bluuebunny/crossref_metadata_2025 huggingface dataset:
Aragonite and calcite preservation in sediments from Lake Iznik related to bottom lake oxygenation and water column depth
Authors: Roeser Patricia , Franz Sven O. , Litt Thomas
Published: July 2016

This study examines the forcing mechanisms driving long‐term carbonate accumulation and preservation in lacustrine sediments in Lake Iznik (north‐western Turkey) since the last glacial. Currently, carbonates precipitate during summer from the alkaline water column, and the sediments preserve aragonite and calcite. Based on X‐ray diffraction data, carbonate accumulation has changed significantly and striking reversals in the abundance of the two carbonate polymorphs have occurred on a decadal time scale, during the last 31 ka cal bp. Different lines of evidence, such as grain size, organic matter and redox sensitive elements, indicate that reversals in carbonate polymorph abundance arise due to physical changes in the lacustrine setting, for example, water column depth and lake mixing. The aragonite concentrations are remarkably sensitive to climate, and exhibit millennial‐scale oscillations. Extending observations from modern lakes, the Iznik record shows that the aerobic decomposition of organic matter and sulphate reduction are also substantial factors in carbonate preservation over long time periods. Lower lake levels favour aragonite precipitation from supersaturated waters. Prolonged periods of stratification and, consequently, enhanced sulphate reduction favour aragonite preservation. In contrast, prolonged or repeated exposure of the sediment–water interface to oxygen results in in situ aerobic organic matter decomposition, eventually leading to carbonate dissolution. Notably, the Iznik sediment profile raises the hypothesis that different states of lacustrine mixing lead to selective preservation of different carbonate polymorphs. Thus, a change in the entire lake water chemistry is not strictly necessary to favour the preservation of one polymorph over another. Therefore, this investigation is a novel contribution to the carbon cycle in lacustrine systems.
Prevention of perceptual‐motor decline by branched‐chain amino acids, arginine, citrulline after tennis match
Authors: Yang C‐C. , Wu C‐L. , Chen I‐F. , Chang C‐K.
Published: July 2016

Perceptual‐motor performance in prolonged tennis matches may be affected by central fatigue. The purpose of this study was to investigate the supplementation of branched‐chain amino acids (BCAA), arginine, and citrulline on tennis‐specific perceptual‐motor performance after a simulated match. Nine male tennis players consumed 0.17 g/kg BCAA, 0.05 g/kg arginine, and 0.05 g/kg citrulline (AA trial), or placebo (PB trial) 1 h before the match. In the perceptual‐motor performance test before and after the match, the subjects hit balls to the opposite direction of the examiner's movement. The AA trial showed significantly higher rate of correct direction than the PB trial after the match (AA trial: 93.63 ± 1.28%, PB trial: 69.09 ± 2.40%). The AA trial also demonstrated significantly higher post‐match accuracy and consistency than the PB trial. The AA trial showed significantly lower heart rate and ratings of perceive exertion during the match, concurrently with a significantly lower plasma total tryptophan/BCAA ratio. Similar post‐match plasma NH3 concentrations were found in both trials while the AA trial was significantly higher in NOx concentration. This study suggested that the supplementation could prevent the decline in perceptual‐motor performance through alleviation of central fatigue by BCAA and prevention of excess hyperammonemia by arginine and citrulline.
Networking Enforced–Comparing Social Services'Collaborative Rationales across Different Welfare Regimes
Authors: Breimo Janne Paulsen , Turba Hannu , Firbank Oscar , Bode Ingo , Sandvin Johans Tveit
Published: July 2016

Collaboration and networking are ubiquitous,versatile features of social service provision in most Western countries. However,it is an open question whether networking means and entails the same across countries. Comparing regulatory frameworks in three jurisdictions representing distinctive‘worlds of welfare services’ –Germany,Norway and Quebec–this article aims at eliciting the normative rationales that underpin and inform local service networks in child welfare and protection(CWP)systems. In Norway,where services are little diversified and largely insular,networking appears as a way of opening up for greater organizational plurality,within and beyond the public sector realm. In Germany in contrast,where services are highly pluralized and fragmented,networks are seen as an instrument for streamlining complexity. As for Quebec–an intermediate case in some respects–networking is envisioned as a catalyst for aligning two co‐existing service streams and mitigating the child protection–family support divide. Interestingly,in all three places,networking is now being enforced through similar highly formalized,top‐down regulatory provisions,even though the intended directions of change differ markedly. This has implications for CWP policy as well as research on networks at large.
Sowing a winter catch crop can reduce nitrate leaching losses from winter‐applied urine under simulated forage grazing: a lysimeter study
Authors: Carey P. L. , Cameron K. C. , Di H. J. , Edwards G. R. , Chapman D. F.
Published: July 2016

