bluuebunny/crossref_metadata_2025 huggingface dataset:
Invasive acacias differ from native dune species in the hyperspectral/biochemical trait space
Authors: Große‐Stoltenberg André , Hellmann Christine , Thiele Jan , Oldeland Jens , Werner Christiane
Published: January 2018

Aim

The impact of invasive species may depend on dissimilarity of their functional traits relative to the native community. Therefore, comparing species traits in a multidimensional space can help to better understand invader impacts, but novel methods are needed to effectively measure multiple traits across diverse plant communities. The main aim was to assess biochemical leaf parameters based on field spectra in a whole‐community approach. Our specific objectives were to assess (1) biochemical differentiation within the plant community, (2) accuracy of spectroscopic prediction models of biochemical parameters, and (3) ability to depict the multivariate differentiation using field spectroscopy.

Location

Mediterranean dune ecosystems, Atlantic coast, southwest Portugal.

Methods

We analysed leaf biomass of 18 species, including two invasive acacias, for C, δ13C, N, δ15N, lignin, fibre and tannin. Additionally, we collected leaf and canopy field spectra of each sampled plant. We used partial least squares (PLS) regression to predict biochemical parameters from field spectra. Further, we assessed the biochemical differentiation of the species using PCA based on wet chemically determined as well as spectroscopically predicted values.

Results

We found high biochemical variation among species and, in particular, marked trait dissimilarity between invasive Acacia spp. and native species, primarily with respect to N content. Biochemical parameters were predicted successfully based on field spectra. Prediction accuracies were particularly high with C, δ13C, N and tannin. A PCA of biochemical parameters showed that invasive Acacia spp. were distinct from native species of the same life form, but grouped with native dwarf shrubs. This pattern was accurately reproduced by a PCA using spectroscopically predicted values.

Conclusions

Invasive Acacia spp. have different leaf traits compared to native species of similar growth form. Their trait dissimilarity likely exacerbates their impacts on the ecosystem. This trait dissimilarity in leaf biochemistry can be accurately predicted with hyperspectral whole‐community models. Thus, field spectroscopy can substantially increase the spatial and temporal resolution of measurements and hence facilitate assessments of ecosystem functioning and invader impacts at ecosystem scale.
Reliability and safety of transnasal compared to conventional endoscopy for detecting oesophageal varices in cirrhotic patients
Authors: Castro Filho Elio C. , Perazzo Hugo , Guimaraes Raquel A. P. , Machado Lilian , Fernandes Flavia F. , Perez Renata M.
Published: January 2018

Background & Aims

Unsedated transnasal endoscopy may be used for detecting oesophageal varices. However, few studies evaluated feasibility and accuracy of this technique. We aimed to evaluate accuracy, interobserver agreement and safety of the transnasal ultrathin compared to conventional endoscopy in patients with cirrhosis.

Methods

This cross‐sectional study included consecutive patients referred for screening or surveillance of oesophageal varices. Patients underwent unsedated transnasal and sedated conventional endoscopies at the same day, which were recorded in a digital video file and randomly analysed by two double‐blinded endoscopists. High‐risk varices were defined by the presence of large calibre or red wale marks. Accuracy, interobserver agreement and safety of transnasal were compared to conventional endoscopy.

Results

One hundred and thirty‐three cirrhotic patients (48% male, aged of 60 ± 5, 34% Child‐Pugh B/C and 71% of cases for variceal screening) were included in the study. The prevalence of oesophageal varices and high‐risk oesophageal varices were 59% (n = 79) and 29% (n = 39) respectively. For the presence of oesophageal varices, transnasal GIE yielded sensitivity of 94% [95% Confidence Interval, CI 88‐99], specificity of 89% [81‐97] as well as positive and negative predictive value of 93% and 91% respectively. A satisfactory interobserver agreement was observed for the presence of oesophageal varices (κ = 0.89) and high‐risk varices (κ = 0.65). No serious adverse events were recorded; transnasal GIE was safe and significantly associated with lower rates of hypoxaemia (P < .0001) and hypotension (P < .0001) compared to conventional endoscopy.

Conclusions

Unsedated transnasal endoscopy was safe and had an excellent accuracy and high interobserver agreement for detecting oesophageal varices and for identifying high‐risk varices in cirrhotic patients.
The Historical Presidency: “Do Something about Life Line”: The Kennedy Administration's Campaign to Silence the Radio Right
Authors: Matzko Paul
Published: January 2018

President John F. Kennedy launched the most successful censorship campaign of the past half century. Its target was the Radio Right, an informal network of conservative broadcasters who reached millions of listeners across the country by the early 1960s. With Kennedy's encouragement, the Internal Revenue Service audited conservative broadcasters to impair their ability to raise money while the Federal Communications Commission discouraged radio stations from airing their programs. The success of the counter–Radio Right campaign contradicts postrevisionist interpretations of Kennedy as a president who grew toward greatness while in office.
“Modifiers” as Verbs: The Case of Mandarin
Authors: Lin Tzong‐Hong Jonah , Yu Jia‐Chi , Chen Tzu‐Ling
Published: January 2018

