bluuebunny/crossref_metadata_2025 huggingface dataset:
Engineering of a modular and synthetic phosphoketolase pathway for photosynthetic production of acetone from CO2 in Synechococcus elongatus PCC 7942 under light and aerobic condition
Authors: Chwa Jun‐Won , Kim Wook Jin , Sim Sang Jun , Um Youngsoon , Woo Han Min
Published: February 2016

Capture and conversion of CO2 to valuable chemicals is intended to answer global challenges on environmental issues, climate change and energy security. Engineered cyanobacteria have been enabled to produce industry‐relevant chemicals from CO2. However, the final products from cyanobacteria have often been mixed with fermented metabolites during dark fermentation. In this study, our engineering of Synechococcus elongatus PCC 7942 enabled continuous conversion of CO2 to volatile acetone as sole product. This process occurred during lighted, aerobic culture via both ATP‐driven malonyl‐CoA synthesis pathway and heterologous phosphoketolase (PHK)‐phosphotransacetylase (Pta) pathway. Because of strong correlations between the metabolic pathways of acetate and acetone, supplying the acetyl‐CoA directly from CO2 in the engineered strain, led to sole production of acetone (22.48 mg/L ± 1.00) without changing nutritional constraints, and without an anaerobic shift. Our engineered S. elongatus strains, designed for acetone production, could be modified to create biosolar cell factories for sustainable photosynthetic production of acetyl‐CoA‐derived biochemicals.
Lead Levels in Landfill Areas and Childhood Exposure: An Integrative Review
Authors: Kim M. Angela , Williams Kimberly A.
Published: February 2016

Objective

Landfills are high‐risk areas for environmental lead exposure for children living in poverty stricken areas in many countries. This review examines landfills and lead toxicity in children. The review discusses the effects of lead toxicity, provides evidenced based recommendations to reduce lead exposure, and identify gaps in the evidence.

Design and Sample

A database search was conducted of articles in English from 1985 to 2014. Ten articles met the inclusion criteria. The Whittemore and Knafl framework and the John Hopkins Research Evidence Appraisal Tool© were used for reviewing the data.

Results

Elevated blood lead levels (BLLs) of children living near landfills were related to increased soil lead levels. Toxic effects of lead included adverse outcomes such as encephalopathy or death for children. Different approaches to decrease lead level include environmental surveillance, BLL screening, and soil abatement which are costly.

Conclusion

Increased BLL through environmental exposure is connected with poor health outcomes and death among children. Evidence‐based prevention included monitoring and screening and costly soil abatement. It is recommended that future studies focus on community education for exposure avoidance for children living near landfill areas.
Personality or Role? Comparisons of Turkish Leaders Across Different Institutional Positions
Authors: Cuhadar Esra , Kaarbo Juliet , Kesgin Baris , Ozkececi‐Taner Binnur
Published: February 2016

Personality approaches to politics are often criticized for not examining the effect that institutional role constraints have on individual beliefs and preferences. When leaders appear to change their stance when they change roles, it is assumed that roles have a determining influence. Modern personality theory and contemporary sociological role theory, however, view the effects of roles as interacting with agents’ personalities. In this article, we investigate this question by comparing personality profiles of three Turkish leaders (Özal, Demirel, and Gül) during their tenure as prime minister and during their subsequent time as president. For Gül, we perform an additional comparison during his time as foreign minister. The personality profiles are in the form of quantitative scores generated from machine‐coded content analysis of leaders’ words using the Leadership Trait Analysis method. We hypothesize that different leaders will be more susceptible to changing role contexts, depending on core personality traits, and that different traits are more likely to change with new roles. Overall, our results suggest that leaders’ traits are fairly resistant to changes across roles and that task orientation is the most likely trait to change as leaders adapt to different role demands and expectations. This study makes a contribution to our understanding of the interaction between personality and political contexts by offering specific theoretically derived hypotheses and by empirically and statistically examining a preliminary set of expectations that could be applied more broadly to other leaders.
The role of top‐down spatial attention in contingent attentional capture
Authors: Huang Wanyi , Su Yuling , Zhen Yanfen , Qu Zhe
Published: February 2016

It is well known that attentional capture by an irrelevant salient item is contingent on top‐down feature selection, but whether attentional capture may be modulated by top‐down spatial attention remains unclear. Here, we combined behavioral and ERP measurements to investigate the contribution of top‐down spatial attention to attentional capture under modified spatial cueing paradigms. Each target stimulus was preceded by a peripheral circular cue array containing a spatially uninformative color singleton cue. We varied target sets but kept the cue array unchanged among different experimental conditions. When participants’ task was to search for a colored letter in the target array that shared the same peripheral locations with the cue array, attentional capture by the peripheral color cue was reflected by both a behavioral spatial cueing effect and a cue‐elicited N2pc component. When target arrays were presented more centrally, both the behavioral and N2pc effects were attenuated but still significant. The attenuated cue‐elicited N2pc was found even when participants focused their attention on the fixed central location to identify a colored letter among an RSVP letter stream. By contrast, when participants were asked to identify an outlined or larger target, neither the behavioral spatial cueing effect nor the cue‐elicited N2pc was observed, regardless of whether the target and cue arrays shared same locations or not. These results add to the evidence that attentional capture by salient stimuli is contingent upon feature‐based task sets, and further indicate that top‐down spatial attention is important but may not be necessary for contingent attentional capture.
Defensive activation to (un)predictable interoceptive threat: The NPU respiratory threat test (NPUr)
Authors: Schroijen Mathias , Fantoni Simona , Rivera Carmen , Vervliet Bram , Schruers Koen , van den Bergh Omer , van Diest Ilse
Published: February 2016

