bluuebunny/crossref_metadata_2025 huggingface dataset:
Location of main occluding areas and masticatory ability in patients with reduced occlusal support
Authors: Nakatsuka Y , Yamashita S , Nimura H , Mizoue S , Tsuchiya S , Hashii K
Published: March 2010

Background:  The purpose of this study was to investigate the differences in location of the main occluding area with reduction of occlusal support and to evaluate the subsequent impairment in masticatory ability.

Methods:  One hundred and two patients were recruited according to the Eichner’s index, which is based on the number of occlusal support zones. Each subject was instructed to clench a piece of temporary stopping in the particular occluding area that was preferably used during mastication. The main occluding area was judged by locating the tooth on which the temporary stopping rested. Subjective masticatory ability was self‐assessed by means of a questionnaire.

Results:  Group classification depending upon the location of the main occluding area was significantly associated with the category of the Eichner’s index. The level of masticatory ability was significantly associated with the category of the Eichner’s index. Moreover, masticatory ability was significantly more impaired in subjects with main occluding areas at the premolar regions compared to those at the molar regions.

Conclusions:  The location of the main occluding area may differ under the influence of the remaining natural teeth. The location of the main occluding area and the masticatory ability are likely to be closely related.
Parosteal osteosarcoma: report of a case and review of the literature
Authors: Huang TC , Monsour PA , Chahoud CD
Published: March 2010

Parosteal osteosarcoma is a rare malignancy of the bone that usually arises in the long bones. Involvement of the oral cavity is rare. Only 12 cases of intraoral parosteal osteosarcoma have been reported in the English language literature. This paper defines the major clinical, radiographic and histologic features of parosteal osteosarcoma and illustrates these with a case of a 33‐year‐old male presenting with a three‐month history of a painless enlarging lump in the right maxilla. A critical and comprehensive review of the English language literature is also provided.
Compromised first permanent molars: an orthodontic perspective
Authors: Ong DC‐V , Bleakley JE
Published: March 2010

The first permanent molar (FPM) is commonly subject to significant compromise which may arise due to caries or endodontic complication, or from developmental anomalies such as hypoplasia. Compromised teeth with questionable prognosis may result in short and long‐term clinical dilemmas. This review article highlights the factors that require careful consideration when a compromised FPM is detected and the importance of timely FPM extraction. Several clinical cases are described in detail to discuss possible treatment options from the orthodontic perspective.
A comparative histological analysis of human pulp following direct pulp capping with Propolis, mineral trioxide aggregate and Dycal
Authors: Parolia A , Kundabala M , Rao NN , Acharya SR , Agrawal P , Mohan M , Thomas M
Published: March 2010

Background:  Permanent teeth pulp exposures have traditionally been treated with calcium hydroxide pulp capping. The aim of this study was to investigate the response of human pulp tissue which were mechanically exposed to a new material, Propolis and compare it with two existing and commonly used pulp capping agents (mineral trioxide aggregate and Dycal).

Methods:  Thirty‐six intact human premolars were mechanically exposed. Teeth were divided into six groups of 6 teeth each and were capped with Propolis, mineral trioxide aggregate and Dycal. Final restoration was done with posterior composite resin using light cured glass ionomer cement as a liner. The teeth were then extracted on the 15th or the 45th day and processed for histological evaluation.

Results:  Differences in inflammatory response and dentine bridge formation of the exposed pulp to the three different materials were statistically calculated using chi‐square test and were found to be non‐significant. There was more pulp inflammation in teeth treated with Dycal than with Propolis and MTA on the 15th as well as on the 45th day. Propolis and MTA showed bridge formation in more teeth, and the bridges were in closer proximity to pulp capping material than teeth treated with Dycal on the 45th day.

Conclusions:  The response of pulps to Propolis as a pulp capping agent was comparable to MTA and Dycal.
Dental students’ knowledge and perceptions of non‐invasive dental caries management
Authors: Pakdaman A , Evans RW , Howe E
Published: March 2010

Background:  An evidence‐based, risk‐specific, and non‐invasive modality for caries management was implemented in the University of Sydney dentistry curriculum. This study reviews its impact on student learning outcomes and their perceptions of the efficacy of a risk‐based caries management.

Methods:  One hundred and nine Year 3 and Year 4 students were invited to complete a questionnaire to assess their understanding of the protocols and their perceptions of both the education process and value of the non‐invasive treatment modality.

Results:  A response rate of 93% Year 3 and 46% Year 4 students was obtained. They correctly identified high and low risk cases but Year 3 students were inclined to misclassify medium risk cases. Most understood correctly that enamel lesions should be arrested and remineralized but were often more radical in dealing with dentine lesions. Students who believed the protocols were useful and who spent more time on preventive care were less likely to restore enamel and dentine lesions.

