bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast Sub-Grid Scale Finite Element Method for the First Order Neutron Transport Equation
Authors: Fang Chao , Wu Hongchun , Cao Liangzhi , Li Yunzhao
Published: October 2018

This paper presents a fast sub-grid scale (SGS) finite element method for the first order neutron transport equation. The spherical harmonics method is adopted for the angular discretization. The sub-grid scale discretization embeds discontinuous component in each element to provide a stabilization term for the continuous finite element formulation. Traditional SGS method uses Riemann decomposition and vacuum boundary assumption to decouple the discontinuous component. Here we propose a new method to perform the decoupling based on the assumption that the convection term of the discontinuous component is proportional to the residual of angular flux in each element. The computing costs for the establishment of the coefficient matrix of discontinuous component are reduced to O(1) from O(n3). Further more, the computing costs for the inversion of the coefficient matrix are reduced to O(n) from O(n3) by applying mass lumping technique. Numerical results show that the new method is not only more efficient but also yields more accurate solution than traditional sub-grid scale method.
Development of Fuel Route/Dropped Load PSA for UK ABWR
Authors: Taniguchi Daisuke , Hirokawa Naoki , Ishiwatari Yuki
Published: October 2018

Generic Design Assessment (GDA) of Hitachi-GE’s United Kingdom (UK) Advanced Boiling Water Reactor (ABWR) was completed in December 2017. Various Probabilistic Safety Assessment/Analyses (PSAs) are utilized to provide the risk insights for design of UK ABWR. This paper provides the characteristics of “Fuel Route/Dropped Load” PSA which is included in the scope of UK ABWR PSA and focuses on the effects of dropped load. “Fuel Route” means the all areas where the new or spent fuels are moved or stored. Shutdown PSA and Spent Fuel Storage Pool (SFP) PSA cover large parts of risk assessment for the fuel route. However, large number of lifting operation such as refueling with fuel handling machine or heavy equipment lifting operation including cask operation by reactor building crane should be considered separately from Shutdown PSA and SFP PSA. That is because dropped loads potentially caused by such lifting operation may not always cause initiating events considered in the Shutdown PSA or SFP PSA but potentially cause a mechanical failure of the spent fuels and subsequent radiological consequences. “Fuel Route/Dropped Load PSA” is additionally developed and quantified to address the potential radiological release due to the lifting operation.
Hydrodynamic Loads Calculation of Pressurizer Safety Valve Discharge Piping Using RELAP/SCDAPSIM
Authors: Jiang S. , Fu Z. , Hohorst J. K.
Published: October 2018

The hydrodynamic loads are very important for the discharge piping design because of the fast opening of the valves and the presence of liquid in the upstream loop seals. Therefore, this work implemented a force balance formulation into the RELAP/SCDAPSIM code to determine the hydrodynamic loads directly. The force balance method, which equates resultant force transmitted from fluid to structural elements as the sum of all pressure and frictional tractions acting on the wetted surface of the element. Then an assessment was performed with RELAP/SCDAPSIM code for EPRI/CE Test No.917, which was a simulation of a hot water loop seal discharge followed by steam discharge through a pressurizer safety valve. In the RELAP/SCDAPSIM calculations, the input data such as valve opening characteristics, initial fluid conditions, system Nodalization, and system component modeling, were based on original RELAP5/MOD1 and RELAP5/MOD3 calculations performed by EPRI. The calculation results were compared with the experimental data as well as the RELAP5/MOD1 and RELAP5/MOD3 calculation to assess the applicability of the RELAP/SCDAPSIM for the hydrodynamic loads calculation. It was demonstrated from the comparisons that the RELAP/SCDAPSIM code with force balance calculation yields very similar hydrodynamic loads to the experimental data as well as the RELAP5/MOD1 and RELAP5/MOD3 calculation results. Therefore, it is recommended that the new force balance calculation implemented in RELAP/SCDAPSIM can be used to calculate the hydrodynamic loads for the hot water loop seal discharge followed by steam discharge transient.
Experimental Study on Bubble Bursting and Droplet Releasing Characteristics Under Different Liquid Phase Conditions
Authors: Chen Hao , Gu Haifeng , Yu Xiang , Zhou Yanmin , Sun Zhongning , Wen Jimin
Published: October 2018

The phenomenon that bubble bursts at the water surface and results in droplets production is one of the source of radioactive aerosol release, when the gas goes through the aerosol pool. Based on this, a high-speed photographic visualization experimental device was used to visualize the bubble bursting process at liquid surface under different conditions. Experimental studies show that: the bursting process of the bubbles with 7mm–28mm in diameter is a Single point rupture process. The process includes bubble rising, bubble cap draining, punctured point appearing, the liquid film rolling-up which forms the liquid ring, droplets emission as liquid ring breaks. The different punctured position changes the process of bubble bursting and the distribution of the droplets, thus the location of punctured position were divided into different area, which mainly locates at the foot of the bubble cap. Furthermore, the change of liquid phase conditions will affects the location of the punctured position, the number and the sizes of droplets. In the experiments, as temperature of the liquid phase changes from 16°C to 60°C, the process of drainage of bubble cap is shortened, and the probability of punctured position at the bottom increases. When punctured position is the same position, the number of droplets decreased and the diameter of droplet increased as temperature was increasing.
Analysis of UO2-BeO Fuel Performance During Normal Conditions and RIA
Authors: He Yanan , Wu Yingwei , Wang Shihuai , Qiu Bowen , Su G. H.
Published: October 2018

