bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation Into the Lifetimes of Solid and Hollow Fatigue Endurance Specimens Using Cyclic Hardening Material Models in Finite Element Analysis
Authors: Gill Peter , James Peter , Currie Chris , Madew Colin , Morley Andrew
Published: October 2017

This paper considers finite element analyses that have been performed to support a fatigue endurance testing programme. This programme is aimed at understanding the influence of Light Water Reactor (LWR) environment on the fatigue life of austenitic steels under thermo-mechanical loading. Testing has typically been performed on membrane loaded fatigue specimens under isothermal conditions. However, a new test facility at Amec Foster Wheeler has been developed to enable hollow specimens to be subjected to thermal and mechanical loading for a range of thermal cycles.

This work has provided a theoretical underpinning of the observed difference in lifetimes between pressurised and unpressurised specimens, and therefore provides a means of mapping data from hollow specimen testing back to solid specimen data. The parameter used to quantify these differences was the Von Mises equivalent strain. This accounts for the additional contributions from radial and hoop strains (which come about due to the internal pressure) and therefore gives enhanced strain amplitude which is fed into the S–N curve. By comparing unpressurised and pressurised lifetimes this way, a direct comparison could be made with test results. This serves two purposes; one is to provide mechanistic understanding of the difference in lifetimes. Secondly the approach will develop an assessment methodology to treat hollow specimens so a direct comparison can be made to bar specimen S–N curves. To provide further confidence in this mechanism being the dominant factor behind this difference, an independent calculation was carried out using multi-axial fatigue life models, namely Brown-Miller and Fatemi-Soci. Good agreement was observed with these models indicating that the Von Mises strain parameter was a valid parameter to characterise the multi-axial strain behaviour at the initiation site.

The increase in Von Mises strain between pressurised and unpressurised specimens was found to be a factor of 1.20 on average. This was slightly less than the experimentally derived strain differences of about 1.25. However, there was another aspect of the test results that required investigation. It has been observed from tests that the hollow specimens had a tendency to fail at a region just after the shoulder, which is where the specimen increases in thickness. Upon inspection of the plastic strains from FEA, it became clear that there was a small increase in strain on the inside surface due to this geometric feature of the specimen. The strain at the high strain region was a factor of 1.025 higher than the centre of the specimen after shakedown. Therefore, when the two effects of geometry and incremental plasticity are combined, the agreement between experiment and FEA is better. There is still a slight difference between the observed factor and the predicted factor, and reasons for this discrepancy are discussed in the paper.
Constraint Assessment for Specimens Tested Under Uniaxial and Biaxial Loading Conditions
Authors: Cao Yupeng , Qian Guian , He Yinbiao , Chao Yuh J. , Niffenegger Markus
Published: October 2017

In the integrity analysis of a reactor pressure vessel (RPV), a postulated shallow crack is subjected to biaxial far-field stresses. However, the fracture toughness Kc or Jc, which is an important material property for the integrity assessment of a RPV, are usually tested with deeply-cracked compact tension [C(T)] or single-edged bending [SE(B)] specimens under uniaxial loading. Thus, the fracture toughness data do not reflect the biaxial loading state that the cracks in a RPV are subjected to. Cruciform bending specimen is therefore developed to simulate the biaxial stress state. In this paper, a series of finite element (FE) simulations of the cruciform specimens containing different crack geometries and of different material properties are conducted. The crack tip constraint is investigated using the J-A2 theory and the stress field near the crack tips is analyzed. The results show that the biaxial effect is material property dependent. This can contribute to the lifetime prediction of a RPV as well as better design of cruciform specimens.
Thermal Stress Ratchet Check in Piping Analysis
Authors: Adibi-Asl R. , Noban M. , Chen E.
Published: October 2017

The ASME B&PV Code, Section III NB-3600 provides a requirement to avoid thermal stress ratcheting under thermal transient conditions. The ratchet check in this code is based on calculating the range of temperature difference between the outside and inside surfaces of the pipe for pairs of load sets. The calculated temperature ranges are then compared with a code equation which is a function of pressure, geometry and material properties.

This paper reviews the thermal stress ratchet requirements in ASME Section III Subsection NB with respect to piping analysis. A simplified formula is proposed for thermal stress ratchet check which eliminates the difficulties and ambiguities associate with the formulation provided in the NB-3600 code. The paper also investigates temperature distributions for various components (including flat plate and pipe) by performing heat transfer analysis. The results are compared with the ratchet limit. Using plate solutions to estimate the temperature range of pipe could sometimes give non-conservative results.
Structural Integrity Assessment of Doel 3 and Tihange 2 RPVs: ASME B&PV Code Section III Primary Stress Re-Evaluation Accounting for the Presence of Hydrogen Flakes
Authors: Dulieu Pierre , Lacroix Valéry
Published: October 2017

During the 2012 outage at Doel 3 and Tihange 2 Nuclear Power Plants, a large number of quasi-laminar indications were detected, mainly in the lower and upper core shells of the Reactor Pressure Vessels (RPVs). The observed indications could subsequently be attributed to hydrogen flaking induced during the component manufacturing process. As a consequence, both units remained core unloaded pending the elaboration of an extensive evaluation demonstrating that they can be safely operated.

