness parameters of cylinder liners were measured at three positions (top dead center, mid-stroke, and bottom dead center) on thrust and anti-thrust side. A qualitative analysis was also carried out by taking surface profiles and Scanning Electron Micrographs at same locations.
A Reassessment of the Alternative Regeneration Cycle
Authors: Dellenback Paul A.
Published: September 2006

Two prior papers and several patents have considered improvements to a gas turbine engine’s cycle efficiency by using two turbines in series with an intermediate heat exchanger that preheats combustion air. This approach allows heating the combustion air to temperatures higher than those that can be achieved with “conventional regeneration” in which the combustion products are fully expanded across a turbine before any heat recovery. Since heat addition in the combustor of the “alternative regeneration” cycle occurs at a higher average temperature, then under certain conditions the cycle efficiency can be higher than that available from a cycle using conventional regeneration. This paper reconsiders the usefulness of the alternative regeneration cycle with more detailed modeling than has been presented previously. The revised modeling shows that the alternative regeneration cycle can produce efficiencies higher than conventional regeneration, but only for a more limited set of conditions than previously reported. For high-technology engines operating at high temperatures, the alternative regeneration cycle efficiencies can be three to four percentage points better than comparable conventional regeneration cycles. For lower-technology engines, which are more typical of those currently installed, improvements in efficiency only occur at lower values of heat exchanger effectiveness, which limits the usefulness of the alternative regeneration cycle. Also considered is an extension to the cycle that employs a second heat exchanger downstream of the second turbine for the purpose of further preheating the combustion air. In its optimum configuration, this “staged heat recovery” can produce additional small improvements of between 0.3 and 2.3 percentage points in cycle efficiency, depending on the particular cycle parameters assumed.
Constrained Optimization of Gas Turbine Tilting Pad Bearing Designs
Authors: Angantyr Anders , Aidanpää Jan-Olov
Published: September 2006

This paper presents the constrained optimization of the tilting pad bearing design on a gas turbine rotor system. A real coded genetic algorithm with a robust constraint handling technique is used as the optimization method. The objective is to develop a formulation of the optimization problem for the late bearing design of a complex rotor-bearing system. Furthermore, the usefulness of the search method is evaluated on a difficult problem. The effects considered are power loss and limiting temperatures in the bearings as well as the dynamics at the system level, i.e., stability and unbalance responses. The design variables are the bearing widths and radial clearances. A nominal design is the basis for comparison of the optimal solution found. An initial numerical experiment shows that finding a solution that fulfills all the constraints for the system design is likely impossible. Still, the optimization shows the possibility of finding a solution resulting in a reduced power loss while not violating any of the constraints more than the nominal design. Furthermore, the result also shows that the used search method and constraint handling technique works on this difficult problem.
Utilization of Low-Calorific Gaseous Fuel in a Direct-Injection Diesel Engine
Authors: Mohammadi Ali , Shioji Masahiro , Ishiyama Takuji , Kitazaki Masato
Published: September 2006

Low-calorific gases with a small portion of hydrogen are produced in various chemical processes, such as gasification of solid wastes or biomass. The aim of this study is to clarify the efficient usage of these gases in diesel engines used for power generation. Effects of amount and composition of low-calorific gases on diesel engine performance and exhaust emissions were experimentally investigated adding hydrogen-nitrogen mixtures into the intake gas of a single-cylinder direct-injection diesel engine. The results indicate that optimal usage of low-calorific gases improves NOx and Smoke emissions with remarkable saving in diesel fuel consumption.
Fourier Neural Networks and Generalized Single Hidden Layer Networks in Aircraft Engine Fault Diagnostics
Authors: Tan H. S.
Published: September 2006

The conventional approach to neural network-based aircraft engine fault diagnostics has been mainly via multilayer feed-forward systems with sigmoidal hidden neurons trained by back propagation as well as radial basis function networks. In this paper, we explore two novel approaches to the fault-classification problem using (i) Fourier neural networks, which synthesizes the approximation capability of multidimensional Fourier transforms and gradient-descent learning, and (ii) a class of generalized single hidden layer networks (GSLN), which self-structures via Gram-Schmidt orthonormalization. Using a simulation program for the F404 engine, we generate steady-state engine parameters corresponding to a set of combined two-module deficiencies and require various neural networks to classify the multiple faults. We show that, compared to the conventional network architecture, the Fourier neural network exhibits stronger noise robustness and the GSLNs converge at a much superior speed.
Design of Aero Gas Turbines Using Hydrogen
Authors: Haglind Fredrik , Singh Riti
Published: September 2006