We show that some elements in Mandarin that have been considered as pre‐verbal adverbial modifiers are actually the main verbs of the sentences. Three sets of phenomena are discussed: the degreegou‘enough’ construction, the “Adv/Adv‐di” contrast, and two types of “mannerwh‐adverbs”. These phenomena make Mandarin a typologically interesting case, as it stands in contrast to languages such as English on the one hand, where adverbs are adjuncts, and to Formosan languages on the other, where manner modifiers realize as the main verb of the sentence. We also discuss the possible parameterization in grammar that is responsible for this distinction. We suggest that grammatical theory provides an option to languages, in the form of a parameter, which licenses complementation of an un‐subcategorized expressionYPto a head X, when X denotes a manner (or more generally, an event modifier) ofYP.
Effectiveness of the Lean process compared to other quality improvement initiatives on length of stay and wait times in healthcare organizations: a systematic review protocol
Authors: Honeycutt Lisa C. , Keller Sheila D.
Published: January 2018

Review question:

What is the effectiveness of the Lean process compared to other quality improvement initiatives on length of stay and wait times in healthcare organizations?
Factors influencing participation in fecal occult blood testing to screen for colorectal cancer in Australia: a scoping review protocol
Authors: Lee Simone , Miller Andrea
Published: January 2018

Review question:

The objective of this scoping review is to examine and map the evidence on the range of factors influencing a person's decision to screen or not screen for colorectal cancer using a fecal occult blood test (FOBT) in Australia, with the view to identifying gaps in the research and informing appropriate questions for future systematic reviews.

The question of this review is: what evidence is available around the barriers and facilitators that influence an individual's decision to screen or not screen for colorectal cancer using a fecal occult blood test in Australia?
Effectiveness of ultrasound-guided peripheral intravenous cannulation in pediatric patients aged under three years: a systematic review protocol
Authors: Yamagami Yuki , Ueki Shingo , Matoba Kei , Makimoto Kiyoko
Published: January 2018

Review question:

The objective of this systematic review is to identify, evaluate and synthesize evidence of effectiveness on ultrasound-guided peripheral intravenous cannulation in pediatric patients aged under three years.

Specially, the review question is: In pediatric patients aged under three years, what is the effect of ultrasound-guided peripheral intravenous cannulation on the first attempt and on the overall success rate, time to cannulation and number of attempts for successful cannulation compared with the traditional blind approach?
Investigations of Rod Positions for Treat M8CAL Analyses
Authors: Weems Zachary , Goluoglu Sedat , DeHart Mark D.
Published: January 2018

The transient reactor test facility (TREAT), a graphite moderated experimental reactor, is scheduled to restart in late 2017. There is now renewed interest in development of capabilities to model and simulate the TREAT transients using three-dimensional coupled physics. To validate existing transient analysis tools as well as those under development, several temperature-limited transients have been modeled and analyzed. These transients are from the M8 calibration (M8CAL) experiment series, a set of experiments performed to calibrate the reactor detectors for the planned M8 series of fuel tests. Detailed reactor models were prepared that were then used to calculate the pretransient and post-transient keff values as well as corresponding reactivity insertions. Alterations to modeled values of shutdown and initial transient rod insertion depths were made to better match the reported experimental values of reactivity insertions assuming just critical pretransient states. It was found that two of the altered media inputs, fuel and Zircaloy-3 cladding, had significant effects on the keff. In addition, increasing shutdown rod insertion by 3–5 cm and decreasing initial transient rod insertion by 1–2 cm gave perfect pretransient keff and total reactivity insertion values. However, the revised positions are as much as a factor of 3–20 different from reported uncertainty of 0.762 cm. This suggests that boron concentration uncertainties may play a significant role in accurately modeling the TREAT transients and should be investigated thoroughly.
Interactive Flow-Induced Vibrations of Two Staggered, Low Mass-Ratio Cylinders in the TrSL3 Flow Regime (2.5 × 104 < Re < 1.2 × 105): Smooth Cylinders
Authors: Ji Chunning , Xu Wanhai , Sun Hai , Wang Rui , Ma Chunhui , Bernitsas Michael M.
Published: January 2018

Flow-induced vibrations (FIVs) of two elastically mounted circular cylinders in staggered arrangement were experimentally investigated. The Reynolds number range for all experiments (2.5 × 104 < Re < 1.2 × 105) was in the transition in shear layer 3 (TrSL3) flow regime. The oscillator parameters selected were: mass ratio m* = 1.343 (ratio of oscillating mass to displaced fluid mass), spring stiffness K = 250 N/m, and damping ratio ζ = 0.02. The experiments were conducted in the low turbulence free surface water (LTFSW) channel in the MRELab of the University of Michigan. A closed-loop, virtual spring–damper system (Vck) was used to facilitate quick and accurate parameter setting. Based on the characteristics of the displacement response, five vibration patterns were identified and their corresponding regions in the parametric plane of the in-flow spacing (1.57 < L/D < 4.57) and transverse cylinder spacing (0 < T/D < 2) were defined. The hydrodynamic forces and frequency characteristics of the vibration response are also discussed.
Burial and Scour of Short Cylinders and Truncated Cones Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Currents
Authors: Chen Ong Muk , Myrhaug Dag
Published: January 2018

