bluuebunny/crossref_metadata_2025 huggingface dataset:
Aeroelastic Flutter of a Flexible Disk Rotating in an Enclosed Compressible Fluid
Authors: Kang Namcheol , Raman Arvind
Published: June 2008

The aeroelastic stability of a thin, flexible disk rotating in an enclosed compressible fluid is investigated analytically through a discretization of the field equations of a rotating Kirchhoff plate coupled to the acoustic oscillations of the surrounding fluid. The discretization procedure exploits Green’s theorem and exposes two different gyroscopic effects underpinning the coupled system dynamics: one describes the gyroscopic coupling between the disk and acoustic oscillations, and another arises from the disk rotation. The discretized dynamical system is cast in the compact form of a classical gyroscopic system and acoustic and disk mode coupling rules are derived. Effects of eigenvalue veering of structure and acoustic dominated modes are investigated in detail. For the undamped system, coupled structure-acoustic traveling waves can destabilize through mode coalescence leading to flutter instability. Regions in parameter space are identified where structure-acoustic traveling waves of specific wave numbers destabilize. The results are expected to be relevant for the design of high speed, low vibration, low noise hard disk drives and optical data storage systems.
A Set-Valued Force Law for Spatial Coulomb-Contensou Friction
Authors: Leine Remco I. , Glocker Christoph
Published: June 2008

The aim of this paper is to develop a contact law for combined spatial Coulomb friction and normal friction torque (drilling friction) as a function of sliding velocity and spin. We will call this extended contact law the Coulomb-Contensou friction law and derive it from a non-smooth velocity pseudo potential. A Runge-Kutta time-stepping method is briefly presented for the numerical simulation of rigid bodies with Coulomb-Contensou friction. The algebraic inclusion describing the contact problem is solved with an Augmented Lagrangian approach. The theory and numerical methods are applied to the Tippe-Top, which illustrates the importance of Coulomb-Contensou friction for the dynamics of systems with friction.
Numerical Identification of Electromagnetic Force Parameters for Linearized Rotordynamic Model of Cage Induction Motors
Authors: Holopainen Timo P. , Tenhunen Asmo , Lantto Erkki , Arkkio Antero
Published: June 2008

The electromechanical interaction in cage induction motors induces additional forces between the rotor and stator. Recently, a linear parametric model was presented for these forces, and the corresponding model was combined with a mechanical rotor model. The electromagnetic system is usually non-linear due to the saturation of magnetic materials. Thus, the effective identification of the force parameters is crucial. Initially, the parameters were identified numerically from the response induced by the whirling rotor. Later on, a method based on the impulse response analysis was presented. The aim of this study was to present the theoretical background of this impulse method, and to present some useful additional features. The derived equations show the mathematical equivalency of this impulse method and the previous whirling method. The results show that the impulse method is numerically effective. In addition, the feasibility of thus obtained simple electromechanical rotor model was demonstrated.
Damper Seal Comparison in a High-Pressure Re-Injection Centrifugal Compressor During Full-Load, Full-Pressure Factory Testing Using Direct Rotordynamic Stability Measurement
Authors: Moore J. Jeffrey , Soulas Thomas A.
Published: June 2008

Rotordynamic stability in high-pressure centrifugal compressors is of great concern to both the original equipment manufacturer (OEM) and the end-user, because of the potential for costly downtime should problems occur. To minimize these problems, damper seals have been developed to provide substantial damping to the rotor system. These seals are placed in the process gas at locations where large pressure differentials occur and contain relatively large lengths and diameters. Previous studies demonstrated the improvement provided by damper seals both analytically and with measurement during full-load, full-pressure testing (Moore, et al. [1]). The present study compares the damping and leakage control performance of two seal geometry, a hole pattern seal and a smooth seal. The smooth seal is intended to simulate a hole pattern seal that has “plugged up” because of contaminants in the process gas. The dimensions of the seals are identical in all other aspects. Two tests were performed using an eight-stage, back-to-back re-injection compressor as the test vehicle. The logarithmic decrement and seal leakage rates results are compared for the two seal designs. Analytical predictions are then compared with the measurements. The smooth seal demonstrates damping similar to the hole pattern design, but has a large leakage penalty.
Nonlinear Response Characteristics of a Cracked Rotor in Maneuvering Aircraft
Authors: Lin Fu-Sheng , Meng Guang , Hahn Eric
Published: June 2008

This paper investigates numerically the nonlinear response of a simple cracked rotor in moving supports, as may occur in aircraft rotors when the aircraft is maneuvering with constant velocity or acceleration. Of particular interest is the influence of the aircraft climb angle. Results show that the climb angle can markedly affect the parameter range for which the system is stable; and over which there results bifurcation, quasi-periodic response or chaotic response. It is shown that aircraft acceleration can also significantly affect the nonlinear behavior of the cracked rotor system, illustrating the possibility for online rotor crack fault diagnosis.
An Original Setup Test Rig for Analysing Lubricated Contact Under Dynamic Normal Excitation Forces
Authors: El Kilali Toufiq , Perret-Liaudet Joe¨l , Mazuyer Denis
Published: June 2008

