bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining and comparing various machine‐learning algorithms to improve dissolved gas analysis interpretation
Authors: Senoussaoui Mohammed El Amine , Brahami Mostefa , Fofana Issouf
Published: May 2018

Since the discovery of dissolved gas analysis (DGA), it is considered as a leading technique for the diagnosis of liquid insulated power equipment. However, accurate analysis results can only be achieved if the measured gases closely reflect the actual equipment condition to enable an appropriate interpretation of these gases. In general, conventional techniques such as the ratio method, key gases, and Duval triangle combined or not with artificial intelligence techniques such as machine‐learning algorithms are used for DGA interpretation. Here, four well‐known machine‐learning algorithms are compared in terms of DGA fault classification – Bayes network, multilayer perceptron, k ‐nearest neighbour, and J48 decision tree. Moreover, the effect of applying ensemble methods such as boosting through the Adaboost algorithm and bootstrap aggregation (bagging) is analysed, and the performances of these algorithms are evaluated. The data for developing classification models was transformed into three forms, other than the raw data. The obtained results clearly presented the efficiency and stability of some algorithms such as the J48 tree and Bayes networks for DGA fault classification, in particular, when the data is appropriately pre‐processed. Moreover, the performance of these algorithms was found to consistently improve by integrating the concepts of multiple models or ensemble methods.
New Tubular Ceramic Membranes from Natural Moroccan Clay for Microfiltration Application
Authors: Ait Taleb A. , El Baraka N. , Saffaj N. , Laknifli A. , Mamouni R. , Fatni A. , El Hammadi A. , El Qacimi N.
Published: May 2018

This paper is devoted the preparation of low cost microfiltration membranes using Moroccan clay powder. The preparation of membrane was composed with two steps: First a macroporous tubular support with a pore diameter 10 μm and porosity 43%. Secondly a microfiltration layer was performed by the slip casting method. A deflocculated slip was obtained by mixing mineral powder of ZrO2, PVA (polyvinyl alcohol) and water, after drying at room temperature for 24 h, the microfiltration layer was heated to 800°C for consolidation. Scanning electron microscopy observation showed homogeneous layers without cracks with an average pore diameter of 0.19 μm for the active layer. Water permeability obtained is about 841 L/h.m2.bar. The membranes have been tested to cleaning of colored wastewater.
LCF and crack growth: recent results obtained by DIC
Authors: Patriarca Luca , Foletti Stefano , Beretta Stefano
Published: May 2018

Nowadays, several components for aerospace and energy applications (i.e., turbine disks, offshore pipelines, and combustor chambers) are designed following a safe-life approach in the low cycle fatigue (LCF) regime. As also in the LCF regime it is worth adopting a damage tolerance design, fatigue life is assessed considering a crack propagating from the first load cycle, starting from an initial defect present in the component’s most-stressed region or from a microstructural feature. In this frame, fatigue crack growth is described considering LCF conditions, where the driving force at the crack tip can be described with the ΔJeffparameter. The paper aims to give an overview of the potential applications and perspectives for the adoption of digital image correlation (DIC) measurements to study LCF nucleation and propagation. A visual technique based on the DIC displacement fields was developed to measure crack opening and closing levels in the presence of large strains. The technique is applied to different materials (steels, AlSi10Mg, nickel-based super-alloys). In addition, further applications of the DIC strain measurements are revised for the study of the nucleation stage and the crack tip process zone.
Influence of defects on axial fatigue strength of maraging steel specimens produced by additive manufacturing
Authors: Rigon Daniele , Meneghetti Giovanni , Görtler Michael , Cozzi Daniele , Waldhauser Wolfgang , Dabalà Manuele
Published: May 2018

Nowadays many materials such as steels, aluminium and titanium alloys can be realised by powder bed solutions melting subsequently powder layers by means of a laser or electron beam (Laser Beam Melting – LBM and Electron Beam Melting – EBM). The microstructure realised by layer-by-layer solidification having high cooling rate cannot be considered isotropic. Therefore, the mechanical properties could be influenced by the building direction. Regarding maraging steel, the study of the influence of the building direction and the heat treatment on the static and axial fatigue strength has been investigated in a previous contribution. A large scatter of the fatigue test results was found because of the presence of detrimental surface and subsurface defects. The aim of this contribution is to present additional axial fatigue test results of maraging steel characterized by different build orientation and providing an analysis of the defects observed at the crack initiation area of the fracture surface.
The effect of texture on the low cycle fatigue property of Inconel 718 by selective laser melting
Authors: Zhou Zhongjiao , Hua Xu , Li Changpeng , Chen Guofeng
Published: May 2018

