bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain Rate and Loading Waveform Effects on an Energy-Based Fatigue Life Prediction for AL6061-T6
Authors: Letcher Todd , Shen M.-H. Herman , Scott-Emuakpor Onome , George Tommy , Cross Charles
Published: December 2013

The energy-based lifing method is based on the theory that the cumulative energy in all hysteresis loops of a specimens’ lifetime is equal to the energy in a monotonic tension test. Based on this theory, fatigue life can be calculated by dividing monotonic strain energy by a hysteresis energy model, which is a function of stress amplitude. Recent studies have focused on developing this method for a sine wave loading pattern — a variable strain rate. In order to remove the effects of a variable strain rate throughout the fatigue cycle, a constant strain rate triangle wave loading pattern was tested. The testing was conducted at various frequencies to evaluate the effects of multiple constant strain rates. Hysteresis loops created with sine wave loading and triangle loading were compared. The effects of variable and constant strain rate loading patterns on hysteresis loops throughout a specimens’ fatigue life are examined.
Supercritical Carbon Dioxide Power Cycle Configurations for Use in Concentrating Solar Power Systems
Authors: Turchi Craig S. , Ma Zhiwen , Dyreby John
Published: December 2013

Concentrating Solar Power (CSP) plants utilize oil, molten salt or steam as the heat transfer fluid (HTF) to transfer solar energy to the power block. These fluids have properties that limit plant performance; for example, the synthetic oil and molten salt have upper temperature limits of approximately 390°C and 565°C, respectively. While direct steam generation has been tested, it requires complex controls and has limited options for integration of thermal energy storage. Use of carbon dioxide as the HTF and power cycle working fluid offers the potential to increase thermal cycle efficiency while maintaining simplicity of operation and thermal storage options.

Supercritical CO2 (s-CO2) operated in a closed-loop recompression Brayton cycle offers the potential of higher cycle efficiency versus superheated or supercritical steam cycles at temperatures relevant for CSP applications. Brayton-cycle systems using s-CO2 have smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine cycles due to the higher density of the fluid and simpler cycle design. Many s-CO2 Brayton power cycle configurations have been proposed and studied for nuclear applications; the most promising candidates include recompression, precompression, and partial cooling cycles.

Three factors are important for incorporating s-CO2 into CSP plants: superior performance vs. steam Rankine cycles, ability to integrate thermal energy storage, and dry-cooling. This paper will present air-cooled s-CO2 cycle configurations specifically selected for a CSP application. The systems will consider 10-MW power blocks that are tower-mounted with an s-CO2 HTF and 100-MW, ground-mounted s-CO2 power blocks designed to receive molten salt HTF from a power tower.
Revisiting the SAFE Diagram for Analysis of Mistuned Bladed Disks
Authors: Allison Timothy C. , Moore J. Jeffrey , Lerche Andrew H. , Simmons Harold R.
Published: December 2013

The SAFE diagram is a design tool that is often used for analyzing modes of concern in bladed disks. The diagram implements the concept of phase cancellation in order to show what bladed disk modes can and cannot be excited by upstream flow obstructions. In many cases, phase cancellation theory dictates that even if a modal frequency corresponds with an excitation order, the mode may not be excited if the total work calculated by integrating the excitation profile around the mode shape is equal to zero. This paper reviews the theory behind the SAFE diagram and explores the effects of blade mistuning on SAFE diagram analysis from both theoretical and experiential viewpoints. Modal test data, mistuned finite element analysis, and two case studies all indicate that mistuned modes may not exhibit the pure nodal diameter patterns that are predicted by a symmetric analysis and are required for phase cancellation. These mistuned asymmetric modes may result in high blade stresses and blade failure even if a SAFE diagram analysis indicates that the mode will not be excited.
Modelling Rain Drop Impact of Offshore Wind Turbine Blades
Authors: Keegan M. H. , Nash D. H. , Stack M. M.
Published: December 2013

The effects of rain and hail erosion and impact damage on the leading edge of offshore wind turbine blades have been investigated.

A literature review was conducted to establish the effects of exposure to these conditions and also to investigate the liquid impact phenomena and their implications for leading edge materials. The role of Explicit Dynamics software modelling in simulating impact events was then also established.

Initial rain impact modelling is then discussed with the results showing good agreement with theoretical predictions both numerically and with respect to the temporal and spatial development of the impact event. Future development of the rain model and a proposed hail model are then detailed.

Planned rain impact and erosion testing work is addressed which will be used to validate, inform and compliment the ongoing modelling efforts.
Vortex Generators for Wind Turbine Blades: A Combined Wind Tunnel and Wind Turbine Parametric Study
Authors: Mueller-Vahl Hanns , Pechlivanoglou Georgios , Nayeri C. N. , Paschereit C. O.
Published: December 2013

Vortex generators (VGs) are passive flow control devices commonly employed to prevent flow separation on wind turbine blades. They mitigate the damaging fatigue loads resulting from stall while increasing lift and consequently lead to rotor torque increase. This work summarizes a research project aimed at optimizing the sectional as well as the full rotor-blade aerodynamics using VGs.