Conclusions:  A modest level of knowledge concerning application of the non‐invasive caries management system to paper‐based clinical case studies was demonstrated. Protocol misinterpretation may reflect inconsistent instruction by some clinical tutors. It is hoped that the promulgation of evidence‐based dentistry will overcome these barriers in future.
A simple method to differentially exclude ants from tree canopies based on ant body size
Authors: Romeu‐Dalmau Carla , Espadaler Xavier , Piñol Josep
Published: March 2010

1. Ants are ubiquitous components of most terrestrial communities. Ant exclusion from tree canopies using sticky barriers is frequently used to ascertain the ant’s role in the community. This method is very effective but cannot differentiate between ant species, and excludes them all from the canopy.

2. Here we describe a simple method which permits free access of small ants to the canopy, and excludes ants larger than a defined size. This method is flexible in the sense that can be adapted to decide to some degree which species of ants in each particular community are allowed access to tree canopies.
Overcoming of a Resonance Stall and the Minimization of Amplitudes in the Transient Resonance of a Vibratory Machine by the Phase Modulation Method
Authors: Michalczyk J. , Bednarski Ł.
Published: March 2010

The present paper elucidates the difficulties faced in the practical implementation of phase modulation methods in the form that was presented by Wang et al. and in the actual systems where the motor driving moment is the control value. A more general model, which takes into consideration the impact of machine vibrations on the rotor angular velocity, was developed. The modification of the phase modulation method is also proposed. The usefulness of such an approach for shaping the transient resonance of the machines with an unbalanced rotor is proven by means of a simulation and an experiment.
Computational Study of a High-Expansion Ratio Radial Organic Rankine Cycle Turbine Stator
Authors: Harinck John , Turunen-Saaresti Teemu , Colonna Piero , Rebay Stefano , van Buijtenen Jos
Published: March 2010

There is a growing interest in organic Rankine cycle (ORC) turbogenerators because they are suitable as sustainable energy converters. ORC turbogenerators can efficiently utilize external heat sources at low to medium temperature in the small to medium power range. ORC turbines typically operate at very high pressure ratio and expand the organic working fluid in the dense-gas thermodynamic region, thus requiring computational fluid dynamics (CFD) solvers coupled with accurate thermodynamic models for their performance assessment and design. This article presents a comparative numerical study on the simulated flow field generated by a stator nozzle of an existing high-expansion ratio radial ORC turbine with toluene as working fluid. The analysis covers the influence on the simulated flow fields of the real-gas flow solvers: FLUENT, FINFLO, and ZFLOW, of two turbulence models and of two accurate thermodynamic models of the fluid. The results show that FLUENT is by far the most dissipative flow solver, resulting in large differences in all flow quantities and appreciably lower predictions of the isentropic nozzle efficiency. If the combination of the k−ω turbulence model and FINFLO solver is adopted, a shock-induced separation bubble appears in the calculated results. The bubble affects, in particular, the variation in the flow velocity and angle along the stator outlet. The accurate thermodynamic models by Lemmon and Span (2006, “Short Fundamental Equations of State for 20 Industrial Fluids,” J. Chem. Eng. Data, 51(3), pp. 785–850) and Goodwin (1989, “Toluene Thermophysical Properties From 178 to 800 K at Pressures to 1000 Bar,” J. Phys. Chem. Ref. Data, 18(4), pp. 1565–1636) lead to small differences in the flow field, especially if compared with the large deviations that would be present if the flow were simulated based on the ideal gas law. However, the older and less accurate thermodynamic model by Goodwin does differ significantly from the more accurate Lemmon–Span thermodynamic model in its prediction of the specific enthalpy difference, which leads to a considerably different value for the specific work and stator isentropic efficiency. The above differences point to a need for experimental validation of flow solvers in real-gas conditions, if CFD tools are to be applied for performance improvements of high-expansion ratio turbines operating partly in the real-gas regime.
Hybrid Wireless-Wired Optical Sensor for Extreme Temperature Measurement in Next Generation Energy Efficient Gas Turbines
Authors: Riza Nabeel A. , Sheikh Mumtaz , Perez Frank
Published: March 2010

Accuracy, reliability, and long lifetimes are critical parameters for sensors measuring temperature in gas turbines of clean coal-fired power plants. Greener high efficiency next generation power plants need gas turbines operating at extremely high temperatures of 1500°C, where present thermocouple temperature probe technology fails to operate with reliable and accurate readings over long lifetimes. To solve this pressing problem, we have proposed the concept of a new hybrid class of all-silicon carbide (SiC) optical sensor, where a single crystal SiC optical chip is embedded in a sintered SiC tube assembly, forming a coefficient of thermal expansion (CTE) matched all-SiC front-end probe. Because chip and host material are CTE matched, optimal handling of extreme thermal ramps and temperatures is possible. In this article, we demonstrate the first successful industrial combustor rig test of this hybrid all-SiC temperature sensor front-end probe indicating demonstrated probe structural robustness to 1600°C and rig test data to ∼1200°C. The design of the rig test sensor system is presented and data are analyzed.
Laser Beam Welding of Open-Porous Metallic Foams for Application in Cooling Structures of Combined Cycle Power Plants
Authors: Reisgen Uwe , Olschok Simon , Longerich Stefan
Published: March 2010