In recent decades, additive manufacturing (AM) technology has shown its great advantages to produce end-use products with complex design and high-added value. However, the AM-specific characters, such as inherent material anomalies (porosity, lack of fusion defects, or inclusions), anisotropy, location-specific properties and residual stresses, prevent AM from widely adoption in safety-critical parts. Therefore, the damage tolerance assessment of AM parts is desperately necessary. In this study, the impact of residual stress and the induced texture (columnar/equiax grain structure) after different heat treatment on the low cycle fatigue (LCF) behavior of Inconel 718 fabricated through selective laser melting (SLM) is investigated. The results showed that the texture of AMed parts can be controlled by suitable heat treatment, based on the residual stress during AM processing acting as the drive force to recrystallization. For SLMed Inconel 718 samples with columnar grains, anisotropic LCF properties exist, while no obvious sensitivity to orientations is shown for samples with equiaxed grains. This work is significantly meaningful to speed up the design-to-product transformation of safety-critical AM parts and optimize the orientation of components for various applications.
Fatigue behavior of 316L austenitic stainless steel in air and LWR environment with and without mean stress
Authors: Chen Wen , Spätig Philippe , Seifert Hans-Peter
Published: May 2018

The fatigue life design curves in nuclear codes are generally derived from uniaxial straincontrolled fatigue test results. Evidently, the test conditions are very different from the actual components loading context, which involves much more complex thermo-mechanical loading including mean stress, static load holding time and variation in water chemistry, etc. In this work, the mean stress and environmental effects on fatigue life of 316L austenitic stainless steel in air and light water reactor (LWR) environment were studied using hollow fatigue specimens and testing under load-controlled condition. Both positive (+50 MPa) and negative (-20 MPa) mean stresses showed beneficial effect on fatigue life in LWR environment and in air. This is tentatively attributed to mean stress enhanced cyclic hardening, which leads to smaller strain response at the same loading force. -20 MPa mean stress was found to increase fatigue limit, whereas the effect of +50 MPa mean stress on fatigue limit is still unclear. The preliminary results illustrate that the environmental reduction of fatigue life is amplified in load-controlled fatigue tests with tensile mean stress.
Changing Mechanisms of Surface Relief and the Damage Evaluation of Low Cycle Fatigued Austenitic Stainless Steel
Authors: Fujimura Nao , Nakamura Takashi , Takahashi Kosuke
Published: May 2018

To quantitatively investigate the cause of the changes in arithmetic mean roughness Ra and arithmetic mean waviness Wa of austenitic stainless steel under low-cycle fatigue loading, precise observation focusing on persistent slip bands (PSBs) and crystal grain deformations was conducted on SUS316NG. During the fatigue tests, the specimen’s surface topography was regularly measured using a laser microscope. The surface topographies were analysed by frequency analysis to separate the surface relief due to PSBs from that due to grain deformation. The height caused by PSBs and that by grain deformation were measured respectively. As a result, both of the heights rose with the increase of usage factor (UF). The amount of increase in the heights with respect to UF increased with strain range. The trend of development of both heights was similar with the trend of Ra and Wa. A comparison between Ra and the height caused by PSBs showed that these values strongly correlated with each other. A comparison between Wa and the height caused by grain deformation also showed that these values strongly correlated with each other. Consequently, the surface texture parameters Ra and Wa represent the changes in the heights of surface reliefs due to PSBs and grain deformation.
Cyclic deformation behaviour and stability of grain-refined 301LN austenitic stainless structure
Authors: Man Jiří , Järvenpää Antti , Jaskari Matias , Kuběna Ivo , Fintová Stanislava , Chlupová Alice , Karjalainen L. Pentti , Polák Jaroslav
Published: May 2018

Low cycle fatigue (LCF) behaviour of metastable austenitic 301LN stainless steel with different grain sizes – coarse-grained (13 μm), fine-grained (1.4 μm) and ultrafine-grained (0.6 μm) – produced by reversion annealing after prior cold rolling was investigated. Fully symmetrical LCF tests with constant total strain amplitudes of 0.5% and 0.6% were performed at room temperature with a low constant strain rate of 2×10-3 s-1. Microstructural changes in different positions within the gauge part of the specimens were examined by optical microscopy (polarized light) and electron backscatter diffraction (EBSD) technique; for quantitative assessment of the volume fraction of deformation induced martensite (DIM) a Feritscope FMP 30 was adopted. The cyclic stress-strain response and specific changes of hysteresis loop shapes in the very early stage of cycling are confronted with the character of DIM formation and its distribution in the whole volume of the material. A possible effect of strain rate (frequency of cycling) on the destabilization of austenitic structure during cyclic straining of materials with different grain sizes is highlighted.
Influence of the surface morphology on the cyclic deformation behavior of HSD® 600 steel
Authors: Klein Matthias W. , Smaga Marek , Beck Tilmann
Published: May 2018

