bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Cone-to-Cylinder Junction Reinforcement Requirements Between ASME Section VIII, Division 1 and Code Case 2286-1
Authors: Bardia Kenhaiya L. , LaBounty Donald G. , Breig Timothy
Published: July 2009

Paragraph UG-28 of the ASME Section VIII, Division 1 provides rules for reinforcement of the cone-to-cylinder junction based on line of support criteria. Code Case 2286, on the other hand, provides rules based on actual stresses versus allowable stresses. In this paper, the authors compare the results of the calculations for the reinforcement of the cone-to-cylinder junction for each method. It was found that, in some cases, the reinforcement method of UG-28 will produce non-conservative results.
Analysis of Strength Margins for Austenitic Stainless Steel Pressure Vessels
Authors: Ma Li , Zheng Jinyang , Miao Cunjian , Qin Yongquan , Han Shuxin , Sheng Shuiping , Shi Caixing
Published: July 2009

Austenitic stainless steel is widely used for boiler and pressure vessels, however the actual stress-based method to determine the allowable stress limits the full usage of plastic metals such as austenitic stainless steel that with low ratio of yield to tensile strength. The parts of ASME and European codes of pressure vessels have been attention of it and some measures have been taken to increase the allowable stress by decreasing the design factors or change the specified yield strength from 0.2% proof strength to 1.0% proof strength etc.; the other important method is to increase the yield strength by pressure strengthening. A series theoretic computation and experimental analysis were carried out based on the systematical survey of these codes including Chinese GB150, ASME VIII-1, ASME VIII-2, EN13345 and EN13458 etc, and the result showed the difference of allowable stress among these codes and indicated that Chinese GB150 is most conservative with high strength margin, whereas EN13458 attendance with pressure strengthening is the best solution to increase the allowable stress as well, which increased the allowable stress 99.3% than that of GB150.
Constraint Effects in Weld Thermal Simulated Steel Specimens
Authors: O̸stby Erling , Thaulow Christian , Nyhus Ba˚rd
Published: July 2009

The brittle fracture constraint effect in two different weld thermal simulated microstructures of a 500 MPa steel is investigated through testing of bending specimens with different a/W ratios. It is found that on average the constraint effect is higher in the CGHAZ microstructure compared to the ICCGHAZ. The procedure for calibration of Weibull parameters proposed by Gao et al. [1] has been applied to the results. It is found that a lower m-value is calibrated for the ICCGHAZ microstructure due to the lower constraint effect observed. Three-parameter representations of the Weibull distribution better represent the distribution of the fracture toughness values compared to two-parameter representations.
Transient Dynamic Responses of an Integrated Air-Liquid-Elastic Tank Interaction System Subject to Earthquake Excitations
Authors: Xiong Ye Ping , Xing Jing Tang
Published: July 2009

Sloshing problems in partially filled tanks are of increasing concerns in many engineering fields such as marine, chemical, aerospace engineering and automobile industry. The interactive dynamic behaviour of liquid and tank due to their interaction under various loading conditions can have vital impact on the integrity and safe operation of the system. Studies of liquid sloshing and its dynamic effect on the containers are necessary in the early design stage. Currently, most investigations on sloshing problems mainly focus on the analysis of liquids in rigid tanks where the fluid-structure interactions were neglected. Studies on fluid-structure interactions are limited to two phases of liquid-tank interactions. Three phase interactions involving air, liquid and elastic tank are rarely considered. In this paper, the dynamic behaviour of an air-liquid-elastic tank interaction system is investigated. The tank filled with air and liquid is supported at four equally spaced positions around the outer shell. The dynamic pressure in the liquid / air and the displacement in the elastic solid are used as variables to formulate the numerical model incorporating a substructure-subdomain approach and numerical simulations are presented based on a developed computer program. The natural frequencies in association with the corresponding vibration modes and the transient dynamic responses of the complex coupled system subject to earthquake excitations are presented. The ground motion data recorded from El-Centro earthquake is used as an earthquake load to the system. Different interactive cases are examined. These include liquid sloshing in a rigid tank, air-liquid interactions in a rigid tank, liquid-elastic tank interactions and three phase air-liquid-tank interactions. The numerical results obtained reveal the complex coupled behaviour of the system as well as the air effect on dynamic displacement and sloshing pressure. This study provides information for the design of liquid / gas filled tanks in which sloshing behaviour is of interest.
Modelling Tow Impregnation of Woven Fabric Reinforcements and Its Application in Liquid Composite Moulding Process Modelling
Authors: Wang Y. , Grove S. M. , Moatamedi M.
Published: July 2009