Within the Collaborative Research Centre 561, “Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants,” open-porous and high-temperature stable Ni-based structures are being developed for the requirements of effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, which allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open-porous metallic foam structure. The open-porous metallic foam is produced by the “slip reaction foam sintering” process, a powder metallurgical process. To join several foams to assemble structural elements, laser beam welding has been used. Different joining strategies have been examined to find out the most suitable method to join these foams. In this paper, the process setups, settings of the different strategies, and results of trials (seam geometry and strength tests) are discussed. The need for graded structures to combine the essential permeability and adequate weldability is also shown.
New Steel Alloys for the Design of Heat Recovery Steam Generator Components of Combined Cycle Gas Plants
Authors: Fernandes Jorge Pinto , Dias Lopes Eduardo Manuel , Maneta Vicente
Published: March 2010

Demand for power is growing everyday, mainly due to emerging economies in countries such as China, Russia, India, and Brazil. During the last 50 years steam pressure and temperature in power plants have been continuously raised to improve thermal efficiency. Recent efforts to improve efficiency leads to the development of a new generation of heat recovery steam generator, where the Benson once-through technology is applied to improve the thermal efficiency. The main purpose of this paper is to analyze the mechanical behavior of a high pressure superheater manifold by applying finite element modeling and a finite element analysis with the objective of analyzing stress propagation, leading to the study of damage mechanism, e.g., uniaxial fatigue, uniaxial creep for life prediction. The objective of this paper is also to analyze the mechanical properties of the new high temperature resistant materials in the market such as 2Cr Bainitic steels (T/P23 and T/P24) and also the 9–12Cr Martensitic steels (T/P91, T/P92, E911, and P/T122). For this study the design rules for construction of power boilers to define the geometry of the HPSH manifold were applied.
Effects of a Reacting Cross-Stream on Turbine Film Cooling
Authors: Anderson Wesly S. , Polanka Marc D. , Zelina Joseph , Evans Dave S. , Stouffer Scott D. , Justinger Garth R.
Published: March 2010

Film cooling plays a critical role in providing effective thermal protection to components in modern gas turbine engines. A significant effort has been undertaken over the last 40 years to improve the distribution of coolant and to ensure that the airfoil is protected by this coolant from the hot gases in the freestream. This film, under conditions with high fuel-air ratios, may actually be detrimental to the underlying metal. The presence of unburned fuel from an upstream combustor may interact with this oxygen rich film coolant jet resulting in secondary combustion. The completion of the reactions can increase the gas temperature locally resulting in higher heat transfer to the airfoil directly along the path line of the film coolant jet. This secondary combustion could damage the turbine blade, resulting in costly repair, reduction in turbine life, or even engine failure. However, knowledge of film cooling in a reactive flow is very limited. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred reactor operating at high temperatures over a flat plate. Surface temperatures, heat flux, and heat transfer coefficients are calculated for a variety of reactor fuel-to-air ratios, cooling hole geometries, and blowing ratios. Emphasis is placed on the difference between a normal cylindrical hole, an inclined cylindrical hole, and a fan-shaped cooling hole. When both air and nitrogen are injected through the cooling holes, the changes in surface temperature can be directly correlated with the presence of the reaction. Photographs of the localized burning are presented to verify the extent and locations of the reaction.
An Active Auxiliary Bearing Control Strategy to Reduce the Onset of Asynchronous Periodic Contact Modes in Rotor/Magnetic Bearing Systems
Authors: Cade Iain S. , Sahinkaya M. Necip , Burrows Clifford R. , Keogh Patrick S.
Published: March 2010

To prevent rotor/stator contact in a rotor/magnetic bearing system, auxiliary bearings may be located along the shaft and at the magnetic bearings. Rotor responses after a contact event may include periodic trapped modes where repeated contact may lead to highly localized thermal stresses. This paper considers an active auxiliary bearing system with a control strategy designed to limit the trapped contact modes in a rotor/magnetic bearing system that are induced by rotor unbalance. The controller is evaluated from a system model and its responses to short duration contact events. An active auxiliary bearing model is introduced to the system where the dynamic response of the bearing is dependent on the controller. From a harmonic decomposition of rotor/bearing contact, dynamic controllers are sought, which limit the numbers of possible periodic solutions for a given rotor unbalance and operating speed. A case study is performed considering a simple two degree of freedom system with passive and active auxiliary bearings. Recovery of a rotor trapped in an asynchronous contact mode is shown with variation of the auxiliary bearing controller parameters.
Active Compressor Stability Management Via a Stall Margin Control Mode
Authors: Liu Yuan , Dhingra Manuj , Prasad J. V. R.
Published: March 2010