This paper concerns a new experimental set-up based on an optical EHL machine fitted with a dynamic excitation system. The test rig has been built and presented in this paper. Apparatus design derives from two previously defined experimental test rig. With this new machine, we can study the dynamic behaviour of lubricated contacts under sliding conditions on the both tribological and dynamical point of view. It allows to measure the oil film thickness and to visualise the lubricated dynamically loaded contact under sliding condition. It allows also to measure the dynamic response (acceleration) of the loaded contact under harmonic or random external normal load excitation superimposed on a static one. Capabilities of the apparatus are given in this paper. In particular, theoretical and experimental results concerning the system natural frequencies.
Multi-Objective Parameter Identification in Structural Dynamics
Authors: Haralampidis Y. , Pavlidou M. , Papadimitriou C.
Published: June 2008

The structural identification problem is formulated in a multi-objective context that allows the simultaneous minimization of the various objectives related to the fit between measured and model predicted data. Thus, the need for using arbitrary weighting factors for weighting the relative importance of each objective is eliminated. The set of admissible solutions are known in multi-objective optimization terminology as Pareto optimal solutions and constitute acceptable compromise solutions that cannot be improved in any objective without causing degradation in one other objective. The strength Pareto evolutionary algorithm is used to obtain the set of Pareto solutions. The use of the proposed methodology is illustrated by identifying the Pareto front and the corresponding set of optimal solutions for a model of a scaled laboratory structure using experimentally obtained modal data.
Implementation of a Genetically Optimized Interpolative Fuzzy Inference Engine in Controlling a Ball-Plate Laboratory Setup
Authors: Lucas Caro , Fatehi Alireza , Shahmirzadi Danial , Takami Mohsen M.
Published: June 2008

This paper goes through giving the results of implementing a genetically optimized interpolative fuzzy engine in controlling a ball-plate laboratory setup. For demonstrating the advantages of our proposed interpolative fuzzy controller over classical fuzzy controllers, we gave some comparison between the fuzzy controllers, one with common CRI inference mechanism and one with our interpolative inference mechanism. As expected, our fuzzy interpolative controller is more efficient than CRI-based controller, with respect to computational space, as well as it is more robust to goal achievement.
Bifurcations and Chaotic Dynamics in an Electrostatically Actuated Impact Microactuator: A Numerical Exploration
Authors: Zhao Xiaopeng , Reddy Chevva Konda , Nayfeh Ali H.
Published: June 2008

We study the dynamics of an electrostatically driven impact actuator. As the name suggests, the impact actuator uses impacts between its moving elements to produce nano-displacements. While on one hand, impact actuators provide a way to produce small displacements with moderate actuation voltages, on the other hand impacts make the underlying dynamics nonsmooth. Impacts are a source of nonlinearity and a careful study of the dynamics is essential in order to ensure a consistent performance of the device. We model the impact microactuator reported by Mita and associates using a two-degree-of-freedom system. A simple impact law based on the coefficient of restitution is used. Our results show that the dynamics can be very complex as the system parameters are varied. Namely, as the amplitude and frequency of excitation are varied, the system exhibits period doubling and grazing bifurcations onto the route to chaos.
Passive Control of Tire Vibration With a Dry Polymer Additive: Experiments and Analysis
Authors: Frank J. E. , Koopmann G. H. , Chen W.
Published: June 2008

A series of highway and laboratory experiments were performed to assess the performance of a vibration-reducing tire additive product. The laboratory dynamometer tests showed that the additive, EQUAL Automotive Formula, reduced the vertical (Z-direction) vibration magnitude at the fundamental frequency (one per tire revolution). The average reduction compared to dual plane balanced wheel assemblies was 29% in on-vehicle acceleration dynamometer testing, and 55% in fixed axle dynamometer testing. Highway experiments showed that both tire-induced and periodic road-induced vibrations were consistently reduced. Videos created of the particles moving dynamically within a rotating tire aided in understanding the mechanism by which tire vibration is reduced. Based on the experimental and video observations, we present an explanation summarizing the vibration reduction behavior as three simultaneous mechanisms.
A Ray-Tracing Approach to Simulation and Evaluation of a Real-Time Quarter Car Model With Semi-Active Suspension System Using Matlab
Authors: Chan Brendan J. , Sandu Corina
Published: June 2008

With the advent of X-by-wire systems, more research has been done in the field of semi-active suspension systems. These systems are not only lighter and less complicated than active suspension systems but also consume less power for operation. Power economy is crucial in an X-by-wire system because all of the safety critical systems run on electrical power in an X-by-wire vehicle. In this study, a comparison will be done on the performance of a real-time non-linear semi-active control scheme versus a passive suspension scheme. This comparison is done by using Matlab graphic visualization and Simulink to generate a graphic model of both simulations and observing the performance of both systems in real time. A mathematical model is created in Simulink and the response, given a certain excitation is output into a graphic object to view the Real-Time response. The main purpose of this study is to provide a method for ride control system engineers to evaluate their design and better visualize the performance of the designed system.
Positioning and Vibration Control of Time-Varying Vibration Systems by Means of Nonstationary Optimal Regulator
Authors: Hara Susumu , Nakamura Kenji , Narikiyo Tatsuo
Published: June 2008