The presented research work investigates the fatigue properties in the low cycle fatigue (LCF) regime of the high manganese metastable austenitic High Strength and Ductility (HSD®) 600 TWIP steel dependent on its surface morphology. The steel features, according to its chemical composition following the alloying concept Mn-Al-Si-C and heat treatment, a fully austenitic microstructure that shows deformation induced twinning at ambient temperature. Due to this microstructural deformation mechanism, HSD® 600 steel has an outstanding combination of strength and formability. Besides monotonic deformation behavior, characterized by tensile tests, cyclic deformation behavior was investigated with varying the surface morphology of fatigue specimens. In order to create different surface morphologies, flat fatigue specimens were excised from larger sheets by waterjet-cutting. Depending on the surface morphology, further climb milling or up-climb milling in the gauge length was performed. The three investigated morphologies (asreceived with rolling skin, climb milled and up-climb milled) differed in roughness, initial residual stresses and initial phase compositions. For all variants, total strain controlled fatigue tests with stepwise increasing load amplitudes as well as total strain controlled single step tests were performed in the low cycle fatigue regime with a load ratio of Rε = -1 and a frequency of f = 0.2 Hz. Beside stress-strain hystereses, the changes in temperature ΔT and the magnetic properties ξ were measured. The magnetic properties directly correlate with the transformation from paramagnetic γ-austenite to ferromagnetic α’-martensite. The cyclic deformation behavior of the HSD® 600 steel in the LCF regime was characterized by cyclic softening until fracture at low total strain amplitudes but changed with increasing total strain amplitudes into initial cyclic hardening followed by cyclic softening. This initial cyclic hardening became more pronounced when the total strain amplitude increased. Furthermore, single step tests at lower total strain amplitudes showed a saturation state before fracture. A comparison between the monotonic and cyclic deformation behavior showed a significant difference of the stress levels at the same amounts of plastic deformation respectively. Nevertheless, the different surface morphologies led to different lifetimes at high total strain amplitudes but to similar lifetimes at lower total strain amplitudes.
Effect of UV Ageing on the fatigue life of bulk polyethylene
Authors: Lamnii Hamza , Nait-Abdelaziz Moussa , Ayoub Georges , Gloaguen Jean-Michel , Maschke Ulrich , Mansoor Bilal
Published: May 2018

Polymers operating in various weathering conditions must be assessed for lifetime performance. Particularly, ultraviolet (UV) radiations alters the chemical structure and therefore affect the mechanical and fatigue properties. The UV irradiation alters the polymer chemical structure, which results into a degradation of the mechanical and fatigue behavior of the polymer. The polymer properties degradation due to UV irradiation is the result of a competitive process of chain scission versus post-crosslinking. Although few studied investigated the effect of UV irradiation on the mechanical behaviour of thermoplastics, fewer examined the UV irradiation effect on the fatigue life of polymers. This study focuses on investigating the effect of UV irradiation on the fatigue properties of bulk semi-crystalline polymer; the low density Polyethylene (LDPE). Tensile specimens were exposed to different dose values of UV irradiation then subjected to fatigue loading. The fatigue tests were achieved under constant stress amplitude at a frequency of 1Hz. The results show an important decrease of the fatigue limit with increasing absorbed UV irradiation dose.
Fatigue initiation mechanisms in elastomers: a microtomography-based analysis
Authors: Glanowski Thomas , Huneau Bertrand , Marco Yann , Le Saux Vincent , Champy Clément , Charrier Pierre
Published: May 2018

The fatigue properties of filled elastomers are strongly related to the population of inclusionsinduced by their complex recipes and mixing/injection processes. The description and the understanding of the basic damage and dissipation mechanisms involved around these inclusions, the influence of their nature, geometry, size, interface and cohesion properties are especially important to optimize the fatigue design of industrial compounds and parts. The objective of the study is to take advantages of tomography observations to characterize the effects of the 3D inclusions on the fatigue resistance of rubber filled with carbon black. An images processing is necessary to dissociate accurately the inclusions of the matrix. The three dimensional observations provide many information on the inclusion’s morphology (size, shape) and their spatial distribution. Moreover, the proposed images processing allows detecting cracks inside and on the surface of the specimen, which offers a better insight on the early stages of the fatigue damage scenario. Then, a numerical model and thermo-mechanical measurements are used to understand why some inclusions become initiation sites. Finally, one activated site is fully described as example.
Multiaxial fatigue study on steel transversal attachments under constant amplitude proportional and non-proportional loadings
Authors: Garcia Martin , Pereira Baptista Claudio A. , Nussbaumer Alain
Published: May 2018

In this study, the multiaxial fatigue strength of full-scale transversal attachment is assessed and compared to original experimental results and others found in the literature. Mild strength S235JR steel is used and an exploratory investigation on the use of high strength S690QL steel and the effect of non-proportional loading is presented. The study focuses on non-load carrying fillet welds as commonly used in bridge design and more generally between main girders and struts. The experimental program includes 33 uniaxial and multiaxial fatigue tests and was partially carried out on a new multiaxial setup that allows proportional and non-proportional tests in a typical welded detail. The fatigue life is then compared with estimations obtained from local approaches with the help of 3D finite element models. The multiaxial fatigue life assessment with some of the well-known local approaches is shown to be suited to the analysis under multiaxial stress states. The accuracy of each models and approaches is compared to the experimental values considering all the previously cited parameters.
Rapid estimation of notch stress intensity factors in 3D large-scale welded structures using the peak stress method
Authors: Campagnolo Alberto , Meneghetti Giovanni
Published: May 2018