The effects of chordwise position, spanwise spacing and VG size were studied with force balance measurements of a 2D wing section. Reducing the distance between adjacent VGs produced large increases in the static stall angle and maximum lift, but also resulted in a significant increase in drag as well as sharp lift excursions at angles exceeding the static stall angle. The optimal chordwise position of the vortex generators was found to be in the range of x/c = 15%–20%, where a comparatively low parasitic drag and a smooth post-stall lift curve were achieved. Particle Image Velocimetry measurements were conducted at various chordwise positions to provide insight into the interaction between adjacent streamwise vortices.

The experimental aerodynamic performance curves of the optimal VG configuration were used to project their effect on wind turbine blade aerodynamics. Three different rotorblades were designed and several stall and pitch regulated wind turbine models were simulated by means of a Blade Element Momentum (BEM) code (QBlade) developed by Smart Blade GmbH. The performance of the rotorblades with and without VGs was simulated in order to assess their effect on the aerodynamic performance and loads. Finally, previously measured steady state performance curves under high-roughness conditions were used to simulate the detrimental effect of surface roughness on the performance of the aforementioned rotorblades. This allows for an estimate of the potential of the VGs to be employed as retrofit elements for performance recovery of blades with a contaminated surface.
Robust Aerodynamic Design of Variable Speed Wind Turbine Rotors
Authors: Minisci Edmondo , Campobasso M. Sergio , Vasile Massimiliano
Published: December 2013

This study focuses on the robust aerodynamic design of the bladed rotor of small horizontal axis wind turbines. The optimization process also considers the effects of manufacturing and assembly tolerances on the yearly energy production. The aerodynamic performance of the rotors so designed has reduced sensitivity to manufacturing and assembly errors. The geometric uncertainty affecting the rotor shape is represented by normal distributions of the pitch angle of the blades, and the twist angle and chord of their airfoils. The aerodynamic module is a blade-element momentum theory code. Both Monte Carlo-based and the Univariate Reduced Quadrature technique, a novel deterministic uncertainty propagation method, are used. The performance of the two approaches is assessed both in terms of accuracy and computational speed. The adopted optimization method is based on a hybrid multi-objective evolutionary strategy. The presented results highlight that the sensitivity of the yearly energy production to geometric uncertainties can be reduced by reducing the rotational speed and increasing the aerodynamic blade loads.
Through Flow Matching of Power Turbine for a Turbo-Compounded Diesel Engine
Authors: Zhao Rongchao , Zhuge Weilin , Zhang Yangjun , Yin Yong , Li Zhigang , Wang Jiawei
Published: December 2013

Turbo-compounding (TC) is a possible solution to make transportation more ecological. Matching the engine with an appropriate power turbine is the key for the turbo-compounded engine performance optimization. Conventionally, the matching work is based on a turbine map. The influences of the turbine geometry parameters on the engine performance are taken into account.

A new matching method based on the turbine through flow model is presented in this paper. The influences of geometry parameters of the power turbine on the diesel engine performance are investigated. The research focuses on the effects of inlet blade radius and height, exit blade angle and tip radius of the power turbine on the engine BSFC and torque. Results show that the outlet blade angle and tip radius have stronger impacts on BSFC and torque of the engine than the inlet blade radius and height. Further studies show that the engine cycle and air mass flow rate are more sensitive to the outlet blade tip radius and angle than the inlet blade radius and height.
Parametric Studies of Nonlinear Damping Behavior of APS Thermal Barrier Coatings Based on Cohesive Interface Model
Authors: Chen Yong , Dong Wei
Published: December 2013

Thermal barrier coatings (TBCs) could reduce the temperature of the turbine blades and allow them working at higher temperatures, which leads to higher durability and reliability of turbine blades, and improves engine performance and fuel efficiency. Recent researches shown that thermal barrier coatings have very good damping properties, which means it could also improve the high cycle fatigue (HCF) life of the turbine blades. Previous studies found that damping of air plasma spray (APS) thermal barrier coatings exhibit non-linearities (amplitude-dependent) due to its microstructures, which consists of several layers of splats with inter- and intra-microstructural micro-cracks. The main purpose of this paper is on the application of a bilinear cohesive interface model to simulate the microstructural features, the damage process and the contact friction between the interfaces of microstructural faults in APS ceramic topcoat. A representative volume element (RVE) model which coupled with the cohesive interface model is built and parametric relations, in terms of interface strength and stiffness, vibration amplitude and vibration cycles, are computed in this paper for understanding the effect of interfacial degradation, de-bonding, sliding, and contact friction between the interfaces of microstructural faults on the nonlinear damping properties. The calculation results could provide a fundamental understanding of the mechanisms responsible for the observed nonlinear energy dissipation and damping properties in APS ceramic coatings.
Analysis on Flutter Characteristics of Transonic Compressor Blade Row by a Fluid-Structure Coupled Method
Authors: Zhang Mingming , Hou Anping , Zhou Sheng , Yang Xiaodong
Published: December 2013