This study discusses the positioning and vibration control of time-varying vibration systems whose parameters are time-varying. We assume that the time-varying parameter of a vibration system is detected by an on-line measurement or Wavelet analysis. This paper treats two control methods based on nonstationary optimal regulators (NORs) for this problem. The first method is a gain-scheduling of NORs. An actual controller is obtained by the interpolation of plural NORs designed a priori. The other one is an NOR design based on Wavelet analysis of the vibration system. In the second case, single NOR derived from the analysis result is applied. This study shows the effectiveness of these methods by numerical calculations and experiments. From the comparison of these methods, this paper suggests suitable applications of NOR according to the characteristics of each control problem.
Sway Reduction on Container Cranes Using Delayed Feedback Controller: Simulations and Experiments
Authors: Masoud Ziyad N. , Nayfeh Nader A. , Nayfeh Ali H.
Published: June 2008

Traditionally, container cranes are modeled as a simple pendulum with a lumped mass at the end of a cable. In the case of large container cranes, the actual configuration of the hoisting mechanism is significantly different; it consists typically of a set of four hoisting cables. These cables are hoisted from four different points on the trolley and are attached on the load side to four points on a spreader bar used to lift containers. The dynamics of the actual hoisting assembly of a container crane is different from that of a simple pendulum. A controller design based on the actual model will more likely result in a response superior to those based on simple models. In this work, a nonlinear mathematical model of the actual container crane is developed. A delayed position-feedback controller is designed. Performance of the controller is simulated on a 1/10 scale model of a 65-ton container crane using the full nonlinear model. Simulation results are verified experimentally on a 1/10 scale model of the same container crane.
Mode-Coupled Regenerative Machine Tool Vibrations
Authors: Kalma´r-Nagy Tama´s , Moon Francis C.
Published: June 2008

In this paper a new 3 degree-of-freedom lumped-parameter model for machine tool vibrations is developed and analyzed. One mode is shown to be stable and decoupled from the other two, and thus the stability of the system can be determined by analyzing the remaining two modes. It is shown that this mode-coupled nonconservative cutting tool model including the regenerative effect (time delay) can produce an instability criteria that admits low-level or zero chip thickness chatter.
Non-Linear Dynamics of a Complex Aircraft Brake System: Experimental and Theoretical Approaches
Authors: Sinou Jean-Jacques , Thouverez Fabrice , Dereure Olivier , Mazet Guy-Bernard
Published: June 2008

Stability and non-linear dynamics in a complex aircraft brake model are investigated. The non-linear contact between the rotors ands the stators, and mechanisms between components of the brake system are considered. The stability analysis is performed by determining the eigenvalues of the jacobian matrix of the linearized system at the equilibrium point. Parametric studies with linear stability theory is conducted in order to determine the effect of system parameters on stability. In order to obtain time-history responses, the complete set of nonlinear dynamic equations may be integrated numerically. But this procedure is both time consuming and costly to perform when parametric design studies are needed. So it is necessary to use nonlinear analysis : the center manifold approach and the rational approximants are used to obtain the limit cycle of the non-linear system and to study the behaviour of the system in the unstable region. Results from these nonlinear methods are compared with results obtained by integrating the full original system. These non-linear methods appear very interesting in regard to computational time and also necessitate very few computer resources.
Dynamic Analysis of a Nonlinear Torsional Flexible Coupling With Elastic Links
Authors: Wu Shiyuan , Bert Charles W.
Published: June 2008

Power transmissions between driving machines and load members are very common in industry. Driving machines include turbines, engines, electrical motors, etc. Load members include turbo-shafts, automotive drive trains, aircraft propeller systems, etc. Various types of mechanisms, such as gears, Oldham couplings, etc., are often used for transmitting power.
Flexural-Torsional Post Critical Behavior of a Cantilever Beam Dynamically Excited: Theoretical Model and Experimental Tests
Authors: Zulli Daniele , Alaggio Rocco , Benedettini Francesco
Published: June 2008

The 3D dynamics of a cantilever beam undergoing large displacements under a sinusoidally varying, concentrated, vertical force at its free end are analyzed in this paper. The Partial Differential Equations (PDEs) of the motion are obtained by using the Principle of Virtual Power. Then a reduced 4 degrees-of-freedom model is obtained using, in a Galerkin approximation, four eigenfunctions of the linearized model. The obtained four Ordinary Differential Equations (ODEs) of the motion are expanded by means of a 3rd order Multiple Time Scales perturbation technique to obtain Amplitude and Phase Modulation Equations (APMEs). The role of the inertial-elastic nonlinear terms, responsible for the coupling of the mass matrix, and of the viscous-elastic nonlinear terms, both usually neglected in the literature, is discussed. A path following procedure applied to the APMEs is used to describe the global dynamical behavior in the plane of the excitation control parameters. The results obtained using the 4 d.o.f. analytical model are compared with those of an experimental aluminium model of the cantilever. The regions of instability of the 1-modal planar solution, in which the nonlinear modal coupling excites out of plane and/or torsional components, are studied.
Application of Taguchi Method to Identify Damage in Cantilever Beam
Authors: Kwon Kye-Si , Lin Rong-Ming
Published: June 2008

