bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Na0.5K0.5NbO3Piezoelectrics by a Solution Coating Approach
Authors: Li Huidong , Shih Wei‐Heng , Shih Wan Y.
Published: July 2008

The solution coating method is shown to provide more homogeneous mixing of the starting powders and purer (Na0.5K0.5)NbO3(NKN) powder than the conventional method thereby rendering cold isostatic pressing unnecessary. Sintering NKN with potassium copper niobate (KCN) by uniaxial pressing gave a relative bulk density of 92%,d33coefficient of 112 pC/N and a loss factor of 1% after 6 h at 1100°C. In contrast, the conventional method yielded 84% relative bulk density and a 31% loss factor after 6 h at 1100°C and the sample was too porous to allow for dielectric and piezoelectric measurements.
β2‐Microglobulin Amyloidosis in Hemodialysis and Peritoneal Dialysis Patients
Authors: Dervisoglu Erkan , Anik Yonca , Erdogan Sarper , Akansel Gur , Yilmaz Ahmet
Published: August 2008

Abstract:  β2‐microglobulin (β2‐M) amyloidosis is an important cause of morbidity in patients on dialysis. In this cross‐sectional study, we evaluated supraspinatus tendon thickness (as a measure of shoulder involvement from β2‐M amyloidosis) in patients who are on hemodialysis (HD) compared with those on continuous ambulatory peritoneal dialysis (CAPD). In 27 patients on HD who were treated with high‐flux dialyzers, 31 patients on CAPD, and 31 healthy volunteers, we performed bilateral shoulder magnetic resonance imaging and measured the supraspinatus tendon thickness using electronic calipers. There were no statistically significant differences in age or dialysis duration between the HD and CAPD patients. Each patient was asked about the presence or absence of shoulder pain. The supraspinatus tendon thickness in HD patients (mean thickness 6.6 ± 1.3 mm, range 3.20–8.80 mm, N = 53) and CAPD patients (6.8 ± 0.9 mm, range 4.9–8.8 mm, N = 61) was not significantly different (P = 0.289); however, the mean thickness in either group was higher than in the healthy controls (5.5 ± 0.6 mm, range 4.3–6.8 mm, N = 61) (HD patients vs. controls: P = 0.000; CAPD patients vs. controls: P = 0.000). Patients with shoulder pain had higher mean supraspinatus tendon thickness measurements than patients without shoulder pain (P = 0.042). The thickness of supraspinatus tendons is not significantly different between patients on CAPD and HD. An association exists between shoulder pain and mean supraspinatus tendon thickness. This hidden complication of ESRD should be further studied in larger populations of dialysis patients.
CONSUMER ATTITUDES AND OPINIONS TOWARD FUNCTIONAL FOODS: A FOCUS GROUP STUDY
Authors: BARRIOS EDITH X. , BAYARRI SARA , CARBONELL INMACULADA , IZQUIERDO LUIS , COSTELL ELVIRA
Published: July 2008

Acceptance of foods with specific health characteristics depends largely on the consumers’ opinion. The objective of this work was to investigate Spanish consumers’ opinions, attitudes and beliefs regarding functional foods in general, and one of the most popular foods, yogurt, in particular. Six consumer focus group interviews were conducted, involving a total of 59 participants. Each group profile was chosen to either complement or contrast the other groups according to previously established criteria (gender, age and educational level). The youngest consumers (18–30 years old) proved, in general, to have a fairly negative attitude toward these types of products, although this attitude varied according to the type of food. For the consumers participating in this study, the most acceptable functional foods were low‐fat foods and some fermented dairy products. Purchase and consumption of yogurt were more dependent on its sensorial qualities and its price than on the nutritional information printed on the label.

PRACTICAL APPLICATIONS

The influence of attitudes, beliefs and opinions on food choice and purchase is specially important in the acceptance of some types of foods (organic or ecological, genetically modified or functional) that are presented to the consumer as a possible alternative to the conventional foods. The application of focus groups can help not only in explaining consumer behavior, but also in designing more effective nutritional education rules and products that satisfy consumer needs and expectations.
NEURAL METHODS OF CALIBRATION OF SENSORS FOR GAS MEASUREMENTS AND AROMA IDENTIFICATION SYSTEM
Authors: OSOWSKI STANISLAW , BRUDZEWSKI KAZIMIERZ , MARKIEWICZ TOMASZ , ULACZYK JAN
Published: July 2008

The article presents the neural methods of calibration of gas sensors for use in an artificial electronic nose for gas measurements. Different neural network solutions will be presented and compared. They include the classical multilayer perceptron, neuro‐fuzzy networks and support vector machines. The other aspect illustrated in the article is the introductory preprocessing of the measured sensor signals in order to attain the highest possible efficiency of the gas measuring system. The theoretical considerations will be supported by the numerical experiments concerning the application of the electronic nose. The first practical aspect is concerned with the application of the developed system for classification problems and will be illustrated in the examples of the recognition of the biocomponents in the gasoline and the recognition of smells of cosmetic cream at the aging process. The second one belongs to the estimation problem and is concerned with the determination of the concentration of the particular gas components in the mixture of gases.