UO2-BeO composite fuel may enable Light Water Reactors (LWRs) to have better safety due to its higher thermal conductivity. Much work have been done on the analysis of UO2-BeO fuel performance during LWRs steady state and Loss of Coolant Accident (LOCA) conditions using hypothetical thermal properties and behaviors models, leading to much uncertainty of the results. In this paper, firstly, fuel swelling and densification models for UO2-BeO fuel were developed based on Halden experiment data. Secondly, UO2-BeO fuel thermal properties and behaviors models have been coded in FRAPCON4.0 and FRAPTRAN2.0 after an evaluation of their applicability to UO2-BeO performance simulation. Then, both UO2-BeO composite fuel and traditional UO2 fuel performance during normal conditions and RIA were done in this paper by modified version of FRAPCON4.0 and FRAPTRAN2.0. Finally, comparisons between UO2-BeO and UO2 performance were conducted. The results shows that the peaking temperature of fuel can be reduced about 200K and 150K during normal conditions and RIA by adopting UO2-BeO, respectively. At the same time, the onset of pellet-cladding mechanic interaction (PCMI) can be delayed about 100days during normal conditions and the weakened PCMI effect can be expected during reactivity insertion accidents (RIA) due to the lower thermal expansion coefficient and temperature distribution for UO2-BeO composite fuel. Also, enthalpy stored in UO2-BeO fuel is reduced about 1/5 compared with that of UO2. However, fission gas release ration of UO2-BeO was a bit larger than that of UO2 due to its higher average burnup. And, further experiments stilled required to gain data for UO2-BeO during high burnup, like possibly reduced thermal conductivity and fission gas release threshold.
Study on PRA Procedure Considering Combination of Multiple Events Using DQFM Methodology
Authors: Yamakawa Hirohisa , Muta Hitoshi
Published: October 2018

Fukushima Daiichi Nuclear Power Station accident occurred by the Great East Japan Earthquake on March 11, 2011. After that, continuous enhancement of nuclear safety is being required in Japan. The accident of Fukushima was caused by the seismic induced tsunami event, namely, multiple events. The other examples of multiple events due to the seismic event are such as internal fire and internal flooding in the nuclear power plants. In addition, structures, such as a building, and piping might be damaged by the seismic event, which could impact component failure dependently. In order to consider these kinds of events, the development of PRA procedures for multiple events caused by the seismic events will be highly demanded. So, we developed a basic PRA methodology for seismic induced tsunami events using “Direct Quantification of Fault Tree using Monte Carlo simulation (DQFM) methodology”. And we verified its applicability through the evaluation.
Acceleration of Plume Dispersion Simulation Using Locally Mesh-Refined Lattice Boltzmann Method
Authors: Onodera Naoyuki , Idomura Yasuhiro
Published: October 2018

A large-scale simulation of the environmental dynamics of radioactive substances is very important from the viewpoint of nuclear security. Recently, GPU has been emerging as one of high performance devices to realize a large-scale simulation with less power consumption. We design a plume dispersion simulation to achieve high performance on the GPU. Lattice Boltzmann method (LBM) is a class of CFD method which is based on a weak compressible formulation. Since the LBM has a simple algorithm with continuous memory accesses, it is suitable for large-scale computation. We apply an adaptive mesh refinement (AMR) method to the LBM. The AMR method arranges fine grids in a necessary region, so that we can realize a multi-scale analysis at high-resolution.

We measure the performance of the LBM code on the GPU-rich supercomputer TSUBAME 3.0 at Tokyo Tech. Good weak scaling from 4 GPUs to 144 GPUs, and 30 times higher node performance is achieved compared with CPUs. The code is validated against a wind tunnel test which was released from the National Institute of Advanced Industrial Science and Technology (AIST). The computational grids are subdivided by the AMR method, and the total number of grid points is reduced to less than 10% compared to the finest meshes. In spite of the fewer grid points, the turbulent statistics and plume dispersion are in good agreement with the experiment data. From these results, it is shown that the present scheme is promising for large-scale local air flow simulations on future exascale supercomputers.
Influence of Spacer Elements on Flow Distribution and Heat Transfer in Experimental Models of Fuel Assemblies
Authors: Kashinsky O. , Kulikov D. , Kurdyumov A. , Lezhnin S. , Lobanov P. , Pribaturin N. , Svetonosov A. , Pacio J. , Stoppel L. , Wetzel T.
Published: October 2018

Experimental investigations of thermal hydraulic properties of coolant flow in experimental models of fuel assemblies (FA) were performed. FA models with 7, 19 and 37 pins in hexagonal arrangement were used as test sections. Friction loss coefficients of smooth rod bundles are presented and compared. Hydraulic resistance of spacing grids with different geometry is discussed. Comparison of obtained data with correlations of Rehme and Idelchik is carried out. Averaged heat transfer dependences on distance from spacer grid top end are presented and compared with different dependences. Experimental results for coolant velocity distribution in subchannels of experimental models were obtained using both Pitot pipe technique and laser Doppler annemometry (LDA). It was shown that a strong disturbance of the flow just behind the spacer grid is present. The flow stabilization occurs at relatively small distances from the spacer elements.
Unsteady CFD Analyses of the Thermal Mixing of the Feedwater in the Downcomer of a BWR
Authors: Le Moigne Yann
Published: October 2018