This paper proposes a detail physical model for the micro-scale flow in plain woven reinforcements. The modelling results are formulated into a mathematical algorithm which is then directly incorporated into a continuum dual-scale model as a ‘sink’ term. When used to model liquid composite moulding (LCM) processes, this incorporated dual-scale model demonstrates the fact that the impregnation of fibre tows lags behind the resin front in macro pore spaces. The modelling results are in agreement with the experimental observations. It has been shown that the unsaturated region at the flow front could increase or have a fixed length under different circumstances. These differences are explained due to the variation in tow impregnation speed (or the time required for the tow to become fully impregnated) which is related to the weave infrastructure and the nesting and packing of plies. The modelling results have also demonstrated the drooping of the inlet pressure when the flow processes are carried out under constant injection rates.
Plant Life Management Models: A Comparison With Analysis of Impact on Both Safety and Non-Safety Issues
Authors: Contri Paolo , Vaisnys Povilas , Elsing Bernhard
Published: July 2009

Due to current social and economical framework, in last years many nuclear power plant owners started a program for the Long Term Operation (LTO)/PLIM (Plant Life Management) of their older nuclear facilities. A PLIM framework requires both a detailed review of the features of the main safety programs (Maintenance, ISI, Surveillance) and a complete integration of these safety programs into the general management system of the plant. Therefore PLiM should address safety as well economics, knowledge management as well as decision making, and provide an overall framework to keep the whole plant in a safe and economically sustainable condition. Moreover, new external factors, such as: large use of subcontractors, need for efficient management of spare parts, request for heavy plant refurbishment programs demand for updated techniques in the overall management of the plant. Therefore new organisational models have to be developed to appropriately support the PLIM framework. In recent years a network of European Research Organisations (SENUF) carried out many R&D tasks aiming at capturing the aspects of the maintenance programs where research is mostly needed and at developing suitable optimised maintenance models. Using the outcome of these initiatives, this paper aims at identifying the technical attributes of the PLIM program more directly affecting the decision for a long-term safe operation of a nuclear facility, and the issues related to its optimal implementation. A comparison of some of the available models is presented and an analysis of the potential impact on safety and non-safety programs is provided in order to support the development of optimised life management models.
Recent Development of the Pressure Vessel Codes and Standards in China
Authors: Shou Binan
Published: July 2009

The recent development of the pressure vessel codes and standards was introduced in this paper. The important technical changes in the codes and standards which will be issued in the near future were also analyzed. Compared Chinese standards to the relative codes in U.S, the feasibility of the Chinese codes and standards being used internationally were discussed.
Dynamic Burst Pressure Simulation of Cylinder-Cylinder Intersections
Authors: Cheng Cunjiang , Widera G. E. Otto
Published: July 2009

In this study, the determination of the burst pressure of a series of cylinder-cylinder intersections representing vessels of diameter D and wall thickness T, and nozzles of diameter d and wall thickness t subjected to short-term dynamic loading is investigated. Dynamic simulations via the use of the finite element method are carried out to determine the effects of dimensionless parameters d/D, D/T and t/T as well as pressure vs. time history. The LS-DYNA software is employed to model and analyze various intersections for the geometric parameter ranges 0.1 ≤ d/D < 1.0, 0.1 ≤ t/T ≤ 3 and 50 ≤ D/T ≤ 250. The use of both solid and shell elements is investigated and applied in this study. A correlation equation to predict the dynamic burst pressure of cylinder-cylinder intersections is proposed based on the parametric finite element analyses. Static test data is used to verify the dynamic correlation equation by applying a relatively long pressure pulse duration.
Plant Life Management of EDF PWR Nuclear Fleet and EPR Flamanville 3 Design: Safety and Pressure Vessels Requirements
Authors: Hedin Franc¸ois
Published: July 2009

Plant life management (PLM) of the 58 EDF nuclear plants takes into account continuous safety improvement, high level operating and maintenance performances goals, ageing / obsolescence management, skills management. Safety approach is described through 3rd ten years safety reassessment of 34 three loops reactors (from 2009). Ageing process management principles are described in particular in relation with an anticipation approach in the field of inservice inspection, routine or heavy (repair, replacement) maintenance : pressure vessels requirements, concerning first, European and French regulation, and the EDF ones are presented. Design of European Pressurised Reactor (EPR) FLAMANVILLE 3 takes into account safety and PVP requirements which are presented, in particular break preclusion approach for the main primary loops and overpressure protection.
Historical Context of Elevated Temperature Structural Integrity for Next Generation Plants: Regulatory Safety Issues in Structural Design Criteria of ASME Section III Subsection NH
Authors: O’Donnell William J. , Hull Amy B. , Malik Shah
Published: July 2009

In 2006, ASME and DOE signed a cooperative agreement to update and expand appropriate materials, construction and design codes for application in future Generation IV nuclear reactor systems that operate at elevated temperatures. The second task in this ASME/DOE Gen-IV Materials Project was to identify issues relevant to ASME Section III, Subsection NH, and related Code Cases that must be resolved for licensing purposes for VHTGRs (Very High Temperature Gas Reactor concepts such as those of PBMR, Areva, and GA); and to identify the material models, design criteria, and analysis methods that need to be added to the ASME Code to cover the unresolved safety issues. The Nuclear Regulatory Commission (NRC) and Advisory Committee on Reactor Safeguards (ACRS) issues which were raised in 1983 in conjunction with the licensing of the Clinch River Breeder Reactor (CRBR) provide the best early indication of regulatory licensing issues for high temperature reactors. The approach to resolve the 25 identified elevated temperature structural integrity licensing issues was never implemented because Congress halted the construction of CRBR. This 1983 list provided the most definitive description of NRC elevated temperature structural integrity concerns. This paper presents both the results of the study by O’Donnell and Griffin [1] and a preliminary analysis by NRC staff of the earlier identified elevated temperature structural integrity issues that attempts to provide updated information for several of the next generation reactor types under consideration.
Recent Reactor Head Drop Analysis for Complying NUREG-0612 Appendix A Guidelines
Authors: Hoang Phuong H. , Amin Mohammad , Mak Chee W.
Published: July 2009