Grazing of winter forage crops is a common management option used in the dairy industry of New Zealand, particularly in the South Island, where they are used to feed nonlactating, pregnant dairy cows prior to calving. However, there is concern that the large crop yields per hectare grazed, combined with a high stocking density of cows, lead to large amounts of urinary nitrogen (N) deposited on bare, wet soil that, in turn, could lead to large nitrate leaching losses. We report the results of a simulated winter forage grazing event using field lysimeters planted with a kale (Brassica oleracea L.) crop. The effect of sowing a ‘catch crop’ of oat (Avena sativa L.) following the simulated winter forage grazing on nitrate leaching losses from urine applied at different times throughout the winter was measured. A catch crop sown between 1 and 63 days after the urine deposition in early winter reduced N leaching losses from urine patches by ~34% on average (range: 19–49%) over the winter–spring period compared with no catch crop. Generally, the sooner the catch crop was sown following the crop harvest, the greater the uptake of N by the catch crop and the greater the reduction in nitrate leaching losses. The results indicate that sowing of a catch crop following winter crop grazing could be an effective management strategy to reduce nitrate leaching as well as increase the N‐use efficiency of dairy winter forage grazing systems.
Phosphatidic Acid Sequesters Sec18p from cis‐SNARE Complexes to Inhibit Priming
Authors: Starr Matthew L. , Hurst Logan R. , Fratti Rutilio A.
Published: July 2016

Yeast vacuole fusion requires the activation of cis‐SNARE complexes through priming carried out by Sec18p/N‐ethylmaleimide sensitive factor and Sec17p/α‐SNAP. The association of Sec18p with vacuolar cis‐SNAREs is regulated in part by phosphatidic acid (PA) phosphatase production of diacylglycerol (DAG). Inhibition of PA phosphatase activity blocks the transfer of membrane‐associated Sec18p to SNAREs. Thus, we hypothesized that Sec18p associates with PA‐rich membrane microdomains before transferring to cis‐SNARE complexes upon PA phosphatase activity. Here, we examined the direct binding of Sec18p to liposomes containing PA or DAG. We found that Sec18p preferentially bound to liposomes containing PA compared with those containing DAG by approximately fivefold. Additionally, using a specific PA‐binding domain blocked Sec18p binding to PA‐liposomes and displaced endogenous Sec18p from isolated vacuoles. Moreover, the direct addition of excess PA blocked the priming activity of isolated vacuoles in a manner similar to chemically inhibiting PA phosphatase activity. These data suggest that the conversion of PA to DAG facilitates the recruitment of Sec18p to cis‐SNAREs. Purified vacuoles from yeast lacking the PA phosphatase Pah1p showed reduced Sec18p association with cis‐SNAREs and complementation with plasmid‐encoded PAH1 or recombinant Pah1p restored the interaction. Taken together, this demonstrates that regulating PA concentrations by Pah1p activity controls SNARE priming by Sec18p.
Weed suppressiveness of paving joint filling materials under diverging water regimes
Authors: De Cauwer B , Faes J , Biesemans N , Claerhout S , Reheul D
Published: July 2016

Since 2015, chemical weed control on public pavements in Flanders has been banned. This necessitates alternative weed control strategies. In this study, growth chamber experiments evaluated the weed suppressive ability of different joint filling materials under various water regimes. The tested materials comprised five unbound standard fillers (white quartz sand, sea sand, limestone 0/2 mm, limestone 2/6.3 mm and porphyry 2/6.3 mm) and two innovative materials (Dansand® and Eco Fugensand®). Their weed suppressiveness was tested in pure and organically polluted states. Germination and biomass accumulation of two weed species that are abundantly found on public pavements (Lolium perenne and Taraxacum officinale) were investigated. Germination and biomass accumulation were lowest in both innovative materials, irrespective of organic contamination level, plant species and water regime. Weed growth in the standard materials was affected by plant species and water regime. Monthly biomass accumulation increased with increasing monthly water supply and number of irrigation days. Furthermore, the materials best capable of reducing weed growth, under all water regimes, even when organically polluted, were the innovative materials and sea sand. The results of this study show that the implemented water regime can influence weed suppressiveness (absolute as well as relative) of a joint filler. Hence, to fully assess weed suppressive ability, commercially launched joint fillers should be tested under diverging water regimes.
Potential of Using Design-Build in Public Procurement
Authors: Blaťák Ing. Jakub
Published: July 2016

Risk is an omnipresent effect in every area of human activity. Ignoring it can cause serious problems. This article is about eliminating risk in public contracts using the design-build method as a possible solution to reduce risk. First, we need to compare the standard method of design-bid-build with its alternative, design-build. Two methods are used in this article to analyse risk – the main method is RIPRAN. The evaluated results provided by the RIPRAN method are processed by research data using a scoring method with a risk map. The analysis is going to detect the difference between the DBB and DB methods, primarily in appearance and its impact on the realization of the whole construction.  The comparison identifies numerous contractual topics and risks included in both and gives deeper insight into risk management, both for the contracting party and also for public procurement. Applying risk analysis strategies and tools to the process will help decision-makers evaluate and select the most suitable delivery method consistently and defensibly. This paper gives generic risk factors related to both project types.
Morphology of Secondary Flows in a Curved Pipe With Pulsatile Inflow
Authors: Plesniak Michael W. , Bulusu Kartik V.
Published: July 2016