This paper provides a practical stochastic method by which the burial and scour depths of short cylinders and truncated cones exposed to long-crested (two-dimensional (2D)) and short-crested (three-dimensional (3D)) nonlinear random waves plus currents can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall second-order wave crest height distribution representing both 2D and 3D nonlinear random waves. Moreover, the formulas for the burial and the scour depths for regular waves plus currents presented by previous published work for short cylinders and truncated cones are used.
Selective Band Gap to Suppress the Spurious Acoustic Mode in Film Bulk Acoustic Resonator Structures
Authors: Serhane Rafik , Hadj-Larbi Fayçal , Hassein-Bey Abdelkader , Khelif Abdelkrim
Published: January 2018

In this work, we investigate numerically the propagation of Lamb waves in a film bulk acoustic resonator (FBAR) structure formed by piezoelectric ZnO layer sandwiched between two Mo electrodes coupled with Bragg reflectors; the system is thus considered as a phononic-crystal (PnC) plate. The aim is to suppress the first-order symmetric Lamb wave mode considered as a spurious mode caused by the establishment of a lateral standing wave due to the reflection at the embedded lateral extremities of the structure; this spurious mode is superposing to the main longitudinal mode resonance of the FBAR. The finite element study, using harmonic and eigen-frequency analyses, is performed on the section of FBAR structure coupled with the PnC. In the presence of PnC, the simulation results show the evidence of a selective band gap where the parasitic mode is prohibited. The quality factor of the FBAR is enhanced by the introduction of the PnC. Indeed, the resonance and antiresonance frequencies passed from 1000 and 980 (without PnC) to 2350 and 1230 (with PnC), respectively. This is accompanied by a decrease in the electromechanical coupling coefficient from 10.60% to 6.61%.
A Novel Method to Compute the Elastic Approach of a Hollow Roller
Authors: Liu Yankui
Published: January 2018

The elastic approach of a w roller compressed by two flat plates is a basic building block in roller bearing design. According to the theory of contact mechanics, a finite element (FE) model was established in this paper to study the contact problem of a hollow roller. Research results show that deformation of the hollow roller due to contact has a strong relationship with roller's hollowness ratio. A new equation for calculating the contact deformation of a hollow roller is proposed. In addition, it is found that the accuracy of existing calculation method for bending deformation is also worth studying, and a new equation for calculating bending deformation of a hollow roller is established by data fitting. The experimental results are also presented to support the results of this work.
Storage and Loss Characteristics of Coupled Poroviscoelastic and Hydrodynamic Systems for Biomimetic Applications
Authors: Smyth Patrick A. , Green Itzhak
Published: January 2018

Biotribology and biomechanics are evolving fields that draw from many disciplines. A natural relationship particularly exists between tribology and biology because many biological systems rely on tribophysics for adhesion, lubrication, and locomotion. This leads to many biomimetic inspirations and applications. The current study looks to mimic the function of articular cartilage in purely mechanical systems. To accomplish this goal, a novel coupling of phenomena is utilized. A flexible, porous, viscoelastic material is paired with a hydrodynamic load to assess the feasibility and benefit of a biomimetic thrust bearing. This study presents the dynamic properties of the coupled system, as determined from transient to steady operating states. The results indicate that bio-inspired bearings may have application in certain tribological systems, including biomechanical joint replacements, dampers, flexible rotordynamic bearings, and seals.
Investigation of Static and Dynamic Seal Performances of a Rubber O-Ring
Authors: Zhang Jie , Xie Jingxuan
Published: January 2018

Rubber O-rings are widely applied in the static and dynamic seals of machinery, energy, chemical, aviation, and other fields. Mechanical behavior and sealing performance of the O-ring were investigated in this paper. Effects of precompression amount, fluid pressure, friction coefficient on the static and dynamic sealing performances of the O-ring were studied. The results show that the maximum stress appears on the inside but not surface of the O-ring. The static sealing performance increases with the increasing of fluid pressure and compression amount. Reciprocating dynamic sealing performance of the rubber O-ring is different with its static sealing performance; the stress distribution and deformation are changing in reciprocating motion. Sealing performance in outward stroke is better than it in the inward stroke. Overturn of the O-ring occurs when the friction torque is greater than the torque that caused by fluid pressure in the inward stroke. Distortion, bitten, and fatigue failure are the main failure modes of the O-ring in the dynamic seal. Those results can be used in design, installation, and operation of rubber O-rings in static and dynamic seals.
Retracted: “Designing a Road-Side Wind Turbine Driven by Winds From the Moving Vehicles” [ASME 2017 International Mechanical Engineering Congress and Exposition, Volume 14: Emerging Technologies; Materials: Genetics to Structures; Safety Engineering and Risk Analysis, Tampa, Florida, USA, November 3–9, 2017, Conference Sponsors: ASME, ISBN: 978-0-7918-5849-3, Copyright © 2017 by ASME. Paper No. IMECE2017-70043, V014T07A001; 8 pages; doi: 10.1115/IMECE2017-70043]
Authors: ASME
Published: January 2018