Mainly owing to the dwindling fossil oil resources and the environmental concerns of discharging greenhouse gases into the atmosphere, it is essential to find an alternative to kerosene for civil aviation. This paper covers the main effects on aero engines when changing to hydrogen fuel. Particularly, emission and performance issues are discussed, but some design matters are also covered. By simply changing to hydrogen, small engine performance gains may be obtained. The results of the calculations suggest that there is the potential to design a combustion system using hydrogen that produces less NOx emissions than any system using kerosene.
A Sequential Approach for Gas Turbine Power Plant Preventative Maintenance Scheduling
Authors: Zhao Yongjun , Volovoi Vitali , Waters Mark , Mavris Dimitri
Published: September 2006

Traditionally, gas turbine power plant preventive maintenance schedules are set with constant intervals based on recommendations from the equipment suppliers. Preventive maintenance is based on fleet-wide experience as a guideline as long as individual unit experience is not available. In reality, the operating conditions for each gas turbine may vary from site to site and from unit to unit. Furthermore, the gas turbine is a repairable deteriorating system, and preventive maintenance usually restores only part of its performance. This suggests a gas turbine needs more frequent inspection and maintenance as it ages. A unit-specific sequential preventive maintenance approach is therefore needed for gas turbine power plant preventive maintenance scheduling. Traditionally, the optimization criteria for preventive maintenance scheduling is usually cost based. However, in the deregulated electric power market, a profit-based optimization approach is expected to be more effective than the cost-based approach. In such an approach, power plant performance, reliability, and the market dynamics are considered in a joint fashion. In this paper, a novel idea that economic factors drive maintenance frequency and expense to more frequent repairs and greater expense as equipment ages is introduced, and a profit-based unit-specific sequential preventive maintenance scheduling methodology is developed. To demonstrate the feasibility of the proposed approach, a conceptual level study is performed using a base load combined cycle power plant with a single gas turbine unit.
A New Criterion to Determine the Start of Combustion in Diesel Engines
Authors: Katrašnik Tomaž , Trenc Ferdinand , Oprešnik Samuel Rodman
Published: September 2006

A new criterion for the determination of the start of combustion (SOC) from the diesel engine in-cylinder pressure diagram was developed. It is defined as the maximum of the third-order derivative of the cylinder pressure with respect to the crank angle. This criterion declares SOC more precisely than other previously published criteria based on pressure diagnostics. This fact was proven analytically and was discernable from the analysis of the experimental data. Besides its accuracy it is also robust enough to allow automatic evaluation of the SOC during processing of the pressure data for a large number of cycles. By applying the first law of thermodynamics analysis to the engine cylinder it was discovered that the third-order derivative of the in-cylinder pressure with respect to the crank angle is the most suitable criterion for determination of the SOC from the in-cylinder pressure diagram. Subsequently, the criterion was validated through experimental data analysis of the in-cylinder pressure diagrams for various engine speeds and loads. In order to evaluate the rate of heat release (ROHR), which formed the base for the experimental validation, in-cylinder pressure diagrams were processed with a computer code based on the first law of thermodynamics. The cylinder pressure was measured with an advanced piezoelectric sensor at the resolution 0.1 deg CA. Top dead center was determined with the capacitive top dead center sensor. Due to the analytic foundation of the developed method and its validation through highly accurate experimental data it can be concluded that new criterion is credible for the determination of the SOC.
A Comparative Study of Different Methods of Using Animal Fat as a Fuel in a Compression Ignition Engine
Authors: Kumar M. Senthil , Kerihuel A. , Bellettre J. , Tazerout M.
Published: September 2006