The USNRC staff provided guidelines in NUREG-0612 for the control of heavy loads to meet the requirements of the Code of Federal Regulations (10 CFR) Sections 50.59 and 50.71(e) relate to the safe handling of heavy loads and load drop analyses to assure fuel assembly integrity and to permit continued decay heat removal in nuclear power plants. The USNRC staff considered plants that had installed single-failure-proof cranes or had completed load drop analyses conforming with the guidelines of Appendix A to NUREG-0612 would remain in conformance with the safe handling guidelines for lifting reactor head during the plant refueling operation. Reactor head drop analyses have been performed recently for a number of US nuclear power plants and have been reviewed by the USNRC staff for complying with the guidelines of Appendix A to NUREG-0612. This paper provides an overview of the methodology, parameters, analysis results and acceptance criteria used in these recent works.
Stochastic Damage Growth Analysis Using EFGM
Authors: Arun C. O. , Rao B. N. , Sivakumar S. M.
Published: July 2009

A stochastic meshless method is presented for solving boundary-value problems in damage mechanics under elastic-plastic conditions that involves random material properties. Material is assumed to have an initial damage, which follows a lognormal filed. An isotropic unified damage law, formulated by Lemaitre is used in this study. A meshless formulation based on element free Galerkin method (EFGM) is developed to predict stochastic structural response. A scaled matrix approach is used for applying the essential boundary conditions in EFGM. The proposed method is based on perturbation technique. First order perturbation technique for damage growth in an elastic plastic analysis is formulated. Newton-Raphson algorithm is used to solve for material nonlinearity. A numerical example is solved to study the effect of random initial damage in the structural response and further damage growth. Monte Carlo technique is used to validate the proposed method.
Impact Forces of Vanes on Rotor Slots in a Rotary Compressor
Authors: Huang Yuan Mao , Yu Z. C.
Published: July 2009

This study analyzes the impact of vanes on rotor slots in a sliding vane rotary compressor that is simulated by impact of two plates. The Hertzian contact rule and the first order shear deformation plate theory with consideration of the shear deformation and the rotary inertia are utilized to generate a mathematical model. Impact forces when a vane locates at various locations and time are calculated. The calculated results are compared and show good agreement with those obtained by using ABAQUS software.
Research and Design of Sealing Device in Hot Water Circulating Pump for High Temperature and High Pressure
Authors: Mu Jiegang , Zheng Shuihua , Deng Hongying , Zhang Shengchang , Cai Zhendong
Published: July 2009

Hot water circulating pump for high temperature and high pressure is important equipment applied in the wide range of industry. However, in China, the seal of this pump is not so good and could not meet the use requirements. In this paper, based on investigations of the seal for this pump in China, the main problem of the seal was found out. Also, a new sealing device of hot water circulating pump for high temperature and high pressure was designed, which was composed of floating ring seal, combined seal, packing seal and special double-decker cooling system. The experiment results show that the new design could improve the seal performance of the pump and meet the use requirements.
Structural Integrity of Bi-Metallic Welds in Piping Fracture Testing and Analysis
Authors: Faidy Claude
Published: July 2009

The French field experience in stainless steel bi-metallic welds (BMW) has shown different degradations like external surface corrosion cracks close to the low alloy steel/stainless steel interface or fabrication defects in different other locations. In many countries, some degradation has been encountered in different type of bi-metallic welds: stainless steel BMW or Ni-based alloy BMW through different degradation mechanisms (corrosions). The critical crack size in different location of a BMW is a key safety issue. To-day, there is no flaw evaluation procedure for this type of components in existing operation codes, like ASME XI [7], RSE-M [6] or R6 rule [5]. Consequently a fracture mechanic procedures is under preparation in the French RSE-M operation Code [6] in order to evaluate the critical crack sizes of defects in different area of a bi-metallic weld. The procedure validation is based on 2 specific experimental projects that have been performed on 6" and 16" bi-metallic welds at room temperature and 300°C. Detailed residual stress measurements and simulation have been done, in order to check their influence on the critical crack size. The major results of these projects are: • no instable crack growth for cracks closed to the fusion line, • crack ductile tearing growth take place in the lower strength material and not in the lower toughness material, • the residual stresses have a negligible effect on the critical crack size, • the crack initiation take a place close to the maximum limit loads, • the ductile crack growth is mainly at the deepest point and negligible on the outer surface (for the cracks considered in these test programs), • no existing engineering methods are really available for this type of cracked components, • the crack distance to the interface is a key parameter in term of toughness, • comparison of notched and pre-crack specimen has been done and confirm a small increase of toughness in the case of electro-eroded crack. After a brief summary of the validation programs, the paper ends with a proposed procedure to analyse the critical crack size in a bi-metallic weld through two methods: an engineering method (1) with large safety factor and an elasto-plastic FEM (Finite Element Method) (2) with lower safety factors. They will be included soon in the RCC-M [8] for design consideration of BMW and the RSE-M [6] codes for service behaviour of BMW. Similar method can be used for different type of BMW (VVER, Ni-based alloy...).
The European Network on Neutron Techniques Standardization for Structural Integrity (NeT)
Authors: Ohms C. , Martins R. V. , Uca O. , Youtsos A. G. , Bouchard P. J. , Smith M. , Keavey M. , Bate S. K. , Gilles P. , Wimpory R. C. , Edwards L.
Published: July 2009