A time domain numerical approach is carried out to enhance the understanding of three dimensional blade row aeroelastic characteristics under the parallel computation. The vibration energy of unsteady aerodynamic force on the entire blade row is investigated using numerical solution of 3-D Navier-Stokes equations, coupled with structure finite element models for the blades to identify modal shapes and the structural deformations simultaneously. Interactions between fluid and structure are dealt with in a coupled manner, based on the interface information exchange until convergence in each time step. With this approach good agreement between the numerical results and the experimental data is observed. The flutter mechanism is analyzed according to deformation of the blades. The effect of inter-blade phase angle (IBPA) is included in the analysis by releasing the hypothesis of constant phase angle between adjacent blades in the traveling wave model. The results illustrate fully three dimensional unsteady nonlinear behaviors, such as limit-cycle oscillation. It is shown that all blades flutter at the same mode and frequency, but not at the same amplitude and IBPA. The analysis of the influence of different tip clearance gaps on the flutter characteristics of the blade row is also performed.
Optimized Steam Turbine Governor Controlling Single or Multiple Grid Faults
Authors: Bennauer Martin , Kreischer Christian , Rosendahl Jens , Werthes Heribert
Published: December 2013

This paper uses simulation results to figure out how SIEMENS handles a single grid fault of a three–phase short circuit close to the power plant and a multiple grid fault of a load rejection due to a three–phase short circuit close to the power plant.

The correct response of the steam turbine governor to the single and the multiple grid fault can increase power plant availability, prevent steam turbine trips and reduce overspeed. Therefore the power supply to the electrical grid can still be maintained, and in case of a de-stabilized electrical grid a black-out could be prevented.

If the steam turbine trips caused by the single or the multiple grid fault the steam turbine runs down and has to be restarted. This could take several hours as worst case. During this time the power plant is not available to support and stabilize the electrical grid.

If the steam turbine governor is able to handle the single grid fault, the power plant is still connected to the grid. This will not further stress the de-stabilized electrical grid.

If the steam turbine governor is able to handle the multiple grid fault, the house load of the power plant will still be provided by the steam turbine. The operator could re-synchronize the power plant with the de-stabilized electrical grid as fast as possible.

In both cases for the single and the multiple grid fault the power plant remains available by the optimized steam turbine governor.
Measurement of Contact Parameters of Flat on Flat Contact Surfaces at High Temperature
Authors: Botto D. , Lavella M. , Gola M. M.
Published: December 2013

In aircraft engines the blade resonant vibration amplitude is normally reduced by increasing the structural damping by using, for example, tip shrouds. These devices dissipate the energy generated at the contact surfaces between the relative motion and the friction force. Contact parameters, principally the friction coefficient and contact stiffness, are required to characterize the dynamics of shrouded blade system. Moreover, if at these contact surfaces severe wear occurs, a loss of interference takes place and the energy dissipated by the shroud decreases. Consequently the blade vibration amplitude increases and a catastrophic blade failure could take place. In this work a test rig for the contact parameter measurements and micro wear characterization of flat-on-flat contact surfaces has been developed. The test rig works at high temperatures of up to 1000 °C, by means of induction heating. One of the specimens was attached to the rig frame, basically an inertial mass and four springs, and subsequently excited by an electromagnetic shaker. The second specimen was allowed to approach the first specimen and to rotate in such a way than the geometric contact between the two surfaces occurred at three points. In this way a real “flat to flat” contact was obtained. The two surfaces were kept in contact by means of a constant normal load. The tangential contact force was measured by a force sensor while the relative displacements between the contact surfaces were measured by two laser vibrometers. The relative displacement was kept under control by acting on the shaker force. Tangential force and relative displacement were used to describe the hysteresis loop and, consequently, to obtain the friction coefficient and contact stiffness during the wear process. The temperature is feedback controlled by using two thermocouples placed within the specimens near the contact surfaces. The expected results are the contact parameters and the wear behaviour of real flat-on-flat contact surfaces. The aim of this work is to describe the design principle of the test rig and present the initial measurements.
Constrained Optimization of a Rotor-Bearing System Based on an Evolutionary Algorithm
Authors: Wang Donghua , Li Wanyou , Liu Zhigang , Liu Zhansheng
Published: December 2013

How to modify a rotor system configuration to adjust some critical speeds distribution for safety and achieve the least change of system configuration at the same time, is a focus in the rotordynamics field. An existing method is introduced and its disadvantages are analyzed. To overcome these difficulties smoothly, a more robust mathematical model for optimal design of critical speeds distribution is presented, with more constraints considered. And a Population-based Evolutionary Algorithm with Elite Strategy (PEAES) is developed to solve the proposed optimization model. The results of study on a rotor system in different cases show that the proposed method can find the optimal solution and may be applicable in the practical design process of rotor systems.
Measured Performance of Two-Stage Centrifugal Compressor Under Wet Gas Conditions
Authors: Bertoneri Matteo , Duni Simone , Ransom David , Podestà Luigi , Camatti Massimo , Bigi Manuele , Wilcox Melissa
Published: December 2013

The oil and gas industry is moving forward to access the most remote gas reserves and enhance the exploitation of the existing installation or postponing their tail-end. To achieve these accomplishments several technology challenges are being unveiled. In topside upstream application both offshore and onshore, one important technology issue is the capability to compress gas with a significant amount of liquids and it assumes a special interest in case of the facilities revamping. Nevertheless is in the subsea environment where this technology issue becomes really challenging. In order to properly design and size a compressor/motor system for subsea wet gas compression, one must be able to adequately predict the compressor performance with mixed phase flow.