PRACTICAL APPLICATIONS

The results presented in the article may find practical application for calibration of the electronic nose in gas measurements. The electronic nose is widely used for smell recognition. It may find practical application in the petroleum, cosmetics or food industry for the assessment of the quality of their products. Military application is also of great interest.
Multiple Parameterization for Hydraulic Conductivity Identification
Authors: Tsai Frank T.‐C. , Li Xiaobao
Published: July 2008

Hydraulic conductivity identification remains a challenging inverse problem in ground water modeling because of the inherent nonuniqueness and lack of flexibility in parameterization methods. This study introduces maximum weighted log‐likelihood estimation (MWLLE) along with multiple generalized parameterization (GP) methods to identify hydraulic conductivity and to address nonuniqueness and inflexibility problems in parameterization. A scaling factor for information criteria is suggested to obtain reasonable weights of parameterization methods for the MWLLE and model averaging method. The scaling factor is a statistical parameter relating to a desired significance level in Occam’s window and the variance of the chi‐squares distribution of the fitting error. Through model averaging with multiple GP methods, the conditional estimate of hydraulic conductivity and its total conditional covariances are calculated. A numerical example illustrates the issue arising from Occam’s window in estimating model weights and shows the usefulness of the scaling factor to obtain reasonable model weights. Moreover, the numerical example demonstrates the advantage of using multiple GP methods over the zonation and interpolation methods because GP provides better models in the model averaging method. The methodology is applied to the Alamitos Gap area, California, to identify the hydraulic conductivity field. The results show that the use of the scaling factor is necessary in order to incorporate good parameterization methods and to avoid a dominant parameterization method.
Property Tax in Urban China
Authors: Li Dan , Song Shunfeng
Published: July 2008

This paper examines China's urban housing sector and proposes that property tax reform be undertaken. Specifically, China should significantly reduce taxes on transactions and introduce property taxes during the possession of houses. This will increase housing affordability as a result of lower transaction costs, reduce speculation because of the higher opportunity cost of holding vacant houses, stabilize the fiscal system by generating more sustainable tax revenue, and improve the efficiency and fairness of the property tax system according to the principles of “ability‐to‐pay” and “user pays”.
China's Inbound Tourist Revenue and Beijing Olympic Games 2008
Authors: Zeng Kaisheng , Luo Xiaohui
Published: July 2008

During the process of economic globalization, China's inbound tourism has developed strongly. The present paper deals with one of the core issues of the international tourism industry: inbound tourist revenue. With the aid of conventional theories and the use of empirical tests, our study identifies some decisive factors that have influenced China's inbound tourist revenue through an analysis of the global and local conditions at macro and micro levels. The findings were then linked to the Olympic Games, the mega event having impacted international tourism. The findings were also linked to further discussions and suggestions for the interactions between the Beijing Olympic Games 2008 and China's inbound tourism.
Generative Approaches to Ergativity
Authors: Aldridge Edith
Published: July 2008

This article surveys the principal generative syntactic analyses that have been proposed for ergativity, found primarily in Inuit, Austronesian, Mayan, and Pama‐Nyungan language families. The main puzzle for generative grammar is how to analyze the behavior of ergative and absolutive arguments in terms of the grammatical functions of subject and object. I show in this article that early approaches tend to treat the absolutive uniformly as a subject or an object, while later analyses move toward disassociating case from grammatical function. Descriptively speaking, this article identifies two types of morphological ergativity, differing in how absolutive case is assigned. Morphological ergativity is also distinguished from syntactic ergativity, which is characterized primarily by a restriction that only absolutives can undergo A’‐movement. In other aspects of the grammar, ergativity is not strikingly different from accusativity.
Family Language Policy
Authors: King Kendall A. , Fogle Lyn , Logan‐Terry Aubrey
Published: July 2008

This article describes the newly emerging field of family language policy, defined as explicit and overt planning in relation to language use within the home among family members, and provides an integrated overview of research on how languages are managed, learned, and negotiated within families. A comprehensive framework for understanding family language policy is sketched by bringing together two independent and currently disconnected fields of study: language policy and child language acquisition. Within such a framework, this article reviews research on the role of language ideologies in shaping family language practices, and on the connection between different family language policies, such as the one person–one language approach, and child language outcomes. We argue that family language policies are important as they shape children's developmental trajectories, connect in significant ways with children's formal school success, and collectively determine the maintenance and future status of minority languages.
Photosensitizing Properties of Triplet β‐Lapachones in Acetonitrile Solution
Authors: Netto‐Ferreira José Carlos , Lhiaubet‐Vallet Virginie , De Oliveira Bernardes Bauer , Ferreira Aurelio Baird Buarque , Miranda Miguel Ángel
Published: July 2008