An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode are described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine.
The Numerical and Experimental Characteristics of Multimode Dry-Friction Whip and Whirl
Authors: Wilkes Jason C. , Childs Dara W. , Dyck Benjamin J. , Phillips Stephen G.
Published: March 2010

The nature of dry-friction whip and whirl is investigated through experimental and numerical methods. A test rig was designed and constructed to demonstrate and record the character of multimode dry-friction whip and whirl. These tests examined steady-state whip and whirl characteristics for a variety of rub materials and clearances. A simulation model was constructed using tapered Timoshenko beam finite elements to form multiple-degree-of-freedom rotor and stator models. These models were reduced by component mode synthesis to discard high-frequency modes while retaining physical coordinates at the rub location to model rotor-stator interaction using a nonlinear contact model with Coulomb friction. Simulations were performed for specific test cases, and compared against experimental data; these comparisons are favorable. Experimental data analysis showed multiple whirl and whip regions, despite claims of previous investigators that these regions are predicted analytically but not produced in simulations or experiments. Spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions.
A New Kind of Multifunctional Energy System Based on Moderate Conversion of Chemical Energy of Fossil Fuels
Authors: Han Wei , Jin Hongguang
Published: March 2010

This paper proposes a new kind of multifunctional energy system (MES) using natural gas and coal to more efficiently and more economically produce methanol and power. Traditional chemical processes pursue high conversion ratios of chemical energy of fuels. The new MES focuses on the moderate conversion of the chemical energy of fuels. To do this, about 50% of the coal is partially gasified with pure oxygen and steam as oxidant, and then the unconverted residuals (char) and natural gas are utilized synthetically by char-fired reforming to generate syngas. The combustion of char drives the methane/steam-reforming reaction. Here, the reforming reaction is also moderately converted, and the reforming temperature is decreased 100–150°C compared with that of the conventional method. The carbon-rich syngas from the partial gasifier of coal and hydrogen-rich syngas from char-fired reformer are mixed together and converted into methanol at a proper conversion ratio (lower than that of the conventional chemical process). Finally, the unconverted syngas is used in a combined cycle as fuel for power generation. As a result, the total exergy efficiency of the new system is 55–60%. Comparing to individual systems, including the integrated gasification combined cycle and the natural gas-based methanol synthesis plants, this new system can generate 10–20% more electricity with the same quantity of fossil fuel input and methanol output. In addition, the possibility of reducing the size of gasifier, reformer, and methanol synthesis reactor may reduce investment costs accordingly. These results may provide a new way to use coal and natural gas more efficiently and economically.
Forced Response of Mistuned Bladed Disks in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results
Authors: Petrov Evgeny , Di Mare Luca , Hennings Holger , Elliott Robert
Published: March 2010

An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.
Experimental Analysis of the Combustion Behavior of a Gas Turbine Burner by Laser Measurement Techniques
Authors: Ax Holger , Stopper Ulrich , Meier Wolfgang , Aigner Manfred , Güthe Felix
Published: March 2010

Experimental results from optical and laser spectroscopic measurements on a scaled industrial gas turbine burner at elevated pressure are presented. Planar laser induced fluorescence on the OH radical and OH∗ chemiluminescence imaging were applied to natural gas/air flames for a qualitative analysis of the position and shape of the flame brush, the flame front and the stabilization mechanism. The results exhibit two different ways of flame stabilization, a conical more stable flame and a pulsating opened flame. For quantitative results, one-dimensional laser Raman scattering was applied to these flames and evaluated on an average and single-shot basis in order to simultaneously determine the major species concentrations, the mixture fraction, and the temperature. The mixing of fuel and air, as well as the reaction progress, could thus be spatially and temporally resolved, showing differently strong variations depending on the flame stabilization mode and the location in the flame.
A Mechanical Approach to Solve Two-Dimensional Static Electrical and Magnetic Fields: Applications to Contact Between Conductors Under Electrical Load
Authors: Hao S. , Wang Q. , Keer L. M.
Published: March 2010

A general approach has been developed to obtain analytical solutions to the boundary-value problems for a two-dimensional conductor under static electric and magnetic fields. This approach is based on a “congruity principle” between a solution of Maxwell’s equation and the corresponding linear elastic plane stress solution with constant mean stress or plane strain solution with constant mean in-plane stress. It also leads to a new avenue to construct analytical solutions of antiplane strain boundary-value problems using plane stress/strain solutions, or vice versa, in linear elastic theory. This approach has been applied for such engineering problems as contact between two conducting solid bodies under electrical load.
A Study on an Automatically Variable Intake Exhaust Injection Timing Turbocharging System for Diesel Engines
Authors: Yang Shiyou , Deng Kangyao , Cui Yi , Gu Hongzhong
Published: March 2010