This paper presents the results from an experimental test program which investigated the performance of a centrifugal compressor at various wet gas conditions with elevated suction pressure. Performance tests are completed on a two stage centrifugal compressor with a mixture of air and water at suction pressures of 20 bar (300 psi). The compressor is subjected to flow with liquid volume fractions ranging from 0 to 5% along three speedlines.

The performance measurements are made in accordance with ASME PTC-10 specifications with an additional torque measurement on the shaft between the compressor and gearbox. At each test condition, once the liquid is injected in the air flow, an increase in pressure ratio occurs. This testifies the compressor is still able to work in presence of water. However, increasing the amount of liquid injected a decreased polytropic head together with an increased absorbed actual power by the compressor cause a deterioration of its efficiency. Moreover when liquid is introduced into the flow, the discharge temperature of the compressor reduces significantly.

The performance results and trends mentioned above are reviewed in the detail in this paper.
Pressure Gain Combustion Application to Marine and Industrial Gas Turbines
Authors: Snyder Philip H. , Nalim M. Razi
Published: December 2013

Renewed interest in pressure gain combustion applied as a replacement of conventional combustors within gas turbine engines creates the potential for greatly increased capability engines in the marine power market segment. A limited analysis has been conducted to estimate the degree of improvements possible in engine thermal efficiency and specific work for a type of wave rotor device utilizing these principles. The analysis considers a realistic level of component losses. The features of this innovative technology are compared with those of more common incremental improvement types of technology for the purpose of assessing potentials for initial market entry within the marine gas turbine market. Both recuperation and non-recuperation cycles are analyzed. Specific fuel consumption improvements in excess of 35% over those of a Brayton cycle are indicated. The technology exhibits the greatest percentage potential in improving efficiency for engines utilizing relatively low or moderate mechanical compression pressure ratios. Specific work increases are indicated to be of an equally dramatic magnitude. The advantages of the pressure gain combustion approach are reviewed as well as its technology development status.
Crack Detection in Shaft Using Lateral and Torsional Vibration Measurements and Analyses
Authors: Tlaisi A. , Akinturk A. , Swamidas A. S. J. , Haddara M. R.
Published: December 2013

In this paper experimental and numerical investigations are carried out to identify the presence of a crack in a cylindrical overhanging shaft with a propeller at the free end. In the experimental study, cracks of different depths are located at the (un-cracked) maximum bending moment position. Shaft response parameters for lateral (using an accelerometer) and torsional vibrations (using shear strain gages fixed at three different locations) are obtained using the modal analysis software, LMS Test Lab™. The experimental results are used to validate the numerical results obtained using the three-dimensional isoparametric elements (element types 186 and 187) available in the ANSYS FEM program; the open crack is embedded in the shaft and the mesh generation is suitably modified to incorporate the stress intensity effects present at the crack tip. From the results it is observed that the rate of change of torsional frequencies that occur during initial crack growth can be better used to detect crack presence in rotating shafts than bending frequencies.
Dynamic Pipeline System Simulation of Multi-Stage Compressor Trains
Authors: Garcia-Hernandez Augusto , Tavares Theodore Sean , Wilcox Melissa
Published: December 2013

An oil and gas company was facing process and mechanical related problems on the multiple-stage compressor trains at two important booster installations. The frequency of these problems has increased lately, and this has led to frequent trips and shut downs. These interruptions affect the operation of the plant leading to a loss in production and consequences of lost revenue for the company. The two platforms each contain one compressor train comprising a four-stage compressor with a gas turbine driver. Each train is fitted with an integrated turbine compressor control panel.

Thus, a detailed dynamic pipeline system simulation of the subject compressor trains was performed in order to provide a series of recommendations that would improve the safe operation and increase the reliability of the compression systems. The analysis included a review of the existing compression systems including all the equipment and hardware related with the compression anti-surge system. In addition, a site visit was performed to review and understand the existing anti-sure control system at each facility. A detailed dynamic model of the multi-stage compression system was built for each train. These models included compressor performance maps, gas compositions for each stage and train, piping yard, recycle, isolation, check and blowdown valves, scrubbers, separators, and coolers.

Several simulation cases were conducted for both the platform systems. These cases evaluated the effect of the delay and travel times of the existing anti-surge valves, delay the coast down action, failure of the non-return valves (NRVs), action of a blowdown valve on the emergency shutdown (ESD) sequences, recycle valve bypasses, check valve arrays, and process upset conditions. In addition, parametric studies were conducted for each of the most important parameters of the system to quantify their effect of any possible modification.