The photochemical reactivity of β‐lapachone (1), nor‐β‐lapachone (2) and 1,2‐naphthoquinone (3) towards amino acids and nucleobases or nucleosides has been examined employing the nanosecond laser flash photolysis technique. Excitation (λ = 355 nm) of degassed solutions of 1–3, in acetonitrile, resulted in the formation of their corresponding triplet excited states. These transients were efficiently quenched by l‐tryptophan, l‐tryptophan methyl ester, l‐tyrosine, l‐tyrosine methyl ester and l‐cysteine (kq ≈ 109 L mol−1 s−1). For l‐tryptophan, l‐tyrosine and their methyl esters new transients were formed in the quenching process, which were assigned to the corresponding radical pair resulting from an initial electron transfer from the amino acids or their esters to the excited quinone, followed by a fast proton transfer. No measurable quenching rate constants could be observed in the presence of thymine and thymidine. On the other hand, efficient rate constants were obtained when 1–3 were quenched by 2′‐deoxyguanosine (kq ≈ 109 L mol−1 s−1). The quantum efficiency of singlet oxygen (1O2) formation from 1 to 3 was determined employing time‐resolved near‐IR emission studies upon laser excitation and showed considerably high values in all cases (ΦΔ = 0.6), which are fully in accord with the ππ* character of these triplets in acetonitrile.
Photodegradation of 2‐chloro Substituted Phenothiazines in Alcohols
Authors: García Carmelo , Piñero Luis , Oyola Rolando , Arce Rafael
Published: July 2008

The mechanisms that trigger the phototoxic response to 2‐chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption‐ and emission‐spectroscopy, 1H‐ and 13C‐NMR and GC‐MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce et al. (J. Med. Chem. 22, 202–204) to explain the large difference between the photodestruction quantum yield of 2‐chlorpromazine (ϕ = 0.46) and 2‐chlorphenothiazine (ϕ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10‐substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient.
A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter
Authors: Paris Cecilia , Lhiaubet‐Vallet Virginie , Jiménez Oscar , Trullas Carles , Miranda Miguel Ángel
Published: July 2008

Novel sunscreens are required providing active protection in the UVA and UVB regions. On the other hand, there is an increasing concern about the photosafety of UV filters, as some of them are not sufficiently photostable. Avobenzone is one of the most frequently employed sunscreen ingredients, but it has been reported to partially decompose after irradiation. In the present work, photophysical and photochemical studies on a methylated avobenzone‐derivative have shown that the diketo form is responsible for photodegradation. A transient absorption was observed at 380 nm after laser flash photolysis excitation at 308 nm. It was assigned to the triplet excited state of the diketo form, as inferred from quenching by oxygen and β‐carotene. This transient also interacted with key building blocks of biomolecules by triplet–triplet energy transfer (in the case of thymidine) or electron transfer processes (for 2′‐deoxyguanosine, tryptophan and tyrosine). Irradiation of the avobenzone derivative in the presence of a triazine UV‐B filter (E‐35852) diminished the undesirable effects of the compound by an efficient quenching of the triplet excited state. Thus, sunscreen formulations including triplet quenchers could provide effective protection from the potential phototoxic and photoallergic effects derived from poor photostability of avobenzone.
Comparative Analysis of Antibiotic Resistance Characteristics of Gram‐negative Bacteria Isolated from Laying Hens and Eggs in Conventional and Organic Keeping Systems in Bavaria, Germany
Authors: Schwaiger K. , Schmied E.‐M. V. , Bauer J.
Published: July 2008

By investigating the prevalence and resistance characteristics of Gram‐negative bacteria from organic and conventional kept laying hens against 31 (Campylobacter: 29) different antibiotics using the microdilution method, we determined to what extent different keeping systems influence bacterial resistance patterns. For this purpose, samples from 10 organic and 10 conventional flocks in Bavaria (Germany) were investigated four times between January 2004 and April 2005. Altogether, 799 cloacal swabs and 800 eggs (contents and shells) were examined. The bacterial investigation performed with standardized cultural methods showed prevalence for all bacteria groups in about the same order of magnitude in the two different keeping systems: Salmonella spp. 3.5% (organic [org]) versus 1.8% (conventional [con]); Campylobacter spp. 34.8%org versus 29.0%con and E. coli 64.4%org versus 69.0%con. Coliforms (Citrobacter, Enterobacter, Pantoea) were only isolated in single cases. In eggs, generally less bacteria were detected, predominantly Escherichia; Salmonella and Campylobacter were only scarcely isolated. Salmonella enterica ssp. enterica serovar Typhimurium (n = 10) were resistant to up to nine, S. of the serogroup B (n = 4) up to six antibiotics. All tested Salmonella (n = 23) proved to be resistant to spectinomycin. Escherichia coli (n = 257org and 276con) from organic layers showed significant lower resistance rates and higher rates of susceptible isolates to nine agents, namely amoxicillin/clavulanic acid, ampicillin, cefaclor, cefoxitin, cefuroxime, doxycycline, mezlocillin, neomycin and piperacillin. In contrast, only two antibiotics turned out to be more effective in conventional isolates (gentamicin and tobramycin). In the case of Campylobacter jejuni (n = 118org and 99con), statistically significantly better rates were observed for isolates from organic flocks concerning imipenem and amoxicillin/clavulanic acid, whereas fosfomycin was more potent in strains from conventional flocks. Results of this study indicate that both resistance rates and mean minimum inhibitory concentrations of bacteria isolated from organic keeping systems have lower values than those from conventional ones, particularly recognizable for E. coli. Thus, organic livestock farming with its restrictions and additional requirements contributes to further effectiveness of antibiotics.
A New Approach to Scan-Trajectory Design and Track: AFM Force Measurement Example
Authors: Kim Kyong-Soo , Zou Qingze , Su Chanmin
Published: August 2008