This paper provides an overview over the work of the European Network on Neutron Techniques Standardization for Structural Integrity (NeT). The network involves some 35 organisations from industry and academia and these partners undertake the application of modern experimental and numerical techniques to problems related to the structural integrity of components, mainly relevant to nuclear applications. While being built around neutron scattering techniques, which are predominantly applied for analyses of welding residual stresses, one of the major strengths of the consortium is the diversity in available experimental and numerical techniques. In the residual stress area, for example, many types of materials characterizations testing, several methods for residual stress analysis, including neutron and X-ray diffraction, deep hole drilling, the contour method and others, and many different ways of numerical analysis employing several commercially available FEM codes can be covered by the partners. Currently the network has embarked on five different Task Groups. Four of these are dealing with welding residual stress assessment, and one applies Small Angle Neutron Scattering for studying thermal ageing processes in duplex stainless steels used for reactor core internals. The work already performed in the context of NeT and the envisaged investigations for the ongoing Task Groups are briefly outlined in this paper. The aim is to give the reader a comprehensive overview of the work of NeT and to shed some light on the potential present in this kind of collaborative effort.
Temperature Dependence of Reactor Water Environmental Fatigue Effects on Carbon, Low Alloy and Austenitic Stainless Steels
Authors: O’Donnell William James , O’Donnell William John
Published: July 2009

Recent studies of the environmental fatigue data for carbon, low alloy and austenitic stainless steels have shown that reactor water effects are significantly less deleterious as temperatures are reduced below 350 °C (662 °F). At temperatures below 150 °C (302 °F) the reduction in life due to reactor water environmental effects is less than a factor of 2, and the existing ASME Code Section III fatigue design curves for air can be used. The latter include a factor of 20 on cycles whereas the ASME Subgroup on Fatigue Strength (SGFS) has determined that a factor of 10 should be used on the mean failure curves which include reactor water effects. These factors account for scatter in the data, surface finish effects, size effects, and environmental effects. Reactor water environmental degradation dependence on temperature is determined using variations of the statistical models developed by Chopra and Shack, Higuchi, Iiada, Asada, Nakamura, Van Der Sluys, Yukawa, Mehta, Leax and Gosselin, References [1 through 22]. Comparisons of the resulting proposed environmental fatigue design criteria with reactor water environmental fatigue data are made. These comparisons show that the Code factors of 2 and 20 on stress and cycles are maintained for air environments, and the 2 and 10 Code factors are maintained for the reactor water environments. Environmental fatigue criteria are given for both worst case strain rates and for arbitrary strain rates. These design criteria do not require the designer to consider sequence of loading, hold times, transient rates, and other operating details which may change during 60 years of plant operation.
Structural Health Monitoring of Long Bone Fractures Using Instrumented Intramedullary Nails
Authors: Wilson Darren , Janna Si
Published: July 2009

Clinical assessment of fracture healing is usually subjective, relying upon the detection of movement (‘feel’) by the surgeon, the patient’s response in terms of pain and confidence, and radiographic evidence of callus and primary bone union. A more quantitative, objective method of measuring the strength of a healing callus would be useful in assessing many aspects, such as the effectiveness of different forms of treatment, the pattern and rate of healing, and the stage at which the patient can return to full weight-bearing activity. The results presented in this paper demonstrate the complexity of monitoring fracture healing in leg stance phase using an instrumented intramedullary (IM) nail equipped with a single sensor. The bone healers exhibited both sigmoidal and linear load responses during fracture healing. Ambulating non-healers demonstrated high nail forces which did not change significantly over time whereas lame non-healers demonstrated a decreasing nail load due to reduced GRF or loosening of fixation.
Integrated Structural Health Monitoring With Guided Waves From Piezoelectric Fibers
Authors: Lissenden Cliff J. , Blackshire James J. , Puthillath Padma K.
Published: July 2009