This work explores a comparative study of different methods of using animal fat as a fuel in a compression ignition engine. A single-cylinder air-cooled, direct-injection diesel engine is used to test the fuels at 100% and 60% of the maximum engine power output conditions. Initially, animal fat is tested as fuel at normal temperature. Then, it is preheated to 70°C and used as fuel. Finally, animal fat is converted into methanol and ethanol emulsions using water and tested as fuel. A drop in cylinder peak pressure, longer ignition delay, and a lower premixed combustion rate are observed with neat animal fat as compared to neat diesel. With fat preheating and emulsions, there is an improvement in cylinder peak pressure and maximum rate of pressure rise. Ignition delay becomes longer with both the emulsions as compared to neat fats. However, preheating shows shorter ignition delay. Improvement in heat release rates is achieved with all the methods as compared to neat fats. At normal temperature, neat animal fat results in higher specific energy consumption and exhaust gas temperature as compared to neat diesel at both power outputs. Preheating and emulsions of animal fat show improvement in performance as compared to neat fat. Smoke is lower with neat fat as compared to neat diesel. It reduces further with all the methods. At peak power output, the smoke level is found as 0.89m−1 with methanol, 0.28m−1 with ethanol emulsions, and 1.7m−1 with fat preheating, whereas it is 3.7m−1 with neat fat and 6.3m−1 with neat diesel. Methanol and ethanol emulsions significantly reduce NO emissions due to the vaporization of water and alcohols. However, NO increases with fat preheating due to high in-cylinder temperature. Higher unburned hydrocarbon and carbon monoxide emissions are found with neat fat as compared to neat diesel at both power outputs. However, these emissions are considerably reduced with all the methods. It is finally concluded that adopting emulsification with the animal fat can lead to a reduction in emissions and an improvement in combustion characteristics of a diesel engine.
A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application
Authors: Chan K. S. , Enright M. P.
Published: September 2006

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MICROFAVA (micromechanical fatigue variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α+β Ti-alloy Ti-6Al-4V.
A Review of Wave Rotor Technology and Its Applications
Authors: Akbari Pezhman , Nalim Razi , Mueller Norbert
Published: September 2006

The objective of this paper is to provide a succinct review of past and current research in developing wave rotor technology. This technology has shown unique capabilities to enhance the performance and operating characteristics of a variety of engines and machinery utilizing thermodynamic cycles. Although there have been a variety of applications in the past, this technology is not yet widely used and is barely known to engineers. Here, an attempt is made to summarize both the previously reported work in the literature and ongoing efforts around the world. The paper covers a wide range of wave rotor applications including the early attempts to use wave rotors, its successful commercialization as superchargers for car engines, research on gas turbine topping, and other developments. The review also pays close attention to more recent efforts: utilization of such devices in pressure-gain combustors, ultra-micro gas turbines, and water refrigeration systems, highlighting possible further efforts on this topic. Observations and lessons learnt from experimental studies, numerical simulations, analytical approaches, and other design and analysis tools are presented.
Nanoscale Heat Conduction Across Metal-Dielectric Interfaces
Authors: Ju Y. “Sungtaek” , Hung Ming-Tsung , Usui Takane
Published: September 2006

We report a theoretical study of heat conduction across metal-dielectric interfaces in devices and structures of practical interest. At cryogenic temperatures, the thermal interface resistance between electrodes and a substrate is responsible for substantial reduction in the maximum permissible peak power in Josephson junctions. The thermal interface resistance is much smaller at elevated temperatures but it still plays a critical role in nanoscale devices and structures, especially nanolaminates that consist of alternating metal and dielectric layers. A theoretical model is developed to elucidate the impact of spatial nonequilibrium between electrons and phonons on heat conduction across nanolaminates. The diffuse mismatch model is found to provide reasonable estimates of the intrinsic thermal interface resistance near room temperature as well as at cryogenic temperatures.
The Thickness of the Liquid Microlayer Between a Cap-Shaped Sliding Bubble and a Heated Wall: Experimental Measurements
Authors: Li Xin , Hollingsworth D. Keith , Witte Larry C.
Published: September 2006

A laser-based method has been developed to measure the thickness of the liquid microlayer between a cap-shaped sliding bubble and an inclined heated wall. Sliding vapor bubbles are known to create high heat transfer coefficients along the surfaces against which they slide. The details of this process remain unclear and depend on the evolution of the microlayer that forms between the bubble and the surface. Past experiments have used heat transfer measurements on uniform-heat-generation surfaces to infer the microlayer thickness through an energy balance. These studies have produced measurements of 20–100 μm for refrigerants and for water, but they have yet to be confirmed by a direct measurement that does not depend on a first-law closure. The results presented here are direct measurements of the microlayer thickness made from a reflectance-based fiber-optic laser probe. Details of the construction and calibration of the probe are presented. Data for saturated FC-87 and a uniform-temperature surface inclined at 2 deg to 15 deg from the horizontal are reported. Millimeter-sized spherical bubbles of FC-87 vapor were injected near the lower end of a uniformly heated aluminum plate. The laser probe yielded microlayer thicknesses of 22–55 μm for cap-shaped bubbles. Bubble Reynolds numbers range from 600 to 4800, Froude numbers from 0.9 to 1.7, and Weber numbers from 2.6 to 47. The microlayer thickness above cap-shaped bubbles was correlated to a function of inclination angle and a bubble shape factor. The successful correlation suggests that this data set can be used to validate the results of detailed models of the microlayer dynamics.
Methods to Accelerate Ray Tracing in the Monte Carlo Method for Surface-to-Surface Radiation Transport
Authors: Mazumder Sandip
Published: September 2006