In this article, two practical issues encountered in the design and track of scan trajectories are studied: One issue is the large output oscillations occurring during the scanning, and the other one is the effect of modeling errors on trajectory tracking. Output oscillations need to be small in scanning operations, particularly for lightly damped systems, such as the piezoelectric actuators and the flexible structures. Moreover, modeling errors are ubiquitous in practical applications. The proposed approach extends the recently developed optimal scan-trajectory design and control method by introducing the prefilter design to reduce the output oscillations. Furthermore, a novel enhanced inversion-based iterative control (EIIC) algorithm is proposed. The EIIC algorithm is then integrated with the optimal scan-trajectory design method to compensate for the effect of modeling errors on the scanning. The convergence of the iterative control law is discussed, and the frequency range of the convergence is quantified. The proposed approach is illustrated by implementing it to the high-speed adhesion-force measurements using atomic force microscope. Simulation and experimental work are presented and discussed to demonstrate the efficacy of the proposed approach. The experimental results show that compared to the conventional DC-gain method, the proposed approach can reduce the tracking error by over 25 times during the force-curve measurements.
Creep Effect of Attached Structures on Bolted Flanged Joint Relaxation
Authors: Nechache Akli , Bouzid Abdel-Hakim
Published: August 2008

The leakage tightness behavior of bolted flange joints is compromised due to high temperature effects and in particular when creep of the materials of the different components of the bolted flanged joint take place. The relaxation of bolted flanged joints is often estimated from the creep of the gasket and the bolts. The creep behavior of the flange ring and the attached structures such as the shell and the hub is often neglected. Apart from an acknowledgement of relaxation due to creep, the designer has no specific tools to accurately assess this effect on the bolt load relaxation. The objective of this paper is to present an analytical approach capable of predicting the bolt load relaxation due to creep of the attached structures. The proposed approach is validated by comparison with 3D FE models of different size flanges. An emphasis will be put towards the importance of including creep of the attached structures in high temperature flange designs.
A Numerical Study of the Impact Response of Laminated Glass Panels
Authors: Rule William Keith
Published: August 2008

This paper describes a study that was undertaken to simulate impacts on laminated float glass/polycarbonate/float glass panels using the Johnson-Holmquist (JH-2) model for brittle materials and the EPIC explicit finite element code. The simulation results are compared with observed impact results obtained by others. The JH-2 model was originally successfully calibrated to treat impact on thick monolithic glass slabs. In this study recent spall strength data for glass reported in the literature was used to revise the JH-2 model for application to thin laminated glass panels — a system of wide technical interest. The JH-2 coefficients developed were further validated by comparison with an additional independent data set obtained from the literature involving glass rod impact data. A good fit to both data sets considered was produced suggesting that the revised JH-2 coefficients proposed are reasonable.
Thermal Protection Provided by Impact Limiters to Containment Seal Within a Truck Package
Authors: Greiner Miles , Chalasani Narayana Rao , Suo-Anttila Ahti
Published: August 2008

The Container Analysis Fire Environment computer code is used to simulate the response of a truck package designed to transport one PWR fuel assembly to 7.2-m-diameter pool fires. Simulations are performed with the package centered over the fire, and offset axially from that location by 1 and 2.5 m. In all simulations the package body is 1 m above the fuel pool. The simulations predict the package containment seal exceeds its temperature of concern for all three package locations. Simulations of a no-impact-limiter version of the package are also performed to quantify the level of thermal protection provide by the limiter. The minimum fire duration that causes the seal to reach its temperature of concern is determined for each configuration. When the center of the no-impact limiter package is within 2.5 m of the pool center, fires shorter than 0.7 hour are capable of causing the seal to reach its temperature of concern. By contrast, the intact package protects the seal in fires that last roughly 2 hours. These results will help risk analysts better understand the effect of package position and the role of the impact limiters on accident consequences.
A Statistical Model for Brittle Fracture of Functionally Graded Materials
Authors: Bezensek Bostjan , Banerjee Anuradha , Hancock John W.
Published: August 2008

