bluuebunny/crossref_metadata_2025 huggingface dataset:
What Happens at the Polling Place: Using Administrative Data to Look Inside Elections
Authors: Burden Barry C. , Canon David T. , Mayer Kenneth R. , Moynihan Donald P. , Neiheisel Jacob R.
Published: July 2016

Tremendous attention has been paid to local election administration since the 2000 presidential election meltdown, yet policy makers still lack basic information about what happens at the polling place. One strategy to understand the interactions between citizens and street‐level election bureaucrats is to turn to administrative data. Using logs collected by polling place workers, the authors analyze more than 66,000 individual incidents recorded from four different statewide elections. Such data provide novel insights and guidance for the administration of elections. Findings indicate that task scale (in terms of the number of ballots) and complexity (in terms of absentee ballots) increase the incident rate. Managerial choices about how polling places are run also matter: the use of electronic voting machines and central count processing of ballots reduce the incident rate, while splitting poll worker shifts increases it. Operator capacity, measured in terms of experience, also reduces the number of incidents.
Effects of acute static, ballistic, and PNF stretching exercise on the muscle and tendon tissue properties
Authors: Konrad A. , Stafilidis S. , Tilp M.
Published: July 2016

The purpose of this study was to investigate the influence of a single static, ballistic, or proprioceptive neuromuscular facilitation (PNF) stretching exercise on the various muscle‐tendon parameters of the lower leg and to detect possible differences in the effects between the methods. Volunteers (n = 122) were randomly divided into static, ballistic, and PNF stretching groups and a control group. Before and after the 4 × 30 s stretching intervention, we determined the maximum dorsiflexion range of motion (RoM) with the corresponding fascicle length and pennation angle of the gastrocnemius medialis. Passive resistive torque (PRT) and maximum voluntary contraction (MVC) were measured with a dynamometer. Observation of muscle‐tendon junction (MTJ) displacement with ultrasound allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate stiffness. Although RoM increased (static: +4.3%, ballistic: +4.5%, PNF: +3.5%), PRT (static: −11.4%, ballistic: −11.5%, PNF: −13,7%), muscle stiffness (static: −13.1%, ballistic: −20.3%, PNF: −20.2%), and muscle‐tendon stiffness (static: −11.3%, ballistic: −10.5%, PNF: −13.7%) decreased significantly in all the stretching groups. Only in the PNF stretching group, the pennation angle in the stretched position (−4.2%) and plantar flexor MVC (−4.6%) decreased significantly. Multivariate analysis showed no clinically relevant difference between the stretching groups. The increase in RoM and the decrease in PRT and muscle‐tendon stiffness could be explained by more compliant muscle tissue following a single static, ballistic, or PNF stretching exercise.
Do Public Officials Trust Citizens? A Welfare State Perspective
Authors: Van de Walle Steven , Lahat Lihi
Published: July 2016

In this exploratory study,we investigate whether public sector officials and non‐public sector officials differ in the trust they have in members of society and whether this difference is associated with the welfare regime in which they work. Using survey data from the sixth round of the European Social Survey,we compare public sector officials'trust to that of non‐public sector officials in 13 countries with four different forms of welfare regimes. Our results demonstrate that public officials have a higher level of trust than non‐public officials do. Furthermore,trust among both public and non‐public sector officials is much higher in social‐democratic regimes,followed by corporatist countries,liberal regimes,Israel(as a unique case)and,lastly,southern European regimes. As expected,public officials'degree of trust reflects the general trends of their societies. Interestingly,in social‐democratic regimes,differences between trust among public and non‐public officials are the highest compared to the other regimes. In addition,an individual‐level analysis in five countries illustrative of each welfare regime indicates that while income,belonging to a minority group,and age are significant factors in explaining public officials'trust,socio‐demographic variables contribute little to the differences between public and non‐public officials. Given the critical role of trust in the functioning of the welfare state,our results imply that further awareness and mechanisms for increasing the degree of trust of citizens among public officials are warranted.
Effect of low‐temperature biochar derived from pig manure and poultry litter on mobile and organic matter‐bound forms of Cu, Cd, Pb and Zn in sandy soil
Authors: Gondek K. , Mierzwa‐Hersztek M.
Published: July 2016