In a BWR, the cooler feedwater is injected in the downcomer of the reactor vessel where it mixes with the recirculation water that is separated from the generated steam at the exit of the core. In order to avoid high temperature fluctuations on the reactor vessel and the structures present in the downcomer, this mixing shall be performed in a controlled manner. In order to improve the design of the feedwater spargers in Olkiluoto Unit 1 and 2 in Finland, the thermal mixing of the feedwater with the reactor water in the vicinity of the spargers has been studied with transient Computational Fluid Dynamics (CFD) calculations. Unsteady Reynolds-Averaged Navier-Stokes (URANS) calculations have been performed to simulate about 40 s of the water mixing. The time history of the variations of the water temperature on the structures in the downcomer has been analyzed. The calculations have been run for several designs of the replacement spargers. The designs have been assessed using transient statistics of the temperature fluctuations. Minimizing the maximum amplitude of the temperature variations, the so-called peak-to-peak value, has been a design objective.
Enhancement of Pressure and Curvature Calculation for the Moving Particle Semi-Implicit Method
Authors: Li Jiazhi , Jang Sunghyon , Yamaguchi Akira
Published: October 2018

This paper aims at illustrating a number of methods for stabilizing pressure solution and improving surface curvature calculation for the simulation using the moving particle semi-implicit (MPS) method. The unphysical numerical oscillation of pressure originated from the original MPS method can be suppressed by adjusting the collision coefficient in the collision model and using a specific weight function for avoiding the occurrence of excessive pressure value when particles get closer. The pressure gradient solver and the poison pressure equations (PPE) are also modified by implementing a mixed source term of velocity divergence and a corrective matrix, respectively. In addition to the pressure field, the surface tension force is essential for correctly deforming the fluid interface between different phases. The curvature calculation is improved with high accuracy by utilizing a contoured continuum surface model where a new scheme for computing the partial derivatives of the mollified color function is proposed. The Gaussian function for smoothing the color function is specified to ensure a better coincidence of the local contour of mollified color values with the interface. Compared to the original MPS method, both modifications and extensions for the pressure and curvature solver can generate more stable and accurate results, which are presented by a few numerical examples, including the hydrostatic pressure, dam break and bubble rising models.
Development of Boron Dilution Model in COBRA-EN
Authors: Yu Hao , Wang Mingjun , Qiu Suizheng , Tian Wenxi , Su G. H.
Published: October 2018

The dilution characteristic of concentrated boron in reactor core is very important for reactivity control during the Small Break Loss of Coolant Accident (SB-LOCA). Nonuniform distribution of the boron concentration may increase the risk of reactivity accidents. However, tracking the boron concentration inside the primary coolant system meets lots of challenges. Hence the development of a thermal-hydraulic code with accurate boron tracking model is necessary.

This paper presents a multidimensional boron transport model based on subchannel software COBRA-EN. The original model gives a poor prediction in tracking the boron concentration of high Re, since it only considers the mass exchange caused by pressure difference and ignores the mass exchange put forward by the turbulent diffusion. In this paper, a new tracking model was proposed and implemented in the COBRA-EN code, in which the turbulent diffusion was considered. Then a 3 × 3 fuel bundle model was adopted to verify the proposed model. The CFD study was also conducted to investigate the feasibility of the new tracking model. The results indicate: (1) the modified boron tracking model are more close to the actual than the original model; (2) the modified model was verified by FLUENT; (3) the model shows defects at low Re due to the ignorance of molecule diffusion.
Dynamic Analysis of Flexible Rotor Suspended by Active Magnetic Bearings With LQR Controller
Authors: Su Yixin , Ma Yanhui , Shi Qian , Yu Suyuan
Published: October 2018

Dynamic characteristics of active magnetic bearing (AMB)-flexible rotor system are closely related to control law. To analyze dynamic characteristics of flexible rotor suspended by AMBs with linear quadratic regulation (LQR) controller, a simple and effective method based on numerical calculation of unbalanced response is proposed in this article. The model of flexible rotor is established based upon Euler-Bernoulli beam theory and Lagrange’s equation. Disc on the rotor and its Gyro effect are taken into account. LQR controller based on error and its derivative is developed to control electromagnetic force of AMB at each degree of freedom (DOF) in real time. Under the unbalanced exciting force, the steady-state response and transient response in time domain of each node of flexible rotor at 0–4000 rad/s are calculated numerically. The critical speeds of rotor are obtained by identification method quickly and easily.
Analyses of Gas Stratification Erosion by a Vertical Jet in Presence of an Obstacle Using the GOTHIC Code
Authors: Andreani Michele , Kapulla Ralf
Published: October 2018