The results of this analysis provide recommendations to solve some of the existing issues while understanding more of the dynamics of the system. It was found that any propose recommendation or change in the sequence or timing of one stage will affect the surrounding stages since they are not only connected through the piping as they are driven by the same gas turbine shaft. Therefore, a very comprehensive analysis was conducted for each train to provide recommendations that would be feasible for implementation while reducing the constant risk of mechanical failure and surge events. Thus, results of the analysis and some of the recommendations obtained are presented in this paper.
Picosecond electrical switching of single-gate metal nanotip arrays
Authors: Tsujino Soichiro , Paraliev Martin
Published: December 2013

Electrical switching of single-gate all metal field emitter arrays is studied to generate subnanosecond electron pulses. By applying a bipolar current pulse method to the metal nanotip array, electron pulses with the duration down to 210 ps were generated. To explore the short-pulse limit of the proposed switching method, the propagation of the gate potential across the array was analyzed by numerical simulation. The result shows that single-gate field emitter arrays with the array diameter of 1 mm can be electrically switched with the duration down to ∼5 ps.
Microcathodoluminescence spectra evolution for planar and nanopillar multiquantum-well GaN-based structures as a function of electron irradiation dose
Authors: Yakimov Eugene B. , Vergeles Paul S. , Polyakov Alexander Y. , Cho Han-Su , Jang Lee-Woon , Lee In-Hwan
Published: December 2013

Effects of low energy electron beam irradiation (LEEBI) of planar and nanopillar InGaN/GaN multiquantum well light emitting diode structures are discussed. The bands observed in microcathodoluminescence (MCL) spectra were attributed to recombination involving two types of InGaN quantum dots with lower (2.92 eV MCL band) and higher (2.75 eV) indium concentration. During the LEEBI treatment, the intensity of both MCL lines first decreased, presumably due to the introduction of radiation defects, then, after the dose of 0.2 C/cm2 increased, reached a maximum and then again decreased. At the same time, the peak energy showed a red shift at low irradiation doses and a blue shift at high doses. The results are explained by an interplay between the increasing density of nonradiative recombination defects and quantum dots during irradiation. The difference between the nanopillar and planar structures is attributed to a stronger impact of surface defects in nanopillars.
Summary of Linezolid Activity and Resistance Mechanisms Detected during the 2012 LEADER Surveillance Program for the United States
Authors: Mendes Rodrigo E. , Flamm Robert K. , Hogan Patricia A. , Ross James E. , Jones Ronald N.
Published: December 2013

This study summarizes the linezolid susceptibility testing results for 7,429 Gram-positive pathogens from 60 U.S. sites collected during the 2012 sampling year for the LEADER Program. Linezolid showed potent activity when tested against 2,980
Staphylococcus aureus
isolates, inhibiting all but 3 at ≤2 μg/ml. Similarly, linezolid showed coverage against 99.5% of enterococci, as well as for all streptococci tested. These results confirm a long record of linezolid activity against U.S. Gram-positive isolates since regulatory approval in 2000.
In Vitro
Activity of Fosfomycin against Escherichia coli Isolated from Patients with Urinary Tract Infections in Canada as Part of the CANWARD Surveillance Study
Authors: Karlowsky James A. , Denisuik Andrew J. , Lagacé-Wiens Philippe R. S. , Adam Heather J. , Baxter Melanie R. , Hoban Daryl J. , Zhanel George G.
Published: December 2013

We tested 868 urinary isolates of
Escherichia coli
collected from 2010 to 2013 as part of the Canadian national surveillance study CANWARD against fosfomycin by using the Clinical and Laboratory Standards Institute (CLSI) agar dilution method with MIC interpretation in accordance with the CLSI M100-S23 (2013) criteria. The concentrations of fosfomycin inhibiting 50 and 90% of the isolates were ≤1 and 4 μg/ml; 99.4% of the isolates were susceptible to fosfomycin.
Klebsiella pneumoniae Induces an Inflammatory Response in an
In Vitro
Model of Blood-Retinal Barrier
Authors: Motta C. , Salmeri M. , Anfuso C. D. , Amodeo A. , Scalia M. , Toscano M. A. , Giurdanella G. , Alberghina M. , Lupo G.
Published: December 2013