Potentially life‐threatening interoceptive sensations easily engage the behavioral defensive system. Resulting fear and anxiety toward interoceptive threat are functionally distinct states that are hypothesized to play a prominent role in the etiology of panic disorder. The present study aimed to investigate whether fear‐ and anxiety‐potentiated startle responses occur to predictable and unpredictable interoceptive threat, respectively. Therefore, we modified the NPU threat test (Schmitz & Grillon, ) and replaced the aversive electrocutaneous stimulus with an aversive interoceptive stimulus (a breathing occlusion, making it briefly impossible to breathe). Healthy participants (N = 48) underwent three instructed conditions. A visual cue signaled the occlusion in the predictable condition (P), whereas another cue was unrelated to the occurrence of the occlusion in the unpredictable condition (U). The safe condition (N) also had a visual cue, but no occlusion. Both fear‐ and anxiety‐potentiated startle blink responses were observed in response to predictable and unpredictable respiratory threat, respectively. The current study presents and validates the NPU respiratory threat test (NPUr) as an ecologically valid paradigm to study both anxiety and fear in response to a panic‐relevant interoceptive threat. The paradigm allows future testing of contextual generalization, investigation of different clinical groups, and more explicit comparisons of defensive responding to interoceptive versus exteroceptive threats.
Leveraging nature's backup plans to incorporate interspecific interactions and resilience into restoration
Authors: Aslan Clare E. , Bronstein Judith L. , Rogers Haldre S. , Gedan Keryn B. , Brodie Jedediah , Palmer Todd M. , Young Truman P.
Published: February 2016

Interspecific interactions are important structuring forces in ecological communities. Interactions can be disturbed when species are lost from a community. When interactions result in fitness gains for at least one participating organism, that organism may experience reduced fitness as a result of interaction disturbance. However, many species exhibit traits that enable individuals to persist and reproduce in spite of such disruptions, resulting in resilience to interaction disturbance. Such traits can result in interaction generalization, phenotypic and behavioral plasticity, and adaptive capacity. We discuss examples of these traits and use case studies to illustrate how restoration practitioners can use a trait‐based approach to examine species of concern, identify traits that are associated with interspecific interactions and are relevant to resilience, and target such traits in restoration. Restoration activities that bolster interaction resilience could include, for example, reintroducing or supporting specific functional groups or managing abiotic conditions to reduce interaction dependence by at‐risk species (e.g. providing structural complexity offering shelter and cover). Resilience may also be an important consideration in species selection for restoration. Establishment of resilient species, able to persist after interaction disturbance, may be essential to restoring to a functioning ecological community. Once such species are present, they could help support more specialized species that lack resilience traits, such as many species of concern. Understanding the conditions under which processes linked to resilience may enable species to persist and communities to reform following interaction disturbance is a key application of community ecology to ecological restoration.
Measuring Associations of the Department of Veterans Affairs' Suicide Prevention Campaign on the Use of Crisis Support Services
Authors: Karras Elizabeth , Lu Naiji , Zuo Guoxin , Tu Xin M. , Stephens Brady , Draper John , Thompson Caitlin , Bossarte Robert M.
Published: February 2016

Campaigns have become popular in public health approaches to suicide prevention; however, limited empirical investigation of their impact on behavior has been conducted. To address this gap, utilization patterns of crisis support services associated with the Department of Veterans Affairs' Veterans Crisis Line (VCL) suicide prevention campaign were examined. Daily call data for the National Suicide Prevention Lifeline, VCL, and 1‐800‐SUICIDE were modeled using a novel semi‐varying coefficient method. Analyses reveal significant increases in call volume to both targeted and broad resources during the campaign. Findings underscore the need for further research to refine measurement of the effects of these suicide prevention efforts.
Cell cycle kinetics, apoptosis rates and gene expressions of MDR‐1, TP53, BCL‐2 and BAX in transmissible venereal tumour cells and their association with therapy response
Authors: Flórez M. M. , Fêo H. B. , da Silva G. N. , Yamatogi R. S. , Aguiar A. J. , Araújo J. P. , Rocha N. S.
Published: February 2016