The GOTHIC code was validated using three experiments carried out in the PANDA facility in the framework of the OECD/NEA project HYMERES. These tests addressed the mixing of an initially stratified atmosphere by means of a vertical jet in the presence of on obstacle (circular plate). This paper reports on the simulations of three experiments, and complementary, quasi-steady state tests without stratification, where the flow structure above the impingement plate could be observed by means of PIV velocity measurements in a region larger than that considered in the transient experiments. Moreover, simulations of similar tests without obstacle conducted during the OECD/SETH-2 are also discussed. The reference, best-estimate model used for the analyses of the three experiments with different flow rates and initial and pressure boundary conditions was built on the base of a multi-step approach. This was based on mesh and modelling sensitivity studies mostly performed for the complementary tests, to assess the capability to represent the flow structure produced by the jet-plate interaction with different meshes around the plate. Generally, the results show that the use of a coarse mesh and the standard k-ε turbulence model permits a reasonable representation of the erosion process, but with a systematic over prediction of the mixing time. The results with the reference model were more accurate for two experiments with two flow rates and same initial conditions and all complementary tests. For the third test with different initial and boundary conditions, however, poor results were obtained with the reference model, which could only be improved by further refining the mesh. These results indicate that a model “qualified” for certain conditions could be inadequate for other cases, and sensitivity studies are necessary for the specific conditions considered in the analyses.
Assessments of Different Turbulence Models in Predicting the Performance of a Butterfly Valve
Authors: Duan Yu , Eaton Matthew D. , Bluck Michael J. , Jackson Christopher
Published: October 2018

This paper presents an assessment of the performance of four eddy viscosity models in STAR-CCM+ 12.04 in simulating water flow through an industrial size butterfly valve: the standard k-ε model, realizable model, lag EB k-ε model and k-ω-SST model. This is achieved by comparing RANS predictions with physical measurements already available in literature. Although the lag EB k-ε model and k-ω-SST model are supposed to have a better ability to capture the anisotropic turbulence effect and flow separations, it has been demonstrated that the standard k-ε model is still a robust model in terms of predicting the flow coefficient (Cv). The general error of Cv by the standard k-ε model is less than 10% for the considered openings with the exception of 80°. This work also demonstrates that the eddy viscosity models have more difficulty predicting the torque coefficient (Ct) than Cv.
iB1350: Part 1 — A Generation III.7 Reactor iB1350 and Defense in Depth (DiD)
Authors: Sato Takashi , Matsumoto Keiji , Hosomi Kenji , Taguchi Keisuke
Published: October 2018

iB1350 stands for an innovative, intelligent and inexpensive boiling water reactor 1350. It is the only Generation III.7 reactor incorporating Fukushima lessons learned and complying with Western European Nuclear Regulation Association (WENRA) safety objectives. It is about twice safer than any existing Gen III.5 reactors. It has 7-day grace period for SBO and SA without containment venting. It enables no evacuation and no long-term relocation in SA. It, however, is based on the well-established proven ABWR. The NSSS and TI are exactly the same as those of the existing ABWR. The iB1350 only enhanced the ABWR safety by adding an outer well (OW) as additional PCV volume, built-in passive safety systems (BiPSS) for SA, DEC systems and an APC shield dome over the containment. The BiPSS include an isolation condenser (IC), an innovative passive containment cooling system (iPCCS), in-containment filtered venting system (IFVS), and innovative core catcher (iCC). All the BiPSS are embedded and protected in the containment building against APC. No specialized safety features remote from the R/B are necessary, which reduces plant cost. The primary system has only one integrated RPV. There are no SGs, no pressurizer, no core makeup tanks, no accumulators, no hot legs, and no cold legs. The iB1350 consists of only one integrated RPV and passive safety systems inside the containment building. This configuration is simpler than the simplest large PWR and as simple as SMR. While SMR have rather small outputs, the iB1350 has 1350 MWe output. It is simple, large and economic. As for the safety design it has an in-depth hybrid safety system (IDHS). The IDHS consists of 4 division active safety systems for DBA, 1 or 2 division active safety systems for DEC and the built-in passive safety systems (BiPSS) for SA. The IDHS is originally based on the four levels of safety that have provided an explicit fourth defense level against devastating external events even before 3.11. It also can be explained along with WENRA Defense in Depth (DiD). It is said that independence between DiD levels are important. However, there are many exceptions for independence between DiD levels. For example, SCRAM is used in DiD2, DiD3a and DiD3b. Any DiD that allows exceptions of independence of DiD levels is fake. The iB1350 is rather based on the three levels of safety proposed by Clifford Beck (AEC, 1967). There is complete independence between level 2 (core systems) and level 3 (containment systems) without any exceptions of independence. DiD without exceptions of independence is a real DiD. Only passive safety reactors can meet the real DiD.
Simulation of Hydrogen Distribution due to In-Vessel Severe Accident in WWER-1000 NPP Containment: A Comparison of CONTAIN and MELCOR Codes Results
Authors: Noorikalkhoran Omid , Gei Massimiliano
Published: October 2018