Two different algorithms to accelerate ray tracing in surface-to-surface radiation Monte Carlo calculations are investigated. The first algorithm is the well-known binary spatial partitioning (BSP) algorithm, which recursively bisects the computational domain into a set of hierarchically linked boxes that are then made use of to narrow down the number of ray-surface intersection calculations. The second algorithm is the volume-by-volume advancement (VVA) algorithm. This algorithm is new and employs the volumetric mesh to advance the ray through the computational domain until a legitimate intersection point is found. The algorithms are tested for two classical problems, namely an open box, and a box in a box, in both two-dimensional (2D) and three-dimensional (3D) geometries with various mesh sizes. Both algorithms are found to result in orders of magnitude gains in computational efficiency over direct calculations that do not employ any acceleration strategy. For three-dimensional geometries, the VVA algorithm is found to be clearly superior to BSP, particularly for cases with obstructions within the computational domain. For two-dimensional geometries, the VVA algorithm is found to be superior to the BSP algorithm only when obstructions are present and are densely packed.
PLANAR CROSSING NUMBERS OF GRAPHS EMBEDDABLE IN ANOTHER SURFACE
Authors: BÖRÖZKY KÁROLY J. , PACH JÁNOS , TÓTH GÉZA
Published: September 2006

Let G be a graph of n vertices with maximum degree d that can be drawn without crossing in a closed surface of Euler characteristic χ. It is proved that then G can be drawn in the plane with at most cχdn crossings, where cχis a constant depending only on χ. This result, which is tight up to a constant factor, is strengthened and generalized to the case when there is no restriction on the degrees of the vertices.
TRÉMAUX TREES AND PLANARITY
Authors: DE FRAYSSEIX HUBERT , DE MENDEZ PATRICE OSSONA , ROSENSTIEHL PIERRE
Published: September 2006

We present a simplified version of the DFS-based Left-Right planarity testing and embedding algorithm implemented in Pigale [1, 2], which has been considered as the fastest implemented one [3]. We give here a full justification of the algorithm, based on a topological properties of Trémaux trees.
CONVEX GRID DRAWINGS OF FOUR-CONNECTED PLANE GRAPHS
Authors: MIURA KAZUYUKI , NAKANO SHIN-ICHI , NISHIZEKI TAKAO
Published: September 2006

A convex grid drawing of a plane graph G is a drawing of G on the plane such that all vertices of G are put on grid points, all edges are drawn as straight-line segments without any edge-intersection, and every face boundary is a convex polygon. In this paper we give a linear-time algorithm for finding a convex grid drawing of every 4-connected plane graph G with four or more vertices on the outer face. The size of the drawing satisfies W + H ≤ n - 1, where n is the number of vertices of G, W is the width and H is the height of the grid drawing. Thus the area W · H is at most ⌈(n - 1)/2⌉ · ⌊(n - 1)/2⌋. Our bounds on the sizes are optimal in a sense that there exist an infinite number of 4-connected plane graphs whose convex drawings need grids such that W + H = n - 1 and W · H = ⌈(n - 1)/2⌉ · ⌊(n - 1)/2⌋.
ON EXTENDING A PARTIAL STRAIGHT-LINE DRAWING
Authors: PATRIGNANI MAURIZIO
Published: September 2006

We investigate the computational complexity of the following problem. Given a planar graph in which some vertices have already been placed in the plane, place the remaining vertices to form a planar straight-line drawing of the whole graph. We show that this extensibility problem, proposed in the 2003 "Selected Open Problems in Graph Drawing" [1], is NP-hard.
ON EMBEDDING A GRAPH ON TWO SETS OF POINTS
Authors: DI GIACOMO EMILIO , LIOTTA GIUSEPPE , TROTTA FRANCESCO
Published: September 2006