Numerous studies conducted so far have shown that biochar has a significant effect on physical, chemical and biological properties of soils. Biochar can be used to alleviate the effects of soil contamination with organic and inorganic compounds, for instance, to reduce the mobility of heavy metals. The aim of the research was to evaluate the effect of pig manure and poultry litter, as well as biochars produced from these materials at a temperature of 300 °C on Cu, Cd, Pb and Zn contents in mobile and organic matter‐bound forms in soil. The research was conducted under laboratory conditions. The materials were introduced into sandy acid soil in doses of 0.5, 1.0 and 2.0% w/w. The application of pig manure‐derived biochar (BPM) and poultry litter‐derived biochar (BPL), depending on the amount added, reduced the mobility of copper from 28 to 69%, from 77 to 100% in the case of cadmium, from 94 to 99% in the case of lead, and from 15 to 97% in the case of zinc. The 2% amendment of pig manure (PM) and poultry litter (PL) caused an increase in the content of Cu extracted with NH4NO3 in comparison with the control treatment. A similar situation was observed in the case of zinc after the application of 0.5 and 1% amendments of pig manure (PM). Cu, Cd, Pb and Zn contents extracted with 0.025 mol C10H22N4O8 were higher than contents of these elements extracted with 1 m NH4NO3, mainly due to different extraction force of the extractants. The obtained results indicate that, compared with the content determined in soil from the control treatment, 1 and 2% amendments of both unconverted and thermally converted materials to the soil had a greater effect on contents of Cu, Pb and Zn in the organic matter‐bound fraction than the 0.5% amendment. The organic materials applied did not affect the content of cadmium in organic matter‐bound fraction.
The Minimum Step Linkage Algorithm and Cumulative Cost Model for Time‐Dependent Shortest Paths
Authors: Indriasari Vini , Dean Denis
Published: July 2016

Real‐word road networks are typically time‐dependent, but research on time‐dependent shortest paths (TDSPs) is not as rich as that on static shortest paths (SSPs). For large networks, some speed‐up techniques are usually applied to compute SSPs. Unfortunately, many of these techniques are impractical for TDSPs, especially the techniques requiring a precomputation because the number of time instances may be incredibly large or even infinite. Therefore, this study introduced a new TDSP technique that is able to overcome the issue of infinite time instances by utilizing network geometry alone for the pre‐computation, namely the Minimum Step Linkage (MSL) algorithm. It works with a data model called Cumulative Cost Model (CCM). The theoretical concepts of the new data model and algorithm are described, and its performances were tested and compared with existing algorithms through a series of simulations.
An Integrated Bio-Anode Using Yeast Extract for a High-Temperature Glucose Fuel Cell
Authors: Kasahara Koichi , Ishitobi Hirokazu , Yamamori Shota , Nakagawa Nobuyoshi
Published: July 2016

By modifying the carbon electrode with a yeast extract (YE) using a support material (SM), a complete bio-anode was established without adding any extrinsic enzymes and mediators in a glucose–air fuel cell. The yeast extract was mixed into a paste with carbon black and an SM, i.e., glutaraldehyde (GA), TritonX-100, polyethyleneglycol, chitosan, or agarose. Chitosan was the best support, producing lower overpotentials and a good stability. Optimization of the paste composition and its loading were carried out for the bio-anode of a glucose–air fuel cell. The fuel cell generated a power of 33 μW cm−2 at 333 K with an aqueous glucose solution without adding any extrinsic enzymes and mediators. It showed about 70% of the initial power output at a stable condition. The bio-anode is expected to be used for energy recovery from hot wastewater-containing glucose.
Unsteady Operation of a Highly Supersonic Organic Rankine Cycle Turbine
Authors: Rinaldi Enrico , Pecnik Rene , Colonna Piero
Published: July 2016

Organic Rankine cycle (ORC) turbogenerators are the most viable option to convert sustainable energy sources in the low-to-medium power output range (from tens of kWe to several MWe). The design of efficient ORC turbines is particularly challenging due to their inherent unsteady nature (high expansion ratios and low speed of sound of organic compounds) and to the fact that the expansion encompasses thermodynamic states in the dense vapor region, where the ideal gas assumption does not hold. This work investigates the unsteady nonideal fluid dynamics and performance of a high expansion ratio ORC turbine by means of detailed Reynolds-averaged Navier–Stokes (RANS) simulations. The complex shock interactions resulting from the supersonic flow (M ≈ 2.8 at the vanes exit) are related to the blade loading, which can fluctuate up to 60% of the time-averaged value. A detailed loss analysis shows that shock-induced boundary layer separation on the suction side of the rotor blades is responsible for most of the losses in the rotor, and that further significant contributions are given by the boundary layer in the diverging part of the stator and by trailing edge losses. Efficiency loss due to unsteady interactions is quantified in 1.4% in absolute percentage points at design rotational speed. Thermophysical properties are found to feature large variations due to temperature even after the strong expansion in the nozzle vanes, thus supporting the use of accurate fluid models in the whole turbine stage.
Heterogeneous Optimization Strategies for Carved and Squealer-Like Turbine Blade Tips
Authors: De Maesschalck C. , Lavagnoli S. , Paniagua G. , Verstraete T. , Olive R. , Picot P.
Published: July 2016