Klebsiella pneumoniae
has become an important pathogen in recent years. Although most cases of
K. pneumoniae
endogenous endophthalmitis occur via hematogenous spread, it is not yet clear which microbial and host factors are responsible for the ability of
K. pneumoniae
to cross the blood-retinal barrier (BRB). In the present study, we show that in an
in vitro
model of BRB based on coculturing primary bovine retinal endothelial cells (BREC) and primary bovine retinal pericytes (BRPC),
K. pneumoniae
infection determines changes of transendothelial electrical resistance (TEER) and permeability to sodium fluorescein. In the coculture model, bacteria are able to stimulate the enzyme activities of endothelial cytosolic and Ca
2+
-independent phospholipase A
2
s (cPLA
2
and iPLA
2
). These results were confirmed by the incremental expression of cPLA
2
, iPLA
2
, cyclo-oxygenase-1 (COX1), and COX2 in BREC, as well as by cPLA
2
phosphorylation. In supernatants of
K. pneumoniae
-stimulated cocultures, increases in prostaglandin E
2
(PGE
2
), interleukin-6 (IL-6), IL-8, and vascular endothelial growth factor (VEGF) production were found. Incubation with
K. pneumoniae
in the presence of arachidonoyl trifluoromethyl ketone (AACOCF
3
) or bromoenol lactone (BEL) caused decreased PGE
2
and VEGF release. Scanning electron microscopy and transmission electron microscopy images of BREC and BRPC showed adhesion of
K. pneumoniae
to the cells, but no invasion occurred.
K. pneumoniae
infection also produced reductions in pericyte numbers; transfection of BREC cocultured with BRPC and of human retinal endothelial cells (HREC) cocultured with human retinal pericytes (HRPC) with small interfering RNAs (siRNAs) targeted to cPLA
2
and iPLA
2
restored the pericyte numbers and the TEER and permeability values. Our results show the proinflammatory effect of
K. pneumoniae
on BREC, suggest a possible mechanism by which BREC and BRPC react to the
K. pneumoniae
infection, and may provide physicians and patients with new ways of fighting blinding diseases.
Development of a Bi-Disciplinary Course in Forensic Science
Authors: Raimondi Stacey L.
Published: December 2013

Forensic science programs and courses have traditionally been housed within chemistry departments at the college/university level, largely because the pioneers of the field were chemists who applied technology that was more chemical than biological in nature. However, with the development of such areas of study as DNA analysis, anatomical studies, and forensic entomology, it is becoming more and more important for forensic science students to have a strong biological background as well as a chemical background. Furthermore, while biology students are typically required to have extensive chemistry training as part of their major, the converse is not true for chemistry students. Therefore, it is possible that a student interested in forensic science could complete a major in chemistry and never have taken a biology class, leaving them woefully under-prepared for any type of masters program or career in forensic science immediately following graduation. Indeed, an examination of available positions in forensic science shows a large number of positions for DNA analysts for which the typical chemistry student would not be prepared without extensive biology training (http://www.aafs.org). Furthermore, positions for medical examiners or pathologists require extensive training in biology in addition to the continued medical training and residency programs. Therefore, it seems imperative that introductory forensic science courses adapt to these needs and be taught with a more bi-disciplinary approach in order to educate students on the whole field rather than one aspect. To that end, a new bi-disciplinary Forensic Science course was developed at Elmhurst College. This course was team-taught by a biology and a chemistry professor so that students would obtain a thorough understanding of the field and techniques used by both biologists and chemists. A description of this new version of a forensic science course follows, focusing on the addition of biology to a traditionally chemical course, the conclusions drawn upon completion of the course, and changes to be made in the future.
Early second trimester uterine scar rupture
Authors: Bharatnur Sunanda , Hebbar Shripad , G Shyamala
Published: December 2013

Spontaneous uterine scar rupture can be lethal in pregnant women. A spontaneous uterine scar rupture in the early mid-trimester is rare and difficult to diagnose. This is a case of a 30-year-old woman (G2P1L1) at 19 weeks of gestation and having undergone a previous caesarean section presented with acute abdomen in shock. Laparotomy revealed a uterine scar rupture, which was resutured after evacuation of products of conception. This case merits that the uterine rupture should be considered as a differential diagnosis in pregnant women presenting with acute abdomen. In this case, although there was uterine rupture in the second trimester and a complete placental separation, fetus was alive which is quite unusual in patients presenting with rupture uterus.
Myositis ossificans: the mimicker
Authors: Govindarajan Arunkumar , Sarawagi Radha , Prakash Manikka Lakshmanan
Published: December 2013

A 14-year-old boy presented with upper backache and a painful swelling in the right paraspinal region for 7 days. He had no history of trauma. MRI showed a non-specific ill-defined heterogeneous lesion, which showed intense postcontrast enhancement. Ultrasonogram showed a peripheral sheet of calcification around the lesion. A CT scan showed a faint rim of calcification, which increased in thickness over weeks, confirming the diagnosis as myositis ossificans. We present our approach to the case and also review the imaging features of different stages of the disease process and their differentials.
Late diagnosis of Lesch-Nyhan disease variant
Authors: Doucet Brian Percy , Jegatheesan Dev , Burke John
Published: December 2013

A 30-year-old man was referred for investigation and management of hyperuricaemia. History included recurrent nephrolithiasis and chronic gout with poor response to medical management. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) enzyme activity was investigated and found to be deficient confirming the diagnosis of Lesch-Nyhan disease. Hyperuricaemia was treated with allopurinol. To prevent nephrolithiasis, the patient was instructed to avoid dehydration and aim for a minimum urine output of 2 L/day. Urinary alkalinisation with potassium citrate was started. The patient was referred for genetic counselling. This case discusses the genetics, pathophysiology, clinical manifestations, diagnosis and management of HGPRT deficiency.
What happens to deformed rocks after deformation? A refined model for recovery based on numerical simulations
Authors: Borthwick V. E. , Piazolo S. , Evans L. , Griera A. , Bons P. D.
Published: December 2013