The Structural Integrity Assessment of the RPVs, through the Flaw Acceptability Assessment, aimed at demonstrating that the identified indications do not jeopardize the integrity of the reactor vessel in all operating modes, transients and accident conditions. This demonstration has been done on the basis of a specific methodology inspired by the ASME B&PV Code Section XI procedure but adapted to the nature and the number of indications found in the Doel 3 and Tihange 2 RPVs.

As requested by Article IWB-3610(d)(2) of ASME B&PV Code Section XI, one of the parts that have to be addressed through the Flaw Acceptability Assessment is the Primary Stress Re-Evaluation assuming local area reductions of the pressure retaining membrane i.e., of the core shells, due to presence of the flaws. This is performed using the limit analysis provided by Article NB-3228.1 of the ASME B&PV Code Section III. Results are compared to those using the plastic analysis of Article NB-3228.3. The acceptance criterion that needs to be verified is that the calculated collapse pressure should be more than 1.5 times the design pressure.

The paper presents the 2D conservative approach developed in order to carry out this analysis dealing with large number and high density of flaws. Furthermore, the paper validates this 2D conservative methodology through detailed 3D XFEM elastic-plastic calculations.
Investigations of In-Plane Fluidelastic Instability in a Multi-Span U-Bend Tube Bundle: Tests in Air Flow
Authors: Feenstra Paul , Sawadogo Teguewinde , Smith Bruce , Janzen Victor , Cothron Helen
Published: October 2017

The tubes in the U-bend region of a recirculating type of nuclear steam generator are subjected to cross-flow of a two-phase mixture of steam and water. There is a concern that these tubes may experience flow-induced vibration, including the damaging effects of fluidelastic instability.

This paper presents an update and results from a series of flow-induced vibration experiments performed by Canadian Nuclear Laboratories for the Electric Power Research Institute (EPRI) using the Multi-Span U-Bend test rig. In the present experiments, the main focus was to investigate fluidelastic instability of the U-tubes subjected to a cross-flow of air. The tube bundle is made of 22 U-tubes of 0.5 in (12.7 mm) diameter, arranged in a rotated triangular configuration with a pitch-over-diameter ratio of 1.5. The test rig could be equipped with variable clearance flat bar supports at two different locations to investigate a variety of tube and support configurations.

The primary purpose of the overall project is to study the effect of flat bar supports on ‘in plane’ (‘streamwise’) instability in a U-tube bundle with realistic tube-to-support clearances or preloads, and eventually in two-phase flow conditions. Initially, the test rig was designed for tests in air-flow using an industrial air blower. Tests with two-phase Freon refrigerant (R-134a) will follow.

This paper describes the test rig, experimental setup, and the challenges presented by simulating an accurate representation of current steam generator designs. Results from the first series of tests in air flow are described.
Technical Background for Alloy 617 Time Dependent Allowable Stresses
Authors: Wright J. K. , Lybeck N. J. , Swindeman R. W. , Jetter R. I. , Sham T.-L. , Wright R. N.
Published: October 2017

Alloy 617 (UNS N06617) 52Ni-22Cr-13Co-9Mo is the leading candidate material for the intermediate heat exchanger for the very high temperature reactor (VHTR). An ASME Task Group on Alloy 617 Qualification has drafted a Code Case for Alloy 617 to allow construction of components conforming to the requirements of Section III, Division 5, Subsection HB, Subpart B “Elevated Temperature Service” for service when Service Loading temperatures exceed the temperature limits established in Subsection HB, Subpart A.

There are two categories of allowable stress levels in Division 5, Subsection HB, Subpart B. The first category, identified as So, applies to Design Loadings and the second category, identified as Smt, applies to Service Loadings. Both categories are based on the lesser of time dependent and time independent properties. The time dependent properties control at higher temperatures where creep effects are significant.

The Design condition time-independent allowable stresses are determined per the criteria given in Appendix 5 of Section II, Part D and are based on extrapolated 100,000-hour creep properties. The time dependent allowable stress values for Service Loadings, St, as a function of time and temperature, up to the maximum design lifetime and use temperature, are required for the applications of the Service condition limits. The criteria for establishing St for base metal for each specified time, t, are based on the lesser of

1. 100% of the average stress required to obtain 1% total strain

2. 80% of the minimum stress to cause the initiation of tertiary creep, 67% of the minimum stress to cause rupture

3. Minimum stress-to-rupture curves are also required in the applications of the Service condition limits.

In this paper, the technical background for time dependent allowable stress values for Alloy 617 is presented. These values are being recommended to the ASME Code committees for approval, but are subject to change upon feedback from Code committees.
Impact of Undetected Fabrication Flaws on LBB Risk
Authors: Kurth Robert , Sallaberry Cédric , Kurth Elizabeth , Brust Frederick
Published: October 2017