A multiplicity of secondary flow morphologies is produced in the arterial network due to complexities in geometry (such as curvature, branching, and tortuosity) and pulsatility in the blood flow. In clinical literature, these morphologies have been called “spiral blood flow structures” and have been associated with a protective role toward arterial wall damage in the ascending and abdominal aorta. Persistent secondary flow (vortical) structures as observed experimentally in planar cross sections have been associated with flow instabilities. This study presents the results of two rigorous in vitro experimental investigations of secondary flow structures within a 180-deg bent tube model of curved arteries. First, phase-averaged, two-component, two-dimensional, particle image velocimetry (2C-2D PIV) experiments were performed at the George Washington University. Second, phase-locked, three-component, three-dimensional magnetic resonance velocimetry (3C-3D MRV) measurements were done at the Richard M. Lucas Center at Stanford University. Under physiological (pulsatile) inflow conditions, vortical patterns of a variety of scales, swirl magnitudes (strengths), and morphologies were found. A continuous wavelet transform (CWT) algorithm (pivlet 1.2) was developed for coherent structure detection and applied to out-of-plane vorticity (ω) fields. Qualitative comparisons of coherent secondary flow structures from the PIV and magnetic resonance velocimetry (MRV) data were made. In addition to the qualitative depiction of such planar vortical patterns, a regime map has also been presented. The phase dependence of the secondary flow structures under physiological flow conditions and the concomitant 3D nature of these vortical patterns required the full resolution of the flow field achieved by MRV techniques.
Highly Efficient Probabilistic Finite Element Model Updating Using Intelligent Inference With Incomplete Modal Information
Authors: Zhou K. , Tang J.
Published: July 2016

A highly efficient probabilistic framework of finite element model updating in the presence of measurement noise/uncertainty using intelligent inference is presented. This framework uses incomplete modal measurement information as input and is built upon the Bayesian inference approach. To alleviate the computational cost, Metropolis–Hastings Markov chain Monte Carlo (MH MCMC) is adopted to reduce the size of samples required for repeated finite element modal analyses. Since adopting such a sampling technique in Bayesian model updating usually yields a sparse posterior probability density function (PDF) over the reduced parametric space, Gaussian process (GP) is then incorporated in order to enrich analysis results that can lead to a comprehensive posterior PDF. The PDF obtained with densely distributed data points allows us to find the most optimal model parameters with high fidelity. To facilitate the entire model updating process with automation, the algorithm is implemented under ansys Parametric Design Language (apdl) in ansys environment. The effectiveness of the new framework is demonstrated via systematic case studies.
Stability of Two-Immiscible-Fluid Systems: A Review of Canonical Plane Parallel Flows
Authors: Mohammadi Alireza , Smits Alexander J.
Published: July 2016

A brief review is given on the stability of two-fluid systems. Our interest is primarily driven by drag reduction using superhydrophobic surfaces (SHS) or liquid-infused surfaces (LIS) where the longevity and performance strongly depends on the flow stability. Although the review is limited to immiscible, incompressible, Newtonian fluids with constant properties, the subject is rich in complexity. We focus on three canonical plane parallel flows as part of the general problem: pressure-driven flow, shear-driven flow, and flow down an inclined plane. Based on the linear stability, the flow may become unstable to three modes of instabilities: a Tollmein–Schlichting wave in either the upper fluid layer or the lower fluid layer, and an interfacial mode. These instabilities may be further categorized according to the physical mechanisms that drive them. Particular aspects of weakly nonlinear analyses are also discussed, and some directions for future research are suggested.
Verification and Validation in Fluids Engineering: Some Current
Issues
Authors: Roache Patrick J.
Published: July 2016

The following current issues in verification and validation (V&V) are discussed: probability bounds analysis (PBA) versus the traditional probability distribution function (PDF) approach as used in the ANSI Standard document ASME V&V 20-2009; strict frequentist versus Bayesian approaches; model form uncertainty (and confusion) in prediction versus validation; Popper's philosophical falsificationism versus common sense; climate model trend validations versus climate change deniers; and V&V state of the art versus practice. Also, the many fundamental contributions to modern V&V practice in the history of the ASME Fluids Engineering Division and the Journal of Fluids Engineering (JFE) are described.
Cityplot: Visualization of High-Dimensional Design Spaces With Multiple Criteria
Authors: Knerr Nathan , Selva Daniel
Published: July 2016