Deformation, in large parts of the middle crust, results in strained rocks consisting of grains with variable dislocation densities and microstructures which are characterized by gradual distortion and subgrain structures. Post-deformation residence of these rocks at elevated temperatures results in microstructural adjustments through static recovery and recrystallization. Here, we employ a numerical technique to simulate intragrain recovery at temperatures at or below the deformation temperature. The simulation is based on minimization of the stored energy, related to misorientation through local rotation of physical material points relative to their immediate environment. Three temperature- and/or deformation-geometry-dependent parameters were systematically varied: (1) deformation-induced dislocation types, (2) dislocation mobility and (3) size of dislocation interaction volume. Comparison with previously published
in situ
experiments shows consistency of numerical and experimental results. They show temperature- and dislocation-type-dependent small-scale fluctuations in subgrain-boundary misorientations and orientation variation within subgrains. These can be explained by the combined effect of increase in dislocation interaction volume and activation of climb. Our work shows microstructure can be significantly modified even if the post-deformational temperature is at or below the deformation temperature: a scenario relevant for most deformed rocks.
Controlled and self-organized routing for large-scale wireless sensor networks
Authors: Kominami Daichi , Sugano Masashi , Murata Masayuki , Hatauchi Takaaki
Published: December 2013

Improving the scalability and robustness of wireless sensor networks is an important task, and much research on self-organization has been conducted toward this end. However, desired behavior is not yet guaranteed in much larger networks based on pure self-organization. In this article, we propose a controlled potential-based routing protocol implementing a novel
controlled self-organization
scheme that also allows for external control. The scheme obtains close-to-optimal network behavior by this external control which controls a part of nodes in the network. We show that global traffic flow can be controlled through simulation experiments with a multi-sink sensor network. For example, traffic loads can be equalized among heterogeneously distributed sink nodes, and load balancing among the relay nodes based on remaining energy can bring an approximate four times extension of network lifetime. The proposed method is furthermore robust to message loss and resilient to failure of the sink node.
The GINSENG system for wireless monitoring and control
Authors: O'donovan Tony , Brown James , Büsching Felix , Cardoso Alberto , Cecílio José , Ó Jose Do , Furtado Pedro , Gil Paulo , Jugel Anja , Pöttner Wolf-Bastian , Roedig Utz , Silva Jorge Sá , Silva Ricardo , Sreenan Cormac J. , Vassiliou Vasos , Voigt Thiemo , Wolf Lars , Zinonos Zinon
Published: December 2013

Today's industrial facilities, such as oil refineries, chemical plants, and factories, rely on wired sensor systems to monitor and control the production processes. The deployment and maintenance of such cabled systems is expensive and inflexible. It is, therefore, desirable to replace or augment these systems using wireless technology, which requires us to overcome significant technical challenges. Process automation and control applications are mission-critical and require timely and reliable data delivery, which is difficult to provide in industrial environments with harsh radio environments. In this article, we present the GINSENG system which implements performance control to allow us to use wireless sensor networks for mission-critical applications in industrial environments. GINSENG is a complete system solution that comprises on-node system software, network protocols, and back-end systems with sophisticated data processing capability. GINSENG assumes that a deployment can be carefully planned. A TDMA-based MAC protocol, tailored to the deployment environment, is employed to provide reliable and timely data delivery. Performance debugging components are used to unintrusively monitor the system performance and identify problems as they occur. The article reports on a real-world deployment of GINSENG in an especially challenging environment of an operational oil refinery in Sines, Portugal. We provide experimental results from this deployment and share the experiences gained. These results demonstate the use of GINSENG for sensing and actuation and allow an assessment of its ability to operate within the required performance bounds. We also identify shortcomings that manifested during the evaluation phase, thus giving a useful perspective on the challenges that have to be overcome in these harsh application settings.
Joint
k
-coverage and data gathering in sparsely deployed sensor networks -- Impact of purposeful mobility and heterogeneity
Authors: Ammari Habib M.
Published: December 2013