On-going assessments of the impact of active degradation mechanisms in US nuclear power plants previously approved for leak before break (LBB) relief are being performed with, among other methods, the extremely low probability of rupture (xLPR) code being developed under a memorandum of understanding between the US Nuclear Regulatory Commission (US NRC) and the Electric Power Research Institute (EPRI) [1]. This code finished with internal acceptance testing in July of 2016 and is undergoing sensitivity and understanding analyses and studies in preparation for its general release. One of the key components of the analysis tool is the integration of inspection methods for damage and the impact of leak detection on the risk of a pipe rupture before the pipe is detected to be leaking. While it is not impossible to detect a crack or defect that is less than 10% of the pipe wall thickness current ASME code does not give credit for inspections identifying a crack of this size. This study investigates the impact of combining the probabilistic analysis results from xLPR with a pre-existing flaw to determine the change, if any, to the risk. Fabrication flaws were found to have a statistically significant impact on the risk of rupture before leak detection.
Exploratory Analysis to Estimate Axial Fracture Toughness for Zr-2.5Nb Pressure Tubes Using Test Data From Small Curved Compact Specimens
Authors: Xu Steven X. , Wallin Kim
Published: October 2017

Zr-2.5Nb pressure tubes are in-core, primary coolant containment of CANDU(1) nuclear reactors. Technical requirements for in-service evaluation of pressure tubes are provided in the Canadian Standards Associate (CSA) N285.8. These requirements include the evaluation of service conditions for protection against fracture of operating pressure tubes and demonstration of leak-before-break. Axial fracture toughness for pressure tubes is a key input in the evaluation of fracture protection and leak-before-break. The 2015 Edition of CSA N285.8 provides a pressure tube axial fracture toughness prediction model that is applicable to pressure tubes late life conditions. The fracture toughness prediction model in CSA N285.8-15 is based on rising pressure burst tests performed on pressure tube sections with axial cracks under simulated pressure tube late life conditions.

Due to the associated high cost of testing and high consumption of pressure tube material, it is not practical to perform a large number of fracture toughness burst tests. On the other hand, more fracture toughness data is required to improve the existing pressure tube axial fracture toughness prediction model. There is strong motivation to estimate pressure tube axial fracture toughness using test data from small specimens. The estimated pressure tube fracture toughness using test data from small specimens can fill the gaps in the burst test toughness data, as well as provide information on material variability and data scatter. Against this background, an exploratory analysis of estimating pressure tube axial fracture toughness using test data from small curved compact specimens has been performed and is described in this paper. The estimated values of pressure tube axial fracture toughness using the test data from small curved compact specimens are compared with the measured toughness from burst tests of pressure tube sections with axial cracks to check the feasibility of this approach.
Scanning Kelvin Probe Force Microscopy Study of Hydrogen Distribution and Evolution in Duplex Stainless Steel
Authors: An Bai , Hua Zhengli , Iijima Takashi , Gu Chaohua , Zheng Jinyang , San Marchi Chris
Published: October 2017

Detecting hydrogen distribution at micro- and nano-scale is important for understanding the mechanisms of hydrogen embrittlement in metals. In this study, scanning Kelvin probe force microscopy (SKPFM), which can detect the variation of surface contact potential difference (CPD) caused by hydrogen, is applied to investigate the hydrogen distribution and evolution in thermally hydrogen-charged (HC) super duplex stainless steel. The SKPFM observations reveal that the CPD distribution becomes nonuniform in both the ferrite and austenite phases after hydrogen charging, implying that hydrogen distributes heterogeneously in the two phases. The average CPDs of both the ferrite and austenite phases are significantly decreased and the difference of CPD between two phases reaches a maximum shortly after thermal hydrogen-charging. The average CPDs of both the ferrite and austenite phases recover and the difference of CPD between two phases is decreased upon release of the hydrogen. These results are discussed in terms of the hydrogen outgasing behavior and the difference of hydrogen diffusivity in the two phases.
Experimental Investigation of Nickel Alloy 600 Strain Hardening Recovery
Authors: Andrieu Antoine , Rossillon Frederique , Rolland Gilles , Hendili Sofiane , Albrecht David
Published: October 2017

Prediction of residual stresses in welds is essential in order to evaluate the integrity of a component subject to degradation mechanisms such as Stress Corrosion Cracking. During welding operations, complex thermo-mechanical and metallurgical processes take place and lead to microstructural changes such as dynamic recovery and dynamic recrystallization. These microstructural changes induce a modification of hardening behavior that should be taken into account to accurately evaluate residual stresses through numerical simulations. A large test campaign was carried out in order to measure the recovery and recrystallization kinetics of Ni base alloy 600. Tests consisted in introducing 20% of plastic-strain at room temperature and then applying a thermal cycle with a Gleeble heat treatment simulator under stress release conditions. The comparison of mechanical properties prior to heat treatment and after heat treatment allows the evaluation of the recovery parameter that could be considered during welding numerical simulations. During this test campaign, various thermal cycles were applied. Experimental results show that the whole data points can be described as a function of Larson-Miller parameter. Mechanical results, metallurgical investigations and first numerical simulations are also presented in this paper.
Buckling Strength Evaluation of Locally Wall Thinning Elbow
Authors: Sakai Michiya , Matsuura Shinichi , Morita Ryo , Inada Fumio , Onishi Shigenobu
Published: October 2017