In the early-phase design of complex systems, a model of design performance is coupled with visualizations of competing designs and used to aid human decision-makers in finding and understanding an optimal design. This consists of understanding the tradeoffs among multiple criteria of a “good” design and the features of good designs. Current visualization techniques are limited when visualizing many performance criteria and/or do not explicitly relate the mapping between the design space and the objective space. We present a new technique called Cityplot, which can visualize a sample of an arbitrary (continuous or combinatorial) design space and the corresponding single or multidimensional objective space simultaneously. Essentially a superposition of a dimensionally reduced representation of the design decisions and bar plots representing the multiple criteria of the objective space, Cityplot can provide explicit information on the relationships between the design decisions and the design criteria. Cityplot can present decision settings in different parts of the space and reveal information on the decision → criteria mapping, such as sensitivity, smoothness, and key decisions that result in particular criteria values. By focusing the Cityplot on the Pareto frontier from the criteria, Cityplot can reveal tradeoffs and Pareto optimal design families without prior assumptions on the structure of either. The method is demonstrated on two toy problems and two real engineered systems, namely, the NASA earth observing system (EOS) and a guidance, navigation and control (GNC) system.
Experimental Results on Lamellar-Type Solid Lubricants in Enhancing Minimum Quantity Lubrication Machining
Authors: Kien Nguyen Trung , Park Kyung-Hee , Kwon Patrick Y.
Published: July 2016

This paper studies the effect of various lamellar-type solid lubricants (graphite and hBN) that can be mixed into a lubricant to potentially improve the machinability of minimum quantity lubrication (MQL) machining. To examine this, the solid lubricants are classified into particles and platelets based on their aspect ratios as well as their respective sizes. In particular, the particles are classified into microparticles and nanoparticles based on their dimensions (average radius), while the platelets were classified, based on their average thickness, into two types: the “microplatelets” if the thickness is typically up to few tens of microns and the “nanoplatelets” if the thickness is well below a tenth of a micron (even down to few nanometers). Our previous work has shown that the mixture of an extremely small amount (about 0.1 wt. %) of the graphitic nanoplatelets and vegetable oil immensely enhanced the machinability of MQL machining. In this paper, many lubricants, each mixed with a particular variety of nano- or micro-platelets or one type of nanoparticles, were studied to reveal the effect of each solid lubricant on MQL machining. Prior to the MQL machining experiment, the tribological test was conducted to show that the nanoplatelets are overall more effective than the microplatelets and nanoparticles in minimizing wear despite of no significant difference in friction compared to pure vegetable oil. Consequently, the MQL ball-milling experiment was conducted with AISI 1045 steel yielding a similar trend. Surprisingly, the oil mixtures with the microplatelets increased flank wear, even compared to the pure oil lubricant when the tools with the smooth surface were used. Thus, the nanoscale thickness of these platelets is a critical requirement for the solid lubricants in enhancing the MQL machining process. However, maintaining the nanoscale thickness is not critical with the tools with the rough surfaces in enhancing the MQL process. Therefore, it is concluded that finding an optimum solid lubricant depends on not only the characteristics (material as well as morphology) of solid lubricants but also the characteristic of tool surface.
Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions
Authors: Sullivan-Lewis Elliot , McDonell Vincent
Published: July 2016

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.
Helical Axis Data Visualization and Analysis of the Knee Joint Articulation
Authors: Millán Vaquero Ricardo Manuel , Vais Alexander , Dean Lynch Sean , Rzepecki Jan , Friese Karl-Ingo , Hurschler Christof , Wolter Franz-Erich
Published: July 2016

We present processing methods and visualization techniques for accurately characterizing and interpreting kinematical data of flexion–extension motion of the knee joint based on helical axes. We make use of the Lie group of rigid body motions and particularly its Lie algebra for a natural representation of motion sequences. This allows to analyze and compute the finite helical axis (FHA) and instantaneous helical axis (IHA) in a unified way without redundant degrees of freedom or singularities. A polynomial fitting based on Legendre polynomials within the Lie algebra is applied to provide a smooth description of a given discrete knee motion sequence which is essential for obtaining stable instantaneous helical axes for further analysis. Moreover, this allows for an efficient overall similarity comparison across several motion sequences in order to differentiate among several cases. Our approach combines a specifically designed patient-specific three-dimensional visualization basing on the processed helical axes information and incorporating computed tomography (CT) scans for an intuitive interpretation of the axes and their geometrical relation with respect to the knee joint anatomy. In addition, in the context of the study of diseases affecting the musculoskeletal articulation, we propose to integrate the above tools into a multiscale framework for exploring related data sets distributed across multiple spatial scales. We demonstrate the utility of our methods, exemplarily processing a collection of motion sequences acquired from experimental data involving several surgery techniques. Our approach enables an accurate analysis, visualization and comparison of knee joint articulation, contributing to the evaluation and diagnosis in medical applications.
Early-Age Stress and Pressure Developments in a Wellbore Cement Liner: Application to Eccentric Geometries
Authors: Petersen Thomas , Ulm Franz-Josef
Published: July 2016