The Peak Stress Method (PSM) is an engineering, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which takes advantage of the singular linear elastic peak stresses from FE analyses with coarse meshes. Originally, the PSM was calibrated to rapidly estimate the NSIFs by using 3D, eight-node brick elements, taking advantage of the submodeling technique. 3D modelling of large-scale structures is increasingly adopted in industrial applications, thanks to the growing spread of high-performance computing (HPC). Based on this trend, the application of PSM by means of 3D models should possibly be even more speeded up. To do this, in the present contribution the PSM has been calibrated under mode I, II and III loadings by using ten-node tetra elements, which are able to directly discretize complex 3D geometries without the need for submodels. The calibration of the PSM has been carried out by analysing several 3D mode I, II and III problems. Afterwards, an applicative example has been considered, which is relevant to a large-scale steel welded structure, having overall size on the order of meters. Two 3D FE models, having global size of tetra elements equal to 5 and 1.66 mm, have been solved by taking advantage of HPC, being the global number of degrees of freedom equal to 10 and 140 millions, respectively. The NSIFs values estimated at the toe and root sides according to the PSM have been compared with those calculated by adopting a shell-to-solid technique.
Multi-axial fatigue life assessment of high speed car body based on PDMR method
Authors: Liu Chaotao , Wu Pingbo , Li Fansong
Published: May 2018

This article mainly introduces a method of converting the acceleration signal of body bolster obtained by the circuit test into the load of the air spring seat of vehicle body. This method mainly decomposes the body's movement posture into the form of ups and downs, roll and nod. Then formulate the test plan according to the performance of the body fatigue test bench. The vertical and horizontal displacements and longitudinal force are used as control commands.Taking advantage of vehicle body fatigue test bench to reproduce these basic types of vibration. Establish the transfer function of the acceleration of the bolster and the displacement excitation of the air spring, and then obtaining the load of the air spring seat. Finally, the multi-axial fatigue life assessment of the vehicle body was performed using the obtained load combined with the Moment of Load Path Method and the Path-Dependent Maximum Range Method.
Load spectra and fatigue damage: applications to the automotive industry
Authors: Facchinetti Matteo Luca
Published: May 2018

High cycle fatigue behaviour of materials is historically assessed with constant amplitude and variable amplitude loads, respectively. Thus, a long-lasting debate is extremely active in the academic community, trying to link experimental results coming from these different approaches. Overcoming all this, since the 1970s several industrial fields have been choosing to consider representative customer load spectra (in terms of amplitude, not frequency) as the best way to test both materials and structures. In particular, the automotive industry makes use of specific car loading spectra, regularly fed by the customer knowledge and practised on proving grounds. This paper presents a highlight on such spectra, neglecting any sequence effect of the load time history, thus accepting the Palmgren-Miner’s rule as an assumption. Whereas a recent communication on this very topic focused on the basic occurrence spectra, which is absolutely independent from the material properties of the car parts, here we deal with the final damage assessment. Obviously, it is worth knowing which part of the spectrum is mainly responsible for the most relevant fatigue damage.
Thermo-mechanical fatigue damage behavior for Ni-based superalloy under multiaxial loading
Authors: Li Dao-Hang , Shang De-Guang
Published: May 2018

The fatigue damage behavior was experimentally investigated in different axial-torsional thermo-mechanical loading conditions for Ni-based superalloy GH4169. The strain controlled tests were carried out with the same von Mises equivalent mechanical strain amplitude of 0.8% in the temperature range from 360°C to 650°C. The results show that the fatigue life is drastically reduced when the axial mechanical strain and the temperature are in-phase, which can be due to that the creep damage is induced by the tensile stress at high temperature. Moreover, the fatigue life is further decreased when the axial mechanical strain and the shear strain are out-of-phase, which can be attributed to that the non-proportional hardening can increase the creep and the oxidation damages. Furthermore, the tensile stress is crucial to the nucleation of creep cavities at high temperature compared with the shear stress. The tensile and shear stresses all can increase the creep damage under fatigue loading at high temperature. In addition, the oxidation damage can be induced during cyclic loading at high temperature, and it can be increased by the tensile mean stress caused in non-isothermal loading.
Through-process modelling of welding and service of 9Cr steel power plant components under load-following conditions
Authors: Mac Ardghail Padraig , Harrison Noel , Leen Sean B
Published: May 2018

This paper is concerned with the development of a through-process model to predict the in-service performance of high-temperature, 9Cr steel, power plant components. A multi-pass welding simulation is conducted using the finite element software Abaqus. A user-material subroutine, including microstructure evolution and a physically-based constitutive model, is employed to predict the mechanical response of the material during welding and to predict welding residual stresses. Points are sampled from the FE geometry and their microstructure parameters and residual stress values are used in a uniaxial code to predict the relative in-service lives of the different weld regions under load-following power plant operating conditions. It is shown that post-weld heat treatment significantly improves predicted life and that there is a strong correlation between predicted microstructure before service and the predicted in-service life.
Failure mechanisms and fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint up to ultra-long life regime
Authors: Zhu Ming-Liang , Xuan Fu-Zhen
Published: May 2018