A new turbocharging system, named automatically variable intake exhaust injection timing (AVIEIT), is proposed. Its main purpose is to improve the performance of low-speed high torque operating conditions and improve the economy of high-speed operating conditions for high-speed supercharged intercooled diesel engines. The principle of the AVIEIT turbocharging system is presented. A control mechanism for the proposed AVIEIT system used for a truck diesel engine is introduced. An engine simulation code has been developed. In this code, a zero-dimensional in-cylinder combustion model, a one-dimensional finite volume method-total variation diminishing model for unsteady gas flow in the intake and exhaust manifolds, and a turbocharger model are used. The developed code is used to simulate the performances of diesel engines using the AVIEIT system. Simulations of a military use diesel engine “12V150” and a truck diesel engine “D6114” using the AVIEIT system have been performed. Simulation results show that the in-cylinder charge air amount of the diesel engine with the AVIEIT system is increased at low-speed high torque operating conditions, and the fuel economy is improved at high-speed operating conditions. In order to test the idea of the AVIEIT system, an experiment on a truck diesel engine D6114 equipped with an AVIEIT control mechanism has been finished. The experiment results show that the AVIEIT system can improve the economy of high-speed operating conditions. Both the simulation and experiment results suggest that the AVIEIT system has the potential to replace the waste-gate and variable geometry turbocharger turbocharging systems.
In-Cylinder Flow Computational Fluid Dynamics Analysis of a Four-Valve Spark Ignition Engine: Comparison Between Steady and Dynamic Tests
Authors: Ramajo Damian E. , Nigro Norberto M.
Published: March 2010

Numerical and experimental techniques were applied in order to study the in-cylinder flow field in a commercial four-valve per cylinder spark ignition engine. Investigation was aimed at analyzing the generation and evolution of tumble-vortex structures during the intake and compression strokes, and the capacity of this engine to promote turbulence enhancement during tumble degradation at the end of the compression stroke. For these purposes, three different approaches were analyzed. First, steady flow rig tests were experimentally carried out, and then reproduced by computational fluid dynamics (CFD). Once CFD was assessed, cold dynamic simulations of the full engine cycle were performed for several engine speeds (1500 rpm, 3000 rpm, and 4500 rpm). Steady and cold dynamic results were compared in order to assess the feasibility of the former to quantify the in-cylinder flow. After that, combustion was incorporated by means of a homogeneous heat source, and dynamic boundary conditions were introduced in order to approach real engine conditions. The combustion model estimates the burning rate as a function of some averaged in-cylinder flow variables (temperature, pressure, turbulent intensity, and piston position). Results were employed to characterize the in-cylinder flow field of the engine and to establish similarities and differences between the three performed tests that are currently used to estimate the engine mean flow characteristics (steady flow rig, and cold and real dynamic simulations).
The Contact Problem in Ultrasonic Traveling-Wave Motors
Authors: Sattel Thomas , Hagedorn Peter , Schmidt Joachim
Published: March 2010

In this paper the contact mechanism between stator and rotor will be considered in detail, which plays a key role in ultrasonic motors. A planar contact model for the stator-rotor interaction in traveling-wave type ultrasonic motors is derived, including rotor flexibility and differenciating between stick and slip regions in the contact zones. The model analysis shows that depending on the motor’s operating conditions, complicated contact behavior may occur with several stick-slip subzones in each contact zone. The typical nonlinear resonance observed in ultrasonic motors can be explained with the present analysis. Both the stiffness of the contact layer and of the rotor may drastically influence the speed-torque characteristics. The results will contribute to a better understanding of the contact mechanics in ultrasonic motors.
Low Dimensional Approximations to Ferroelastic Dynamics and Hysteretic Behavior Due to Phase Transformations
Authors: Wang Linxiang X. , Melnik Roderick V. N.
Published: March 2010

In this paper, a low dimensional model is constructed to approximate the nonlinear ferroelastic dynamics involving mechanically and thermally-induced martensite transformations. The dynamics of the first order martensite transformation is first modeled by a set of nonlinear coupled partial differential equations (PDEs), which is obtained by using the modified Ginzburg–Landau theory. The Chebyshev collocation method is employed for the numerical analysis of the PDE model. An extended proper orthogonal decomposition is then carried out to construct a set of empirical orthogonal eigenmodes of the dynamics, with which system characteristics can be optimally approximated (in a specified sense) within a range of different temperatures and under various mechanical and thermal loadings. The performance of the low dimensional model is analyzed numerically. Results on the dynamics involving mechanically and thermally-induced phase transformations and the hysteresis effects induced by such transformations are presented.
Kinematic Limit Analysis of Nonassociated Perfectly Plastic Material by the Bipotential Approach and Finite Element Method
Authors: Chaaba Ali , Bousshine Lahbib , De Saxce Gery
Published: March 2010