A model has been developed to assess the structural assessment of functionally graded materials in which yield strength and toughness vary spatially. The yield strength of the material at any point is deterministic, but varies spatially. The local cleavage toughness also varies spatially, but is statistically distributed following a two parameter Weibull model. The Weibull moduli quantify reliability and the second Weibull parameter is interpreted in terms of the mean toughness of the local material. The model intended to determine the crack propagation direction and failure probabilities of a stationary pre-crack. The effect of simple yield strength and toughness gradients are discussed, before the model is applied to experimental data on laser welded joints.
A New Formulation to Take Into Account the Interaction Between Mechanical and Thermal Loadings for the Analytical Estimation of J Parameter
Authors: Marie S. , Delaval C.
Published: August 2008

For combined mechanical and thermal loads, the analytical method to calculate the fracture mechanics parameter J for cracked pipes in the annex A16 of the RCC-MR 2002 code presents two options: the first one is the RSE-M method and the second option is based on a strong interaction where the mechanical and thermal loads are affected. It is then shown for this second option that the J parameter is strongly over-estimated for a significant mechanical load level. A new equation is proposed based on a summation of the mechanical Jme and of the thermal Jth corrected to take into account the interaction. This interaction depends on the relative significance of the mechanical loads compared to the thermal loads, and takes into account the nature of the mechanical loads: It is then shown that the amplification due to the mechanical loads has to be limited, according to the nature of the mechanical loads (axial load, bending moment, pressure,...) and the type of defect (circumferential or longitudinal, semi-elliptical shape,...) under consideration. A validation is realized using a F.E. calculation data: several defects are considered, with different mechanical loads and thermal load (linear gradient of temperature, thermal shock,...).
Forced Response of Continuous System With Hysteresis Loop Characteristics: System With Quadrilateral Hysteresis Loop Characteristics
Authors: Aoki Shigeru , Watanabe Takeshi
Published: August 2008

This paper deals with steady-state response of a continuous system with collision characteristics. Considering the energy loss in a collision, an analytical method of approximate solution for the continuous system with symmetrical hysteresis loop characteristics is presented. The resonance curves of nonlinear response obtained from approximate solution are shown as discontinuous line, and are discussed the phenomenon.
SMILE: Validation of the Warm-Pre-Stress Effect With a Cylindrical Thick-Walled Specimen
Authors: Kerkhof Klaus , Roos Eberhard , Bezdikian Georges , Moinereau Dominique , Taylor Nigel
Published: August 2008

The Reactor Pressure Vessel (RPV) is an essential component, which is liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to pressurized thermal shock (PTS) transients made at an European level generally does not necessarily consider the beneficial effect of the load history (Warm Pre-stress, WPS). The SMILE project — Structural Margin Improvements in aged embrittled RPV with Load history Effects — aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect. It also aims to harmonize the different approaches in the national codes and standards regarding the inclusion of the WPS effect in a RPV structural integrity assessment. The project includes significant experimental work on WPS type experiments with C(T) specimens and a PTS type transient experiment on a large component. This paper deals with the results of the PTS type transient experiment on a component-like specimen subjected to WPS- loading, the so called Validation Test, carried out within the framework of work package WP4. The test specimen consists of a cylindrical thick walled specimen with a thickness of 40mm and an outer diameter of 160mm, provided with an internal fully circumferential crack with a depth of about 15mm. The specified load path type is Load-Cool-Unload-Fracture (LCUF). No crack initiation occurred during cooling (thermal shock loading) although the loading path crossed the fracture toughness curve in the transition region. The benefit of the WPS-effect by final reloading up to fracture in the lower shelf region, was shown clearly. The corresponding fracture load during reloading in the lower shelf region was significantly higher than the crack initiation values of the original material in the lower shelf region. The post test fractographic evaluation showed that the fracture mode was predominantly cleavage fracture also with some secondary cracks emanating from major crack.
Effect of High-Pressure Hydrogen Gas on Fracture of Austenitic Steels
Authors: San Marchi C. , Balch D. K. , Somerday B. P.
Published: August 2008

Applications requiring the containment and transport of hydrogen gas at pressures greater than 70 MPa are anticipated in the evolving hydrogen economy infrastructure. Since hydrogen is known to alter the mechanical properties of materials, data are needed to guide the selection of materials for structural components. The objective of this study is to characterize hydrogen-assisted fracture in two austenitic steels, 21Cr-6Ni-9Mn (21-6-9) and 22Cr-13Ni-5Mn (22-13-5), as well as explore the role of yield strength and small concentrations of ferrite on hydrogen-assisted fracture. The testing methodology involves exposure of uniaxial tensile specimens to high-pressure hydrogen gas in order to precharge the specimens with hydrogen, then subsequently testing the specimens to measure strength and ductility. In all cases, the alloys remained ductile despite precharging to hydrogen concentrations >1 at%, this is substantiated by reduction in area of >50% and fracture surfaces dominated by microvoid coalescence. Low concentrations of ferrite and moderate changes in yield strength did not affect the hydrogen-assisted fracture of 21-6-9 and 22-13-5 respectively.
Predicting Steam Generator Auxiliary Feedwater Nozzle Thermal Stratification Transients and Fatigue Effects in Complex Systems
Authors: Cranford E. L. , Gray M. A. , Sahgal S.
Published: August 2008