A robust damage identification technique is presented such that the location and severity of damages can be identified in presence of random errors in measured data as well as systematic errors in analytical model. In order to identify damage efficiently, the concept of design of experiment using orthogonal array is used for screening main effects of each parameter which corresponds to possible damage location in FE model. Then, Taguchi method, which has been widely used for robust design in industry, is applied to the optimization of the objective function, which is defined by the difference between measured and analytical modal data, by updating the parameters in analytical FE model in an iterative way. The numerical simulation of cantilever beam shows that various types of damages can be identified effectively with reasonable accuracy.
Experiments on Linear and Nonlinear Control of a Multi-DOF Parallel Mechanism
Authors: Riebe Sandor , Ulbrich Heinz
Published: June 2008

Parallel kinematics with multi degrees-of-freedom (DOF), like hexapod-systems, are mostly used in applications where high demands on position accuracy are required and/or high accelerations are needed. Adequate control concepts are essential in order to achieve the desired dynamic response. This paper deals with a comparative study of two structural different control concepts applied on a parallel robot with six degrees-of-freedom. The first one is a decentral linear approach and the second one is a multivariable nonlinear approach. The two concepts are presented and implemented on an experimental hexapod-system. In order to verify the used dynamic model comparisons between simulation and measurement results are shown. Finally, experiments have been carried out to compare the control laws with respect to their motion tracking performance.
An Experimental Investigation of the Parametric Resonance in a Buckled Beam
Authors: Yabuno Hiroshi , Ohkuma Manami , Lacarbonara Walter
Published: June 2008

The principal parametric resonance of the second mode of a simply supported buckled beam is experimentally investigated. The simultaneous presence of prestress - compressive load - and initial curvature in the post-buckling range makes this system an interesting prototypical structural system with quadratic and cubic nonlinearities. Using three different experimental setups, frequency-response curves have been obtained for different excitation amplitudes. Moreover, the space-time characteristics of the nonlinear parametric-resonance motions have been measured and discussed. In particular, using a high-speed videocamera, interesting features of the motions have been found. There is a clear evidence of a zero-to-one internal resonance between the first (low-frequency) and second (high-frequency) mode.
Experimental Studies on Artificial Vibration Oil Production
Authors: Sun Ren-yuan
Published: June 2008

A new system for artificial vibration simulation was designed and the effect of artificial vibration on core permeabilities, oil recovery factors under different stage of waterflooding was studied. Experiments show that action of artificial vibration can improve the permeability of cores and oil recovery factors. The oil recovery increment was related to the vibrating parameters including vibrating frequency, amplitude and time. Some oilfield applications and new trends of Artificial Vibration Oil Production (AVOP) were also introduced.
Intercontinental differentiation in Medicago rigidula
Authors: Small Ernest , Brookes Brenda , Crawford Eric J.
Published: June 2008

European and Asian plants assignable to Medicago rigidula (L.) All., as this species is currently interpreted, were found to differ morphologically. Indeed, a combination of morphological, geographical, and interbreeding evidence supports the recognition of the European and Asian plants presently interpreted as M. rigidula as separate species. The best characters for distinguishing plants of the two continents are number of pollen pores (pollen consistently 3-pored in European plants, and consistently 4-pored in Asian plants), number of coils in the pod (averaging 4.5 in European plants, 5.5 in Asian), and fruit spine morphology (usually more hooked and longer in European compared to Asian plants). Plants of North Africa require further study, but the specimens examined were generally closer to European than to Asian plants. The chromosome number of 28 Asian collections, 24 European collections, and 3 African collections was constant, with n = 7.
Medicago rigiduloides, a new species segregated from M. rigidula
Authors: Small Ernest
Published: June 2008

The European and African phases of M. rigidula (L.) All. are retained as this species. The Asian phase is segregated as M. rigiduloides E. Small sp. nov.
Net alignment of cellulose in the periclinal walls of the shoot apex surface cells in Kalanchoe blossfeldiana. I. Transition from vegetative to reproductive morphogenesis
Authors: Nelson Amy J.
Published: June 2008

The apical dome geometry and the pattern of net cellulose alignment in the periclinal walls of the surface cells of Kalanchoe blossfeldiana were examined during vegetative morphogenesis, during reproductive morphogenesis, and during the transition between the two development states. Photoperiodically induced and noninduced shoot apices were dissected, stained, and viewed under a dissecting microscope. The surface cell layer(s) was removed from the stem apex and examined under a polarizing microscope. The results indicated that correlations exist between the pattern of cellulose alignment on the apex surface and the pattern of organ initiation. Tangential cellulose alignment is always present at the periphery of the shoot apex, and alignment of cellulose at the incipient sites of organ formation is such as to provide circumferential reinforcement for emerging organs. The results also showed that a change in dome geometry is one of the earliest events during the floral transition. This change in geometry is correlated with a change in the pattern of surface cellulose and leads to a change in the developmental state of the apex. Key words: shoot, phyllotaxis, cellulose, flower, organogenesis.
The dispersal of winged fruits and seeds differing in autorotative behaviour
Authors: Greene D. F. , Johnson E. A.
Published: June 2008