Superior rotor tip geometries possess the potential to simultaneously mitigate aerodynamic losses and severe thermal loads onto the rotor overtip region. However, classical design strategies are usually constrained to a specific type of geometry, narrowing the spread of shape topologies considered during the design phase. The current paper presents two novel multi-objective optimization methodologies that enable the exploration of a broad range of distinct tip configurations for unshrouded rotor blades. The first methodology is a shape optimization process that creates a fully carved blade tip shape defined through a Bezier surface controlled by 40 parameters. Combined with a differential evolution (DE) optimization strategy, this approach is applied to a rotor blade for two tip gap sizes: 0.85% (tight) and 1.38% (design) of the blade span. The second methodology is based on a topology optimization process that targets the creation of arbitrary tip shapes comprising one or multiple rims with a fixed height. The tip section of the blade has been divided into more than 200 separate zones, where each zone can be either part of an upstanding rim or part of the cavity floor. This methodology was tested with a level-set approach in combination with a DE optimizer and coupled to an optimization routine based on genetic algorithms (GAs). The current study was carried out on a modern high-pressure turbine operating at engine-like Reynolds and high subsonic outlet Mach numbers. A fully hexahedral unstructured mesh was used to discretize the fluid domain. The aerothermal performance of each tip profile was evaluated accurately through Reynolds-averaged Navier–Stokes (RANS) simulations adopting the shear-stress transport (SST) turbulence model. Multi-objective optimizations were set for both design strategies that target higher aerodynamic rotor efficiencies and simultaneous minimization of the heat load. This paper illustrates a wide variety of profiles obtained throughout the optimization and compares the performance of the different strategies. The research shows the potential of such novel methodologies to reach new unexplored types of blade tip designs with enhanced aerothermal performances.
Theoretical Prediction of Laminar Burning Speed and Ignition Delay Time of Gas-to-Liquid Fuel
Authors: Yu Guangying , Askari Omid , Hadi Fatemeh , Wang Ziyu , Metghalchi Hameed , Kannaiyan Kumaran , Sadr Reza
Published: July 2016

Gas-to-liquid (GTL), an alternative synthetic jet fuel derived from natural gas through Fischer–Tropsch (F–T) process, has gained significant attention due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay, laminar burning speed, and emission characteristics has been experimentally studied. However, the development of chemical mechanism to predict those parameters for GTL fuel is still in its early stage. The GTL aviation fuel from Syntroleum Corporation, S-8, is used in this study. For theoretical predictions, a mixture of 32% iso-octane, 25% n-decane, and 43% n-dodecane by volume is considered as the surrogate for S-8 fuel. In this work, a detailed kinetics model (DKM) has been developed based on the chemical mechanisms reported for the GTL fuel. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL over a wide range of temperatures, pressures, and equivalence ratios. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the steady one-dimensional premixed flame code from CANTERA is used in conjunction with the chemical mechanisms to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions. Comparison of ignition delay and laminar burning speed shows that the Ranzi et al. mechanism has a better agreement with the available experimental data, and therefore is used for further evaluation in this study.
Computational Assessment of the Relation Between Embolism Source and Embolus Distribution to the Circle of Willis for Improved Understanding of Stroke Etiology
Authors: Mukherjee Debanjan , Jani Neel D. , Selvaganesan Kartiga , Weng Christopher L. , Shadden Shawn C.
Published: July 2016