Transmissible venereal tumour (TVT) generally presents different degrees of aggressiveness, which makes them unresponsive to conventional treatment protocols. This implies a progressive alteration of their biological profile. This study aimed to evaluate the cytotoxicity, cell survival, apoptosis and cell cycle alterations in TVT cell cultures subjected to treatment with vincristine. Similarly, it assessed possible implications of MDR‐1, TP53, BCL‐2, and BAX gene expressions in eight TVT primary cultures for both resistance to chemotherapy and biological behaviour. When comparing TVT cells receiving vincristine to those untreated, a statistical difference related to increased cytotoxicity and decreased survival rates, and alterations in G1 and S cell cycle phases were found but without detectable differences in apoptosis. Increased MDR‐1 gene expression was observed after treatment. The groups did not differ statistically in relation to the TP53, BAX and BCL‐2 genes. Although preliminary, the findings suggest that such augmented expression is related to tumour malignancy and chemotherapy resistance.
Diffuse leptomeningeal histiocytic sarcoma in the cerebrospinal fluid of 2 dogs
Authors: Cluzel Caroline , Aboulmali Abdelkerim Ahamat , Dugas Stéphanie , Pey Pascaline , Olive Julien , Gara‐Boivin Carolyn
Published: February 2016

Two adult male castrated dogs were evaluated for progressive paraparesis and ataxia. Neurologic examination showed severe ataxia, delayed proprioceptive placement in the pelvic limbs, pain upon palpation of the lumbar spine as well as facial paresis in one dog, and decreased withdrawal reflex of the pelvic limbs in the other dog. Magnetic resonance imaging (MRI) in both dogs showed diffuse meningeal and intramedullary lesions. However, no evidence of a mass was found. Biopsies could not be performed safely due to the location of the lesions. Cerebrospinal fluid (CSF) examination revealed an inflammatory pleocytosis associated with increased protein concentration and numerous large atypical round cells, often multinucleated. Nuclear fragmentation, micronuclei, and rare atypical mitoses were observed. Immunocytochemistry revealedCD1+andCD11c+staining, which, in concert with the morphology confirmed the diagnosis of histiocytic sarcoma (HS). Euthanasia was elected due to poor prognosis. Histopathologic examination showed diffuse spinal and meningeal infiltration withCD18+neoplastic cells, without any evidence of mass formation, which completed the diagnosis of diffuse leptomeningeal HS involving the brain and the spinal cord. Canine central nervous system (CNS) HS has been seldom reported in the literature, with only isolated cases identified on CSF cytology. The cases reported here are remarkable in describing a diffuse CNS leptomeningeal HS associated with neoplastic cells in the CSF of dogs without a tumor mass. These cases emphasize the potential critical importance of CSF analysis in providing an antemortem diagnosis of neoplasia in neurologic patients.
MULTIDETECTOR COMPUTED TOMOGRAPHIC AND LOW‐FIELD MAGNETIC RESONANCE IMAGING ANATOMY OF THE QUADRIGEMINAL CISTERN AND CHARACTERIZATION OF SUPRACOLLICULAR FLUID ACCUMULATIONS IN DOGS
Authors: Bertolini G. , Ricciardi M. , Caldin M.
Published: February 2016

Focal fluid accumulations in the supracollicular region are commonly termed quadrigeminal cysts and may be either subclinical or associated with neurologic deficits in dogs. Little published information is available on normal imaging anatomy and anatomic relationships for the canine quadrigeminal cistern. Objectives of this observational, cross‐sectional study were to describe normal quadrigeminal cistern anatomy and determine the prevalence and characteristics of supracollicular fluid accumulations in dogs. Normal descriptions were accomplished using computed tomographic (CT) cisternography in one canine cadaver, and CT and magnetic resonance imaging (MRI) studies of the brain in four prospectively recruited dogs with no evidence of intracranial disease. Prevalence and characteristics descriptions were accomplished using a retrospective review of brain CT or MRI studies performed during the period of 2005–2015. The normal quadrigeminal cistern consistently exhibited a complex H shape and was separated from the third ventricle by a thin membrane. Prevalence of supracollicular fluid accumulations (SFAs) was 2.19% among CT studies (n = 4427) and 2.2% among MRI studies (n = 626). Dogs with SFA were significantly younger than control dogs (P < 0.0001). Shih‐tzu (OR = 111.6), Chihuahua (OR = 81.1), and Maltese (OR = 27.6) breed dogs were predisposed (P < 0.0001). Among dogs with SFAs, the following three patterns were defined: (1) third ventricle (49.54%), (2) quadrigeminal cistern (13.51%), and (3) both third ventricle and quadrigeminal cistern (36.93%). Authors recommend that the term supracollicular fluid accumulation (SFA) should be used rather than the term quadrigeminal cyst to describe these focal fluid accumulations in dogs.
Design Tools for Patterned Self-Folding Reconfigurable Structures Based on Programmable Active Laminates
Authors: Peraza Hernandez Edwin A. , Hartl Darren J. , Malak Richard J. , Akleman Ergun , Gonen Ozgur , Kung Han-Wei
Published: February 2016