Coverage is one of the fundamental concepts in the design of wireless sensor networks (WSNs) in the sense that the monitoring quality of a phenomenon depends on the quality of service provided by the sensors in terms of how well a field of interest is covered. It enables the sensors to detect any event that may occur in the field, thus, meeting the application-specific requirements. Several applications require
k
-
coverage
, where each point in the field is covered by at least
k
sensors, which helps increase data availability to ensure better data reliability. Achieving
k
-coverage of a field of interest becomes a more challenging issue in sparsely deployed WSNs. Though the problem of coverage in WSNs has been well studied in the literature, only little research efforts have been devoted to the case of sparsely deployed WSNs. Thus, in this article, we investigate the problem of
k
-coverage in sparse WSNs using static and mobile sensors, which do not necessarily have the same communication range, sensing range, and energy supply. Precisely, we propose an optimized, generalized framework for
k
-coverage in sparsely deployed WSNs, called
k
-SCHEMES, which exploits sensor heterogeneity and mobility. First, we characterize
k
-coverage using heterogeneous sensors based on
Helly
's Theorem. Second, we introduce our energy-efficient four-tier architecture to achieve mobile
k
-coverage of a region of interest in a field. Third, on top of this architecture, we suggest two data-gathering protocols, called direct data-gathering and forwarding chain-based data-gathering, using the concept of mobile proxy sink. We found that the second data-gathering protocol outperforms the first one. For energy-efficient forwarding, we compute the minimum transmission distance between any pair of consecutive mobile proxy sinks forming the forwarding chain as well as the corresponding optimum number of mobile proxy sinks in this chain. We corroborate our analysis with several simulation results.
STARR-DCS
Authors: Cuevas Ángel , Urueña Manuel , Veciana Gustavo de , Yadav Aditya
Published: December 2013

This article presents a novel framework for data-centric storage (DCS) in a wireless sensor and actor network (WSAN) that employs a randomly selected set of data replication nodes, which also change over time. This enables reductions in the average network traffic and energy consumption by adapting the number of replicas to applications' traffic, while balancing energy burdens by varying their locations. To that end, we propose and validate a simple model to determine the optimal number of replicas, in terms of minimizing average traffic/energy consumption, based on measurements of applications' production and consumption traffic. Simple mechanisms are proposed to decide when the current set of replication nodes should be changed, to enable new applications and nodes to efficiently bootstrap into a working WSAN, to recover from failing nodes, and to adapt to changing conditions. Extensive simulations demonstrate that our approach can extend a WSAN's lifetime by at least 60%, and up to a factor of 10× depending on the lifetime criterion being considered. The feasibility of the proposed framework has been validated in a prototype with 20 resource-constrained motes, and the results obtained via simulation for large WSANs have been also corroborated in that prototype.
Improving wireless link simulation using multilevel markov models
Authors: Kamthe Ankur , Carreira-Perpiñán Miguel Á , Cerpa Alberto E.
Published: December 2013

Modeling the behavior of 802.15.4 links is a nontrivial problem, because 802.15.4 links experience different level of dynamics at short and long time scales. This makes the design of a suitable model that combines the different dynamics at different time scales a nontrivial problem. We propose a novel multilevel approach, the M&M model, involving hidden Markov models (HMMs) and mixtures of multivariate Bernoullis (MMBs) for modeling the long and short time-scale behavior of wireless links from 802.15.4 test beds. We characterize the synthetic traces generated from our model of the wireless link in terms of the mean and variance of the packet reception rates from the data traces, comparison of distributions of run lengths, and conditional packet delivery functions of successive packet receptions (1's) and losses (0's). Our results show that when compared to the closest-fit pattern matching model in TOSSIM, the proposed modeling approach is able to mimic the behavior of the data traces quite closely, with differences in packet reception rates of the empirical and simulated traces of less than 1.9%; on average and 6.6% in the worst case. Moreover, the simulated links from our proposed approach were able to account for long runs of 1's and 0's as observed in empirical data traces.
Automated generation of polyhedral process networks from affine nested-loop programs with dynamic loop bounds
Authors: Nadezhkin Dmitry , Nikolov Hristo , Stefanov Todor
Published: December 2013

The Process Networks (PNs) is a suitable parallel model of computation (MoC) used to specify embedded streaming applications in a parallel form facilitating the efficient mapping onto embedded parallel execution platforms. Unfortunately, specifying an application using a parallel MoC is a very difficult and highly error-prone task. To overcome the associated difficulties, we have developed the
pn
compiler, which derives specific Polyhedral Process Networks (PPN) parallel specifications from sequential static affine nested loop programs (SANLPs). However, there are many applications, for example, multimedia applications (MPEG coders/decoders, smart cameras, etc.) that have adaptive and dynamic behavior which cannot be expressed as SANLPs. Therefore, in order to handle dynamic multimedia applications, in this article we address the important question whether we can relax some of the restrictions of the SANLPs while keeping the ability to perform compile-time analysis and to derive PPNs. Achieving this would significantly extend the range of applications that can be parallelized in an automated way.

The main contribution of this article is a first approach for automated translation of affine nested loop programs with dynamic loop bounds into input-output equivalent Polyhedral Process Networks. In addition, we present a method for analyzing the execution overhead introduced in the PPNs derived from programs with dynamic loop bounds. The presented automated translation approach has been evaluated by deriving a PPN parallel specification from a real-life application called Low Speed Obstacle Detection (LSOD) used in the smart cameras domain. By executing the derived PPN, we have obtained results which indicate that the approach we present in this article facilitates efficient parallel implementations of sequential nested loop programs with dynamic loop bounds. That is, our approach reveals the possible parallelism available in such applications, which allows for the utilization of multiple cores in an efficient way.