This paper introduces a predictive model for the stress and pressure evolutions in a wellbore cement liner at early ages. A pressure state equation is derived that observes the coupling of the elastic changes of the solid matrix, the eigenstress developments in the solid and porespaces, and the mass consumption of water in course of the reaction. Here, the transient constitution of the solid volume necessitates advancing the mechanical state of the poroelastic cement skeleton incrementally and at constant hydration degree. Next, analytic function theory is employed to assess the localization of stresses along the steel–cement (SC) and rock–cement (RC) interfaces by placing the casing eccentrically with respect to the wellbore hole. Though the energy release rate due to complete debonding of either interface is only marginally influenced by the eccentricity, the risk of evolving a microcrack along the thick portion of the sheath is substantially increased. Additionally, it is observed that the risk of microannulus formation is principally affected by the pressure rebound, which is engendered by the slowing reaction rate and amplified for rock boundaries with low permeability.
Measurements of Decompression Wave Speed in Binary Mixtures of Carbon Dioxide and Impurities
Authors: Botros K. K. , Geerligs J. , Rothwell B. , Robinson T.
Published: July 2016

Shock tube tests were conducted on a number of binary CO2 mixtures with N2, O2, CH4, H2, CO, and Ar impurities, from a range of initial pressures and temperatures. This paper provides examples of results from these tests. The resulting decompression wave speeds are compared with predictions made utilizing different equations of state (EOS). It was found that, for the most part (except for binaries with H2), the GERG-2008 EOS shows much better performance than the Peng–Robinson (PR) EOS. All binaries showed a very long plateau in the decompression wave speed curves. It was also shown that tangency of the fracture propagation speed curve would normally occur on the pressure plateau, and hence, the accuracy of the calculated arrest toughness for pipelines transporting these binary mixtures is highly dependent on the accuracy of the predicted plateau pressure. Again, for the most part, GERG-2008 predictions of the plateau are in good agreement with the measurements in binary mixtures with N2, O2, and CH4. An example of the determination of pipeline material toughness required to arrest ductile fracture is presented, which shows that prediction by GERG-2008 is generally more conservative and is therefore recommended. However, both GERG-2008 and PR EOS show much worse performance for the other three binaries: CO2 + H2, CO2 + CO, and CO2 + Ar, with CO2 + H2 being the worst. This is likely due to the lack of experimental data for these three binary mixtures that were used in the development of these EOS.
The Welded Joint Strength Reduction Factors of Modified 9Cr–1Mo Steel for the Advanced Loop-Type Sodium Cooled Fast Reactor
Authors: Yamashita Takuya , Wakai Takashi , Onizawa Takashi , Satoh Kenichiro , Yamamoto Kenji
Published: July 2016

Creep strength enhanced ferritic (CSEF) steels including ASME Gr.91 are widely used in fossil power plants. In the advanced loop-type sodium-cooled fast reactor (SFR), modified 9Cr–1Mo steel (ASME Gr.91) is going to be adopted as a structural material. Modified 9Cr–1Mo steel was registered in the Japan Society of Mechanical Engineers (JSME) code as a new structural material for SFRs in the year 2012. The creep-rupture curve of the base metal of this steel was standardized using region splitting analysis method. According to this method, creep-rupture data were divided into two regions, high-stress and low-stress regimes, and those regions were individually evaluated by regression analyses with the Larson–Miller parameter (LMP). The difference in the creep failure mechanisms between the high-stress and low-stress regions was considered in this method. The boundary between these regions was half of the 0.2% proof stress of the base metal at the corresponding temperature. In the modified 9Cr–1Mo steel welded joint, creep strength may markedly degrade, especially in the long-term region. This phenomenon is known as “type-IV” damage due to creep voids and cracks in the fine-grained heat-affected zone (HAZ). There is no precedent for indicating the obvious creep strength degradation of welded joints under SFR temperatures (550 °C or less). Although obvious strength degradation of the welded joints has not yet been observed at 550 °C, it is fair to assume that the strength degradation will occur due to very long-term creep. Therefore, considering strength degradation due to “type-IV” damage is necessary. This paper proposes the creep-rupture curve and the welded joint strength-reduction factor (WJSRF). The creep-rupture curve of the welded joint was proposed by employing a second-order polynomial equation with LMP using region splitting analysis method, which is used for the base metal as well. The WJSRFs were proposed on the basis of design creep-rupture stress strength. The resulting allowable stress was conservative compared with that prescribed in ASME code and the Japan domestic regulation for thermal plants. In addition, the design of the hot-leg pipe in SFR was reviewed considering the WJSRFs.
Comparison of the Sensitivity to Foreign Particle Ingestion of the GE-F101 and P/W-F100 Engines to Modern Aircraft Engines
Authors: Cosher Christopher R. , Dunn Michael G.
Published: July 2016