Active structural health monitoring of plate-like structures can be performed with ultrasonic guided waves. The activation of ultrasonic guided waves from embedded piezoelectric fibers in carbon fiber reinforced polymer (CFRP) laminated plates is investigated. Finite element analysis simulations of wave propagation from an array of embedded parallel piezoelectric fibers are presented. A quasi-isotropic CFRP having piezoelectric fibers embedded at the midplane is studied. The number and spacing of piezoelectric fibers is varied in order to activate different modes at different frequencies. The simulation results (i) characterize the displacement profile through the thickness of the CFRP plate, (ii) enable visualization of mode excitability, and (iii) demonstrate the source influence. The results indicate that the embedded fibers have a strong potential for either hot spot monitoring or distributed monitoring of large areas. However, due to the size, spacing, and activation of embedded fibers the source influence causes the mode excitability to differ from that of a conventional comb transducer.
Damage Assessment of Tensegrity Structures Using Piezo Transducers
Authors: Panigrahi Ramakanta , Gupta Ashok , Bhalla Suresh
Published: July 2009

This paper presents a low-cost experimental technique to carry out damage assessment of structures using dynamic strain measured by of surface-bonded piezo transducers. The technique is applied on a single module tensegrity structure, 1m×1m in size and then extended to a tensegrity grid structure, 2m×2m size, fabricated using galvanised iron (GI) pipes and mild steel cables. A single piezoelectric-ceramic (PZT) patch bonded on a strut measures the dynamic strain during an impact excitation of the structure. Damage is identified from the frequency response function (FRF) obtained after domain transformation of the PZT patch’s response. For the grid structure, damage is localized using changes in the three natural frequencies observed experimentally and the corresponding mode shapes obtained numerically. The technique is found to be very expedient and at the same time cost effective, especially for preliminary damage detection in the structures.
Adaptive Key Component Control for Nonlinear Evolving Systems
Authors: Balas Mark J. , Frost Susan A.
Published: July 2009

The inheritance of subsystem traits in Evolving Systems is an important area of study. Evolving Systems are autonomously controlled subsystems which self-assemble into a new Evolved System with a higher purpose. Evolving Systems of aerospace structures often require additional control when assembling to maintain stability during the entire evolution process. If certain passivity traits of the subsystem components are inherited in the Evolving System, then it is possible to use an adaptive controller to restore stability in the Evolving System. This paper develops the theory for Nonlinear Evolving Systems and illustrates it with a simple example.
Aircraft Dynamics for Symmetric and Asymmetric V-Shape Morphing Wings
Authors: Cuji Edgar , Garcia Ephrahim
Published: July 2009

This paper will present the effect of the aircraft turning dynamics for symmetric and asymmetric V-shape changing wings. The aerodynamic forces will be calculated using a 3D aerodynamic model developed that utilizes a modern adaptation of Prandtl’s lifting-line method which can be used for wings of arbitrary camber, sweep and dihedral. The method will be applied to analyze symmetric and asymmetric V-shaped wing configuration of interest for morphing aircraft application. The V-shaped wing has two sections, an out-of-plane dihedral section and a horizontal section. A study of the lift characteristics for symmetric and asymmetric with and without flap deflection will be presented. An investigation as to how the partial dihedral will affect the dynamics of the vehicle, in turning, for wings with asymmetric flap deflection is performed. An comparison of the different turning performance measurements, turning radius, bank angle, load factor, turning rate and roll moment coefficient will be presented.
Characterization of Optical Fiber Bragg Gratings as Strain Sensors Considering Load Direction
Authors: Emmons Michael C. , Karnani Sunny , Mohanchandra K. P. , Carman Gregory P. , Trono Stefano , Richards W. Lance
Published: July 2009

This study investigates the influence of lay-up and load direction on embedded optical fiber Bragg gratings (FBGs) used as strain sensors. FBGs have shown great promise for application to structural health monitoring with advantages of small size and cylindrical geometry readily allowing for embedment within fiber reinforced composites. Characterization of the embedded FBGs is necessary to develop a rugged and reliable strain sensor. This paper specifically explores the effects of loading direction on the FBG strain outputs. A well behaved baseline case is established with results for gratings loaded parallel to the optical fiber direction while embedded parallel to the adjacent structural fibers in a quasi-isotropic composite. Results and analysis are also presented for a case involving a composite fabricated with the optical and structural fibers parallel to each other but perpendicular to the loading direction. Extremely good results are obtained relating FBG strain measurements with that of surface mounted resistance strain gauges.
Adopting Supervisor for Bolt Loosening Detection by Using Smart Washer
Authors: Tanaka Tohru , Okugawa Masayuki
Published: July 2009

The objective of this study is the loosening detection of bolted joints without human involvement by applying the concept of structural health monitoring. The smart washer which consists of the flexible cantilever beam enables to detect bolt loosening by using self-sensing and actuation functions of piezoelectric material. The basic principle of how to detect bolt loosening is to the dynamics characteristics of a smart washer system which varies depending on bolt tightening axial tension. The natural frequency of the smart washer was identified by using the subspace state space identification method described in previous papers. However, the previous method has the problems that The identification and modeling error degrade the fault detection accuracy. This paper proposes a bolt loosening detection method based on the model-based Fault Detection and Isolation technique. The numerical simulations and the experiments results were performed to verify the possibility of the loosening detection by using the smart washer with observer-based supervisor. Improvement of bolt loosening detection accuracy is confirmed by comparing the proposed method with the previous method.
Compensation of Hystetresis Nonlinearties in Smart Actuators
Authors: Al Janaideh Mohammad , Rkaheja Subash , Su Chun-Yi
Published: July 2009