Engineering inspired by origami has the potential to impact several areas in the development of morphing structures and mechanisms. Self-folding capabilities in particular are necessary in situations when it may be impractical to exert external manipulations to produce the desired folds (e.g., as in remote applications such as in space systems). In this work, origami principles are utilized to allow planar sheets to self-fold into complex structures along arbitrary folds (i.e., no hinges or pre-engineered locations of folding). The sheets considered herein are composed of shape memory alloy (SMA)-based laminated composites. SMAs are materials that can change their shape by thermal and/or mechanical stimuli. The generation of sheets that can be folded into the desired structures is done using origami design software such as Tachi's freeform origami. Also, a novel in-house fold pattern design software capable of generating straight and curved fold patterns has been developed. The in-house software generates creased and uncreased fold patterns and converts them into finite element meshes that can be analyzed in finite element analysis (FEA) software considering the thermomechanically coupled constitutive response of the SMA material. Finite element simulations are performed to determine whether by appropriately heating the planar unfolded sheet it is possible to fold it into the desired structure. The results show that a wide range of self-folding structures can be folded via thermal stimulus. This is demonstrated by analyzing the folding response of multiple designs generated from freeform origami and the newly developed in-house origami design software.
Physicochemical Characterization and Pyrolysis Kinetic Study of Sugarcane Bagasse Using Thermogravimetric Analysis
Authors: Varma Anil Kumar , Mondal Prasenjit
Published: February 2016

The present study was conducted to investigate the physicochemical properties and pyrolysis kinetics of sugarcane bagasse (SB). The physiochemical properties of SB were determined to examine its potential for pyrolysis. The physiochemical properties such as proximate analysis, ultimate analysis, heating values, lignocellulosic composition, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) of SB were investigated. The pyrolysis experiments were conducted in a nonisothermal thermogravimetric analyzer (TGA) to understand the thermal degradation behavior of SB. The activation energy (Ea) of SB pyrolysis was calculated by model-free Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) methods. Average values of activation energy determined through KAS and OFW methods are found as 91.64 kJ/mol and 104.43 kJ/mol, respectively. Variation in the activation energy with degree of conversion was observed, which shows that pyrolysis is a complex process composed of several reactions. Coats–Redfern method was used to calculate the pre-exponential factor and reaction order. Conversion of SB due to heat treatment computed by using the kinetic parameters is found to be in good agreement with the experimental conversion data, and the maximum error limit between the experimental and predicted conversions is 8.5% for 5 °C/min, 6.0% for 10 °C/min, and 11.6% for 20 °C/min. The current investigation proves the suitability of SB as a potential feedstock for pyrolysis.
A Measurement Device for Online Monitoring of Total Tar in Gasification Systems
Authors: Gredinger A. , Schweitzer D. , Dieter H. , Scheffknecht G.
Published: February 2016

Tars produced during the thermal conversion of coal or especially biomass is one of the major obstacles for the application of gasification systems. They limit the use of the producer gas in engines or turbines or, in further processes like in methanization or conversion to other secondary fuels or chemicals, without further gas cleaning. The determination of the tar content with conventional methods is very time consuming and does not allow continuous online monitoring of the gas quality. One approach to avoid these drawbacks is an automatic system developed at the University of Stuttgart that monitors the tar concentration in the producer gas online and semicontinuous during the gasification process. The technique is based on a flame ionization detector (FID) difference measurement of the hydrocarbons in the producer gas, where the condensable hydrocarbons—the tars—are condensed on a suitable filter material. This work shows the further development of the measurement technique, the choice of a suitable tar filter material for the underlying difference measurement, and a first verification of the system with real producer gas at a 20 kWth bench scale gasifier.
A New Subgrid Model for the Heat and Mass Transfer Between a Hot Gas and Char Particles in Dense-Bed Reactors
Authors: Schulze S. , Nikrityuk P.
Published: February 2016

This work is devoted to the development and verification of a new intrinsic-based subgrid model for moving char particles gasifying in a hot flue gas or syngas environments consisting of CO2/H2O/CO species. The distinguishing feature of our model relative to the submodels published in the literature is that it takes into account the thermal and chemical nonequilibrium between the particle's surface and its center. Thus, our model is able to predict temperature and species gradients inside the particles. The main focus of the new submodel is to demonstrate the crucial role of intrinsic-based heterogeneous reactions in the adequate prediction of carbon conversion rates for char particles gasification in fixed-bed and fluidized-bed gasifiers. The new model is verified against steady-state, particle-resolved computational fluid dynamics (CFD)-based, three-dimensional simulations carried out for different volume fractions of solid phase in a control volume (CV). Acceptable agreement has been demonstrated. Finally, to demonstrate our new model's predictions, we carried out several unsteady simulations for different ambient temperatures and Reynolds numbers. The importance of simultaneous change of char porosity and particles size during gasification has been demonstrated for different regimes indicated by the Damköhler numbers.
Multi-objective Numerical Investigation of a Generic Airblast Injector Design
Authors: Comer Adam L. , Kipouros Timoleon , Stewart Cant R.
Published: February 2016