The work described in this paper utilizes dust ingestion experimental results obtained using three Pratt/Whitney F-100, two GE F-101, one Pratt/Whitney J-57, and three Pratt/Whitney TF-33 military engines and two different combustor rigs (one utilizing a sector of the Pratt/Whitney F-100 annular combustor and the other utilizing an Allison T-56 can combustor) to scale results so that these previous experiments can be used to approximate the response of more current aircraft engines to foreign particle ingestion. Modern engines experience a combination of compression system erosion and material deposition in the combustor and on the high-pressure turbine (HPT) inlet vanes (and rotor blade complications) whereas the older engines (P/W TF-33 and J-57) experienced primarily an erosion problem as a result of the lower turbine inlet temperatures (TIT). As part of the results presented in this paper, the scaled estimates of material accumulation and component degradation have been compared to documented in-flight ash encounters, specifically KLM Flight 867, British Airways Flight 009, Qantas Flight 370, and an NASA scientific research flight. The results of the study allow one to make estimates of the time to initial issues for the RR RB-211, the GE CF-6, the GE/Snecma CFM-56, and the P/W JT9-D engines encountering dust clouds of specific concentration. Current engine certification procedures do not require any specific test condition that would approach the engine issues described in this paper.
Response Surface Optimization of an Ammonia–Water Combined Power/Cooling Cycle Based on Exergetic Analysis
Authors: García Jesús M. , Vasquez Padilla Ricardo , Sanjuan Marco E.
Published: July 2016

Finding optimal operating conditions of solar-based power and cooling systems is always a challenge. Performance of these systems is highly dependent on several important parameters, which influence not only the long-term efficiency but also its technical and economic feasibility. This paper studies the operation/configuration problem of an ammonia–water power and cooling cycle using an exergetic and statistical analysis. The Modeling developed in Matlab® and REFPROP 9.0 was used to calculate the thermodynamic properties of the ammonia–water mixture. The thermodynamic model and properties of the ammonia/water mixture were validated with previous models found in the literature. Optimal operating conditions of the combined cycle were obtained by using response surface technique and the ratio between exergetic efficiency and exergy destruction was used as response variable. The results showed that the response variable is highly influenced by the ammonia concentration, pressure ratio (PR), turbine efficiency, and pinch point temperature in the heat exchanger. Finally, the combined cycle was integrated with a solar field using two types of concentrated solar collectors.
Samarium electrodeposited acetate and oxide thin films on stainless steel substrate characterized by XPS
Authors: Myhre Kristian , Burns Jonathan , Meyer Harry , Sims Nathan , Boll Rose
Published: July 2016

Characterization of a samarium thin film deposited on a stainless steel substrate using electrodeposition was carried out with a Thermo Scientific K-Alpha X-ray photoelectron spectrometer. Two types of samarium electrodeposition samples were studied, one as-deposited and one heated to 700 °C in an air atmosphere. Survey scans include peaks coming from the stainless steel substrate, such as Fe and Cr. An x-ray photoelectron spectroscopy (XPS) survey spectrum, Sm 3d, C 1s, and O 1s narrow scans are shown. It was determined, using XPS, that the heating process decomposed the deposited Sm acetate to Sm2O3.
Fluorocarbon based atomic layer etching of Si3N4 and etching selectivity of SiO2 over Si3N4
Authors: Li Chen , Metzler Dominik , Lai Chiukin Steven , Hudson Eric A. , Oehrlein Gottlieb S.
Published: July 2016

Angstrom-level plasma etching precision is required for semiconductor manufacturing of sub-10 nm critical dimension features. Atomic layer etching (ALE), achieved by a series of self-limited cycles, can precisely control etching depths by limiting the amount of chemical reactant available at the surface. Recently, SiO2 ALE has been achieved by deposition of a thin (several Angstroms) reactive fluorocarbon (FC) layer on the material surface using controlled FC precursor flow and subsequent low energy Ar+ ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO2 from the surface. In the present article, the authors describe controlled etching of Si3N4 and SiO2 layers of one to several Angstroms using this cyclic ALE approach. Si3N4 etching and etching selectivity of SiO2 over Si3N4 were studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Surface chemistries of Si3N4 were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si3N4 has a lower physical sputtering energy threshold than SiO2, Si3N4 physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si3N4 to SiO2 ALE etching selectivity was observed for these FC depleted conditions. By optimization of the ALE process parameters, e.g., low ion energies, short ESLs, and/or high FC film deposition per cycle, highly selective SiO2 to Si3N4 etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si3N4 surfaces. This highly selective etching is explained by a lower carbon consumption of Si3N4 as compared to SiO2. The comparison of C4F8 and CHF3 only showed a difference in etching selectivity for FC depleted conditions. For FC accumulation conditions, precursor chemistry has a weak impact on etching selectivity. Surface chemistry analysis shows that surface fluorination and FC reduction take place during a single ALE cycle for FC depleted conditions. A fluorine rich carbon layer was observed on the Si3N4 surface after ALE processes for which FC accumulation takes place. The angle resolved-XPS thickness calculations confirmed the results of the ellipsometry measurements in all cases.
Effect of the addition of Si into Nb2O5 coatings on their structural, optical, and mechanical properties
Authors: Mirabal-Rojas Roberto , Muhl Stephen , Rodil Sandra E. , Camps Enrique , Lejeune Michael , Zeinert Andreas
Published: July 2016