Stroke caused by an embolism accounts for about a third of all stroke cases. Understanding the source and cause of the embolism is critical for diagnosis and long-term treatment of such stroke cases. The complex nature of the transport of an embolus within large arteries is a primary hindrance to a clear understanding of embolic stroke etiology. Recent advances in medical image-based computational hemodynamics modeling have rendered increasing utility to such techniques as a probe into the complex flow and transport phenomena in large arteries. In this work, we present a novel, patient-specific, computational framework for understanding embolic stroke etiology, by combining image-based hemodynamics with discrete particle dynamics and a sampling-based analysis. The framework allows us to explore the important question of how embolism source manifests itself in embolus distribution across the various major cerebral arteries. Our investigations illustrate prominent numerical evidence regarding (i) the size/inertia-dependent trends in embolus distribution to the brain; (ii) the relative distribution of cardiogenic versus aortogenic emboli among the anterior, middle, and posterior cerebral arteries; (iii) the left versus right brain preference in cardio-emboli and aortic-emboli transport; and (iv) the source–destination relationship for embolisms affecting the brain.
Canyoneering Fluid Mechanics
Authors: Brennen Christopher Earls
Published: July 2016

Extreme sports such as canyoneering have expanded greatly since the turn of the century yet little scientific attention has been paid to the analyses of the dangers of those activities. The author was much involved in promoting one such sport, namely canyoneering, and presents this paper as an example of the kind of fluids engineering analyses that are needed in order to objectively quantify those dangers and properly advise the participants. In canyoneering, the primary fluid-related sources of danger are the impact of falling water on the human body and the dangers a swimmer faces in a plunge pool. This paper presents rough evaluations of both dangers.
Design of Deformable Tools for Sheet Metal Forming
Authors: Iorio Lorenzo , Pagani Luca , Strano Matteo , Monno Michele
Published: July 2016

Traditionally, industrial sheet metal forming technologies use rigid metallic tools to plastically deform the blanks. In order to reduce the tooling costs, rubber or flexible tools can be used together with one rigid (metallic) die or punch, in order to enforce a predictable and repeatable geometry of the stamped parts. If the complete tooling setup is built with deformable tools, the final part quality and geometry are hardly predictable and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The FEM simulation model has been first validated by comparing the experiments done at different levels of the process parameters. After the experimental validation of the FEM model, a compensation algorithm has been implemented for reducing the error between the simulated component and the designed one. The tooling setup is made of machined thermoset polyurethane (PUR) punch, die, and blank holder, for the deep drawing of an aluminum part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic. The proposed procedure is iterative. It allows, already after the first iteration, to reduce the geometrical deviation between the actual stamped part and the designed geometry. This methodology represents one step toward the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.
Mass Customization: Reuse of Digital Slicing for Additive Manufacturing
Authors: Kwok Tsz-Ho , Ye Hang , Chen Yong , Zhou Chi , Xu Wenyao
Published: July 2016

Additive manufacturing, also known as three-dimensional (3D) printing, enables production of complex customized shapes without requiring specialized tooling and fixture, and mass customization can then be realized with larger adoption. The slicing procedure is one of the fundamental tasks for 3D printing, and the slicing resolution has to be very high for fine fabrication, especially in the recent developed continuous liquid interface production (CLIP) process. The slicing procedure is then becoming the bottleneck in the prefabrication process, which could take hours for one model. This becomes even more significant in mass customization, where hundreds or thousands of models have to be fabricated. We observe that the customized products are generally in a same homogeneous class of shape with small variation. Our study finds that the slicing information of one model can be reused for other models in the same homogeneous group under a properly defined parameterization. Experimental results show that the reuse of slicing information has a maximum of 50 times speedup, and its utilization is dropped from more than 90% to less than 50% in the prefabrication process.
MAXFAS: Mechatronic Arm Exoskeleton for Firearm Aim Stabilization
Authors: Baechle Daniel M. , Wetzel Eric D. , Agrawal Sunil K.
Published: July 2016

This article details the design, fabrication, and application of a mechatronic arm exoskeleton for firearm aim stabilization (MAXFAS), which senses and damps involuntary tremors in the arm. Human subject experiments were carried out using the device in a simulated shooting and aiming task. Results indicate that MAXFAS reduced arm tremors and improved shooting performance while wearing the device. Residual performance improvement after removing the device and possible training function of MAXFAS will also be discussed.
Layerwise Analyses of Compact and Thin-Walled Beams Made of Viscoelastic Materials
Authors: Filippi Matteo , Carrera Erasmo , Regalli Andrea M.
Published: July 2016