External thermocouple measurements on auxiliary feedwater piping revealed thermal transient cycles that warranted evaluation and monitoring. Development of a fatigue monitoring system for the associated steam generator auxiliary feedwater nozzles required consideration of a number of complex factors. The thermal transients measured on the external surface often indicated the presence of thermal stratification cycling of the contained fluids. The characteristics of the transients were influenced by complex combinations of the thermal hydraulic influence of four interacting systems. The transient characteristics were found to be very sensitive to small changes in the system parameters. This paper describes methods used to simulate these complex system characteristics and obtain reasonable predictions of local thermal transient characteristics that correlate with the measured data. The predicted transient loads are used to calculate the related stress and fatigue impact in the nozzles.
Novel Ultrasonic Testing of Complex Welds
Authors: Messer Barry , Fuentes Jose R. , Tarleton Bart , den Boer Peter
Published: August 2008

Fluor and RTD have recently applied an ultrasonic testing (UT) technique that incorporates a phased array to field and shop operations. The new technique allows verification of weld integrity for difficult to access welds such as branch connection fittings and full penetration groove welds with fillet reinforcements. Verification of these types of welds is a necessity for power, oil and gas facilities, in particular, those operating under high pressure, high temperature, and corrosive environments. Historically, visual inspections of welds and radiograph testing (RT) have been used, but these methods are costly, time-consuming, and cannot match the benefits of the new UT phased array (UT-PA) method. The UT-PA technique has an arrangement of multiple piezoelectric elements that are independently controlled for developing synchronized and manageable sonic waves. The technique requires less time than conventional UT, is not hazardous as compared to RT, and allows for 100% volumetric inspection. Other advantages of UT-PA include its ease of use, increased accuracy, and development of instantaneous digital inspection records for tracking defect propagations in the future. The present work describes the application of this nondestructive examination (NDE) technique to a branched connection of an ASTM B564 outlet fitting to both an ASTM A608 modified 20Cr-32Ni-Nb statically cast header and an HP45 modified tee. An outline of the advantages for the UT-PA method is also included which explains the rationale that, in the future, will cause the welding industry to rely more on modified UT advanced imaging.
ASME Subcommittee XI Initiatives for the Detection and Correction of Boric Acid Corrosion of Pressure Retaining Low Alloy Steel Components in Pressurized Water Reactor Plants
Authors: McClanahan Jerry
Published: August 2008

In pressurized water reactor power plants sodium pentaborate is commonly used as a soluble chemical neutron absorber to control the reactivity level within the reactor core. This chemical solution of boron in the reactor primary cooling water forms a mild boric acid. The main reactor coolant system pressure vessels, i.e., the nuclear reactor and the steam generators, are protected internally from this corrosive solution by a corrosion resistant cladding. The nuclear power industry has recorded instances of leakage from the primary coolant system resulting in corrosion of these pressure vessels on their outer surfaces. In 2002 a primary coolant leak resulted in the nearly complete loss of the pressure retaining capability of the reactor vessel closure head at a domestic nuclear power plant. In response to this event the ASME Subcommittee XI has undertaken to establish inspection rules for pressurized water reactor plants for the detection of primary coolant leakage and the resulting corrosion of low alloy steel components. This paper discusses the history of this issue and the development of inspection rules designed to ensure the early detection of primary coolant system leakage and the possible resulting corrosion prior to loss of the pressure retaining capability of primary coolant system components.
In-Plane Vibration of Nonprismatic Curved Beam Structures Considering the Effect of Shear Deformation Solved by DQEM
Authors: Chen Chang-New
Published: August 2008

The development of differential quadrature element method in-plane vibration analysis model of curved nonprismatic beam structures considering the effect of shear deformation was carried out. The DQEM uses the differential quadrature to discretize the governing differential eigenvalue equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.
Thermal Stress Analysis and Evaluation of Sealing Performance in Pipe Flange Connections With Spiral Wound Gaskets Under Elevated Temperature and Internal Pressure
Authors: Sawa Toshiyuki , Takagi Yoshio , Tatsuoka Teruhisa
Published: August 2008