In a previous study [1], the seismic behavior of a piping system with local thinning elbow caused by liquid droplet impingement erosion (LDI) was evaluated using hybrid seismic testing method in Central Research Institute of Electric Power Industry (CRIEPI). In those studies, torsional buckling and wrinkles occurred at locally wall thinning elbow under large amplitude seismic motion of eight times the design basis earthquake based on the allowable stress level. It was concluded that buckling should be considered as a failure mode. In this study, the torsion buckling under out-of-plane bending of locally wall thinning elbows could be demonstrated by finite element analyses. Torsion buckling deformation agreed well with test result and the critical buckling deformation was clarified by comparing parameter analyses. The buckling formula was proposed to prevent the torsion buckling of locally wall thinning elbow.
Low Cycle Fatigue Tests With the Use of Miniaturized Test Specimens
Authors: Dzugan Jan , Prochazka Radek , Konopik Pavel
Published: October 2017

Determination of mechanical properties with the use of sub-sized specimens is topic a high interest nowadays. The application of the sub-sized samples is quite wide for all cases where only limited amount of the experimental material is available such as evaluation of additively manufactured products properties, residual life of in-service components, properties determination of developed nano-structured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of components, weld joints and so on. Concerning this large application field it would be very useful to prepare standard for small size samples especially for the most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep.

Current paper is going to deal with the low fatigue (LCF) properties assessment with the use of miniaturized specimens’. There were proposed specimen geometries with the use of FEM analysis and testing procedures for considered mini-specimens tests were developed. In the case of strain controlled LCF tests, contactless testing system had to be established for testing of small sized specimens, where it is not possible to apply standard mechanical extensometers for test control. Moreover, LCF procedure for high temperature tests was also successfully established here. The LCF results were subsequently used for Manson-Coffin parameters determination. Results of low cycle tests for several steels are confronted with the results of standard sized specimens with very good agreement for all considered conditions.
Method for Unified Safety Assessment With Respect to Plastic Collapse in Design and In-Service Defect Analyses
Authors: von Unge Petter , Brickstad Björn
Published: October 2017

The purpose of this work is to establish a method for safety assessment with respect to plastic collapse, which is consistent for design assessment in accordance with Section III of the ASME Boiler and Pressure Vessel Code and assessment of in-service defects.

In the Swedish nuclear power industry, a procedure is used for assessment of in-service defects that is based on failure assessment diagrams according to the R6-method combined with a safety evaluation system corresponding to Section III and XI of the ASME Code. The Swedish procedure was originally based on R6 Revision 3 combined with the 1995 edition of the ASME Code. In recent years the procedure has been updated to correspond to current versions of R6 and ASME. These updates include a transition to the updated definition of flow stress as well as structural factors against plastic collapse that was included in the 2002 Addenda of ASME 2001 Section XI.

Following these updates, discrepancies were found between plastic collapse analyses made in accordance with Section III and assessments of in-service defects. Due to this, a project was initiated to make the procedure for assessment of in-service defects consistent with Section III analyses. An in-depth study of the flow stress definitions and structural factors in Section XI was initiated. This study found that the structural factors are based on approximations to get material independence. These approximations uses mean values based on a number of materials which was found to be quite inaccurate for many materials used in the Swedish nuclear power industry and can differ up to about 15 % compared to Section III analyses.

A method has been developed to calculate material specific structural factors that gives a near perfect match between plastic collapse according to Section III and the Swedish procedure for assessment of cracks. The method is based on the methodology for structural factors in Section XI, but excludes the assumptions made to get material independent structural factors. The method is presented and comparisons show the agreement to Section III and highlight cases of large discrepancies in Section XI.
Investigation on Effect of Analysis Variables on Structural Integrity of the Nuclear Piping Under Beyond Design Basis Earthquake
Authors: Kim Jong-Sung , Lee Suk-Hyun , Kweon Hyeong Do
Published: October 2017

In this study, effect of analysis variables on structural integrity of nuclear piping under beyond design basis earthquake was investigated via performing dynamic time history seismic analysis. A finite element model of the piping system such as shut-down cooling line was developed combining solid and beam elements. Dynamic time history analysis was performed via finite element elastic plastic stress analysis. Validity of the dynamic time history analysis procedure was verified via comparing with the previous study results. Finally, the effect of analysis variables such as finite element characteristics, transition length between elbow and straight line, fluid effect, etc. was investigated via performing parametric dynamic time history seismic analysis. As a result, it was found that use of the 1st incompatible element is recommended, the transition length is the same as curvature of the elbow, and fluid has to be considered.
Viscoelastic and Damage Model of Polyethylene Pipe Material for Slow Crack Growth Analysis
Authors: Zhang Yue , Luo Xiangpeng , Shi Jianfeng
Published: October 2017