The above referenced paper has been removed from publication. (March 10, 2020)

Copyright © 2020 by ASME
Modelling, Analyses and Optimization for Exergy Performance of an Irreversible Intercooled Regenerated Brayton CHP Plant: Part 1 — Thermodynamic Modelling and Parametric Analyses
Authors: Chen Lingen , Yang Bo , Feng Huijun , Ding Zemin
Published: January 2018

A variable-temperature heat reservoir irreversible intercooling regenerated Brayton combined heat and power (CHP) plant model is set up in this paper. The model considers the heat transfer losses in all the heat exchangers, the working substance pressure drop loss in the piping, and the expansion and compression losses in turbine and compressor. Exergy output rate and exergy efficiency are considered as the research targets, and their analytical formulae are obtained. The optimal performances are gotten by optimizing the intercooled pressure ratio and total pressure ratio. The influences of some important parameters on the performances are studied in detail. Besides, the relation of exergy output rate versus exergy efficiency is investigated, and the curve is loop-shaped one. The results indicate that optimum heat capacity rate matching between the heat reservoir and working substance, and optimum heat consumer required temperature exist respectively, which generate double-maximal exergy output rate and double-maximal exergy efficiency, respectively. The heat conductance allocation optimization of all the heat exchangers will be carried out in Part 2 of this paper.
A Numerical Study of Diffusion of Nanoparticles in a Viscous Medium During Solidification
Authors: Rahman Kazi M. , Amin M. Ruhul , Mian Ahsan
Published: January 2018

In the field of additive manufacturing process, laser cladding is widely considered due to its cost effectiveness, small localized heat generation and full fusion to metals. Introducing nanoparticles with cladding metals produces metal matrix nanocomposites which in turn improves the material characteristics of the clad layer. The strength of the laser cladded reinforced metal matrix composite are dependent on the location and concentration of the nanoparticles infused in metals. The governing equations that control the fluid flow are standard incompressible Navier-Stokes and heat diffusion equation whereas the Euler-Lagrange approach has been considered for particle tracking. The mathematical formulation for solidification is adopted based on enthalpy porosity method. Liquid titanium has been considered as the initial condition where particle distribution has been assumed uniform throughout the geometry. During the solidification process of liquid titanium, particle flow and distribution has been observed until the entire geometry solidified. A numerical model implemented in a commercial software based on control volume method has been developed that allows to simulate the fluid flow during solidification as well as tracking nanoparticles during this process. The influence of the free surface of the melt pool has a high importance on the fluid flow as well as the influence of pure natural convection. Thus both buoyancy and Marangoni convection have been considered in terms of fluid flow in the molten region. A detailed parametric study has been conducted by changing the Marangoni number, convection heat transfer coefficient, constant temperature below the melting point of titanium and insulated boundary conditions to analyze the behavior of the nanoparticle movement. With the change in Marangoni number and solidification time, a significant change in particle distribution has been observed. The influence of increase in Marangoni number results in a higher concentration of nanoparticles in some portions of the geometry and lack of nanoparticles in rest of the geometry. The high concentration of nanoparticles decrease with a decrease in Marangoni number. Furthermore, an increase in the rate of solidification time limits the nanoparticle movement from its original position which results in different distribution patterns with respect to the solidification time.
A Study of the Solids Transport Characteristics in the Non-Newtonian Fluid With Inclined Annulus
Authors: Han Sang-Mok , Woo Nam-Sub , Kim Young-Ju
Published: January 2018

During drilling, the precipitation velocity of cuttings within an annulus depends on the density, configuration, and size of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm × 30 mm) device. In this experiment, the pressure loss and the particle transport ratio were measured in upward flow of Newtonian and non-Newtonian fluids. These quantities were influenced by particle concentration within the flow, pipe rotation, flow rate, and inclination of the annulus. For both water and CMC (carboxymethylcellulose) solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become. The experimental uncertainty of this study varies from a minimum of 3% to a maximum of 9% depending on the experimental conditions.
Development of a Nonlinear, C1-Beam Finite-Element Code for Actuator Design of Slender Flexible Robots
Authors: Murakami Hidenori , Rios Oscar , Ono Takeyuki
Published: January 2018

For actuator design and motion simulations of slender flexible robots, planar C1-beam elements are developed for Reissner’s large deformation, shear-deformable, curbed-beam model. Internal actuation is mechanically modeled by a rate-form of beam constitutive relation, where actuation curvature is prescribed at each time. Geometrically, a curbed beam is modeled as a frame bundle, whereby at each point on beam’s curve of centroids a moving orthonormal frame is attached to a cross section. After a finite element discretization, a curve of centroids is modeled as a C1-curve, employing cubic shape functions for both planar coordinates with an arc-parameter. The cubic shape functions have already been utilized in linear Euler-Bernoulli beams for the interpolation of transverse displacement. To define the rotation angle of each cross section or the attitude of the moving frame, quadratic shape functions are used introducing a middle node, resulting in three angular nodal displacements. As a result, each beam element has total eleven nodal coordinates.