The application of micrometeorological models of heavy particle dispersal to winged diaspores (samaras) requires that the diaspores maintain stable flight and that descent velocity is constant with respect to vertical air motion. Others have argued that these assumptions may be invalid for autorotating samaras and that bilaterally symmetric samaras will disperse farther than asymmetric samaras in conditions of large horizontal wind velocities (and (or) high turbulence) because the asymmetric morphology is inherently less stable in flight. Therefore, application of these models may not be appropriate for asymmetric samaras. Experimental and natural releases of asymmetric and symmetric samaras reported here indicate that the two samara morphologies respond similarly to a given flow regime. Thus, in modelling dispersal, the autorotation of the samaras can be ignored, and the samaras can be regarded as heavy particles descending at a constant rate from source to deposition site. Key words: winged seeds, descent velocity, dispersal, Fraxinus americana, Acer negundo, micrometeorological dispersal models.
Essais de caractérisation cytochimique des structures de l'interface au niveau du réseau de Hartig dans l'association ectomycorhizienne entre la truffe (Tuber melanosporum) et le noisetier (Corylus avellana)
Authors: Pargney Jean-Claude
Published: June 2008

The interface established between Tuber melanosporum and Corylus avellana was studied cytochemically (PATAg test, Swift's reaction, wheat germ agglutinin – colloidal gold labelling) to characterize cell wall and matrix components. By combining ultrastructural cytochemistry and selective extractions of polysaccharides by various solvents (EDTA, dimethyl sulfoxide, methylamine) or enzymes (pectinase, cellulase, cytohelicase), some ultrastructural features were made evident. Ultrastructural cytochemical tests demonstrate different domains in the matrix. Cell wall and matrix components are similar, but the fungal chitin is not detected in the matrix. Key words: ectomycorrhiza, interface, ultrastructural cytochemistry, selective extractions.
Basal heave analysis of excavations with consideration of anisotropic undrained strength of clay
Authors: Hsieh Pio-Go , Ou Chang-Yu , Liu Hui-Tzu
Published: June 2008

In this study, two cases of excavation to failure were utilized to investigate reasonable analysis methods for basal heave analysis. Three types of tests were carried out to obtain the undrained shear strength of clay in excavations, including the field vane (FV) shear test, the triaxial unconsolidated undrained (UU) shear test, the K0-consolidated undrained axial compression (CK0U-AC) test, the K0-consolidated undrained axial extension (CK0U-AE) test, and the K0-consolidated undrained direct simple shear (CK0U-DSS) test. The analysis results show that the safety factors against basal heave calculated using isotropic undrained strength from the UU test appear acceptable in both excavations, but the results are highly empirical. Safety factors calculated from the FV test tend to be irregular. Moreover, the safety factors were overestimated using the CK0U-AC test results. On the other hand, the safety factors computed using anisotropic undrained strength yielded reasonable results. If we perform simplified anisotropic analysis using the average value of the CK0U-AC and CK0U-AE test results or the undrained strength obtained from the CK0U-AC and CK0U-AE tests utilized in the active and passive sides of the failure surface, respectively, the results will be close to those from anisotropic undrained strength analysis but on the conservative side. Therefore, anisotropic undrained strength analysis and simplified anisotropic analysis are recommended for basal heave analysis.
Bearing capacity of strip footings on purely frictional soil under eccentric and inclined loads
Authors: Loukidis D. , Chakraborty T. , Salgado R.
Published: June 2008

The finite element method is used for the determination of the collapse load of a rigid strip footing placed on a uniform layer of purely frictional soil subjected to inclined and eccentric loading. The footing is set on the free surface of the soil mass with no surcharge applied. The soil is assumed to be elastic – perfectly plastic following the Mohr–Coulomb failure criterion. Two series of analyses were performed, one using an associated flow rule and one using a nonassociated flow rule. The first series is in accordance with bearing capacity solutions currently used in shallow foundation design practice, while the second one is consistent with the dilatancy exhibited by sands in reality. Both probe-type analyses and swipe-type analyses were undertaken. Analyses for associated and nonassociated flow rules yield essentially the same trends regarding the effective width, inclination factor, and normalized vertical force – horizontal force – moment (V–H–M) failure envelope. The results show that the inclination factor depends on the value of the friction angle, whereas the effective width does not.
A case study on the post-construction deformation of concrete face rockfill dams
Authors: Won Myoung-Soo , Kim You-Seong
Published: June 2008

Concrete face rockfill dams (CFRDs) are considered to be fundamentally safe, especially against leakage, and to be a low-cost alternative at many sites. Their design is based on empirical experiences rather than theory. The present paper describes post-construction deformation and leakage using 27 CFRD case studies. The analysis shows that deformation normal to the face slab is larger than the post-construction crest settlement when the dam height exceeds 100 m and that the long-term leakage rate increases rapidly when the dam height exceeds 125 m.
Evaluation of soil state from SBP and CPT: A case history
Authors: Ghafghazi Mohsen , Shuttle Dawn A.
Published: June 2008