It is known that welded joint is much “weaker” than base metal due to discontinuities of geometry, materials and residual stresses. It seems current international design rules do not adopt a uniform approach to weld efficiency, which is often defined as the ratio of the strength of a welded joint to the strength of base metal, in their guidance for creep and fatigue design of welds. This appears to be a great barrier for the application of nuclear welded structures which has a prolonged design lifetime of 60 years. In this work, fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint, machined from welded steam turbine rotors for nuclear power plant, was investigated by performing axially push-pull cyclic loads tests with both cross-weld and pure base metal specimens up to very high cycle fatigue regime under ultrasonic frequency at ambient temperature. The effects of residual stress, strain localization, and microdefects in mismatched steels on failure mechanisms of welds were discussed thoroughly. Results show that fatigue strength reduction factor is varied in the range of 0.95-0.975, and is found to be dependent on fatigue lifetime for the first time. It is indicated that variation of fatigue strength reduction factor are associated with transition of crack initiation from specimen surface in high cycle fatigue regime to interior micro-defects in very high cycle fatigue regime. Comparing existing codes and standards for fatigue design of welds with experimental data indicates the over-conservativeness of present code-based design method. This implies a micro-defect based fatigue design approach is required for long life safe and reliability of weldments.
Effect of heat treatment on fatigue crack initiation of laser powder bed fusion stainless steel 316L
Authors: Zhang Meng , Sun Chen-Nan , Zhang Xiang , Goh Phoi Chin , Wei Jun , Hardacre David , Li Hua
Published: May 2018

Laser powder bed fusion (L-PBF) is an emerging additive manufacturing technique for building structural components. L-PBF processing defects, such as lack of fusion pores, promote fatigue crack initiation and shorten the fatigue life. With well-controlled processing, critical pores can be avoided such that the microstructure-driven intergranular crack initiation mode becomes operative. In this work, the fatigue crack initiation behaviours of as-built and solution annealed L-PBF stainless steel 316L were studied. Crack initiation of the as-built samples is driven by de-bonding of the dendritic grain boundaries. High temperature annealing results in the formation of thermally-induced defects, possibly via the reheat cracking mechanism and the nucleation of pre-existing gas pores. As heat treating could have led to recrystallization and annihilation of the original grain boundary defects, the thermally-induced defects became the new sites for crack initiation. In addition, heat treatment incurred significant reduction in yield strength, such that the interaction of fatigue and ratcheting strain accumulation dominated the deformation behaviour of the material. The resulting fatigue strength in the finite life regime was reduced by about 13% but the fatigue endurance limit was not affected.
Crack nucleation in solid materials under external load - simulations with the Discrete Element Method
Authors: Klejment Piotr , Dębski Wojciech
Published: May 2018

Numerical analysis of cracking processes require an appropriate numerical technique. Classical engineering approach to the problem has its roots in the continuum mechanics and is based mainly on the Finite Element Method. This technique allows simulations of both elastic and large deformation processes, so it is very popular in the engineering applications. However, a final effect of cracking - fragmentation of an object at hand can hardly be described by this approach in a numerically efficient way since it requires a solution of a problem of nontrivial evolving in time boundary conditions. We focused our attention on the Discrete Element Method (DEM), which by definition implies “molecular” construction of the matter. The basic idea behind DEM is to represent an investigated body as an assemblage of discrete particles interacting with each other. Breaking interaction bonds between particles induced by external forces imeditelly implies creation/evolution of boundary conditions. In this study we used the DEM approach to simulate cracking process in the three dimensional solid material under external tension. The used numerical model, although higly simplified, can be used to describe behaviour of such materials like thin films, biological tissues, metal coatings, to name a few.
Optimization of Contact Edge Profile for Minimizing Contact Pressure in a Press-fitted Shaft
Authors: Lee Dong-Hyung , Choi Ha-Young , Kwon Seok-Jin , Seo Jeong-Won
Published: May 2018

In the shrink or press-fitted shafts such as railway axles, the rotor of a steam turbine or coupling, a high-stress concentration takes place in the close of contact edge due to relative slip between shaft and boss in a press-fitted shaft and this is a major cause of fatigue failure of the shaft. The object of this paper is to build a finite element analysis model for analysing press-fitted and bending load condition in a pressfitted assembly and is to propose a hub shape optimization method to minimize a contact pressure in the close of shaft contact edge. Numerical asymmetric-axisymmetric finite element model was developed to predict the contact stress state of the press-fitted shaft. Global optimization method, genetic algorithm, and local optimization method, sequential quadratic programming, was applied to the press-fitted assembly to optimize the hub contact edge geometry. The results showed that the maximum contact pressure with optimized hub shape decreased more than 60% compared to conventional hub shape, the maximum contact stress affecting fatigue life reduced about 47%. In addition, hub shape optimization design could be a useful tool, able to increase the load capabilities of press fits concerning wear and fatigue behaviour.
Numerical study of the burner parameters on the thermal field in a sulfur recovery unit thermal reactor
Authors: Yeh Chun-Lang
Published: May 2018