Smart actuators such shape memory alloy (SMA) actuators and piezoceramic actuators exhibit different hysteresis loops. In this paper, a generalized Prandtl-Ishlinskii model is utilized for modeling and compensation of hysteresis effects in smart actuators. In the formulated model, a generalized play operator together with a density is integrated to form the generalized Prandtl-Ishlinskii model. The capability of the formulated model to characterize hysteresis in smart actuators is demonstrated by comparing its outputs with experimental results obtained from different smart actuators. Furthermore, an analytical inverse of the generalized Prandtl-Ishlinskii model is derived for compensations in different smart actuators. Such compensation is experimentally illustrated by piezoceramic actuator.
Energy Dissipation Capacity of Friction-Type Reinforcing Members Installed at a Transmission Tower
Authors: Park Ji-Hun , Moon Byoung-Wook , Lee Sung-Kyung , Min Kyung-Won
Published: July 2009

Friction-type reinforcing members (FRMs) developed for the purpose of enhancing the wind-resistant performance of transmission towers are tested experimentally. The FRMs, in the middle of which slotted bolted connections (SBCs) are installed, are placed on the outside of tower legs, and provide additional damping and stiffness to the tower structure under bending deformations. Firstly, the SBCs used in the FRMs are tested for various frictional sliding interface conditions. Secondly, the FRMs are installed on a 1/2 scale plane tower substructure and cyclic loading tests are conducted. Energy dissipation capacity and effects from local deformations of the FRMs and joint slips are investigated. From the test results, remarkable energy dissipation capacity, reaching to the 2.4 times of that before the installation of the FRMs, is observed. However, the local deformation of the SBC and joint slip should be prevented for more reliable design of the FRMs.
Excitation Design for Damage Detection Using Iterative Adjoint-Based Optimization
Authors: Bement Matthew T. , Bewley Thomas R.
Published: July 2009

This paper presents a method for designing excitations for the purpose of enhancing the detectability of damage. The field of structural health monitoring (SHM) seeks to assess the integrity of structures for the primary purpose of moving from time-based maintenance to a more cost effective condition-based maintenance strategy. Consequently, most approaches to SHM are nondestructive in nature. One common nondestructive approach is known as vibration-based SHM. In this approach, a structure is instrumented with an array of sensors at various locations. The structure is then excited and its dynamic response recorded. This response is then interrogated to extract features that are correlated with damage. A survey of the SHM literature [1], [2], reveals that a great deal of attention has been paid to the data interrogation portion of the SHM process, with almost no attention paid to the excitation design. This focus is quite understandable in many applications where only ambient excitation is available, such as most civil engineering applications. However there are many applications where the excitation is selectable (e.g., most wave propogation approaches to SHM), and, indeed, where proper excitation selection is essential. As a simple example, consider a beam or column with a crack that is nominally closed due to a preload. If the provided excitation is not sufficient to open and close the crack, the detectability of the crack in the measured output will be severely limited.
Theoretical and Experimental Investigation of an L-Shape Beam Structure
Authors: Cao Dong-Xing , Zhang Wei , Yao Ming-Hui
Published: July 2009

Flexible multi-beam structures are significant components of large space station, architecture engineering and other structural systems. The understanding of the dynamic characteristics of these structures is essential for their design and control of vibrations. In this paper, the planar nonlinear vibrations and chaotic dynamics of an L-shape flexible beam structure will be investigated using theoretical and experimental methods. The L-shape beam structure considered here is composed of two flexible beams with right-angle. The governing equations of motion for the L-shape beam structure are established firstly. Then, the method of multiple scales is utilized to obtain a four-dimensional averaged equation. Numerical method is used to analyze the nonlinear dynamic responses and chaotic motions. Finally, The experimental apparatus and schemes for measuring the amplitude of nonlinear vibrations for the L-shape beam structure are introduced briefly. Then, the detailed analysis for experimental data and signals which represent the nonlinear responses of the beam structure are given.
A Stochastic Mechano-Chemical Model for Cooperative Motor Protein Dynamics
Authors: Krishnan Arjun , Epureanu Bogdan I.
Published: July 2009

The Peskin-Oster model for single molecule experiments on kinesin is extended to analyze the motion of two motors cooperatively pulling a bead in a kinesin motility assay. The various assumptions inherent in the model are tested for the case of two motors, and justified rigorously. We formulate a Markov process similar to the single motor case, and simulate the master equations on a restricted set { − N, ···, N} for each motor. The model is simulated for different initial configurations, and motors with identical parameters are found to synchronize in expectation, both spatially and in phase. It is found that synchronization is faster at higher loads and for higher adenosine triphosphate (ATP) concentrations. From a physical perspective, it is shown that the motors move to a configuration where the load is shared equally between them.
Nonlinear Position Control of Smart Actuators Using Model Predictive Sliding Mode Control
Authors: Kim Byeongil , Washington Gregory N.
Published: July 2009