Limit analysis is one of the most fundamental methods of plasticity. For the nonstandard model, the concept of the bipotential, representing the dissipated plastic power, allowed us to extend limit analysis theorems to the nonassociated flow rules. In this work, the kinematic approach is used to find the limit load and its corresponding collapse mechanism. Because the bipotential contains in its expression the stress field of the limit state, the kinematic approach is coupled with the static one. For this reason, a solution of kinematic problem is obtained in two steps. In the first one, the stress field is assumed to be constant and a velocity field is computed by the use of the kinematic theorem. Then, the second step consists to compute the stress field by means of constitutive relations keeping the velocity field constant and equal to that of the previous step. A regularization method is used to overcome problems related to the nondifferentiability of the dissipation function. A successive approximation algorithm is used to treat the coupling question. A simple compression-traction of a nonassociated rigid perfectly plastic material and an application of punching by finite element method are presented in the end of the paper.
Probability Density Function Solution of Nonlinear Oscillators Subjected to Multiplicative Poisson Pulse Excitation on Velocity
Authors: Zhu H. T. , Er G. K. , Iu V. P. , Kou K. P.
Published: March 2010

The stationary probability density function (PDF) solution of the stochastic responses is derived for nonlinear oscillators subjected to both additive and multiplicative Poisson white noises. The PDF solution is governed by the generalized Fokker–Planck–Kolmogorov (FPK) equation and obtained with the exponential-polynomial closure (EPC) method, which was originally proposed for solving the FPK equation. The extended EPC solution procedure is presented for the case of Poisson pulses in this paper. In order to evaluate the effectiveness of the solution procedure, nonlinear oscillators are investigated under multiplicative Poisson white noise excitation on velocity and additive Poisson white noise excitation. Both weakly and strongly nonlinear oscillators are considered, respectively. In the numerical analysis, both the unimodal and bimodal stationary PDFs of oscillator responses are obtained with the EPC method and Monte Carlo simulation. Compared with the simulation results, good agreement is achieved with the presented solution procedure in the case of the polynomial degree being 6, especially in the tail regions of the PDFs of the system responses.
Multi-Order Stress Intensity Factors Along Three-Dimensional Interface Corners
Authors: Kuo Tai-Liang , Hwu Chyanbin
Published: March 2010

Usually in the study of singularity problems, only the most critical singular order is considered. For three-dimensional interface corner problems, if only the most critical singular order of stresses is considered, it is possible to lose the opportunity to compute the full modes of stress intensity factors. To fully understand the failure behavior of three-dimensional interface corners, a definition of the stress intensity factors for the lower singular orders is proposed in this paper based on that of the most critical singular order. Moreover, to compute the proposed multi-order stress intensity factors accurately and efficiently, a path-independent H-integral, which has been proven useful for the two-dimensional interface corners, is now modified into a domain-independent H-integral for the three-dimensional interface corner problems. Because the stress intensity factors characterize the fracture behavior focused on an arbitrary tip along the corner front, based on anisotropic elasticity the near tip solutions and complementary solutions of two-dimensional generalized plane strain problems are introduced and then utilized for computation of three-dimensional H-integral. To illustrate the validity of the present work, several three-dimensional numerical examples are analyzed and compared with the existing published solutions. Finally, two examples about the interface corners, which occur frequently in electric packages, are solved to show the feasibility and practicability of the proposed approach.
A Modified Fractional Calculus Approach to Model Hysteresis
Authors: Sunny Mohammed Rabius , Kapania Rakesh K. , Moffitt Ronald D. , Mishra Amitabh , Goulbourne Nakhiah
Published: March 2010

This paper describes the development of a fractional calculus approach to model the hysteretic behavior shown by the variation in electrical resistances with strain in conductive polymers. Experiments have been carried out on a conductive polymer nanocomposite sample to study its resistance-strain variation under strain varying with time in a triangular manner. A combined fractional derivative and integer order integral model and a fractional integral model (with two submodels) have been developed to simulate this behavior. The efficiency of these models has been discussed by comparing the results, obtained using these models, with the experimental data. It has been shown that by using only a few parameters, the hysteretic behavior of such materials can be modeled using the fractional calculus with some modifications.
A Theory Relating Creep and Relaxation for Linear Materials With Memory
Authors: Koeller R. C.
Published: March 2010