Let R and B be two sets of points such that the points of R are colored red and the points of B are colored blue. Let G be a planar graph such that |R| vertices of G are red and |B| vertices of G are blue. A bichromatic point-set embedding of G on R ∪ B is a crossing-free drawing of G such that each blue vertex is mapped to a point of B, each red vertex is mapped to a point of R, and each edge is a polygonal curve. We study the curve complexity of bichromatic point-set embeddings; i.e., the number of bends per edge that are necessary and sufficient to compute such drawings. We show that O(n) bends are sometimes necessary. We also prove that two bends per edge suffice if G is a 2-colored caterpillar and that for properly 2-colored caterpillars, properly 2-colored wreaths, 2-colored paths, and 2-colored cycles the number of bends per edge can be reduced to one, which is worst-case optimal.
TWO FIXED-PARAMETER TRACTABLE ALGORITHMS FOR TESTING UPWARD PLANARITY
Authors: HEALY PATRICK , LYNCH KAROL
Published: September 2006

In this paper we consider the problem of testing an arbitrary digraph G = (V,E) for upward planarity. In particular we describe two fixed-parameter tractable algorithms for testing the upward planarity of G. The first algorithm that we present can test the upward planarity of G in O(2t · t! · |V|2)-time where t is the number of triconnected components of G. The second algorithm that we present uses a standard technique known as kernelisation and can test the upward planarity of G in O(|V|2 + k4 · (2k)!)-time, where k = |E| - |V|.
CONVEX DRAWINGS OF PLANE GRAPHS OF MINIMUM OUTER APICES
Authors: MIURA KAZUYUKI , AZUMA MACHIKO , NISHIZEKI TAKAO
Published: September 2006

In a convex drawing of a plane graph G, every facial cycle of G is drawn as a convex polygon. A polygon for the outer facial cycle is called an outer convex polygon. A necessary and sufficient condition for a plane graph G to have a convex drawing is known. However, it has not been known how many apices of an outer convex polygon are necessary for G to have a convex drawing. In this paper, we show that the minimum number of apices of an outer convex polygon necessary for G to have a convex drawing is, in effect, equal to the number of leaves in a triconnected component decomposition tree of a new graph constructed from G, and that a convex drawing of G having the minimum number of apices can be found in linear time.
RESILIENT LKH: SECURE MULTICAST KEY DISTRIBUTION SCHEMES
Authors: SAFAVI-NAINI REIHANEH , WANG HUAXIONG , WONG DUNCAN S.
Published: September 2006

Multicasting has become the main mode communication for providing a wide range of Internet services such as video broadcasting and multi-party teleconferencing, where data must be delivered to multiple recipients. The main focus of the work on securing multicast applications has been to control access and to ensure that only authorised users can access the broadcast. The authorised group is not fixed and may change over time and hence efficient methods of re-keying are of very important. Logical Key Hierarchy (LKH) schemes are schemes that use a logical tree to assign keys to users: each user will be attached to a leaf of the tree and will own all the keys allocated to the nodes from that leaf to the root of the tree. In this paper we propose a new LKH scheme in which only a subset of leaves are attached to users. This allows separation of the key sets of the users and providing protection against collusion attack. This property combined with the logarithmic size of the group controller storage makes the approach very attractive. We give a number of constructions, the best of which also has logarithmic cost for users' key storage and communication.
REPRESENTATIONS AND PROPERTIES OF GENERALIZED Ar STATISTICS
Authors: DAOUD M.
Published: September 2006

A generalization of Ar statistics is proposed and developed. The generalized Ar quantum statistics is completely specified by a set of Jacobson generators satisfying a set of triple algebraic relations. Fock–Hilbert representations and Bargmann–Fock realizations are derived.
EXOTIC PARTICLES AND w∞-ALGEBRAS IN TWO- AND HIGH-DIMENSIONAL SPACES
Authors: DOUARI J.
Published: September 2006

We construct a set of noncommuting translation operators in two- and high-dimensional lattices. The algebras they close are w∞-algebras. The construction is based on the introduction of noncommuting elementary link operators which link two neighborhood sites in the lattice. This type of operators preserve the braiding nature of exotic particles living basically in two-dimensional space.
THE HIGGS SECTOR ON A TWO-SHEETED SPACE–TIME
Authors: MACESANU COSMIN , WALI KAMESHWAR C.
Published: September 2006

We present a general formalism based on the framework of noncommutative geometry, suitable to the study of the standard model of electroweak interactions, as well as that of more general gauge theories. Left- and right-handed chiral fields are assigned to two different sheets of space–time (a discretized version of Kaluza–Klein theory). Scalar Higgs fields find themselves treated on the same footing as the gauge fields, resulting in spontaneous symmetry breaking in a natural and predictable way. As a first test, we apply the formalism to the Standard Model, where one can predict the Higgs mass and the top Yukawa coupling. The results obtained for this case are similar with results obtained in alternate formulations. We then study the left–right symmetric model, where we show that this framework imposes interesting constraints on the type and coefficients of terms appearing in the Higgs potential.
GENERALIZED DUAL SYMMETRY OF NON-ABELIAN THEORIES AND THE FREEZING OF αs
Authors: DAS C. R. , LAPERASHVILI L. V. , NIELSEN H. B.
Published: September 2006