In combustor design for aero-engines, engineers face multiple opposing objectives with strict constraints. The trend toward lean direct injection (LDI) combustors suggests a growing emphasis on injector design to balance these objectives. Decades of empirical and analytical work have produced low-order methods, including semi-empirical and semi-analytical correlations and models of combustors and their components, but detailed modeling of injector and combustor behavior requires computational fluid dynamics (CFD). In this study, an application of low-order methods and published guidelines yielded generic injector and combustor geometries, as well as CFD boundary conditions of parameterized injector designs. Moreover, semi-empirical correlations combined with a numerical spray combustion solver provided injector design evaluations in terms of pattern factor, thermoacoustic performance, and certain emissions. Automation and parallel coordinate visualization enabled exploration of the dual-swirler airblast injector design space, which is often neglected in published combustor design studies.
A Method to Reduce the Energy Localization in Mistuned Bladed Disks by Application-Specific Blade Pattern Arrangement
Authors: Hohl Andreas , Wallaschek Jörg
Published: February 2016

The focus of the paper is the analysis of mistuning, which are small deviations of the blade properties, e.g., due to manufacturing tolerances. The resonant amplitudes of turbine blades are very sensitive to these deviations which can lead to significantly increased vibratory response of some blades with the increased risk of high cycle fatigue. The main part of the paper discusses about the methods that can be used to find blade patterns which are insensitive to energy localization. The sensitivity of the forced response against harmonic mistuning, which is a harmonic alignment of the blades respective to the mistuning factors of the single blades, is examined. A previously developed reduced order model (ROM) is used to efficiently conduct Monte Carlo simulations (MCSs). Especially the influence of the variance of the harmonically mistuned blade patterns is discussed. On the basis of this analysis, rules are developed to suppress the energy localization. The rules are mainly focused on the alignment of the blades around the bladed disk. The approach also takes advantage of the special properties of harmonic mistuning patterns. An assignment of the blades to insensitive harmonic mistuning patterns with a specific variance and number of periods is used to reduce the maximum of the amplification factor of the forced response. A similar approach uses intentional mistuning patterns with different blade types which are aligned harmonically and are insensitive to an additional stochastic mistuning. In case of specific combinations of the dependent parameters, especially the variance of the mistuning factors and the number of periods, the energy localization can be reduced considerably.
Optimal Power Management of Hydraulic Hybrid Mobile Machines—Part II: Machine Implementation and Measurements
Authors: Hippalgaonkar Rohit , Ivantysynova Monika
Published: February 2016

The problem of achieving maximum system efficiency through near-optimal supervisory control (or system power management) in mobile off-highway machines is a theoretically challenging problem. It has been tackled for the first time in this work for displacement-controlled (DC) hydraulic hybrid multi-actuator machines such as excavators, through a two-part publication. In Part I, the theoretical aspects of this problem were outlined, supported by simulations of the theoretically optimal supervisory control (relying on dynamic programming) as well as a novel, implementable rule-based supervisory control strategy (designed to replicate theoretically optimal results). In Part II of the publication, the world's first prototype hydraulic hybrid excavator using throttle-less DC actuation is described, together with machine implementation of the novel supervisory control strategy proposed in Part I. The design choice, or set of component sizes implemented on the prototype, was driven by an optimal sizing study that was previously done. Measurement results from implementation of two different supervisory control strategies are also presented and discussed—the first, a conservative, suboptimal strategy that commanded a constant engine speed and proved that drastic engine downsizing can be performed in excavator and similar applications. The second strategy implemented was the novel, near-optimal rule-based strategy (or the “minimum-speed” strategy) proposed in Part I that exploited all available system degrees-of-freedom, by commanding the minimum-required engine speeds (to meet DC actuator flow requirements) at every instant in time. While the actual engine was not downsized on the prototype excavator, both the single-point and minimum-speed strategies showed that for the aggressive, digging cycles that such machines are typically used for, the DC hydraulic hybrid architecture enables engine operation at or near 50% of maximum engine power without loss of productivity. As described in Part I, actually downsizing the engine by 50% with use of the near-optimal, minimum-speed strategy will enable significant gains in efficiency (in terms of grams of fuel consumed) over standard valve-controlled architectures (55%) as well as DC nonhybrid architectures (25%) in cyclical operation.
Observer Design for Singularly Perturbed Systems With Multirate Sampled and Delayed Measurements
Authors: Yang Chunyu , Zhang Lingli , Zhou Linna
Published: February 2016

This paper considers observer design problem of singularly perturbed systems (SPSs) with multirate sampled and delayed measurements. The outputs are classified into two sets which are measured at different sampling rates and subject to transmission delays. The error system is modeled as a continuous-time SPS with a slow-varying delay and a fast-varying delay. A new Lyapunov functional taking the delay properties into account is constructed. Based on the Lyapunov–Krasovskii functional, sufficient conditions for stability of the error system are proposed by which an observer design method is proposed. A realistic example is used to illustrate the obtained results.
Transition of a Steady to a Periodically Unsteady Flow for Various Jet Widths of a Combined Wall Jet and Offset Jet
Authors: Mondal Tanmoy , Das Manab Kumar , Guha Abhijit
Published: February 2016