The purpose of this paper is to suggest a linear theory of materials with memory, which gives a description for the similarities resulting when the various analytical and experimental methods used to reduce the creep and relaxation data are imposed on the observational changes in curvature that take place in both the creep compliance and relaxation modulus graphs. On a Log-Log graph both have one, two, or at most three pairs of changes in curvature depending on whether the material is a fluid or solid. These changes in curvature have been observed in many experiments and various regions have been discussed and classified. Section 1 gives a few of the many applications of fractional calculus to physical problems. In Sec. 2 an equation that contains both integration and differentiation is presented using geometrical observations about the relationship between the changes in curvature in the relaxation modulus and creep compliance based on published experiments. In Sec. 3 the generalized function approach to fractional calculus is given. In Sec. 4 a mechanical model is discussed. This model is able to share experimental data between the creep and relaxation functions, as well as the real and imaginary parts of the complex compliance or the complex modulus. This theory shares information among these three experimental methods into a unifying theory for solid materials when the loads are within the linear range. Under a limiting case, this theory can account for flow so that the material need not return to its original shape after the load is removed. The theory contains one physical parameter, which is related to the speed of sound and a group of phenomenological parameters that are functions of temperature and the composition of the material. These phenomenological parameters are relaxation times and creep times. This theory differs from the classical polynomial constitutive equations for linear viscoelasticity. It is a special case of Rabotnov’s equations and Torvik and Bagley’s fractional calculus polynomial equations, but it imposes symmetry conditions on the stress and strain when the material is a solid. Sections 56 are comments and conclusions, respectively. No experimental results are given at this time since this paper presents the foundations of materials with memory as related to experimental data. The introduction of experimental data to fit this theory will result in the breakdown of an important part of this research.
A Study for the Influence of Work Hardening on Bending Stiffness of Truss Core Panel
Authors: Tokura Sunao , Hagiwara Ichiro
Published: March 2010

Honeycomb panel is widely used as flooring or wall material in various structures, e.g., buildings, aircraft, flooring members of railway car, and so on, due to high stiffness and lightness at present. Honeycomb panel, however, has a disadvantage that the adhesive used to glue honeycomb core and top plate may burn by fire. On the other hand, truss core panel has equivalent stiffness as honeycomb panel and is expected to be an alternative to honeycomb panel as it is safer for fire. To replace honeycomb panel with truss core panel, it is necessary to investigate the stiffness of truss core panel for bending, shear, compression, and so on. The bending case with a three-point bending model of truss core panel is chosen here. Four cases of analysis with/without work hardening effect and thickness change using two types of shell formulation are performed. These cases are compared with an equivalent honeycomb model. The study showed the effect of work hardening is very important to assess bending stiffness of truss core panel. It is also observed that the use of suitable shell formulation is necessary to obtain reliable result. In addition, the truss core panel shows bending stiffness comparable with conventional honeycomb panel.
Influence of Ductile
Damage Evolution on the Collapse Load of Frames
Authors: Chica Edwin
L. , Ibán Antolín
L. , Terán José M.
G. , López-Reyes Pablo
M.
Published: March 2010

In this note we analyze the influence of four damage models on the collapse load of a structure. The models considered here have been developed using the hypothesis based on the concept of effective stress and the principle of strain equivalence and they were proposed by Lemaitre and Chaboche (1990, Mechanics of Solid Materials), Wang (1992, “Unified CDM Model and Local Criterion for Ductile Fracture—I. Unified CDM Model for Ductile Fracture,” Eng. Fract. Mech., 42, pp. 177–183), Chandrakanth and Pandey (1995, “An Isotropic Damage Model for Ductile Material,” Eng. Fract. Mech., 50, pp. 457–465), and Bonora (1997, “A Nonlinear CDM Model for Ductile Failure,” Eng. Fract. Mech., 58, pp. 11–28). The differences between them consist mainly in the form of the dissipative potential from which the kinetic law of damage is derived and also in the assumptions made about some parameters of the material.
Characterization of worn Ti–Si cathodes used for reactive cathodic arc evaporation
Authors: Zhu J. Q. , Eriksson A. , Ghafoor N. , Johansson M. P. , Sjölén J. , Hultman L. , Rosén J. , Odén M.
Published: March 2010

The microstructural evolution of Ti1−xSix cathode surfaces (x=0,0.1,0.2) used in reactive cathodic arc evaporation has been investigated by analytical electron microscopy and x-ray diffractometry. The results show that the reactive arc operated in N2 atmosphere induces a 2–12 μm thick N-containing converted layer consisting of nanosized grains in the two-phase Ti and Ti5Si3 cathode surface. The formation mechanism of this layer is proposed to be surface nitriding and redeposition of macroparticles formed during the deposition process. The surface roughness of the worn Ti1−xSix cathodes increases with increasing Si content, up to 20 at. %, due to preferential erosion of Ti5Si3.
Solvent-Mediated Electron Hopping: Long-Range Charge Transfer in IBr
−
(CO
2
) Photodissociation
Authors: Sheps Leonid , Miller Elisa M. , Horvath Samantha , Thompson Matthew A. , Parson Robert , McCoy Anne B. , Lineberger W. Carl
Published: March 2010

CO
2
Lends a Hand

Solvent plays a complex and multifaceted role in facilitating charge transfer events. One obstacle to understanding its influence is that solvent molecules are in constant motion; just teasing out their arrangement in space at the point in time when an electron hops from one substrate to another is often a great challenge.