There are many polymorphs of Nb2O5, each with interesting properties that have been explored for biomedical, photocatalytic, and optical applications. However, Nb2O5 is not generally used for mechanical applications owing to its low hardness (8 GPa). The objective of this work was to evaluate the effects resulting from the addition of silicon (Si) into the Nb2O5 structure, with the aim of increasing its hardness through the formation of a nanostructured composite coating. In this paper, the authors report the structure and mechanical properties of Nb2O5 as a function of the silicon content (0–5.5 at. %). The coatings were deposited on silicon and D2 steel substrates using a confocal-dual magnetron sputtering system using a mixture of argon and oxygen (80:20) with each magnetron (Nb and Si targets) independently driven. The coatings were annealed at 550 °C to obtain a crystalline structure. However, analysis of the optical properties indicated the persistence of a substoichiometric amorphous phase. Despite the contribution of the amorphous phase, the mechanical–tribological properties were slightly improved after Si incorporation. The hardness reached a maximum of 17.6 GPa for the samples deposited at 50 W in the Si target, coupled with a reduction in both the coefficients of friction and wear.
Compact mirror-tunable laser interference system for wafer-scale patterning of grating structures with flexible periodicity
Authors: Hung Yung-Jr , Chang Ping-Chien , Lin Yu-Nung , Lin Jia-Jin
Published: July 2016

This paper presents a novel mirror-tunable laser interference system for the wafer-scale patterning (>4-in.) of submicron grating structures with a flexible periodicity (200–1000 nm) in a compact and cost-effective manner. The proposed system guides and splits the laser beam into two expanded light beams propagating in a downward direction to be reflected by rotatable ultraviolet mirrors to produce interference patterns. The incident angle of two light beams can be controlled by rotating the mirrors until they match the targeted periodicity of the grating, without the need to reconfigure the optical paths. The fact that light polarization changes with the rotation angle of the mirrors necessitates the use of a half-wave plate along each optical path to adjust the direction of polarization perpendicular to the plane of incident light. The proposed system enables large-area fabrication and wide-range grating tunability, making it highly useful for applications that require wafer-scale patterning of submicron periodic structures, such as flexible wire-grid polarizers for displays, patterned sapphire substrates for light-emitting diodes, and Bragg gratings for distributed feedback lasers.
Acoustic Poisson-like effect in periodic structures
Authors: Titovich Alexey S. , Norris Andrew N.
Published: July 2016

Redirection of acoustic energy by 90° is shown to be possible in an otherwise acoustically transparent sonic crystal. An unresponsive “deaf” antisymmetric mode is excited by matching Bragg scattering with a quadrupole scatterer resonance. The dynamic effect causes normal unidirectional wave motion to strongly couple to perpendicular motion, analogous to the quasi-static Poisson effect in solids. The Poisson-like effect is demonstrated using the first flexural resonance in cylindrical shells of elastic solids. Simulations for a finite array of acrylic shells that are impedance and index matched to water show dramatic acoustic energy redirection in an otherwise acoustically transparent medium.
Tunable phononic crystals based on piezoelectric composites with 1-3 connectivity
Authors: Croënne Charles , Ponge Marie-Fraise , Dubus Bertrand , Granger Christian , Haumesser Lionel , Levassort Franck , Vasseur Jérôme O. , Lordereau Albert , Pham Thi Mai , Hladky-Hennion Anne-Christine
Published: July 2016

Phononic crystals made of piezoelectric composites with 1–3 connectivity are studied theoretically and experimentally. It is shown that they present Bragg band gaps that depend on the periodic electrical boundary conditions. These structures have improved properties compared to phononic crystals composed of bulk piezoelectric elements, especially the existence of larger band gaps and the fact that they do not require severe constraints on their aspect ratios. Experimental results present an overall agreement with the theoretical predictions and clearly show that the pass bands and stop bands of the device under study are easily tunable by only changing the electrical boundary conditions applied on each piezocomposite layer.
Random acoustic metamaterial with a subwavelength dipolar resonance
Authors: Duranteau Mickaël , Valier-Brasier Tony , Conoir Jean-Marc , Wunenburger Régis
Published: July 2016

The effective velocity and attenuation of longitudinal waves through random dispersions of rigid, tungsten-carbide beads in an elastic matrix made of epoxy resin in the range of beads volume fraction 2%–10% are determined experimentally. The multiple scattering model proposed by Luppé, Conoir, and Norris [J. Acoust. Soc. Am. 131(2), 1113–1120 (2012)], which fully takes into account the elastic nature of the matrix and the associated mode conversions, accurately describes the measurements. Theoretical calculations show that the rigid particles display a local, dipolar resonance which shares several features with Minnaert resonance of bubbly liquids and with the dipolar resonance of core-shell particles. Moreover, for the samples under study, the main cause of smoothing of the dipolar resonance of the scatterers and the associated variations of the effective mass density of the dispersions is elastic relaxation, i.e., the finite time required for the shear stresses associated to the translational motion of the scatterers to propagate through the matrix. It is shown that its influence is governed solely by the value of the particle to matrix mass density contrast.
Analytical analysis of slow and fast pressure waves in a two-dimensional cellular solid with fluid-filled cells
Authors: Dorodnitsyn Vladimir , Van Damme Bart
Published: July 2016