The cone pressuremeter test (CPT) is widely used to determine the in situ “state” of cohesionless soils. However, although the CPT is simple, inexpensive, and accurate the subsequent interpretation contains substantial uncertainties even with modern approaches. Self-bored pressuremeters (SBP) have the opposite attributes. Obtaining good SBP data is difficult in sands, but the subsequent evaluation can be rather precise. This paper compares estimates of the in situ state parameter, ψ, from CPT and SBP tests carried out in a uniform hydraulic fill. This case history is unusual in that (i) the fill was well controlled and uniform, (ii) comprehensive laboratory strength data exists, (iii) the CPT was calibrated for the fill in a large chamber, and (iv) good SBP data exist. These SBP and CPT tests are independently analyzed using a calibrated critical state model implemented in a large strain finite element code. The effects of ageing and fabric are considered. The resulting most probable in situ state parameters for the fill from the CPT are close to those derived from the SBP. Although not proof of accuracy (validation) of either test, since ground truth is not known, the results lend support to the adequacy of the interpretation methodology used for both. Further improvements are discussed.
Side resistance rock sockets in sandstone, mudstone, and shale
Authors: Williams A. F. , Pells P. J. N.
Published: June 2008

The fundamental parameters of rock strength, rock mass stiffness, and interface roughness that control the development of side shear in a rock socketed pile are discussed on the basis of results from laboratory model socket tests, constant stiffness direct shear tests, and instrumented prototype piles. Based on the understanding of these fundamental parameters and on a survey of socket field test results, an empirical design method is proposed for side shear only sockets. This design method considers both the maximum load capacity and settlement criteria for single sockets.
Prediction of frequency and amplitude of foundations at resonance
Authors: Sridharan A. , Nagendra M. V.
Published: June 2008

This note presents the statistical analysis carried out on some of the available experimental results to predict the resonant frequency and maximum displacement amplitude of a machine foundation – soil system under vertical vibration as a function of the size and weight of the foundation and of the excitation level. A total of 442 experimental results of Fry, Novak, and Raman have been analysed using nonlinear regression analysis. The results obtained compared well with predictions obtained from the popular theoretical models, and the coefficient of correlation obtained from the analysis was satisfactory in most of the cases.
Laboratory-scale tests on anchored retaining walls supporting backfill with surface loading
Authors: Anderson W. F. , Hanna T. H. , Ponniah D. A. , Shah S. A.
Published: June 2008

Laboratory-scale tests simulating field construction procedures have been carried out to examine the behaviour of the soil–wall–anchor system when a rigid retaining wall, restrained by anchors, supports a sand backfill on which there is surface loading. Two main series of tests have been carried out, one with a uniform load applied over the whole backfill surface, and the other with a strip load applied parallel to the wall and at a varying distance from it. In both series of tests the intensity of loading was varied, and in the series with uniform loading on the backfill the effects of varying anchor inclination were studied. During all stages of construction wall movements, earth pressures, anchor loads, wall base reaction, and backfill surface subsidence were monitored. Although a conservative approach was used in the determination of the anchor loads, wall movements, and consequently backfill subsidence, were considerable. Similar movements at full scale could lead to settlement damage in a structure founded on a shallow mat or strip footings on a backfill, so tentative suggestions are made for more conservative earth pressure distribution assumptions for design purposes for the two cases studied.
Temperature effects on strength and deformation behaviour of rocks in Southern Ontario
Authors: Wai Raymond S. C. , Lo K. Y.
Published: June 2008

A laboratory program to study the effects of temperature up to 350 °C on the strength and deformation properties of rocks was carried out. Particular attention was paid to the experimental procedure to avoid premature thermal cracking of the specimens. It was shown that the thermal–mechanical behaviour varies with the rock type. For granitic gneiss, the deformation modulus increases slightly with temperature up to 120 °C, then decreases at a rate of about 25% per 100 °C. Poisson's ratio generally decreases with increasing temperature up to 250 °C. The uniaxial compressive strength of granitic gneiss decreases with increasing temperature at a rate of the order of 30 MPa per 100 °C. The deformation properties of the granitic gneiss are also dependent on the temperature history of the specimen.In contrast, both the deformation and strength behaviour of the limestone appear to be insensitive to temperature change.
Model investigation of the performance of single anchors and groups of anchors
Authors: Ghaly Ashraf , Hanna Adel
Published: June 2008

Experimental investigations on the performance of single and groups of vertical screw anchors installed in dense, medium, and loose sands are presented. An experimental setup was instrumented to allow the measurement of the total pullout load, upward displacement, sand surface deflection, and stress development in the sand layer during all phases of testing. A sand placing technique was developed and utilized over all the testing program to ensure reproducibility of the predetermined unit weight. Stresses measured within sand deposits indicated that the tested sands were overconsolidated due to the application of mechanical compaction. Special tests were conducted on colored–layered sand to define the nature of the failure mechanism. The results of these tests, together with the measurements of the deflection of the sand surface, were employed to establish the shape of the rupture surface which could be represented by a segment of a logarithmic spiral. Groups of three, four, six, and nine anchors were tested in this investigation. The effect of installation depth, spacing between anchors, and sand characteristics on the ultimate pullout load of the group was examined. The experimental setup was instrumented to allow the measurement, of the total pullout load of the group as well as that of individual anchors in the group. Load distribution among the anchors of a group is discussed in terms of anchor location and the applied load level. At failure, all anchors contribute almost equally to the uplift capacity. Group efficiencies were calculated and compared. An installation procedure was proposed to avoid differential upward displacement during the uplifting process and to provide uniform load distribution on the different anchors of the group. Key words : anchors, failure mechanism, group action, model tests, sand, uplift capacity.
Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents
Authors: Ngwendson Julius N , Schultze Cassandra M , Bollinger Jordan W , Banerjee Anamitro
Published: June 2008