In the present paper, a dual jet consisting of a wall jet and an offset jet has been numerically simulated using two-dimensional unsteady Reynolds-Averaged Navier–Stokes (RANS) equations to examine the effects of jet width (w) variation on the near flow field region. The Reynolds number based on the separation distance between the two jets (d) has been considered to be Re = 10,000. According to the computational results, three distinct flow regimes have been identified as a function of w/d. For w/d ≤ 0.5, the flow field remains to be always steady with two counter-rotating stable vortices in between the two jets. On the contrary, within the range of 0.6 ≤ w/d < 1.6, the flow field reveals a periodic vortex shedding phenomenon similar to what would be observed in the wake of a two-dimensional bluff body. In this flow regime, the Strouhal number of vortex shedding frequency decreases monotonically with the progressive increase in the jet width. For w/d ≥ 1.6, the periodic vortex shedding is still evident, but the Strouhal number becomes insensitive to the variation of jet width.
Effect of Winglet-Shroud Tip With Labyrinth Seals on Aerodynamic Performance of a Linear Turbine Cascade
Authors: Liu Yan , Zhang Min , Zhang Tianlong , Zhang Mengchao , He Ying
Published: February 2016

This paper is a continuous study of a previously investigated novel winglet-shroud (WS) tip configuration. Two additional sealing fins are fixed on the WS tip to further reduce tip leakage. This configuration is referred to WS with seals (WSS) tip. Secondary flow structures and total pressure loss coefficients on a transverse plane downstream of the blade trailing edge are measured. Flow in a blade cascade is also numerically simulated to obtain more information of flow fields. Compared with the WS tip, both experimental and numerical results show that the WSS tip can further improve the aerodynamic performance as expected. Relative to the plain tip, the WSS and WS tips can reduce total pressure loss on one plane downstream of the blade trailing edge by 50% and 28%, respectively. This is mainly due to reduced intensity of tip leakage vortex (TLV). For the tip leakage mass flow rate, the WS tip decreases it by 33.6%, while the implement of two additional sealing fins contributes to an extremely high reduction of 88.7%. This demonstrates that the use of sealing fins is effective to control the tip leakage flow and improve flow fields. In addition, a deeper analysis by applying a normalized helicity scheme to identify the evolution of different vortices and by tracing trajectories of the fluid near the tip offers credible supports for results.
A Numerical Study of the Benefits of Electrically Assisted Boosting Systems
Authors: Burke Richard D.
Published: February 2016

An electric compressor and an electrically assisted turbocharger have been applied to a 2.0 L gasoline and a 2.2 L diesel engine 1D wave dynamic model. A novel approach is presented for evaluating transient response using swept frequency sine wave functions and Fourier transforms. The maximum electrical power was limited to 6% of the maximum engine power (12 kW and 5 kW, respectively). The systems were evaluated under steady-state and transient conditions. Steady-state simulations showed improved brake mean effective pressure (BMEP) at low-engine speeds (below 2500 rpm) but electric power demand was lower (3 kW versus 8 kW) when the electric compressor was on the high-pressure side of the turbocharger. This was due to the surge limitation of the turbocharger compressor. The electrically assisted turbocharger offered little opportunity to increase low-speed BMEP as it was constrained by compressor map width. Rematching the turbo could address this but also compromise high-engine speeds. BMEP frequency analysis was conducted in the region of 0.01–2 Hz. This was repeated at fixed engine speeds between 1000 rpm and 2000 rpm. Spectral analysis of the simulated response showed that the nonassisted turbocharger could not follow the target for frequencies above 0.1 Hz, whereas the electrically assisted device showed no appreciable drop in performance. When assessing the electric power consumption with the excitation frequency, a linear trend was observed at engine speeds below 1500 rpm but more complex behavior was apparent above this speed where BMEP levels are high but exhaust energy was scarce.
Postinjection Strategy for the Reduction of the Peak Pressure Rise Rate of Neat n-Butanol Combustion
Authors: Jeftić Marko , Zheng Ming
Published: February 2016

Enhanced premixed combustion of neat butanol in a compression ignition engine can have challenges with regards to the peak pressure rise rate (PRR) and the peak in-cylinder pressure. It was proposed to utilize a butanol postinjection to reduce the peak PRR and the peak in-cylinder pressure while maintaining a constant engine load. Postinjection timing and duration sweeps were carried out with neat n-butanol in a compression ignition engine. The postinjection timing sweep results indicated that the use of an early butanol postinjection reduced the peak PRR and the peak in-cylinder pressure and it was observed that there was an optimal postinjection timing range for the maximum reduction of these parameters. The results also showed that an early postinjection of butanol increased the nitrogen oxide emissions, and a Fourier transform infrared spectroscopy (FTIR) analysis revealed that late postinjections increased the emissions of unburned butanol. The postinjection duration sweep indicated that the peak PRR was significantly reduced by increasing the postinjection duration at constant load conditions. There was also a reduction in the peak in-cylinder pressure. Measurements with a hydrogen mass spectrometer showed that there was an increased presence of hydrogen in the exhaust gas when the postinjection duration was increased but the total yield of hydrogen was relatively low. It was observed that the coefficient of variation for the indicated mean effective pressure was significantly increased and that the indicated thermal efficiency was reduced when the postinjection duration was increased. The results also showed that there were increased nitrogen oxide, carbon monoxide, and total hydrocarbon (THC) emissions for larger postinjections. Although the use of a postinjection resulted in emission and thermal efficiency penalties at medium load conditions, the results demonstrated that the postinjection strategy successfully reduced the peak PRR, and this characteristic can be potentially useful for higher load applications where the peak PRR is of greater concern.
Free-Edge Interlaminar Stresses in Angle-Ply Laminates: A Family of Analytic Solutions
Authors: Goodsell Johnathan , Byron Pipes R.
Published: February 2016