A sulfur recovery unit (SRU) thermal reactor is the most important equipment in a sulfur plant and is negatively affected by high temperature operations. In this paper, the effect of burner parameters, including the clearance of the acid gas tip and the inlet air swirler angle, on the thermal field in a SRU thermal reactor are investigated numerically, with the aim to reduce the high temperature inside the thermal reactor and to ensure an acceptable sulfur recovery. The simulation results show that the burner with a smaller clearance of the acid gas tip produces a lower temperature, a lower exit SO2 mole fraction and higher exit S2 and H2S mole fractions. Among the clearancs of the acid gas tip investigated, the horizontal clearance of 152.4mm and vertical clearance of 240mm yield the lowest temperature, exit SO2 mole fraction and highest exit S2, H2S mole fractions. The burner with a smaller inlet air swirler angle produces a higher temperature, a higher exit SO2 mole fraction and lower exit S2 and H2S mole fractions. Among the swirler angles investigated, 60° yields the lowest temperature, exit SO2 mole fraction and highest exit S2 , H2S mole fractions.
Cognitive diagnostic assessment based on knowledge structure
Authors: Huang Sue-Fen
Published: May 2018

The purpose of this study is to provide an integrated method of fuzzy theory basis for individualized concept structure analysis. In order to insight the misconception of learning basic mathematics and progress teaching. This method integrates Fuzzy Logic Model of Perception (FLMP) and Interpretive Structural Modelling (ISM). The combined algorithm could analyze individualized concepts structure based on the comparisons with concept structure of expert. In this paper, some well-known knowledge structure assessment methods will be discussed. For item connection, Bart et al ordering theory and Takeya’s item relational structure provided ordering coefficient to construct item relationships and hierarchies. For concepts or skills connection, Warfield’s ISM and Lin et al Concept Advanced Interpretive Structural Modelling (CAISM) provided to construct graphic relationship among elements and display the individualized concept hierarchy structure by numeric and picture. Samples contain 427 which come from Min-Hwei Junior College. Subjects were analyzed by CAISM. It shows the traditional assessment is not the only criteria; it must be combined with other assessment tools. The result shows that CAISM gives meaningful learning and lacks of learners.
Impact of chronic stress on periodontal health
Authors: Gunepin Mathieu , Derache Florence , Trousselard Marion , Salsou Bruno , Risso Jean-Jacques
Published: May 2018

Introduction: Periodontal diseases are caused by pathogenic microorganisms that induce increases in of local and systemic proinflammatory cytokines, resulting in periodontal damage. The onset and evolution of periodontal diseases are influenced by many local and systemic risk factors. Educational objective: In this article, we aim to review the results of the research on the impact of chronic stress on the occurrence, development, and response to periodontal disease treatments and on the pathophysiological mechanisms of periodontal disease. Conclusion: Chronic stress has a negative impact on the occurrence, development, and response to the treatment of periodontal disease via indirect actions on the periodontium. This can result from behavioral changes caused by stress (poor dental hygiene, smoking, etc.) and a direct neuroimmunoendocrinological action related to the consequences (particularly immunological) of the secretion of certain chemicals (e.g., cortisol) induced by the activation of the hypothalamus and the autonomic nervous system in response to stress. These factors necessitate multidisciplinary management (e.g., physician, oral surgeon, and psychologist) of patients to identify subjects with chronic stress and to employ countermeasures to decrease the impact of stress on the periodontium.
Hemostatic powder application for control of acute upper gastrointestinal bleeding in patients with gastric malignancy
Authors: Kim Yeong , Park Jun , Kim Eun , Shin Sung , Lee Sang , Lee Young
Published: May 2018

Background and study aims Despite use of various endoscopic therapies in patients with tumor-related bleeding, various rates of successful immediate hemostasis and short-term rebleeding have been reported. We aimed to evaluate preliminary results of use of the EndoClot polysaccharide hemostatic system (PHS) in patients with acute upper gastrointestinal bleeding (UGIB) from a gastric malignancy.

Patients and methods We retrospectively analyzed data from a prospectively collected database of 12 patients with acute UGIB from a gastric malignancy who had been treated with EndoClot PHS. The EndoClot air compressor was used to propel 2 g of absorbable modified polymer particles onto the bleeding site. We checked successful immediate hemostasis, rebleeding events and mortality within 30 days.

Results Twelve patients were enrolled in the study. The median patient age was 72.5 years (range, 57 – 89). The initial median hemoglobin level was 6.75 g/dL (range, 5.4 – 8.9). The median systolic blood pressure was 114 mmHg (range, 86 – 153). Eleven patients had advanced gastric cancer and one patient had a gastrointestinal stromal tumor. The lower body of the stomach was the most common tumor location (58.3 %), and the median tumor size was 40 mm (range, 15 – 100). Immediate hemostasis was achieved in all patients, and rebleeding developed in 2 of 12 patients (16 %), 3 and 5 days after treatment. There were no significant Endoclot PHS-related adverse events, and there was no all-cause mortality at 30 days after the intervention.