Polyethylene (PE) pipe is widely used for oil and gas transportation. Slow crack growth (SCG) is the main failure mechanism of PE pipes. Current SCG resistance testing methods for PE pipes have significant drawbacks, including high cost, time-comsuming and uncertain reliability. Alternative method is in need to reduce the testing time and/or cost. In this paper, a numerical model is proposed by taking the viscoelastic and damage effect of PE material into account. The material behavior is described on the basis of linear viscoelastic integral constitutive model, along with damage effect in effective configuraion concept. Three dimensional incremental form of damage viscoelastic model is derived and implemented by ABAQUS UMAT. It is found that the curve of tensile displacement via time, as well as the curve of crack opening displacement via time from numerical results fit well with those from the standard PENT test (ASTM 1473). Based on the proposed model, SCG failure process is analyzed, and the effects of damage parameters on SCG process are furtherly studied and discussed.
Analysis of Tension and Bending Response to Characterize Elastic-Plastic Material Behavior
Authors: Metzger Don , Reinhardt Wolf
Published: October 2017

The integrity of components can be affected by certain material degradation mechanisms that cause a loss of ductility. In cases where the component loading is primarily in bending, a loss of ductility can significantly reduce the load capacity. Material degradation may be determined by component testing involving the bending mode. In such cases, characterizing the material response in terms of yield stress, ultimate stress and failure strain is complicated by the nature of the load curve due to bending. The objective of this work is to examine in detail the relationship between tensile and bending response, with particular attention to the condition of decreasing ductility.
VBA APP for the Calculation of Optimal Tightening Sequences for Ring Type Joints
Authors: Coria Ibai , Abasolo Mikel , Aguirrebeitia Josu , Heras Iker
Published: October 2017

For pressure vessels gasketed joints, obtaining a uniform bolt load distribution is mandatory in order to ensure leak-free service of the joint. However, due to the elastic interaction phenomenon, it is difficult to achieve a uniform bolt load distribution. To address this difficulty, standards recommend tightening sequences that have shown good performance. However, these sequences have to be carried out in several passes; in addition, the standards point out that each assembler should develop its particular tightening sequences.

In order to overcome these disadvantages, it is possible to find methods that provide a particular tightening sequence with which a uniform bolt load is obtained in a single pass tightening sequence. The most popular method is the Elastic Interaction Coefficients Method (EICM).

In previous works [1,2], a new methodology called Tetraparametric Assembly Method (TAM) was developed for ASME Ring Type Joints (RTJ). In comparison with the EICM, the TAM provides very accurate results with much lower cost. In this work, the TAM has been implemented in Microsoft Excel (programmed in Visual Basic for Application), to obtain in a few seconds an optimal tightening sequence for most RTJ (NPS, Class and SCHD) for any target load and any assembly pattern using one or two passes.
Check Valve Flow and Disk Lift Simulation Using CFD
Authors: Farrell Ronald , Ezekoye L. Ike , Rain Mark
Published: October 2017

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an investigation on the application of CFD to characterize the opening and closing of check valves. Specifically, using CFD results, a procedure was developed to determine valve flow coefficients (CV) as a function of disk lift positions as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The method could be used for a wide range of check valves such as swing check valves, lift check valves, tilting disk check valves, or inline check valves. Using CFX which is a part of the ANSYS suite of finite element programs, examples of the predictive nature of CFD to characterize check valve performance are presented to address swing check and lift check valve designs. It is shown that balancing flow-induced forces on the disk and considering the disk assembly weight in the process is sufficient to model the valve lift behavior. Analysis results from this approach were compared with available test data of the modeled valves. The comparison showed good agreement, thus validating that both flow coefficients (CV) and flow rates across the valves at different disk lift positions can be reasonably predicted with this approach. The results of this study suggest that this approach can be used for valve design optimization and flow analysis of check valves. However, it should be pointed out that CFD is an evolving technology and is not a substitute for testing. The use of this tool compliments testing and, if carefully managed, can save valve development cost.
Analytical Modelling of Elastic Interaction in Bolted Flange Gasketed Joints
Authors: Zhu Linbo , Bouzid Abdel-Hakim , Hong Jun
Published: October 2017

Bolted flange joints are widely used in the fossil and nuclear power plants and other industrial complex. During their assembly, it is extremely difficult to achieve the target bolt preload and tightening uniformity due to elastic interaction. In addition to the severe service loadings the initial bolt load scatter increases the risk of leakage failure.