Sheps
et al.

(p.
220
; published online 4 March) have studied a highly simplified prototype system, in which a single CO
2
molecule coordinates, as a solvent might, to an IBr
−
ion in the gas phase. A combination of ultrafast photoelectron spectroscopy and theoretical simulations was applied that suggests that even this solitary interaction is sufficient to induce electron transfer from iodide to bromine during a dissociation reaction. Energy channeled through CO
2
-bending vibrations promoted formation of I(CO
2
) and Br
−
.
Proteome analysis of the normal and Ogura (ogu) CMS anthers of Brassica napus to identify proteins associated with male sterility
Authors: Sheoran Inder S. , Sawhney Vipen K.
Published: March 2010

In the Ogura (ogu) cytoplasmic male sterility (CMS) system in Brassica napus  L., male sterility is caused by a defect in the mitochondrial gene and, under our growth conditions, stamens produced are carpelloid. We analyzed the proteome of ogu and normal anthers with the objective of identifying differentially expressed proteins and their potential roles in pollen development and male sterility. By using differential in-gel electrophoresis, we detected over 2300 spots on 2-D gels of normal and ogu anthers and of the 167 spots with 2-fold or higher expression, 120 were analyzed by MALDI-TOF/TOF mass spectrometry and 94 proteins were identified searching against NCBI and Brassica EST databases. Proteins up-regulated in normal anthers included those associated with carbohydrate and energy metabolism (e.g., fructose bisphosphatase, ATP synthase, malate dehydrogenase, and cytochrome c oxidase), cell wall remodeling (e.g., β-1,3-glucanase and pectinesterase), aldehyde dehydrogenase (ALDH), photosynthesis, and flavonoid synthesis. Proteases were identified in both the normal and ogu anthers, but a number of protease inhibitors were up-regulated in ogu anthers. The activities of ALDH and β-1,3-glucanase were also much higher in normal anthers by comparison with ogu anthers. This study documents the proteomic basis of mitochondrial–nuclear interaction in the control of ogu CMS in B. napus.
Effects of summer temperature on fungal endophyte assemblages in Japanese beech (Fagus crenata) leaves in pure beech stands
Authors: Hashizume Yousuke , Fukuda Kenji , Sahashi Norio
Published: March 2010

Fungal endophyte assemblages in leaves of Japanese beech ( Fagus crenata Blume) trees were investigated in pure beech stands at four localities with different summer temperatures covering the natural distribution range of the species. Ascochyta fagi Woronich was dominant at every site, and the infection density (ID) of this fungus was higher at sites with low maximum air temperatures. The growth rate of A. fagi on potato dextrose agar was inhibited by temperatures above 30 °C. These results suggest that the population density of A. fagi on Japanese beech leaves is influenced by summer temperatures. However, the number of species and Shannon index of diversity (H′) of endophytic fungi increased with increasing air temperature and a negative correlation was observed between the ID of A. fagi and the diversity of other endophytes. The species composition of minor endophytes was site-specific and may reflect geographic and genetic distances between beech stands.
Saprobic and parasitic interactions ofConiochaeta velutinawith mosses
Authors: Davey Marie L. , Tsuneda Akihiko , Currah Randolph S.
Published: March 2010

During a survey of fungi associated with boreal bryophytes in Alberta, Canada, an isolate of Coniochaeta velutina (Coniochaetaceae, Coniochaetales), an opportunistic tree-pathogen and saprobe, was obtained from Hylocomium splendens (Hedw.) Schimp. (Hylocomiaceae, Hypnales). This isolate exhibited phylogenetic affinities to C. velutina isolated from vascular plants. In vitro characterization of its interactions with the model host Funaria hygrometrica Hedw. (Funariaceae, Funariales) demonstrated that it readily forms both anamorph and teleomorph states on the moss. Infected hosts exhibited no macroscopic symptoms or, occasionally, became weakly chlorotic, suggesting that the fungus is a parasite. However, cellulase and polyphenolic oxidase enzyme production suggest it may also be a latent saprobe. Vegetative hyphae of C. velutina directly penetrated rhizoids and frequently elicited a papilla-formation host response, neither of which have been reported in vascular plants infected with C. velutina. The Lecythophora anamorph of C. velutina was produced within host rhizoids, a new phenomenon among bryophilous fungi. Ascomata were produced superficially on F. hygrometrica, although the rhizoid the ascoma is initiated on frequently becomes embedded in the mature peridium. Given the ability of C. velutina to infect, persist, and reproduce on moss hosts, understory bryophytes may represent an inoculum reservoir that contributes to the disease cycle of C. velutina on tree species.