The implementation of a nonlinear finite element code is facilitated by the principle of virtual work, which yields Reissner’s large deformation curbed beam model as the Euler-Lagrange equations. For time integration, the Newmark method is utilized.

Finally, as applications of the code, a few inchworm motions induced by different actuation curvature fields are presented.
Performance Evaluation of Asymmetric CPC-PVT Collectors Connected in Series
Authors: Nitsas M. T. , Koronaki I. P.
Published: January 2018

In this study, a series of thermal-photovoltaic collectors with hybrid reflector geometry and flat plate receiver is investigated experimentally and analytically through fundamental equations regarding solar collectors. The series of five compound parabolic thermophotovoltaic collectors are located in Athens, Greece and the experiments took place in June at open circuit state, i.e. the collectors were not electrically connected. The developed model combines optical and thermal analysis. The main objective of this study is to determine the thermal and the exergetic performance of the collectors under various operating conditions. For these reasons, the developed model is validated with the respective experimental data and afterwards, the solar collector model is examined parametrically for different tilt angles. The experiments are performed with water as heat transfer fluid and for low temperature levels up to 60°C. The final results proved that the investigated solar collectors are able to produce about 2.8 kW useful heat for low working fluid mass flow rates exhibiting at the same time an exergetic efficiency of nearly 1.4%. Also, the results of the developed model showed that the maximization of the produced thermal energy during summer occurs at a tilt angle of 10°.
Molecular Dynamics Investigation of Phase Change Induced by Ultrafast Laser Irradiation
Authors: Ji Pengfei , Rong Yiming , Zhang Yuwen , Tang Yong
Published: January 2018

Irradiated by ultrafast laser pulse, the phase change phenomena in aluminum film are investigated via molecular dynamics simulation. The embedded-atom method potential is employed to describe atomic interactions. The laser heating is modeled by adding a kinetic energy term to the laser pulse irradiated atom at each time step. The resolidification is realized by thermal conduction to cool down locally melted atoms. The temporal and spatial distribution of atomic motion is recorded to compute the temperature evolution and structure change during melting and resolidification processes. The interface between solid and liquid is identified via Ackland analysis. Due to the temperature difference, diffraction profile of the resolidified aluminum is found different from the aluminum before laser irradiation. The simulation results provide helpful information on the atomic scale temperature variation and structure transformation underlying ultrafast laser induced phase change.
Numerical Investigation of a Tunnel Fire Under Longitudinal Ventilation
Authors: Stokos Konstantinos G. , Lygidakis Georgios N. , Nikolos Ioannis K. , Tsangaris Sokrates
Published: January 2018

A numerical investigation was performed, applying a relatively recently developed in-house academic solver against a fire case in a tunnel with longitudinal ventilation. In particular, two such test cases were encountered, whose differences are focused on the ventilation velocity, as well as on the heat release rate of the imposed heat source. The proposed methodology considers the solution of the Navier-Stokes and energy equations in conjunction with a finite-volume radiative heat transfer method and a wall conduction model. In that way the most important aspects of fire phenomena in tunnels are taken into account and, consequently, a more realistic simulation of them is succeeded. The predicted results (temperature profiles downstream the heat source, back-layering lengths, flame angles, etc.) were compared satisfactorily with those of corresponding numerical simulations and available experimental data, demonstrating the equal potential of the proposed solver for such test cases, despite different methodologies were followed. Moreover, the contribution of the aforementioned radiation and wall conduction modeling to the final solution was thoroughly examined. The incorporation of these models is revealed of crucial importance for the extraction of realistic temperature profiles and backflows, while the same does not apply for the prediction of the flame angles.
Flexible, User- and Product-Centered Framework for Developing Frugal Products Based on a Case Study of a Vehicle for Sub-Saharan Africa
Authors: Šoltés Martin , Kappler Daniel , Koberstaedt Sascha , Lienkamp Markus
Published: January 2018

Through design thinking, a team of researchers and students from Nigeria, Ghana and Germany has identified rural transportation as a key enabler for addressing the most pressing challenges in the developing world. Since 2013, the team has been working together on designing a new vehicle concept for Sub-Saharan Africa.