The objective of this paper is to present an analytical model to predict the bolt tension change due to elastic interaction during the sequence of initial tightening. The proposed analytical model is based on the theory of circular beams on linear elastic foundation. The elastic compliances of the flanges, the bolts, and the gasket due to bending, twisting and axial compression are involved in the elastic interaction. The developed model can be used to optimize the initial bolt load tightening to obtain a uniform final preload under minimum number of tightening passes. The approach is validated using finite element analysis and experimental tests conducted on a NPS 4 class 900 weld neck bolted flange joint.
Nuclear Power Plant Fires and Explosions: Part IV — Water Hammer Explosion Mechanisms
Authors: Leishear Robert A.
Published: October 2017

Water hammers, or fluid transients, compress flammable gasses to their autognition temperatures in piping systems to cause fires or explosions. While this statement may be true for many industrial systems, the focus of this research are reactor coolant water systems (RCW) in nuclear power plants, which generate flammable gasses during normal operations and during accident conditions, such as loss of coolant accidents (LOCA’s) or reactor meltdowns. When combustion occurs, the gas will either burn (deflagrate) or explode, depending on the system geometry and the quantity of the flammable gas and oxygen. If there is sufficient oxygen inside the pipe during the compression process, an explosion can ignite immediately. If there is insufficient oxygen to initiate combustion inside the pipe, the flammable gas can only ignite if released to air, an oxygen rich environment. This presentation considers the fundamentals of gas compression and causes of ignition in nuclear reactor systems. In addition to these ignition mechanisms, specific applications are briefly considered. Those applications include a hydrogen fire following the Three Mile Island meltdown, hydrogen explosions following Fukushima Daiichi explosions, and on-going fires and explosions in U.S nuclear power plants. Novel conclusions are presented here as follows.

1. A hydrogen fire was ignited by water hammer at Three Mile Island.

2. Hydrogen explosions were ignited by water hammer at Fukushima Daiichi.

3. Piping damages in U.S. commercial nuclear reactor systems have occurred since reactors were first built. These damages were not caused by water hammer alone, but were caused by water hammer compression of flammable hydrogen and resultant deflagration or detonation inside of the piping.
Phenylalanine residues act as membrane anchors in the antimicrobial action of Aurein 1.2
Authors: Shahmiri Mahdi , Cornell Bruce , Mechler Adam
Published: October 2017

Aurein 1.2 is a small cationic antimicrobial peptide, one of the shortest peptides that can exert antimicrobial activity at low micromolar concentrations. Aurein 1.2 is a surface acting peptide, following the “carpet” mechanism of thresholded membrane disruption. It is generally assumed that the activity of such cationic α-helical membrane disrupting peptides is charge driven. Here, the authors show that instead of charge interactions, aromatic phenylalanine residues of the Aurein 1.2 sequence facilitate the membrane binding. The activity of the wild type peptide was compared to mutants in which the Phe residues were substituted, singly and in tandem, with alanine. Measurements by quartz crystal microbalance, impedance spectroscopy, and dye leakage experiments demonstrated that single residue mutants retain a much-reduced activity whereas the deletion of both Phe residues prevents membrane disruption entirely. The single residue mutants exhibited an altered mechanism of action, permeabilizing but not dissolving the target membranes. These results offer a new design rule for membrane disrupting peptides with potential pharmacological applications.
Two-dimensional active raypath separation using examination of the roots of the spectrum polynomial
Authors: Jiang Longyu , He Runguo , Hong Yaping , Wu Jiasong , Shu Huazhong
Published: October 2017

The application of the root multiple signal classification algorithm for raypath separation was motivated by the dramatic reduction in processing time of the multiple-signal classification algorithm. However, the algorithm provides classification only in the direction of the arrival domain and fails to separate raypaths arriving at the array with similar directions of arrival. Moreover, for many applications in shallow water (such as ocean acoustic tomography and active sonar), the emitted signal is known and can be used as a priori information to improve the resolution. Thus, in this study, a two-dimensional active wideband classification algorithm is developed using the examination of the roots of the spectrum polynomial in the angle versus time domain. A two-step strategy is developed to enable extension to the two-dimensional case. The results of simulations confirm that the proposed algorithm achieves almost identical resolution as the existing two-dimensional algorithms while offering a significant reduction in computation time.
Why is auditory frequency weighting so important in regulation of underwater noise?
Authors: Tougaard Jakob , Dähne Michael
Published: October 2017

A key question related to regulating noise from pile driving, air guns, and sonars is how to take into account the hearing abilities of different animals by means of auditory frequency weighting. Recordings of pile driving sounds, both in the presence and absence of a bubble curtain, were evaluated against recent thresholds for temporary threshold shift (TTS) for harbor porpoises by means of four different weighting functions. The assessed effectivity, expressed as time until TTS, depended strongly on choice of weighting function: 2 orders of magnitude larger for an audiogram-weighted TTS criterion relative to an unweighted criterion, highlighting the importance of selecting the right frequency weighting.
Student-Athletes’ Organization of Activism at the University of Missouri: Resource Mobilization on Twitter
Authors: Yan Grace , Pegoraro Ann , Watanabe Nicholas M.
Published: October 2017