The quantum Yang–Mills theory, describing a system of fields with nondual (chromoelectric g) and dual (chromomagnetic [Formula: see text]) charges and revealing the generalized dual symmetry, is developed by analogy with the Zwanziger formalism in QED. The renormalization group equations (RGE's) for pure non-Abelian theories are analyzed for both constants, α = g2/4π and [Formula: see text]. The pure [Formula: see text] gauge theory is investigated as an example. We consider not only monopoles, but also dyons. The behavior of the total SU(3) β-function is investigated in the whole region of α≡αs: 0≤α < ∞. It is shown that this β-function is antisymmetric under the interchange α ↔ 1/α and is given by the well-known perturbative expansion not only for α≪1, but also for α≫1. Using an idea of the Maximal Abelian Projection by 't Hooft, we have considered the formation of strings — the ANO flux tubes — in the Higgs model of scalar monopole (or dyon) fields. In this model we have constructed the behavior of the β-function in the vicinity of the point α = 1, where it acquires a zero value. Considering the phase transition points at α≈0.4 and α≈2.5, we give the explanation of the freezing of αs. The evolution of [Formula: see text] with energy scale μ and the behavior of V eff (μ) are investigated for both, perturbative and nonperturbative regions of QCD. It was shown that the effective potential has a minimum, ensured by the dual sector of QCD. The gluon condensate [Formula: see text], corresponding to this minimum, is predicted: [Formula: see text], in agreement with the well-known results.
ON THE BEKENSTEIN–HAWKING ENTROPY, NONCOMMUTATIVE BRANES AND LOGARITHMIC CORRECTIONS
Authors: KRAUSE AXEL
Published: September 2006

We extend our earlier work on the possible microscopic origin of the Bekenstein–Hawking entropy to higher-dimensional space–times. The mechanism of counting chain-like states is shown to work for space–times with event horizon wrapped by a Euclidean doublet (E1,M1)+(E2,M2) of electric–magnetic dual brane pairs of type II string-theory or M-theory. Noncommutativity on the brane worldvolume enters naturally the derivation of the Bekenstein–Hawking entropy including the correct prefactor. Moreover, a logarithmic correction with prefactor 1/2 is predicted.
ROLE OF FINAL STATE INTERACTIONS IN THE B MESON DECAY INTO TWO PIONS
Authors: DEANDREA ALDO , LADISA MASSIMO , NARDULLI GIUSEPPE , LAPORTA VINCENZO , SANTORELLI PIETRO
Published: September 2006

We estimate final state interactions in the B-meson decays into two pions by the Regge model. We consider Pomeron exchange and the leading Regge trajectories that can relate intermediate particles to the final state. In some cases, most notably B→π0π0 and B→π+π-, the effect is relevant and produces a better agreement between theory and experiment.
IMPROVEMENTS TO THE SPHERICAL COLLAPSE MODEL
Authors: DEL POPOLO ANTONINO
Published: September 2006

We study the joint effect of dynamical friction, tidal torques and cosmological constant on clusters of galaxy formation. We show that within high-density environments, such as rich clusters of galaxies, both dynamical friction and tidal torques slow down the collapse of low-ν peaks producing an observable variation in the time of collapse of the perturbation and, as a consequence, a reduction in the mass bound to the collapsed perturbation. Moreover, the delay of the collapse produces a tendency for less dense regions to accrete less mass, with respect to a classical spherical model, inducing a biasing of over-dense regions toward higher mass. We show how the threshold of collapse is modified if dynamical friction, tidal torques and a non-zero cosmological constant are taken into account and we use the Extended Press–Schecter (EPS) approach to calculate the effects on the mass function. Then, we compare the numerical mass function given in D. Reed, Mon. Not. R. Astron. Soc.346, 565 (2003) with the theoretical mass function obtained in the present paper. We show that the barrier obtained in the present paper gives rise to a better description of the mass function evolution with respect to other previous models, R. K. Sheth and G. Tormen, Mon. Not. R. Astron. Soc.308, 119 (1999) and R. K. Sheth and G. Tormen, Mon. Not. R. Astron. Soc.329, 61 (2002).