This paper investigates a novel nonlinear positioning control methodology for piezoelectric stack actuators. Piezoelectric devices become very common recently for precise positioning, primarily due to the fact that they are solid state and can be accurately controlled by a voltage or current input. However, hysteresis decreases positioning accuracy and could lead to instability. The ultimate goal is to reduce it so that the piezoelectric device has a nearly linear relationship between the input field and output strain. The main purpose of this research is the reduction of the hysteresis utilizing a hysteresis model and a nonlinear model-based controller. A novel control method called model predictive sliding mode control (MPSMC) will be utilized on an actuator using a nonlinear energy-based hysteresis model. The idea of MPSMC is to implement model predictive control techniques to improve sliding mode control by forcing the system to reach the sliding surface in an optimal manner. Simulations and experiments were conducted to verify the technique.
Development of a Low-Cost Automated Tension Estimation System for Cable-Stayed Bridges
Authors: Cho Soojin , Lynch Jerome Peter , Yun Chung-Bang
Published: July 2009

Cable tension force is one of the most important structural parameters to monitor in cable-stayed bridges. For example, cable tension needs to be monitored during construction and maintenance to ensure the bridge is not overloaded. To economically monitor tension forces, this study proposes the use of an automated wireless tension force estimation system (WFTES) developed solely for cable force estimation. The design of the WFTES system can be divided into two parts: low-cost hardware and automated software. The low-cost hardware consists of an integrated platform containing a wireless sensing unit constructed from commercial off-the-shelf components, a low-cost commercial MEMS accelerometer, and a signal conditioning board for signal amplification and filtering. With respect to the automated software, a vibration-based algorithm using estimated modal parameters and information on the cable sag and bending stiffness is embedded into the wireless sensing unit. Since modal parameters are inputs to the algorithm, additional algorithms are necessary to extract modal features from measured cable accelerations. To validate the proposed WFTES, a scaled-down cable model was constructed in the laboratory using steel rope wire. The wire was exposed to broad-band excitations while the WFTES recorded the cable response and embedded algorithms interrogated the measured acceleration to estimate tension force. The results reveal the embedded algorithms properly identify the lower natural frequencies of the cable and make accurate estimates of cable tension. This paper concludes with a summary of the salient research findings and suggestions for future work.
The Effect of Hydrogel Phase on Stress Relaxation Properties of a Novel Hydrogel Fibrous Composite Scaffold for Ligament Tissue Engineering
Authors: Freeman Joseph W. , Woods Mia D. , Laurencin Cato T.
Published: July 2009

The anterior cruciate ligament (ACL) is necessary for normal knee stability and movement. The ACL supports the knee and limits anterior translation of the femur beyond the tibia, which could cause a dislocation and fracture of bones in the knee. Unfortunately the ACL is also the most frequently injured ligament of the knee with severe disruptions requiring surgical intervention. One surgical option is replacement of the ligament with autografts, allografts, or artificial replacements. Unfortunately, all of these options have drawbacks.
Resistivity reduction by external oxidation of Cu–Mn alloy films for semiconductor interconnect application
Authors: Iijima J. , Fujii Y. , Neishi K. , Koike J.
Published: July 2009

A self-forming barrier process using Cu–Mn alloy has been reported to exhibit excellent reliability for interconnect lines in advanced semiconductor devices. However, Mn increases resistivity. In this work, the authors investigated optimum annealing conditions to remove Mn from the Cu–Mn alloy by forming an external Mn oxide and to reduce resistivity to a level of pure Cu. The results were interpreted by an external oxidation mechanism of Mn atoms.
Coupling Mechanics to Charge Transport in Carbon Nanotube Mechanical Resonators
Authors: Lassagne Benjamin , Tarakanov Yury , Kinaret Jari , Garcia-Sanchez Daniel , Bachtold Adrian
Published: July 2009

Tuning Carbon Nanotube Resonances

Nanoscale resonators can be used in sensing and for processing mechanical signals. Single-walled carbon nanotubes have potential design advantages as resonators in that their oscillatory motion could be coupled to electron transport (see the Perspective by

Hone and Deshpande

).

Steele
et al.

(p.
1103
, published online 23 July) and

Lassagne
et al.

(p.
1107
, published online 23 July) report that the resonance frequency of a suspended single-walled carbon nanotube can be excited when operated as a single-electron transistor at low temperatures. Electrostatic forces are set up when the carbon nanotubes charge and discharge. The resonance frequency depends on applied voltages, and the coupling is strong enough to drive the mechanical motion into the nonlinear response regime. Differences in the responses of the devices in the two studies reflect in part the different quality factors of the resonators and different cryogenic temperatures.
Prevalence of radiological signs of femoroacetabular impingement in patients presenting with long-standing adductor-related groin pain
Authors: Weir A , de Vos R J , Moen M , Hölmich P , Tol J L
Published: July 2009

Objective

A decreased range of motion (ROM) of the hip joint is known to predispose to athletic groin injury. Femoroacetabular impingement (FAI) of the hip leads to a reduced ROM. This study examined the prevalence of radiological signs of FAI in patients presenting with long-standing adductor-related groin pain (LSARGP).