The aim of the project is to provide the rural population in Sub-Saharan Africa with an attractive mobility concept that helps to prevent the rural exodus and strengthens the independence of the rural regions. A promising concept must consider the specific market requirements and the resources available locally in order to address the heart of the problem as a “First Mile Vehicle”.

This paper aims to introduce a holistic framework for frugal innovation and to analyze the process of deriving the vehicle concept meeting regional requirements until it is ready for serial production. The focus, therefore, is demand-driven development of a multifunctional electric vehicle that primarily provides mobility for the individual and transport of people and goods as a possible commercial basis.

The result of the research and design process is a vehicle concept that meets the needs of the people living in rural areas of Sub-Saharan Africa. The first fully functional prototype of this vehicle was presented to the public at the Technical University of Munich in May 2016.
Evaluation of Pulmonary Arterial Hypertension Using Computational Fluid Dynamics Simulation
Authors: Taherian Shahab , Rahai Hamid , Shin Jamie , Feldman Jeremy , Waddington Thomas
Published: January 2018

In silico study of the relationships between flow conditions, arterial surface shear stress, and pressure was investigated in a patient with pulmonary arterial hypertension (PAH), using multi-detector Computed Tomography Angiography (CTA) images and Computational Fluid Dynamics (CFD). The CTA images were converted into 3D models and transferred to CFD software for simulations, allowing for patient-specific comparisons between in silico results with clinical right heart catheterization pressure data. The simulations were performed using two different methods of outlet boundary conditions: zero traction and lumped parameter model (LPM) methods. Outlet pressures were set to a constant value in zero traction method, which can produce flow characteristics solely based on the segmented distal arteries, while the lumped parameter model used a three-element Windkessel lumped model to represent the distal vasculature by accounting for resistance, compliance, and impedance of the vasculature. Considering existing limitations with both approaches, it was found that the lumped parameter Windkessel outlet boundary condition provides a better correlation with the clinical RHC pressure results than the zero traction constant pressure outlet boundary condition.
An Empirical Prediction Law for Quasi-Static Nail-Particle Board Penetration Resistance
Authors: Nili Ahmadabadi Zahra , Laville Frédéric , Guilbault Raynald
Published: January 2018

The present study belongs to a broader investigation aiming to reduce noise emissions in nail guns. This noise reduction objective may be achieved by nail gun concept design improvements. However, modifying the tool design requires precise understanding of it dynamics. Therefore a dynamic model of the system including accurate predictions of the tribo-dynamic interactions at the wood-nail interface generating the penetration resistance forces (PRF) appears to be essential. Since different wood products possess different structural/material properties, PRF is first evaluated for various types of wood product individually. Ref. [1] develops the PRF modeling strategy and examines the nail penetration process for plywood samples. The present paper proposes an empirical model predicting PRF imposed on nails when penetrating particle board (PB) at quasi-static velocities (20–500 mm/min range). A universal testing machine (MTS) is used to drive the nails into the wood samples. Each wood sample is composed of five panels PB screwed together. The sample size is chosen to reduce the boundary influence on the penetration process and to avoid the complete perforation of the sample. To eliminate the possible acceleration influence, the penetration speed is maintained at constant amplitudes. The MTS machine measured PRF as a function of the position. The objective is to prepare a formulation predicting PRF as a function of nail position. In order to extend the prediction formula application range, the analysis reduces the studied factors to dimensionless parameters. The analysis shows that the PB fabrication process results in panels presenting three regions of different hardness modulus. As a result, at the region transitions the PRF curves show large amplitude fluctuations. This layered heterogeneity makes the development of a high precision prediction model representing various nail sizes very difficult. Nevertheless, the final model produces PRF evaluations with overall precision greater than 88% for most of the nail penetration.
Study on Coal Particle Combustion Characteristics and NO Emission in a Hot Laminar Gas Flow
Authors: Gu MingYan , Yan Dawei , He XianHui , Yan Dan , Liu FengShan , Chu HuaQiang
Published: January 2018

The combustion and NO formation characteristics of coal particles of different size distributions in a laminar gas flow were investigated by numerical simulation. The variation of coal particle size distribution was obtained by changing the mass ratio of small-sized coal to large-sized coal. The gas-phase combustion was modeled using GRI-Mech 3.0. The particle motion was simulated using a trajectory model. The results show that the coal particle size distribution has a significant impact on combustion process and NO distribution. Coal particles of uniform size at either 105 or 75 μm results in a higher NO concentration than coal consisting of both the large and the small particles. The smaller-sized coal particles experience a rapid volatile release, a higher maximum gas temperature, and a higher maximum NO concentration. Increasing the mass ratio of the smaller-sized coal particles changes the gas temperature and the averaged NO distribution and lowers the maximum NO concentration.
Creep-Damage-Induced Deterioration of the Strength of Ni-Base Superalloy due to the Change of its Microstructure
Authors: Sakamoto Hayato , Suzuki Ken , Miura Hideo
Published: January 2018