When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n-butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The E/Z ratio seems to depend on the amount of the base used and the phosphonium salt involved.Key words: phosphonium salts, homocoupling, 1,2-diarylalkene, Ylids.
ON N = 2 SUPERFIELD FOR N = 2 VECTOR SUPERMULTIPLET IN TWO-DIMENSIONAL SPACETIME
Authors: SHIMA KAZUNARI , TSUDA MOTOMU
Published: June 2008

We focus on the superfield formulation for an N = 2 vector supermultiplet in two-dimensional spacetime and explicitly show that the Wess–Zumino gauge condition for an N = 2 superfield is compatible with familiar SUSY (plus U(1) gauge) transformations for the vector supermultiplet. N = 2 SUSY invariant mass and Yukawa interaction terms for the vector supermultiplet are also constructed from the superfield explicitly in addition to a free (kinetic) action.
Exercise training impacts the myocardial metabolism of older individuals in a gender-specific manner
Authors: Soto Pablo F. , Herrero Pilar , Schechtman Kenneth B. , Waggoner Alan D. , Baumstark Jeffrey M. , Ehsani Ali A. , Gropler Robert J.
Published: June 2008

Aging is associated with decreases in aerobic capacity, cardiac function, and insulin sensitivity as well as alterations in myocardial substrate metabolism. Endurance exercise training (EET) improves cardiac function in a gender-specific manner, and EET has been shown to improve whole body glucose tolerance, but its effects on myocardial metabolism are unclear. Accordingly, we studied the effect of EET on myocardial substrate metabolism in older men and women. Twelve healthy older individuals (age: 60–75 yr; 6 men and 6 women) underwent PET with [15O]water, [11C]acetate, [11C]glucose, and [11C]palmitate for the assessment of myocardial blood flow (MBF), myocardial O2 consumption (MV̇o2), myocardial glucose utilization (MGU), and myocardial fatty acid utilization (MFAU), respectively, at rest and during dobutamine infusion (10 μg·kg−1·min−1). Measurements were repeated after 11 mo of EET. Maximal O2 uptake (V̇o2max) increased ( P = 0.005) after EET. MBF was unaffected by training, as was resting MV̇o2; however, posttraining dobutamine MV̇o2 was significantly higher ( P = 0.05), as was MGU ( P < 0.04). Although overall dobutamine MFAU was unchanged, posttraining dobutamine MFAU increased in women ( P = 0.01) but decreased in men ( P = 0.03). Thus, EET in older individuals improves the catecholamine response of myocardial glucose metabolism. Moreover, gender differences exist in the myocardial fatty acid metabolic response to training. These findings suggest a role for altered myocardial substrate metabolism in modulating the cardiovascular benefits of EET in older individuals.
Activation of Epidermal Growth Factor Receptor and Its Downstream Signaling Pathway by Nitric Oxide in Response to Ionizing Radiation
Authors: Lee Hyung-Chahn , An Sungkwan , Lee Hansoo , Woo Sang-Hyeok , Jin Hyeon-Ok , Seo Sung-Keum , Choe Tae-Boo , Yoo Doo-Hyun , Lee Su-Jae , Hong Young-Joon , Park Myung-Jin , Rhee Chang-Hun , Park In-Chul , Hong Seok-Il
Published: June 2008

Epidermal growth factor receptor (EGFR) is activated by ionizing radiation (IR), but the molecular mechanism for this effect is unknown. We have found that intracellular generation of nitric oxide (NO) by NO synthase (NOS) is required for the rapid activation of EGFR phosphorylation by IR. Treatment of A549 lung cancer cells with IR increased NOS activity within minutes, accompanied by an increase of NO. 2-Phenyl-4,4,5,5,-tetramethylimidazolline-1-oxyl-3-oxide, an NO scavenger, and NG-monomethyl-l-arginine, an NOS inhibitor, abolished the increase in intracellular NO and activation of EGFR by IR. In addition, an NO donor alone induced EGFR phosphorylation. Transient transfection with small interfering RNA for endothelial NOS reduced IR-induced NO production and suppressed IR-induced EGFR activation. Overexpression of endothelial NOS increased IR-induced NO generation and EGFR activation. These results indicate a novel molecular mechanism for EGFR activation by IR-induced NO production via NOS. (Mol Cancer Res 2008;6(6):996–1002)
Subfascial Hematomas and Hemoperitoneum after Cesarean Section: Prevalence according to Closure and Non-Closure of the Parietal Peritoneum
Authors: Malvasi Antonio , Tinelli Andrea , Tinelli Raffaele , Serio Gabriella , Pellegrino Marcello , Mettler Liselotte
Published: June 2008