During a severe accident or Beyond Design Basis Accident (BDBA), the reaction of water with zirconium alloy as fuel clad, radiolysis of water, molten corium-concrete interaction (MCCI) and post-accident corrosion can generate a source of hydrogen. In the present work, hydrogen distribution due to in-vessel reaction (between zircaloy and steam) has been simulated inside a WWER-1000 reactor containment. In the first step, the thermal hydraulic parameters of containment have been simulated for a DECL (Double Ended Cold Leg) accident (DBA phase) in both short and long time and the effects of spray as Engineering Safety Features (ESFs) on mitigating the parameters have been studied. In the second step, it has been assumed that the accident developed into an in-vessel core melting accident. While in pre-phase of core melting (severe accident phase), hydrogen will be produced as a result of zircaloy and steam reaction (BDBA phase), the hydrogen distribution has been simulated for 23 cells inside the reactor containment by using CONTAIN 2.0 (Best estimate code) and MELCOR 1.8.6 codes. Finally, the results have been compared to FSAR results. As it can be seen from the comparisons, both CONTAIN and MELCOR codes can predict the results in good agreement with FSAR (ANGAR code) results. CONTAIN shows peak pressure around 0.36 MPa in short-term and this amount is about 0.38 and 0.4 MPa for MELCOR and ANGAR (FSAR) results respectively. All these values are under design pressure that is around 0.46 MPa. Cell 20 has the maximum mole fraction of hydrogen in long-term about 9.5% while the maximum amount of hydrogen takes place in cell 22. The differences between the results of codes are because of different equations, Models, Numerical methods and assumptions that have been considered by the codes. The simulated Hydrogen Distribution Map (HDM) can be used for upgrading the location of HCAV systems and Hydrogen Mitigator features (like the recombiners and ignitors) inside the containment to reduce the risk of hydrogen explosion.
Phylogenomic Analysis of Extraintestinal Pathogenic
Escherichia coli
Sequence Type 1193, an Emerging Multidrug-Resistant Clonal Group
Authors: Johnson Timothy J. , Elnekave Ehud , Miller Elizabeth A. , Munoz-Aguayo Jeannette , Flores Figueroa Cristian , Johnston Brian , Nielson Daniel W. , Logue Catherine M. , Johnson James R.
Published: October 2018

The fluoroquinolone-resistant sequence type 1193 (ST1193) of
Escherichia coli
, from the ST14 clonal complex (STc14) within phylogenetic group B2, has appeared recently as an important cause of extraintestinal disease in humans. Although this emerging lineage has been characterized to some extent using conventional methods, it has not been studied extensively at the genomic level.
Anterior spinal cord syndrome as a rare complication of acute bacterial meningitis in an adult
Authors: Ng Kwang Sheng , Abdul Halim Sanihah
Published: October 2018

Acute bacterial meningitis is not an uncommon central nervous system infection. In severe cases, it can be associated with various neurological or systemic complications. However, acute spinal cord dysfunction rarely occurs. We report a case of bacterial meningitis complicated with spinal cord infarction despite adequate treatment with antibiotics and corticosteroid therapy. He had residual paraplegia and was fully dependent in the activity of daily living.
Non-uraemic calciphylaxis (NUC) postliver transplantation
Authors: Frunza-Stefan Simona , Poola-Kella Silpa , Silver Kristi
Published: October 2018

Calciphylaxis is a rare and life-threatening disease characterized by cutaneous arteriolar stenosis and vascular thrombosis leading to skin ischaemia and necrosis. While calciphylaxis occurs mostly in patients with end-stage renal disease, the disorder has been described in patients with normal renal function, namely non-uraemic calciphylaxis (NUC). A 41-year-old African-American woman presented with a painful ulcerative rash on her thighs and right buttock 2 months after undergoing an orthotopic liver transplantation. She underwent debridement of the lesions and an excisional biopsy of one of the lesions, which revealed calciphylaxis. She was treated with sodium thiosulfate, cinacalcet and hyperbaric oxygen with complete resolution of the lesions 4–5 months after presentation. While she was treated with a course of high-dose glucocorticoids after the transplant, she did not have other risk factors for calciphylaxis. NUC should be considered in the differential diagnosis of necrotic skin lesions in postliver transplant patients.
Triphasic response of pituitary stalk injury following TBI: a relevant yet uncommonly recognised endocrine phenomenon
Authors: Goel Ansha , Farhat Freba , Zik Chad , Jeffery Michelle
Published: October 2018

The triphasic response of pituitary stalk injury has previously been described in a minority of patients following intracranial surgery, however, this phenomenon can also occur after traumatic brain injury. We present the case of a 20-year-old male who experienced the triphasic response of pituitary stalk injury (central diabetes insipidus, syndrome of inappropriate antidiuretic hormone and central diabetes insipidus again) after striking his head on a concrete curb. His history and presentation highlight the importance of recognising the distinctive symptoms of each individual stage of pituitary stalk injury, and using the appropriate diagnostic tools and therapies to guide further management.
Lifestyles and mindsets of Olympic, Paralympic and world champions: is an integrated approach the key to elite performance?
Authors: Burns Lauren , Weissensteiner Juanita Ruth , Cohen Marc
Published: October 2018

Objectives

The holy grail of any nation in the global sporting race is to better understand, replicate and sustain podium winning performances on the world stage. International sporting bodies advocate a holistic approach to the athletic profile and environmental and system-level factors required for world-class sporting performance, yet key lifestyle, relational, training and performance practices are commonly overlooked. We aimed to explore the contribution, interplay, and impact of lifestyle and psychological factors among a sample of world-class, champion athletes.