Although social media has been increasingly noted as an outlet for athletes to openly address social issues, there has been very little systematic examination on the organizational capacity of social media. To address this, our study seeks to focus on the strike organized by the football players through Twitter at the University of Missouri in 2015. Specifically, it adopts the theoretical framework of resource mobilization and conducts a comprehensive analysis composed of two parts. First, by identifying geographic characteristics and participant groups for #ConcernedStudent1950, it seeks to reveal the mobilization scope and impact. Second, a social network analysis is used to delineate the organizational dynamics of the players’ protest networks. The results yield both theoretical and practical implications for athletes’ engagement in social activism in the digital era.
Changes in water consumption linked to heavy news media coverage of extreme climatic events
Authors: Quesnel Kimberly J. , Ajami Newsha K.
Published: October 2017

Media-related public awareness of extreme drought in California is linked to changes in urban water use behavior.
Memristive stochastic plasticity enables mimicking of neural synchrony: Memristive circuit emulates an optical illusion
Authors: Ignatov Marina , Ziegler Martin , Hansen Mirko , Kohlstedt Hermann
Published: October 2017

Memristive devices help address the binding problem: Their memory supports a transient connectivity in oscillator networks.
A drug pocket at the lipid bilayer–potassium channel interface
Authors: Ottosson Nina E. , Silverå Ejneby Malin , Wu Xiongyu , Yazdi Samira , Konradsson Peter , Lindahl Erik , Elinder Fredrik
Published: October 2017

We map a binding site for small-molecule compounds that target voltage-gated K channels at the lipid bilayer–channel interface.
Biosensing near the neutrality point of graphene
Authors: Fu Wangyang , Feng Lingyan , Panaitov Gregory , Kireev Dmitry , Mayer Dirk , Offenhäusser Andreas , Krause Hans-Joachim
Published: October 2017

Using the charge neutrality point promises low-noise graphene electronic sensors.
NASA weighs trimming WFIRST to hold down costs
Authors: Clery Daniel
Published: October 2017

Price tag for major space telescope is now $3.6 billion.
Revamp animal research rules, report urges
Authors: Cornwall Warren
Published: October 2017

Research organizations call for single agency to be in charge, but critics raise concerns.
Big data and the industrialization of neuroscience: A safe roadmap for understanding the brain?
Authors: Frégnac Yves
Published: October 2017

New technologies in neuroscience generate reams of data at an exponentially increasing rate, spurring the design of very-large-scale data-mining initiatives. Several supranational ventures are contemplating the possibility of achieving, within the next decade(s), full simulation of the human brain.
Response to Comment on “The extent of forest in dryland biomes”
Authors: Bastin J.-F. , Mollicone D. , Grainger A. , Sparrow B. , Picard N. , Lowe A. , Castro R.
Published: October 2017

Schepaschenko
et al
. question our findings, claiming that we did not refer to all existing maps and that we did not account for all sources of uncertainty. In our response, we detail our selection criteria for reference maps, which clarify why the work of Schepaschenko
et al
. was not used, and we explain why our uncertainty assessment is complete and how it was misunderstood by Schepaschenko
et al
.
Plasmepsins on the antimalarial hit list
Authors: Boddey Justin A.
Published: October 2017

Two studies identify plasmepsins IX and X as new antimalarial drug targets
The bacterium has landed
Authors: Hughes Kelly T. , Berg Howard C.
Published: October 2017

Mechanosensing mechanisms for surface recognition by bacteria allow biofilm
formation
Gene Acquisition by a Distinct Phyletic Group within Streptococcus pneumoniae Promotes Adhesion to the Ocular Epithelium
Authors: Antic Irena , Brothers Kimberly M. , Stolzer Maureen , Lai Han , Powell Evan , Eutsey Rory , Cuevas Rolando A. , Miao Xinyu , Kowalski Regis P. , Shanks Robert M. Q. , Durand Dannie , Hiller N. Luisa
Published: October 2017

Changes in the gene content of pathogens can modify their ability to colonize and/or survive in different body sites in the human host. In this study, we investigate a gene acquisition event and its role in the pathogenesis of
Streptococccus pneumoniae
(pneumococcus). Our findings suggest that the gene encoding the predicted surface protein SspB has been transferred from
Streptococcus suis
(a distantly related streptococcal species) into a distinct set of pneumococcal strains. This group of strains distinguishes itself from the remainder of pneumococcal strains by extensive differences in genomic composition and by the ability to cause conjunctivitis. We find that the presence of
sspB
increases adherence of pneumococcus to the ocular epithelium. Thus, our data support the hypothesis that a subset of pneumococcal strains has gained genes from neighboring species that enhance their ability to colonize the epithelium of the eye, thus expanding into a new niche.
Example of monitoring measurements in a virtual eye clinic using ‘big data’
Authors: Jones Lee , Bryan Susan R , Miranda Marco A , Crabb David P , Kotecha Aachal
Published: October 2017

Aim

To assess the equivalence of measurement outcomes between patients attending a standard glaucoma care service, where patients see an ophthalmologist in a face-to-face setting, and a glaucoma monitoring service (GMS).