Conclusions Endoclot PHS represents a new alternative, complementary, and promising therapy for patients with an acute UGIB from a gastric malignancy.
EUS-guided thrombin injection for management of gastric fundal varices
Authors: Frost John , Hebbar Srisha
Published: May 2018

Background and study aims Cyanoacrylate glue is recommended first-line endoscopic therapy for gastric fundal varices but it is difficult to use and carries a risk of embolization. Thrombin is preferred by many in the UK, but its effectiveness can be difficult to establish at endoscopy and the rate of re-bleeding is higher. Endoscopic ultrasound (EUS) can help assess variceal blood flow and has the potential to improve both targeting and effectiveness of injection therapy. Whereas there is already some data for its use with glue, little data currently exist in relation to its use with thrombin.

Patients and methods We present a series of patients treated with EUS-guided thrombin injection over the last 4 years. Thrombin was injected under EUS guidance with the intention of obliterating flow within the fundal varices. Outcomes reviewed included whether haemostasis was achieved, the dose of thrombin required for endosonographic variceal obliteration, the incidence of re-bleeding, and procedural related adverse events.

Results Eight patients received EUS-guided thrombin: 3 with active bleeding and 5 as elective prevention. In 2/3 (66 %) patients with active bleeding haemostasis was achieved after a single dose with complete variceal obliteration. 1/3 (33 %) had no alteration in blood flow despite 10 000 IU. None of the elective prevention group had further bleeding and obliteration was observed in 4/5 (80 %). A range of 600 to 10 000 IU of thrombin was used and there were no adverse procedure-related outcomes.

Conclusions Our results are promising and suggest that EUS-guided thrombin injection may have a role in managing bleeding from gastric fundal varices.
Current Soccer Footwear, Its Role in Injuries and Potential for Improvement
Authors: Blanchard Sylvain , Palestri Jérôme , Guer Jean-Luc , BEHR Michel
Published: May 2018

Soccer is the most popular sport in the world and generates great financial revenue. It is also a sport whose practice has evolved considerably in terms of intensity and commitment, and in which the intrinsic risk of injury (not directly related to an interaction with the environment) is particularly high. In this context, the cleated shoe as a major component of soccer equipment may play a key role in the overexposure to injury. Soccer shoe evolution is all the more challenging, because design and mechanical structure differ in many points compared to other modern shoes developed for sports such as running, tennis and basketball.

This critical review aims to elucidate the characteristics of modern soccer footwear and their possible link to soccer-specific injuries, focusing on the following areas: (1) ergonomics, comfort and proprioception; (2) shoe mechanical characteristics; (3) field surfaces and shoe design.
In Vivo Tibial Fit and Rotational Analysis of a Customized, Patient-Specific TKA versus Off-the-Shelf TKA
Authors: Schroeder Lennart , Martin Gregory
Published: May 2018

In total knee arthroplasty (TKA), surgeons often face the decision of maximizing tibial component fit and achieving correct rotational alignment at the same time. Customized implants (CIMs) address this difficulty by aiming to replicate the anatomical joint structure, utilizing data from patient-specific knee geometry during the manufacturing. We intraoperatively compared component fit in four tibial zones of a CIM to that of three different off-the-shelf (OTS) TKA designs in 44 knees. Additionally, we assessed the rotational alignment of the tibia using computed tomography (CT)-based computer aided design model analysis. Overall the CIM device showed significantly better component fit than the OTS TKAs. While 18% of OTS designs presented an implant overhang of 3 mm or more, none of the CIM components did (p < 0.05). There was a larger percentage of CIMs seen with optimal fit (≤1 mm implant overhang to ≤1 mm tibial bone undercoverage) than in OTS TKAs. Also, OTS implants showed significantly more component underhang of ≥3 mm than the CIM design (37 vs. 18%). The rotational analysis revealed that 45% of the OTS tibial components showed a rotational deviation of more than 5 degrees and 4% of more than 10 degrees to a tibial rotational axis described by Cobb et al. No deviation was seen for the CIM, as the device is designed along this axis. Using the medial one-third of the tibial tubercle as the rotational landmark, 95% of the OTS trays demonstrated a rotational deviation of more than 5 degrees and 73% of more than 10 degrees compared with 73% of CIM tibial trays with more than 5 degrees and 27% with more than 10 degrees. Based on our findings, we believe that the CIM TKA provides both better rotational alignment and tibial fit without causing overhang of the tibial tray than the three examined OTS implants.
Less Invasive Modified Extradural Temporopolar Approach for Paraclinoid Lesions: Operative Technique and Surgical Results in 80 Consecutive Patients
Authors: Toyooka Terushige , Takeuchi Satoru , Tomiyama Arata , Nakao Yasuaki , Yamamoto Takuji , Wada Kojiro , Mori Kentaro , Otani Naoki
Published: May 2018

Background Extradural temporopolar approach for paraclinoid lesions can provide extensive and early exposure of the anterior clinoid process, and complete mobilization and decompression of the optic nerve and internal carotid artery, which can prevent intraoperative neurovascular injury. The present study investigated the usefulness of our less invasive modified technique and discussed its operative nuances.