Methods

Open-ended, semistructured face-to-face interviews were conducted with 10 World, Olympic and Paralympic Champion athletes that covered their sporting development and athletic profile including their mindset, training and competition practices, along with lifestyle and other key factors to which they attributed their success. A thematic approach guided by grounded theory principles, was employed to source and analyse their perspectives and experiences and determine common themes.

Results

Four dominant and overlapping themes emerged: psychological attributes, interpersonal relationships, performance strategies and lifestyle practices. All athletes attributed their success to psychological rather than physical factors, and the vast majority relied on mental rehearsal skills and recovery practices.

Conclusion

The athletic profile and support required to reach and sustain podium-level performance is multidimensional, integrated and individualised and psychological factors are paramount. Championship performance is likely to occur at the intersection of psychological prowess, interpersonal support, effective performance strategies and lifestyle. An integrated approach inclusive of these dimensions can be used to guide athlete development and support at both an individual level and a collective level.
Vanishing racial disparities in drowning in Florida
Authors: Gorsuch Marina Mileo , Myers Jr. Samuel L , Lai Yufeng , Steward Devan , Motachwa Rachel
Published: October 2018

Objectives

To examine the change in the racial disparity in drowning in Florida from 1970 to 2015 and to analyse the contextual factors associated with white, black and Hispanic drowning rates in Florida from 2007 to 2015.

Methods

Our outcome variable is county-level annual drowning rates by race, ethnicity, sex and age group. We computed county-level contextual data, including emergency weather events, temperature, extreme weather, number of pools, quality of pools, coastline, swimming participation rates and prominent black competitive swim teams.

Results

Between 1970 and 1990, the disparity in drowning rates between white and black males in Florida decreased dramatically. By 2005, the overall age-adjusted drowning rates converged. This convergence was most striking for those aged 10–34 and 35–64. While the gap has declined dramatically, there remains a racial disparity in drownings among those aged 10–34.

Conclusions

Overall, racial disparities in drowning have disappeared in Florida. However, some disparities remain. There is a persistent disparity in drownings among those aged 10–34.
Clinical presentation and management of African horse sickness in two dogs
Authors: Whitehead Zandri , le Roux Christelle , O'Dell Nicolize , Hanekom Josef
Published: October 2018

A 10‐month‐old, spayed, female beagle (case 1) and an unrelated two‐year‐old, intact, female labrador retriever (case 2), both living in Pretoria, South Africa, presented individually on separate occasions with acute onset dyspnoea and severe hypoxia. Thoracic radiographs demonstrated severe, diffuse interstitial to alveolar lung patterns with mild pleural and mediastinal effusion. Mixed airway inflammation was seen on transtracheal aspirate cytology in case 1. Both cases received supportive therapy, but only one dog survived (case 2). African horse sickness (AHS) was diagnosed at necropsy based on histopathology and immunohistochemistry in case 1 and was diagnosed antemortally using reverse transcriptase‐PCR on whole blood in case 2. To the authors’ knowledge, this is the first report to detail the haematological, biochemical, thoracic radiological, arterial blood gas and transtracheal aspirate cytology findings of AHS in dogs. This report also describes the treatment of a dog surviving clinical AHS infection.
Predicting species distribution from fishers’ local ecological knowledge: a new alternative for data-poor management
Authors: Lopes Priscila F.M. , Verba Júlia T. , Begossi Alpina , Pennino Maria Grazia
Published: October 2018

Many developing countries lack information to manage their endangered species, urging the need for affordable and reliable information. We used Bayesian hierarchical spatial models, with oceanographic variables, to predict the distribution range of Epinephelus marginatus, the dusky grouper, for the entire Southwest Atlantic. We ran a model using scientific information gathered from the literature and another using information gathered from fishers on species presence or absence. In both models, temperature was an important determinant of species occurrence. The predicted occurrence of the dusky grouper overlapped widely (Schoener’s D = 0.71; Warren’s I = 0.91) between the models, despite small differences on the southern and northern extremes of the distribution. These results suggest that basic information provided by fishers on species occurrence in their area can be reliable enough to predict species occurrence over large scales and can be potentially useful for marine spatial planning. Fishers’ knowledge may be an even more viable alternative to data collection than what was previously thought, for countries that both struggle with financial limitations and have urgent conservation needs.
Synchronization of Slow Cortical Rhythms During Motor Imagery-Based Brain–Machine Interface Control
Authors: Barios Juan A. , Ezquerro Santiago , Bertomeu-Motos Arturo , Nann Marius , Badesa Fco. Javier , Fernandez Eduardo , Soekadar Surjo R. , Garcia-Aracil Nicolas
Published: October 2018