Methods

The average mean deviation (MD) measurement on the visual field (VF) test for 250 patients attending a GMS were compared with a ‘big data’ repository of patients attending a standard glaucoma care service (reference database). In addition, the speed of VF progression between GMS patients and reference database patients was compared. Reference database patients were used to create expected outcomes that GMS patients could be compared with. For GMS patients falling outside of the expected limits, further analysis was carried out on the clinical management decisions for these patients.

Results

The average MD of patients in the GMS ranged from +1.6dB to −18.9dB between two consecutive appointments at the clinic. In the first analysis, 12 (4.8%; 95% CI 2.5% to 8.2%) GMS patients scored outside the 90% expected values based on the reference database. In the second analysis, 1.9% (95% CI 0.4% to 5.4%) GMS patients had VF changes outside of the expected 90% limits.

Conclusions

Using ‘big data’ collected in the standard glaucoma care service, we found that patients attending a GMS have equivalent outcomes on the VF test. Our findings provide support for the implementation of virtual healthcare delivery in the hospital eye service.
Musculoskeletal injury profiles in professional Women’s Tennis Association players
Authors: Dakic Jodie G , Smith Belinda , Gosling Cameron M , Perraton Luke G
Published: October 2017

Objective

The physical demands of professional tennis combined with high training/match loads can contribute to musculoskeletal injury. The objectives of this study were to (1) describe the type, location and severity of injuries sustained during a 12-month tennis season in a cohort of professional female tennis players on the Women’s Tennis Association (WTA) tour and (2) prospectively investigate associations between training/match loads and injury.

Methods

52 WTA players competing at the Australian Open (2015) consented to participate. Injuries reported to WTA medical staff were classified using tennis-specific guidelines. Individual match exposure data were collected for all matches played at international level in 2015 and expressed per 1000 hours of WTA competition matchplay (MP) and 1000 match exposures (MEs). Variables associated with the number of injuries in the season and loss of time from competition were identified with regression analysis.

Results

The injury incidence rate (IR) was 56.6 (95% CI: 49.5 to 64.6) per 1000 hours of MP or 62.7 (95% CI: 54.8 to 71.6) per 1000 MEs, although the IR of injuries resulting in loss of time from competition was lower (12.8 per 1000 hours of MP, 92 injuries/100 players). Lower limb (51%) and muscle/tendon (50%) injuries were the most common site and type of injury. Common specific injury site subcategories were the thigh, shoulder/clavicle, ankle and knee in order of frequency. Various measures of match load were significantly associated with injury.

Conclusion

This study prospectively analysed injury profiles, including severity across an entire season of professional tennis, and investigated the relationship between training/match loads and injury. These data may help medical professionals develop injury risk identification and prevention programmes.
Cognitive complexity of clients and counsellors during motivation-based treatment for smoking cessation: an observational study on occasional smokers in a US college sample
Authors: Conway Lucian Gideon , Harris Kari Jo , Catley Delwyn , Gornick Laura Janelle , Conway Kathrene Renee , Repke Meredith A , Houck Shannon C
Published: October 2017

Objective

Motivational interviewing (MI) is a widely used and promising treatment approach for aiding in smoking cessation. The present observational study adds to other recent research on why and when MI works by investigating a new potential mechanism: integrative complexity.

Setting

The study took place in college fraternity and sorority chapters at one large midwestern university.

Participants

Researchers transcribed MI counselling sessions from a previous randomised controlled trial focused on tobacco cessation among college students and subsequently scored clients’ and counsellors’ discussions across four counselling sessions for integrative complexity.

Interventions

This is an observational secondary analysis of a randomised controlled trial that tested the effectiveness of MI. We analysed the relationship between integrative complexity and success at quitting smoking in the trial.

Primary and secondary outcome measures

Success in quitting smoking:Participants were categorised into two outcome groups (successful quitters vs failed attempters), created based on dichotomous outcomes on two standard variables: (1) self-reported attempts to quit and (2) number of days smoked via timeline follow-back assessment procedures that use key events in participants’ lives to prompt their recall of smoking.

Results

We found (1) significantly higher complexity overall for participants who tried to quit but failed compared with successful quitters (standardised β=0.36, p<0.001, (Lower Confidence Interval.)LCI=0.16, (Upper Confidence Interval)UCI=0.47) and (2) the predictive effect of complexity on outcome remains when controlling for standard motivational and demographic variables (partialr(102)=−0.23, p=0.022).

Conclusions

Taken together, these results suggest that cognitive complexity is uniquely associated with successful quitting in MI controlled trials, and thus may be an important variable to more fully explore during treatment.