Methods We retrospectively reviewed medical charts of 80 consecutive patients with neoplastic (21 patients) and vascular lesions (59 patients) who underwent the modified extradural temporopolar approach between September 2009 and March 2014.

Results Preoperative visual acuity worsened in 4 patients (5.0%) and worsening of visual field function occurred in 10 patients (12.5%). Postoperative outcome was good recovery in 71 patients, moderate disability in 6, severe disability in 2, and death in 1 (due to reruptured aneurysm). No operation-related mortality occurred in the series.

Conclusion Less invasive modified extradural temporopolar approach is safe and can be recommended for the surgical treatment of deeply located aneurysms and skull base tumors to reduce the risk of intraoperative optic neurovascular injury.
Predictors of patient reluctance to wake early in the morning for bowel preparation for colonoscopy: a precolonoscopy survey in city-wide practice
Authors: Shafer L. , Walker J. , Waldman C. , Michaud V. , Yang C. , Bernstein C. , Hathout L. , Park J. , Sisler J. , Wittmeier K. , Restall G. , Singh H.
Published: May 2018

Introduction Many endoscopists do not use split-dose bowel preparation (SDBP) for morning colonoscopies. Despite SDBP being recommended practice, they believe patients will not agree to take early morning bowel preparation (BP). We assessed patients’ opinions about waking early for BP.

Methods A self-administered survey was distributed between 08/2015 and 06/2016 to patients in Winnipeg, Canada when they attended an outpatient colonoscopy. Logistic regression was performed to determine predictors of reluctance to use early morning BP.

Results Of the 1336 respondents (52 % female, median age 57 years), 33 % had used SDBP for their current colonoscopy. Of the 1336, 49 % were willing, 24 % neutral, and 27 % reluctant to do early morning BP. Predictors of reluctant versus willing were number of prior colonoscopies (OR 1.20; 95 %CI: 1.07 – 1.35), female gender (OR 1.65; 95 %CI: 1.19 – 2.29), unclear BP information (OR 1.86; 95 %CI: 1.21 – 2.85), high BP anxiety (OR 2.02; 95 %CI: 1.35 – 3.02), purpose of current colonoscopy being bowel symptoms (OR 1.40; 95 %CI: 1.00 – 1.97), use of 4 L of polyethylene glycol laxative (OR 1.45; 95 %CI: 1.02 – 2.06), not having SDBP (OR 1.96; 95 %CI: 1.31 – 2.93), and not having finished the laxative for the current colonoscopy (OR 1.66; 95 %CI: 1.01 – 2.73). Most of the same predictors were identified when reluctance was compared to willing or neutral, and in ordinal logistic regression.

Conclusions Almost three-quarters of patients do not express reluctance to get up early for BP. Among those who are reluctant, improving BP information, allaying BP-related anxiety, and use of low volume BP may increase acceptance of SDBP.
Communication: Modular path integral: Quantum dynamics via sequential necklace linking
Authors: Makri Nancy
Published: May 2018

It is shown that dynamical properties of extended systems (spin arrays, large organic molecules, or molecular aggregates) characterized primarily by local potential interactions (bond stretching, bending, and torsional interactions) can be obtained efficiently from fully quantum mechanical path integral calculations through sequential linking of the quantum paths or path integral necklaces corresponding to adjacent groups of atoms, which comprise the “modules.” The scheme is applicable to complex chemical systems and is characterized by linear or sublinear scaling with system size. It is ideally suited to studies of vibrational energy flow and heat transport in long molecules (which may also be attached to solids), as well as simulations of exciton-vibration dynamics in molecular aggregates.
Single-step fabrication of polydimethylsiloxane microwell arrays with long-lasting hydrophilic inner surfaces
Authors: Gowa Oyama Tomoko , Barba Bin Jeremiah Duenas , Hosaka Yuji , Taguchi Mitsumasa
Published: May 2018

We propose a single-step fabrication method for polydimethylsiloxane (PDMS) cell-adhesive microwell arrays with long-lasting (>10 months in aqueous medium) hydrophilic inner surfaces without the need for any chemical treatment such as development. Irradiation of a PDMS film with a low-energy electron beam (55 kV) in air generated a ∼40-μm-thick hydrophilic silica-like layer on the PDMS surface, which was the key to the prolonged hydrophilicity. Moreover, the concomitant compaction of the irradiated area produced dozens-of-micrometers-deep concave wells. The hydrophilic microwells generated on the hydrophobic non-irradiated PDMS surface easily trapped nano-/picoliter droplets and cells/single-cells. In addition, the surfaces of the microwells offered stable and favorable cell-adherent environments. The method presented here can realize stable and reliable lab-on-chips and cater to the expanding demand in biological and medical applications.