A family of analytic solutions for the prediction of interlaminar stresses in angle-ply laminates has been developed and is presented in a unified form and as a unique set of solutions. The uniqueness of the formulation is demonstrated for the class of thermomechanical states of deformation for which the solutions are valid. These are shown to be limited to the specific cases wherein only two in-plane stress components and one interlaminar stress components are nonzero. Interlaminar shear stress in the angle-ply laminate subjected to thermomechanical loading conditions of uniaxial extension, uniform temperature change, and anticlastic bending is shown to make up the family of solutions in the unified formulation. Further, these are shown to comprise the complete set of the solutions and the conditions which control the limitations of this family of solutions are articulated.
A Study of Acoustic Wave Resonance in Water-Filled Tubes With Different Wall Thicknesses and Materials
Authors: Mokhtari Alireza , Chatoorgoon Vijay
Published: February 2016

Acoustic resonance of a fluid-filled tube with closed and open outlet ends for zero and turbulent mean flows is investigated both experimentally and numerically for different wall materials and thicknesses. The main goal is to create a data bank of acoustic wave resonance in fluid-filled tubes at a frequency range of 20–500 Hz to validate and verify numerical prediction models used by the nuclear industry and to determine if there is a better method with existing technology. The experimental results show that there is a strong effect of turbulent flow, wall material, and wall thickness on resonant amplitudes at frequencies above ∼250  Hz. A numerical investigation is performed solving the linear wave equation with constant and frequency-dependent damping terms and a computational fluid dynamic (CFD) code. Comparing the one-dimensional (1D) and CFD results shows that CFD solution yields better predictions of both resonant frequency and amplitude than the 1D solution without the need for simplified added damping methods, which are required by the 1D methodology. This finding is valid especially for frequencies higher than ∼300  Hz.
Computational Modeling of the Effects of Transient Blood Flow Characteristics and Wall Thickness on the Rupture of Abdominal Aortic Aneurysm
Authors: Pal Pinaki
Published: February 2016

Precise estimation of wall stress distribution within an abdominal aortic aneurysm (AAA) is clinically useful for prediction of its rupture. In this paper a computational fluid dynamic model incorporating two-way coupled fluid-structure interaction is employed to investigate the role of laminar-turbulent flow transition and wall thickness in altering the distribution and magnitude of wall stress in an AAA. Blood flow in axially symmetric aneurysm models governed by a compliant wall mechanics was simulated. Menter’s hybrid k-epsilon/k-omega shear stress transport (SST) model with a correlation-based transition model was used to capture laminar-turbulent transition in the blood flow. Realistic physiological transient boundary conditions were prescribed. The numerical model was validated against experimental data available from the literature. Fluid flow analysis showed the formation of recirculating vortices at the proximal end of the aneurysm after the peak systole which then, moved towards the distal end of the aneurysm along with the bulk flow and were dissipated eventually due to viscous effects. These vortices interacted with the aortic wall and led to local pressure rise. Von Mises stress distribution on the aneurysm wall and location of its peak value were computed and compared with those of a separate numerical simulation performed using a laminar viscous flow model. The predicted peak wall stress was found to be significantly higher for the SST model as compared to the laminar flow model. The location of maximum stress shifted more towards the posterior end of the aneurysm when laminar-turbulent flow transition was considered. In addition, a small reduction of 0.4 mm in wall thickness resulted in the elevation of peak wall stress by a factor of 1.4. The present study showed that capturing flow transition in an AAA is essential to accurate prediction of its rupture. The proposed numerical model provides a robust computational framework to gain more insight into AAA biomechanics and to accurately estimate wall stresses in realistic aneurysm configurations.
Limit Load Analysis of Pressurized Containers
Authors: Sklorz C. , Otremba F. , Reich F.
Published: February 2016

Limit load analysis is a well known method to calculate the allowable design pressure of container components. A limit load of a pressurized container is achieved, when the stress of a wall and the flow stress are equal. In the following paper the transferability of limit load analysis from small scale tank containers up to large scale containers (railway tank) are investigated. Finite element calculations are carried out and compared with experimental results. It can be concluded that the limit load analysis works very well. Furthermore, the yield strength of the material should be used as flow stress.
A Comparison of Computed Deflections of Symmetric Angle-Ply Laminate Plates by the Ritz Method and the Finite Element Method
Authors: Carroll Kenneth , Gutierrez-Miravete Ernesto
Published: February 2016