In this paper, the thermal stress distributions at the interfaces between pipe flanges and the gasket under elevated temperature and internal pressure were calculated by using the theory of elasticity and the finite element method (FEM) taking into account hysteresis in the stress-strain curves of spiral wound gasket. Leakage tests were performed using helium gases. In addition, the effects of temperature on the sealing performance were examined by using an actual pipe flange connection with spiral wound gasket under elevated temperature. By using the calculated contact stress distributions and the results of the leakage tests, the sealing performance was evaluated.
Numerical Modelling of Fluid Structure Interaction in Blood Vessels
Authors: Owens Pericevic Ian , Moatamedi Moji , Souli M hamed
Published: August 2008

This paper examines the capabilities offered by the fluid structure interaction (FSI) algorithms in LS-DYNA for solving problems in vascular biomechanics. In this work a case was examined in which the onset of a pressure pulse was simulated at the entrance of a straight segment of artery. The resulting dynamic response in the form of a propagating pulse wave through the vessel wall was analyzed and compared to both previous numerical results and theory. The results from the three dimensional model compared well to the theoretical description of an idealized thin-walled artery. Results were further compared to those obtained from similar research. The numerical methodologies applied in the three dimensional model were used in the development of an experiment providing a realistic physical model of a carotid artery in its physiological state. The experiment is to be used for further validation of the numerical code.
A Rapid Testing Procedure to Characterize Fundamental Sealing Behavior of Gaskets
Authors: Kobayashi Takashi
Published: August 2008

In this paper, a testing procedure to obtain fundamental sealing behavior of gasket is discussed. The testing procedure consists of 12 combinations of gasket stresses and internal pressures. It takes about 3 hours to complete one test, which is acceptable for gasket manufacturers. In order to clarify the validity of the testing procedure, measurements of leak rates of compressed fiber sheet gaskets were carried out and also experiments to check a detectable leak rate by the soapy bubble test were carried out separately. It has shown that the fundamental sealing behavior can be well characterized using the proposed testing procedure with reasonable time and cost.
Testing of Fracture Toughness Under Biaxial Loading
Authors: Brumovsky Milan , Lauerova Dana , Palyza Jiri
Published: August 2008

Reactor pressure vessels under some special regimes (i.e. pressurized thermal shock) are loaded by a strongly biaxial tensile stresses whose ratio can reach even an opposite value in comparison with normal operating conditions. Pressure vessel integrity as well as its life assessment is performed on the basis of fracture mechanics where normally only uniaxial fracture toughness of materials are used as material inputs. Special biaxial tests on cruciform type specimens with thickness up to 90 mm were tested in Nuclear Research Institute (NRI) Rez - special testing equipment and testing methods including measurements have been developed and realized. Testing equipment with maximum loading up to 1.5 MN allows to reach different biaxial loading ratios between 0 and 2. During tests, carried out mostly at low temperatures, specimens deflections, strains, load and crack opening displacement are measured and then evaluated. In NRI Rez comparative experimental tests on cruciform and beam specimens were performed. The aim of these tests was to examine the effect of crack depth and biaxial loading on fracture toughness for reactor pressure vessel material 15Kh2MFA. For evaluating the tests, the FEM (program SYSTUS) was used. The performed tests confirm shallow crack effect, i.e. increase of fracture toughness for shallow cracks compared to that one of deep cracks. Further, the performed experiments show decrease of fracture toughness of shallow cracks loaded biaxially compared to uniaxial loading of shallow cracks. Quantitatively, the fracture toughness decrease was about 20%.
Application of Ductile Cracking Criterion to the Assessment of Girth Weld Integrity for High Strength Linepipe
Authors: Ishikawa Nobuyuki , Endo Shigeru , Igi Satoshi , Sadasue Teruki
Published: August 2008

Fracture behavior of high strength linepipes with weld defects is of great interest for the integrity of pipeline system. Especially, in the seismic or permafrost area, where large ground displacement can be expected, linepipe materials need to have sufficient resistance against brittle and ductile fracture under large deformation. Wide plate tensile test with surface flaw in the girth weld metal of X100 linepipe demonstrated that tensile limit is dominated by ductile crack initiation and its propagation. Conditions for ductile crack initiation for the base materials and girth weld joints of Grade X80 and X100 linepipes were investigated in this study. It was shown that ductile cracking occurs in the notch tip region of the wide plate specimen when notch tip equivalent plastic strain reaches the same critical value as determined by the small-scale tests. Therefore, “the equivalent plastic strain” in the critical regions can be used as a transferable parameter to predict ductile crack initiation behavior. Assessment methodology for tensile limit of high strength linepipe girth weld with respect to preventing ductile cracking was proposed. The effect of strength matching of girth weld and base metal Y/T ratio on limit remote strain as well as allowable defect size was investigated analytically. Increasing strength matching and lowering Y/T ratio of base material can lead to higher limit strain to ductile cracking of girth weld. These effects of material properties were validated by weld wide plate tensile tests. Therefore, careful selection of material properties should be important to improve resistance against ductile cracking of linepipe girth welds under large deformation field.
Study on Tube Pulling Apart Load in Tubular Heat Exchangers With FEA Method
Authors: Gao Zengliang , Sun Weiming , Jin Weiya , Zhang Kangda
Published: August 2008