Ni-base superalloys are widely used for various power plants and jet engines. Since the operating temperature of thermal plants and equipment has been increasing to improve their thermal efficiency for decreasing the emission of carbon-dioxide, the initially designed microstructure was found to change gradually during their operation. Since this change of microstructure should deteriorate the strength of the materials, sudden unexpected fracture should occur during the operation of the plants and equipment. Therefore, it is very important to clarify the dominant factor of the change of the microstructure and the relationship between the microstructure and its strength for assuring the stable and reliable operation of the plants and equipment. In this study, the change of the strength of a grain and a grain boundary of Ni-base superalloys caused by the change of their microstructure was measured by using a micro tensile test system in a scanning ion microscope. A creep test was applied to bulk alloys at elevated temperatures and a small test sample was cut from the bulk alloy with different microstructure caused by creep damage by using focused ion beams. The test sample was fixed to a silicon beam and a micro probe, respectively, by tungsten deposition. Finally, the test sample was thinned to 1μm and the sample was stretched to fracture at room temperature. The change of the order of atom arrangement of the sample was evaluated by applying electron back-scatter diffraction (EBSD) analysis quantitatively. In this study, the quality of grains in Ni-base superalloys was analyzed by using image quality (IQ) value calculated by using Hough transform of the observed Kikuchi pattern. It was found that the order of atom arrangement was deteriorated monotonically during the creep tests and this deterioration corresponded to the change of the microstructure clearly. Both the yield strength and the ultimate tensile strength of a grain in the alloys decreased drastically with the change of the microstructure, in other words, the IQ value of the grains. There was a clear relationship between the IQ value of a grain and its strength. Therefore, this IQ value is effective for evaluating the crystallinity of the alloys and the remained strength of the damaged alloys. The change of the microstructure was dominated by the strain-induced anisotropic accelerated diffusion of component elements of the alloys and the activation energy of the diffusion was determined quantitatively as a function of temperature and the applied stress.
Effect of Inclination on Heat Transfer in Large Flattened-Tube Steam Condensers
Authors: Davies William A. , Kang Yu , Hrnjak Pega , Jacobi Anthony M.
Published: January 2018

An experimental study of convective steam condensation inside a large, inclined, flattened-tube air-cooled condenser for power plants is presented. This is the second of a two-part study. The first part presents pressure drop and visualization results, while this study presents the experimental method along with heat transfer results.

The condenser in this study is steel with brazed aluminum fins. The condenser measures 10.72m in length, with a cross section of 214 mm × 18 mm. The condenser tube was cut in half lengthwise and covered with a polycarbonate viewing window in order to provide visualization access simultaneously with the heat transfer measurements. Inlet steam mass flux ranged from 6.2–9.5 kg m−2 s−1, and condenser capacity varied from 25–31 kW. The angle of inclination was varied from horizontal to 75° downward. The experiments were performed with a uniform fin-face velocity of crossflowing air at 2.2 m/s.

Condenser capacity was found to increase linearly with increasing downward inclination angle of the condenser, at a rate of 0.048% per degree of inclination below horizontal. This improvement was found to be the result of improved drainage and increased void fraction near the condenser outlet.
Design for Disassembly Method As Sustainable Product Evaluation Tool: Example of Underground Escalator
Authors: Shetty Devdas , Xu Jiajun
Published: January 2018

Sustainable design and manufacturing considers a product’s full life cycle and the impact that its design, manufacture, use, and retirement can have not only on business but also the environment and society. Designers are becoming steadily aware of this problem, and are employing techniques that allow them to design with greater responsibility – Sustainable Product Design; in particular, the Design for Disassembly (DFD) is recommended as a technique of sustainable product design. In the case of a durable good with a long-life cycle or a product with parts subject to wear, maintainability/serviceability may be more important than initial product acquisition cost, and the product must be designed for easy maintenance. The DFD principles identify the ease with which products can be fabricated, maintained, serviced, and recycled.

This paper examines and identifies a “Rating Chart” technique which can be used to evaluate DFD. It is demonstrated through a case study of underground escalator housing, in which different types of failure modes and defects occur in the major components of escalator drive systems, such as the motor and its drive chain system, handrail and its drive system, bearings/lubrication systems that are in adjunct with the bearing shaft assembly. Through the Rating Chart method proposed for DFD, the deficiency of the original design of escalator drive system was accessed and compared with the proposed sustainable design approach, in which the product maintainability can be significantly improved and the maintenance time can be greatly reduced. The paper concludes by showing the importance of sustainable product design for products working under extreme working conditions.
Design and Optimization of a Highly Sensitive and Linearity Piezoresistive Pressure Sensor Based on a Combination of Cross Beam-Peninsula-Membrane Structure
Authors: Anh Vang Tran , Zhang Xianmin , Zhu Benliang
Published: January 2018