Aim: To compare early hemorrhagic complications and the surgical and clinical outcome in the closure and non-closure of the parietal peritoneum in cesarean section (CS) patients. Material and Methods: We retrospectively evaluated 2,576 post-CS women subdivided and compared in two groups by open and closed parietal peritoneum (group I, n = 1,580, group II, n = 996). Results: The ultrasonographical detection of 23 blood collections (0.89%) was 14 in group I and 9 in group II, and of these we surgically treated 11 patients in group I and 8 patients in group II, with no statistical difference (p > 0.05); all group I patients showed hemoglobin point decreases and needed blood transfusions, with statistical significance (p < 0.05) linked to more severe early complications that make the post-CS outcome worse; no difference was confirmed in terms of antibiotic administration (p > 0.05). Conclusions: There was a significant increase of blood loss and transfusions in the first group. As the posterior surface of the Retzius space is open and if post-CS pathological bleeding occurs, blood can invade the peritoneal cavity causing a hemoperitoneum, with the possibility of hemorrhagic shock and a worse clinical outcome.
Cocaine and the Eye: A Historical Overview
Authors: Grzybowski Andrzej
Published: June 2008

Cocaine was brought to Europe after the discovery of America. In the 19th century, the active component of coca leaves, named cocaine, was extracted and several researchers started experimenting with the substance, describing many physiological and pathological effects of its action. The first scholar to practically demonstrate the possibility of using cocaine solution in medicine, mostly ophthalmology, was Carl Koller. Following this remarkable achievement cocaine became the substance most frequently applied for different types of anaesthesia. Halsted and Hall reported the first successful nerve block of the interior dental nerve with 4% cocaine solution. In 1892, Schleich published the results of his studies in which he used a 0.1–0.2% solution of cocaine hydrochloride intra- and subcutaneously, introducing the so-called infiltration anaesthesia. At the end of the 19th century it was, however, demonstrated that cocaine possessed many undesirable effects, including addiction, which triggered off interest in other, less toxic, anaesthetics.
Leukemic Cluster Growth in Culture Is an Independent Risk Factor for Acute Myeloid Leukemia and Short Survival in Patients with Myelodysplastic Syndrome
Authors: Bernimoulin Michael , Stern Martin , Tichelli André , Jotterand Martine , Gratwohl Alois , Nissen Catherine
Published: June 2008

In patients with myelodysplastic syndrome (MDS) precursor cell cultures (colony-forming unit cells, CFU-C) can provide an insight into the growth potential of malignant myeloid cells. In a retrospective single-center study of 73 untreated MDS patients we assessed whether CFU-C growth patterns were of prognostic value in addition to established criteria. Abnormalities were classified as qualitative (i.e. leukemic cluster growth) or quantitative (i.e. strongly reduced/absent growth). Thirty-nine patients (53%) showed leukemic growth, 26 patients (36%) had strongly reduced/absent colony growth, and 12 patients showed both. In a univariate analysis the presence of leukemic growth was associated with strongly reduced survival (at 10 years 4 vs. 34%, p = 0.004), and a high incidence of transformation to AML (76 vs. 32%, p = 0.01). Multivariate analysis identified leukemic growth as a strong and independent predictor of early death (relative risk 2.12, p = 0.03) and transformation to AML (relative risk 2.63, p = 0.04). Quantitative abnormalities had no significant impact on the disease course. CFU-C assays have a significant predictive value in addition to established prognostic factors in MDS. Leukemic growth identifies a subpopulation of MDS patients with poor prognosis.
Mesenteric Ischemia – Outcome after Surgical Therapy in 83 Patients
Authors: Dahlke M.H. , Asshoff L. , Popp F.C. , Feuerbach S. , Lang S.A. , Renner P. , Slowik P. , Stoeltzing O. , Schlitt H.J. , Piso P.
Published: June 2008

Background: Intestinal ischemia is the prime vascular emergency for the visceral surgeon. However, the diagnosis of mesenteric ischemia is difficult, the surgical options are often limited and the overall outcome is generally poor. Methods: We report on a single center series of 83 patients undergoing surgery for mesenteric ischemia during a 3-year period. Risk factors, clinical presentation, type and timing of imaging studies and their implications for surgical therapy and outcome are analyzed. Results: Hypertension and diabetes were the most common risk factors (68/64% of all patients). Abdominal pain was the most general symptom upon presentation to the surgical unit (73%). Two-phase, contrast-enhanced computed tomography was applied as the standard preoperative imaging modality (correct diagnosis in 69%). Bowel resections were necessary in most patients; approaches to restore blood flow by vascular surgery interventions were applied in 17 patients (20%). The overall morbidity and mortality rate in our study cohort was expectedly high (59% 1 month mortality). Conclusion: The diagnosis and surgical treatment of mesenteric ischemia remains a major difficulty. We recommend preoperative CT analysis followed by an aggressive indication for early surgical exploration and bowel resection. An attempt of revascularization is justified for selected patients with limited macrovascular disease.