Tube pulling apart loads of tube-and-shell heat exchangers are very complicated, because these loads are affected by many factors, such as, tube to tubesheet joint structure, pressure, and temperatures. The tubes may break or be fouled during the service, which will result in change of tube metal temperatures and affect pulling loads. Some tubes may be pulled out from the tubesheet because of too much high tube pulling apart loads and the heat exchanger cannot be operated normally. Depending on the different flow passes of the fluid and the temperature change in the service, the tube pulling loads for several cases with different temperature distribution are calculated and analyzed for a heat exchanger using finite element (FE) method. The results show that the pulling loads of different tubes are different obviously. The pulling loads of the heat exchanger are assessed with ASME Code. The maximum pulling load is over the allowable force. FE method is a good technique to assess the distribution of the pulling loads and the location of the maximum pulling load. So it is useful and important to use FE method for forecasting the break and leak of the tubes.
Development of Safe Inspection Standards and FFS Assessment Procedures in Japan
Authors: Tahara Takayasu , Kikuchi Tsutomu , Watanabe Tomohiro
Published: August 2008

Recently, Codes and Standards for FFS assessment has been developing and applied in United States and other countries such as API RP579 as a series of maintenance procedures for pressure equipment. Activities developing FFS assessment procedures are progressing, but have not been authorized to apply actual maintenance of pressure equipment in Japan. This paper presents recent activities developing safe inspection system for high pressure equipment, typical examples of troubles due to metal loss damages and some problems of FFS assessment in maintenance works in Japan.
Vorticity Field and Acoustic Sources in a Turbulent Flow at Very Low Mach and High Reynolds Numbers
Authors: Brac Jean , Lanfrey Pierre-Yves , Sagaut Pierre
Published: August 2008

Vortex or eddy identification is still a complex problem from both the experimental and the theoretical standpoints. The different intuitive and mathematical criteria used to identify vortices are reviewed and observations are made about the weaknesses of most of the criteria. Jeong & Hussain [10] define a new method based on a mathematical criterion. We propose improving this method to yield a simple, accurate and suitable vortex definition. It is successfully applied to an unstable shear layer over a cavity in a pipe. In addition, a link between the vortex criterion and acoustic sources as defined by Lighthill is emphasized.
INTHERPOL Thermal Fatigue Test
Authors: Curtit F. , Stephan J. M.
Published: August 2008

The INTHERPOL testing facility, developed at EDF R&D is designed in order to perform pure thermal fatigue test on tubular specimen under mono-frequential thermal load. INTHERPOL specimens consist of a 300 mm length and 400 mm diameter pipe comprising a circumferential welding located at a distance of 200 mm from the bottom of the specimen. According to the test considered, the models can have various types of industrial surface finish and various configurations of welded joints. Thermal cycling is carried out on a 70 mm broad sector of the internal surface of the specimen. The cold shock is generated by the pulverization of a cold-water spray while the hot shock is obtained by submitting the cooled surface to an intense infrared radiation. Four tests have been carried out with a thermal amplitude of 120 to 140°C and a cycle’s duration ranging of 5 to 8 seconds on mock-up including several surface finish. Each fatigue test is stopped periodically in order to detect the initiation and the evolution of the cracks by intermediate die penetrant inspections. During the test, the temperature is measured by using thermocouples. The recorded temperatures are used as input data to perform finite element simulations in order to obtain the stress and strain fields necessary to interpret experimental results.
Information Processing Techniques: A Major Asset for the Aging and Life Management of Key NPP Components
Authors: Just V. E. , Ricard B. , Chatellier L. , Fournier L. , Hai¨k P.
Published: August 2008

The life management of a nuclear power plant raises several major issues amongst which ranks the aging management of the key components of the plant, both from a technical and an economic point of view. Decision-makers are thus faced with the need to define the best strategy in order to achieve the best possible performance while meeting all regulatory requirements. EDF R&D is therefore deeply involved in developing advanced decision-making support tools so the EDF Engineering and Generation Divisions can optimize the long-term management of NPP components. In this paper we wish to provide the reader with an overview of how advanced information processing techniques such as signal and image processing algorithms and knowledge-based information systems recently contributed to the improvement of in-service inspections, condition-based maintenance, and asset management. First we focus on how multi-dimensional image reconstruction techniques increase component durability as they dramatically improve defect positioning and sizing when applied to radiographic data or ultrasonic data. We then detail current research work regarding the development of next generation prognostics systems which allow condition-based maintenance to take simultaneously into account monitoring data (for early fault detection), time-dependent aging models (for degradation kinetics), expert opinion as well as a quantified evaluation of the impact (on reliability and costs) of every potential decision. Lastly we describe how knowledge-based systems can help top level decision-makers get a transverse, long-term view on how a life-management investment strategy translates into plant availability, avoided costs and improved component durability.