When a simply supported composite plate is subjected to a lateral load, the presence of the twist coupling stiffnesses in the governing differential equations of equilibrium does not allow the determination of an exact solution for the deflection and numerical methods must be used. This paper describes a comparison of computed approximations to the deflection of composite laminates subjected to transverse loading obtained using the Ritz method and the finite element method. The Ritz method is implemented with the symbolic manipulation program Maple and ANSYS is used to perform the finite element calculations. Reliable results are obtained using both methods.
Modeling of the Mechanical Properties of a Polymer-Metal Foam Interpenetrating Phase Composite
Authors: Gao Jiayun , Rayess Nassif
Published: February 2016

An interpenetrating phase composite is made by injection molding thermoplastic polymers into the voids of open-cell aluminum foam. Two types of polypropylene and an acetyl were mechanically introduced into the open cells of a Duocel® aluminum foam. Prior experimental work revealed that the combination of the polymer and the metal foam yields a hybrid that is stiffer than the polymer alone but has a reduced tensile strength. A finite element model using a tetrakaidecahedral unit cell is used to model the metal foam ligaments with the polymer occupying the remaining space. The geometric model as well as the interface between the two materials were validated against the experimental results. The resulting conclusions are that the aluminum ligaments oriented along the load direction cause an increase in stiffness but ligaments oriented laterally cause stress concentration that yield lower strength. The finite element model is used to give both qualitative and quantitative explanations of the physics of the interrelations between the metal foam and the polymer.
Effect of Reverse Bending Method on Pre-Crack Straightness in CTOD Test of Welded Thick Steel Plates
Authors: Jeong Sehwan , Kim Hyun-su , Shin Sang-beom , Park Tae-jong
Published: February 2016

This study deals with the reverse bending method as a residual stress modification technique for CTOD test of the thick weld. In the reverse bending method, the residual stress around the notch tip of the specimen is redistributed by compressive plastic deformation by reverse bending load. The reverse bending method requires a smaller level of applying load comparing to the local compression method. However, the excessive reverse load may introduce the excessive plastic deformation in way of notch tip which can affect the CTOD value of the weld. So, this study investigates how to establish the proper bending load for ultra-thick weld. In order to do it, stress intensity factor was determined by the plastic zone size around the notch tip by 3-dimensional finite element analysis. The validation of the reverse bending method was verified by examining the configuration of pre-crack at CTOD weld test specimen with various thickness and strength.
Characterization of Electrical Conductivity of Carbon Nanotube Composites
Authors: Gong Shen , Zhu Zhenghong , Li Jun
Published: February 2016

This work investigated and characterized the electrical conductivity of carbon nanotubes (CNT)/polymer composites. Surface modification has been applied to improve the homogeneous dispersion of MWCNTs in epoxy. After treatment, MWCNTs were mixed into low viscosity epoxy matrix at room temperature. Dispersion and structural integrity of MWCNTs before and after surface modification were examined by SEM images. The dispensability of treated MWCNTs and electrical conductivity of nanocomposites are evaluated and also compared with MWCNTs/polymer composites in literature prepared using the same commercial MWCNTs. The electrical conductivity of MWCNTs and MWCNTs/epoxy composites were evaluated by the four-point probe method. The results of electrical property will lay a foundation for establishing the relationship between electrical resistance and strain of MWCNTs/epoxy composites. The results also confirm that reducing CNT agglomerate size can greatly improve the electrical conductivity of composite and decrease the percolation threshold.
Analytical Modeling of Residual Stress in Railroad Rails Using Critically Refracted Longitudinal Ultrasonic Waves With COMSOL Multiphysics Module
Authors: Manchem Lakshmi Divya , Srinivasan Malur N. , Zhou Jiang
Published: February 2016

Assessment of residual stresses in railroad rails without destructing the material plays a vital role in rail road safety. Ultrasonic testing is a commonly used nondestructive technique to determine the stresses in any structure. Ultrasonic stress evaluation technique is based on acoustoelastic effect which refers to the changes in the speed of the elastic wave propagation in a structure undergoing static elastic deformations. Critically refracted longitudinal (LCR) waves can be used as the propagating waves because it is a bulk wave and can reflect the surface and subsurface characteristics by the wave property linked to material elasticity. In this paper, a COMSOL Multiphysics module-based Finite Element Method (FEM) model is developed and numerical simulations are carried out for critically refracted longitudinal wave propagation in a railroad rail head for residual stresses. The time travel data results from this FEM Model are validated with reported experimental results.
Continuum Model for Effective Properties of Orthotropic Octet-Truss Lattice Materials
Authors: Challapalli Adithya , Ju Jaehyung
Published: February 2016

Cellular materials, often called lattice materials, are increasingly receiving attention for their ultralight structures with high specific strength, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. In alignment with emerging additive manufacturing (AM) technology, realization of the structural applications of the lattice materials appears to be becoming faster. Considering the direction dependent material properties of the products with AM, by directionally dependent printing resolution, effective moduli of lattice structures appear to be directionally dependent. In this paper, we develop a constitutive model of a lattice structure, which is an octet-truss with a base material having an orthotropic material property considering AM. One case study is conducted with an orthotropic property of a base material in 3D Printing. A polyjet based 3D printing material having an orthotropic property with a 9% difference in the principal direction provides difference in the axial and shear moduli in the octet-truss by 2.3 and 4.6%.