Modulation of sensorimotor rhythm (SMR) power, a rhythmic brain oscillation physiologically linked to motor imagery, is a popular Brain–Machine Interface (BMI) paradigm, but its interplay with slower cortical rhythms, also involved in movement preparation and cognitive processing, is not entirely understood. In this study, we evaluated the changes in phase and power of slow cortical activity in delta and theta bands, during a motor imagery task controlled by an SMR-based BMI system. In Experiment I, EEG of 20 right-handed healthy volunteers was recorded performing a motor-imagery task using an SMR-based BMI controlling a visual animation, and during task-free intervals. In Experiment II, 10 subjects were evaluated along five daily sessions, while BMI-controlling same visual animation, a buzzer, and a robotic hand exoskeleton. In both experiments, feedback received from the controlled device was proportional to SMR power (11–14[Formula: see text]Hz) detected by a real-time EEG-based system. Synchronization of slow EEG frequencies along the trials was evaluated using inter-trial-phase coherence (ITPC). Results: cortical oscillations of EEG in delta and theta frequencies synchronized at the onset and at the end of both active and task-free trials; ITPC was significantly modulated by feedback sensory modality received during the tasks; and ITPC synchronization progressively increased along the training. These findings suggest that phase-locking of slow rhythms and resetting by sensory afferences might be a functionally relevant mechanism in cortical control of motor function. We propose that analysis of phase synchronization of slow cortical rhythms might also improve identification of temporal edges in BMI tasks and might help to develop physiological markers for identification of context task switching and practice-related changes in brain function, with potentially important implications for design and monitoring of motor imagery-based BMI systems, an emerging tool in neurorehabilitation of stroke.
Fragmented Hofer’s geometry
Authors: Kawasaki Morimichi
Published: October 2018

Hofer’s norm (metric) is an important and interesting topic in symplectic geometry. In the present paper, we define fragmented Hofer’s norms which are Hofer’s norms controlled by fragmentation norms and give some observations on fragmented Hofer’s norms.
Spectral analysis for weighted iterated quadrilateral graphs
Authors: Dai Meifeng , Chen Yufei , Wang Xiaoqian , Su Weiyi
Published: October 2018

Much information about the structural properties and dynamical aspects of a network is measured by the eigenvalues of its normalized Laplacian matrix. In this paper, we aim to present a first study on the spectra of the normalized Laplacian matrix of weighted iterated quadrilateral graphs. We analytically obtain all the eigenvalues, as well as their multiplicities from two successive generations. As an example of application of these results, we then derive closed-form expressions for the multiplicative degree Kirchhoff index and the Kemeny’s constant, as well as the number of weighted spanning trees.
The Study of Spatial Frequency Channels for Human Visual System
Authors: Xu Xiangyang , Chen Qiao , Xu Ruixin
Published: October 2018

Similar to auditory perception of sound system, color perception of the human visual system also presents a multi-frequency channel property. In order to study the multi-frequency channel mechanism of how the human visual system processes color information, the paper proposed a psychophysical experiment to measure the contrast sensitivities based on 17 color samples of 16 spatial frequencies on CIELAB opponent color space. Correlation analysis was carried out on the psychophysical experiment data, and the results show obvious linear correlations of observations for different spatial frequencies of different observers, which indicates that a linear model can be used to model how human visual system processes spatial frequency information. The results of solving the model based on the experiment data of color samples show that 9 spatial frequency tuning curves can exist in human visual system with each lightness, R–G and Y–B color channel and each channel can be represented by 3 tuning curves, which reflect the “center-around” form of the human visual receptive field. It is concluded that there are 9 spatial frequency channels in human vision system. The low frequency tuning curve of a narrow-frequency bandwidth shows the characteristics of lower level receptive field for human vision system, the medium frequency tuning curve shows a low pass property of the change of medium frequent colors and the high frequency tuning curve of a width-frequency bandwidth, which has a feedback effect on the low and medium frequency channels and shows the characteristics of higher level receptive field for human vision system, which represents the discrimination of details.
Bifurcation of Nontrivial Periodic Solutions for a Food Chain Beddington–DeAngelis Interference Model with Impulsive Effect
Authors: Shuai Wang , Qingdao Huang
Published: October 2018

In this paper, a food chain Beddington–DeAngelis interference model with impulsive effect is studied. The trivial periodic solution is locally asymptotically stable if the release rate or the release period is suitable. Conditions for permanence of the model are obtained. The existence of nontrivial periodic solutions and semi-trivial periodic solutions are established when the trivial periodic solution loses its stability under different conditions.
HEDGING OF SYNTHETIC CDO TRANCHES WITH SPREAD AND DEFAULT RISK BASED ON A COMBINED FORECASTING APPROACH
Authors: LIU WEN-QIONG , HUANG WEN-LI
Published: October 2018

Hedging of credit derivatives, especially the Collateralized Debt Obligations (CDOs), is the prerequisite of risk management in financial market. Since both spread risk and default risk exist, the models in existing literature resort to the incomplete-market theory to derive the hedging strategies. From another point of view, the construction of hedging strategies of CDO might be regarded as the process of forecasting the changes in value of CDO by the changes in value of hedging instruments. Based on this idea, this paper proposes an alternative hedging approach via the combined forecasting and regression techniques, where the two individual forecasting models are Gaussian copula model and local intensity model, used to hedge against spread risk and default risk, respectively. Finally, the dynamic hedge ratios of CDO tranches with CDS index are derived. A numerical analysis is carried out and the hedge ratios obtained by the new models are compared with those from actual market spreads. It is shown that the model derived in this paper not only provides hedging strategies which agree with the market hedge ratios but that can be effectively implemented as well.
Stochastic Single Footfall Trace Model for Pedestrian Walking Load
Authors: Chen Jun , Ding Guo , Živanović Stana
Published: October 2018