Wave propagation in cellular and porous media is widely studied due to its abundance in nature and industrial applications. Biot's theory for open-cell media predicts the existence of two simultaneous pressure waves, distinguished by its velocity. A fast wave travels through the solid matrix, whereas a much slower wave is carried by fluid channels. In closed-cell materials, the slow wave disappears due to a lack of a continuous fluid path. However, recent finite element (FE) simulations done by the authors of this paper also predict the presence of slow pressure waves in saturated closed-cell materials. The nature of the slow wave is not clear. In this paper, an equivalent unit cell of a medium with square cells is proposed to permit an analytical description of the dynamics of such a material. A simplified FE model suggests that the fluid–structure interaction can be fully captured using a wavenumber-dependent spring support of the vibrating cell walls. Using this approach, the pressure wave behavior can be calculated with high accuracy, but with less numerical effort. Finally, Rayleigh's energy method is used to investigate the coexistence of two waves with different velocities.
Focusing, refraction, and asymmetric transmission of elastic waves in solid metamaterials with aligned parallel gaps
Authors: Su Xiaoshi , Norris Andrew N.
Published: July 2016

Gradient index (GRIN), refractive, and asymmetric transmission devices for elastic waves are designed using a solid with aligned parallel gaps. The gaps are assumed to be thin so that they can be considered as parallel cracks separating elastic plate waveguides. The plates do not interact with one another directly, only at their ends where they connect to the exterior solid. To formulate the transmission and reflection coefficients for SV- and P-waves, an analytical model is established using thin plate theory that couples the waveguide modes with the waves in the exterior body. The GRIN lens is designed by varying the thickness of the plates to achieve different flexural wave speeds. The refractive effect of SV-waves is achieved by designing the slope of the edge of the plate array, and keeping the ratio between plate length and flexural wavelength fixed. The asymmetric transmission of P-waves is achieved by sending an incident P-wave at a critical angle, at which total conversion to SV-wave occurs. An array of parallel gaps perpendicular to the propagation direction of the reflected waves stop the SV-wave but let P-waves travel through. Examples of focusing, steering, and asymmetric transmission devices are discussed.
Rectus Abdominis Injury in Elite Volleyball Players
Authors: Cruz Anna R. , Mautner Kenneth
Published: July 2016

In this case series, three elite college-level female volleyball players between 21 and 22 years old experienced acute abdominal pain during an overhead swinging motion. All three athletes were diagnosed with acute rectus abdominis (RA) muscle strain using musculoskeletal ultrasound, without the need for MRI. Each athlete sustained severe RA injury resulting in substantial loss of playing time and warranted a focused rehabilitation program, which emphasized core strengthening, physical modalities, and altering athletes’ hitting technique. RA muscle strain is a relatively infrequent, yet potentially severe, injury in elite volleyball players that necessitates early diagnosis and treatment to avoid prolonged or incomplete recovery.
Hamstring and Gluteal Muscle Activation During the Assessment of Dynamic Movements
Authors: Oliver Gretchen D. , Stone Audrey , Washington Jessica
Published: July 2016

Recently, sports medicine professionals have shown interest in using dynamic movement assessments to help identify biomechanical risk factors for musculoskeletal injury. Thus the purpose of this study was to propose two movements (single leg step down and single leg lateral hop) that could predict injury and determine if these proposed movements elicited muscle activation of the hamstrings and gluteals. Surface electromyography was employed and muscle activations of the hamstrings and gluteus medius muscles were classified as strong during both the single leg step down (SLSD) and single leg lateral hop (SLLH). Both the hamstrings and gluteus medius muscles are associated with musculoskeletal injury. The SLSD and SLLH cause significantly high muscle activation of both these muscle groups and should be considered for use in dynamic movement assessments.
‘Brexit’ casts pall on future of U.K. science
Authors: Clery Daniel
Published: July 2016

Funding, freedom of movement, and a voice in Europe's science policy are all in question.
Fighting autoimmunity with immune cells
Authors: Leslie Mitch
Published: July 2016

Engineered T cells can selectively destroy sources of enemy antibodies.
CFC bans pay off as Antarctic ozone layer starts to mend
Authors: Hand Eric
Published: July 2016

Study shows hole has shrunk since 2000 thanks to restrictions on chlorine chemicals.
Scientists cheer Senate bill
Authors: Mervis Jeffrey
Published: July 2016

Long-awaited successor to COMPETES Act rejects controversial House approach to managing federal research.
South Africa's bid to end AIDS
Authors: Cohen Jon
Published: July 2016

The tools exist, but the country's epidemic—the largest in the world—won't yield easily.