The sensitivity and linearity trade-off problem has become the hotly important issues in designing the piezoresistive pressure sensors. To solve these trade-off problems, this paper presents the design, optimization, fabrication, and experiment of a novel piezoresistive pressure sensor for micro pressure measurement based on a combined cross beam - membrane and peninsula (CBMP) structure diaphragm. Through using finite element method (FEM), the proposed sensor performances as well as comparisons with other sensor structures are simulated and analyzed. Compared with the cross beam-membrane (CBM) structure, the sensitivity of CBMP structure sensor is increased about 38.7 % and nonlinearity error is reduced nearly 8%. In comparison with the peninsula structure, the maximum non-linearity error of CBMP sensor is decreased about 40% and the maximum deflection is extremely reduced 73%. Besides, the proposed sensor fabrication is performed on the n-type single crystal silicon wafer. The experimental results of the fabricated sensor with CBMP membrane has a high sensitivity of 23.4 mV/kPa and a low non-linearity of −0.53% FSS in the pressure range 0–10 kPa at the room temperature. According to the excellent performance, the sensor can be applied to measure micro-pressure lower than 10 kPa.
Analysis of the Capsizing of a Tanker in the Rhine River
Authors: Otremba Frank , Romero Navarrete José Antonio
Published: January 2018

River transportation conveys economic advantages to industry, when it is compared with road transportation. River vessels transport different types of cargoes that are critical for many industrial processes. Watercrafts can suffer different types of mishaps, including sinking and capsizing. The consequences of such events can be costly from the human and economic perspectives. In this context, a major economic consequence can be the closure of any navigation activities in this type of infrastructure. This situation was observed in the Rhine river in 2011, when a river tanker capsized and provoked the closure of the river for some weeks. Based upon the report of this accident, in this paper a simplified model is proposed to analyze such mishap, to reinforce the conclusions conveyed in the report about the contributing factors for this accident. In particular, the crucial effects associated to the dynamic interaction of the liquid cargo and the ship.
Risk Assessment of Energy Systems Exposed to Climate Change Induced Stresses: A Systematic Framework
Authors: Modarres Mohammad , Pourgol-Mohammad Mohammad
Published: January 2018

This paper discusses conceptual engineering approaches to assessment of risk to energy systems from global climate change. It is critical for energy system stakeholders, especially nuclear sector, to identify and manage the vulnerabilities of energy systems to climate change and exposure to extra stresses. This paper provides an overview of the risk assessment framework applicable to safety, health and widespread prolonged loss of electric power risks, along with examples of tool and techniques used. Two major concerns are gradual climate change risks and short-term sustained weather extremes that may be endured by the energy systems. Risk assessment and management techniques (qualified and quantified) are discussed for both of these conditions. For the long-term gradual climate change, the physics-of-failure approach is proposed to quantify the risks of slow but extensive degradation of critical equipment and structures of the energy systems. For faster evaluation, the qualified methods like FMEA, HAZOP and simpler quantified methods like layer of protection analysis (LOPA) are recommended. Resilience of the energy system is potentially analyzed by estimation of the system risk due to the impacts of climate change. Because climate change can create conditions that will negatively impact the energy sector, resilience becomes increasingly important. The paper also proposes the risk margin approach and stress-strength failure modeling technique as two possible methods of analyzing short-term sustained extreme weather conditions considering the built-in capabilities and safety margins of human operators, components and structures. Energy systems with small or no extra margin for safe production of power will be most vulnerable to adverse exposures from weather extremes potentially created by global and ecological changes. The assessments are accompanied with the uncertainty of various sources.
The Expansion and Drainage Characteristics of AFFF in Low-Pressure Environment
Authors: Sun Qiang , Liu Quanyi , Chen Xiantao , Wang Mingwu , He Yuanhua
Published: January 2018

Tests are conducted in a low-pressure combustion chamber of 3 × 2 × 4.65m3 in volume to investigate the effect of low pressure on the drainage and expansion characteristics of AFFF (Aqueous Film-Forming Foam). A manipulator equipment with the frequency of 4 Hz and the amplitude of 32cm is designed for the foaming of AFFF in the chamber. The parameters of expansion and drainage ratio are obtained under two different ambient pressure of 101kPa and 30kPa. Two fluorocarbon surfactants contained commercial AFFF (AFFF1 is type of 3% and AFFF2 is the type of 6%) that were used in precious studies are both diluted into different quality percentage resolutions, and then achieve foaming in a 130ml measuring cylinder with a cone bottom. The foaming expansion ratio and drainage time are obtained based on the recorded videos. Experimental results show that the expansion ratio of both AFFF1 and AFFF2 resolutions (the expansion ratio <6) is lower under the pressure of 30kPa than that under 101kPa. The drainage time (25% and 50%) of AFFF1 is increasing in the lower pressure environment. On the contrary, 50% drainage time of AFFF2 is shorter under 30kPa than that under 101kPa, but 25% drainage time of AFFF2 is almost the same under two ambient pressures. The variations under low pressure environment are obvious and various from each other, but the further tests should be conducted to reveal and explore the mechanism.