Design

Prospective case series.

Setting

Outpatient Sports Medicine Department.

Patients

34 athletes with LSARGP defined as pain on palpation of the proximal insertion of adductor muscle and a painful, resisted adduction test.

Assessment

A clinician blinded to the results of the radiological assessment performed a physical examination: iliopsoas length, hip ROM and anterior hip impingement test. Anteroposterior pelvic radiographs were examined by a second blinded clinician for the presence of: pistol grip deformity, centrum-collum-diaphyseal angle, femoral head neck ratio, coxa profunda, protrusio acetabuli, lateral centre edge angle, acetabular index and cross-over sign.

Results

The prevalence of radiological signs of FAI was 94% (64/68). The mean number of radiological signs in hips with LSARGP was 1.84 (range 0–4, SD 1.05) and 1.96 (range 0–5, SD 1.12) in asymptomatic groins (p=0.95). The anterior hip impingement test was positive in nine cases. There was no relationship with the number of radiological signs (p=0.95). There was no correlation between hip ROM and the number of radiological signs (p=0.37).

Conclusion

Radiological signs of FAI are frequently observed in patients presenting with LSARGP. Clinicians should be aware of this fact and the possible lack of correlation when assessing athletes with groin pain.
ABSOLUTELY CONTINUOUS SPECTRUM FOR A RANDOM POTENTIAL ON A TREE WITH STRONG TRANSVERSE CORRELATIONS AND LARGE WEIGHTED LOOPS
Authors: FROESE RICHARD , HASLER DAVID , SPITZER WOLFGANG
Published: July 2009

We consider random Schrödinger operators on tree graphs and prove absolutely continuous spectrum at small disorder for two models. The first model is the usual binary tree with certain strongly correlated random potentials. These potentials are of interest since for complete correlation they exhibit localization at all disorders. In the second model, we change the tree graph by adding all possible edges to the graph inside each sphere, with weights proportional to the number of points in the sphere.
RANKING AND SCHOOL AUTONOMY: EFFICIENCY EFFECTS OF NEW INITIATIVES ON THE SINGAPORE EDUCATION SYSTEM
Authors: CHEO ROLAND K.
Published: July 2009

From 1979, the Singapore government started to transform the nature of secondary education in Singapore. In 1979, nine schools were chosen as Special Assistance Plan (SAP) schools. After the call towards reforming the school system in the 1980s, the development of Independent schools evolved. In 1994, a new category — the autonomous school — was established. Besides reforming the school structure, in 1992, the "ST Schools 100" (first published by The Straits Times on 19 August 1992) started to rank the top 50 schools in the Special/Express stream and the top 40 schools in the Normal stream, along with separate tables listing the top value-added schools in both streams. Until quite recently, this ranking scheme had been endorsed by the Ministry of Education since 1992 and published on their website annually since 1995. This paper looks at how these new initiatives have affected secondary school outcomes. Comprising a panel data set of 30 of the top 50 schools in Singapore over the 1991–2001 period, the study looks at the technical efficiency of schools as a response to the introduction of new initiatives using two methodologies. The first baseline approach is that of a Corrected Ordinary Least Squares (COLS) multiple-output distance function. The second methodology used is the technical efficiency frontier effects model as described by Battese and Coelli (1995) and Coelli and Perelman (1996) which is a maximum likelihood estimation technique.
EVALUATION OF MALAYSIAN CAPITAL CONTROLS IN THE SHORT, MEDIUM, AND LONG RUNS
Authors: DAMRONGPLASIT KANNIKA
Published: July 2009

This paper uses monthly data starting from January 1993 until June 2005 to assess the effectiveness of capital controls in restoring the Malaysian economy as compared to the IMF programs in Indonesia, Korea, and Thailand. We analyse various aspects of the economy by employing time-shifted difference-in-difference estimation. To evaluate the effects in the short, medium, and long runs, this study takes into account one to six years of treatment periods. Our estimation results provide strong evidence in favor of capital controls as a more effective crisis solution than the IMF programs in the short and medium runs.
RESERVE POOLING AND ITS IMPLICATION ON OPTIMUM CURRENCY AREA IN ASEAN
Authors: MASRON TAJUL ARIFFIN , YUSOP ZULKORNAIN
Published: July 2009

Regional economic integration in ASEAN, ASEAN Free Trade Area (AFTA), is expected to produce positive outcomes on economic growth in ASEAN especially through its impact on trade and investment. This idea can be strengthened if regional monetary integration is followed. Therefore, focusing on reserve pooling, which is one of the proxy for Optimum Currency Area (OCA) variables, this study intends to examine the feasibility of a common currency in ASEAN. In addition, this study also investigates this idea in the presence of external shock.