Developing a model for the dynamic force generated by a pedestrian’s foot on a supporting structure (single footfall trace model) is crucial to advanced numerical analysis and vibration serviceability assessment of the structure. A reliable model needs to reflect the inter-subject and intra-subject randomness of human walking. This paper introduces a stochastic single footfall trace model in the form of a Fourier series in which body weight, walking frequency, and the first eight harmonics are treated as random variables. An experiment used 73 test subjects, walking at a range of pacing frequencies, to record force time histories and the corresponding gait parameters. Two variability descriptors were used to indicate inter-subject and intra-subject randomness. Further statistical analysis identified the relationships between key parameters as well as the probability distribution functions of random variables. In the final step, an application of the proposed single footfall trace model was developed and tested. The proposed model represented the experimental data well in both time and frequency domains.
Design and interpretation of packer permeability tests for geotechnical purposes
Authors: Preene Martin
Published: October 2018

Packer permeability tests are used routinely in geotechnical investigations to allow estimation of hydraulic conductivity by analysis of pressure/flow rate response during controlled injection of water into a section of borehole, isolated by packers. This paper is a review of the hydraulic fundamentals of the packer permeability test methods and analyses used routinely in geotechnical investigations and discusses the usefulness and limitations of the test. Guidance is given on design of tests, including the maximum hydraulic conductivity that can be measured by the method. Interpretation of tests must recognize that responses are influenced by the entire test system – the host rock, the borehole and any associated zone of disturbance, water quality (injected water and water in the host rock), the packers or isolation system and the head/flow rate measurement system. It is proposed that, for geotechnical projects, presenting test results as a
Q–H
diagram (plotting injection flow rate v. applied excess head) is useful and allows results to be classified against seven conventional and three unconventional test responses. Guidance is given on the selection of values of hydraulic conductivity, for geotechnical design purposes, from various types of test responses.
2PAC
Authors: Tonneau Steve , Fernbach Pierre , Prete Andrea Del , Pettré Julien , Mansard Nicolas
Published: October 2018

Synthesizing motions for legged characters in arbitrary environments is a long-standing problem that has recently received a lot of attention from the computer graphics community. We tackle this problem with a procedural approach that is generic, fully automatic, and independent from motion capture data. The main contribution of this article is a point-mass-model-based method to synthesize Center Of Mass trajectories. These trajectories are then used to generate the whole-body motion of the character.

The use of a point mass model results in physically inconsistent motions and joint limit violations when mapped back to a full- body motion. We mitigate these issues through the use of a novel formulation of the kinematic constraints that allows us to generate a quasi-static Center Of Mass trajectory in a way that is both user-friendly and computationally efficient. We also show that the quasi-static constraint can be relaxed to generate motions usable for computer animation at the cost of a moderate violation of the dynamic constraints.

Our method was integrated in our open-source contact planner and tested with different scenarios—some never addressed before—featuring legged characters performing non-gaited motions in cluttered environments. The computational efficiency of our trajectory generation algorithm (under one ms to compute one second of trajectory) enables us to synthesize motions in a few seconds, one order of magnitude faster than state-of-the-art methods. Although our method is empirically able to synthesize collision-free motions, the formal handling of environmental constraints is not part of the proposed method and left for future work.
An Optimal Algorithm for ℓ
1
-Heavy Hitters in Insertion Streams and Related Problems
Authors: Bhattacharyya Arnab , Dey Palash , Woodruff David P.
Published: October 2018

We give the first optimal bounds for returning the ℓ
1
-heavy hitters in a data stream of insertions, together with their approximate frequencies, closing a long line of work on this problem. For a stream of
m
items in { 1, 2, … ,
n
} and parameters 0 < ε < φ ⩽ 1, let
f

i

denote the frequency of item
i
, i.e., the number of times item
i
occurs in the stream. With arbitrarily large constant probability, our algorithm returns all items
i
for which
f

i

⩾ φ
m
, returns no items
j
for which
f

j

⩽ (φ −ε)
m
, and returns approximations
f˜

i

with |
f˜

i

−
f

i

| ⩽ ε
m
for each item
i
that it returns. Our algorithm uses
O
(ε
−1
log φ
−1
+ φ
−1
log
n
+ log log
m
) bits of space, processes each stream update in
O
(1) worst-case time, and can report its output in time linear in the output size. We also prove a lower bound, which implies that our algorithm is optimal up to a constant factor in its space complexity. A modification of our algorithm can be used to estimate the maximum frequency up to an additive ε
m
error in the above amount of space, resolving Question 3 in the IITK 2006 Workshop on Algorithms for Data Streams for the case of ℓ
1
-heavy hitters. We also introduce several variants of the heavy hitters and maximum frequency problems, inspired by rank aggregation and voting schemes, and show how our techniques can be applied in such settings. Unlike the traditional heavy hitters problem, some of these variants look at comparisons between items rather than numerical values to determine the frequency of an item.