This paper evaluates the vibration characteristics of structures with viscoelastic materials. The mechanical properties of viscoelastic layers have been described with the complex modulus approach. The equations of motion are derived using the principle of virtual displacement (PVD), and they are solved through the finite element method (FEM). Higher-order beam elements have been derived with the Carrera Unified Formulation (CUF), which enables one to go beyond the assumptions of the classical one-dimensional (1D) theories. According to the layerwise approach, Lagrange-like polynomial expansions have been adopted to develop the kinematic assumptions. The complex nonlinear dynamic problem has been solved through an iterative technique in order to consider both constant and frequency-dependent material properties. The results have been reported in terms of frequencies and modal loss factors, and they have been compared with available results in the literature and numerical three-dimensional (3D) finite element (FE) solutions. The proposed beam elements have enabled bending, torsional, shell-like, and coupled mode shapes to be detected.
Aspects of Computational Homogenization at Finite Deformations: A Unifying Review From Reuss' to Voigt's Bound
Authors: Saeb Saba , Steinmann Paul , Javili Ali
Published: July 2016

The objective of this contribution is to present a unifying review on strain-driven computational homogenization at finite strains, thereby elaborating on computational aspects of the finite element method. The underlying assumption of computational homogenization is separation of length scales, and hence, computing the material response at the macroscopic scale from averaging the microscopic behavior. In doing so, the energetic equivalence between the two scales, the Hill–Mandel condition, is guaranteed via imposing proper boundary conditions such as linear displacement, periodic displacement and antiperiodic traction, and constant traction boundary conditions. Focus is given on the finite element implementation of these boundary conditions and their influence on the overall response of the material. Computational frameworks for all canonical boundary conditions are briefly formulated in order to demonstrate similarities and differences among the various boundary conditions. Furthermore, we detail on the computational aspects of the classical Reuss' and Voigt's bounds and their extensions to finite strains. A concise and clear formulation for computing the macroscopic tangent necessary for FE2 calculations is presented. The performances of the proposed schemes are illustrated via a series of two- and three-dimensional numerical examples. The numerical examples provide enough details to serve as benchmarks.
Investigation of the Thermal Performances of Flat, Finned, and v-Corrugated Plate Solar Air Heaters
Authors: Kabeel A. E. , Khalil A. , Shalaby S. M. , Zayed M. E.
Published: July 2016

In this research, the thermal performances of flat, finned, and v-corrugated plate solar air heaters were investigated experimentally. A solar air heater with single glass cover, single pass was designed and tested under prevailing weather conditions of Tanta city (30°43′ N, 31° E), Egypt. The solar air heater was designed to be easy to replace the absorber plate from one to another one. Comparisons between the temperature difference of air across the heater and thermal efficiencies of the flat, finned, and v-corrugated plate solar air heaters were presented. The effect of change in the mass flow rate of air on the outlet air temperature and the thermal efficiency of the heater were also studied when the mass flow rates were 0.062, 0.028, and 0.009 kg/s. The experimental results showed that the maximum value of outlet temperature of the v-corrugated plate solar air heater was 5 and 3.5 °C more than that of flat and finned plates when the mass flow rate was 0.062 kg/s, respectively. And, it increased to be 8 and 5.5 C when the mass flow rate was 0.009 kg/s. It is also indicated that the thermal efficiency of the v-corrugated solar air heater is 8–14.5% and 6–10.5% higher than that of the flat and finned plate heaters, respectively, when the mass flow rate was 0.062 kg/s under the considered configurations and operating conditions. The experimental results also indicated that the convective heat transfer coefficient of the v-corrugated heater reached up to 1.64 and 1.36 times than that of the flat and finned heaters, respectively, when the flow rate was 0.062 kg/s.
Mechanism of Nonsynchronous Blade Vibration in a Transonic Compressor Rig
Authors: Möller Daniel , Jüngst Maximilian , Holzinger Felix , Brandstetter Christoph , Schiffer Heinz-Peter , Leichtfuß Sebastian
Published: July 2016

This paper presents a numerical study on blade vibration for the transonic compressor rig at the Technische Universität Darmstadt (TUD), Darmstadt, Germany. The vibration was experimentally observed for the second eigenmode of the rotor blades at nonsynchronous frequencies and is simulated for two rotational speeds using a time-linearized approach. The numerical simulation results are in close agreement with the experiment in both cases. The vibration phenomenon shows similarities to flutter. Numerical simulations and comparison with the experimental observations showed that vibrations occur near the compressor stability limit due to interaction of the blade movement with a pressure fluctuation pattern originating from the tip clearance flow. The tip clearance flow pattern travels in the backward direction, seen from the rotating frame of reference, and causes a forward traveling structural vibration pattern with the same phase difference between blades. When decreasing the rotor tip gap size, the mechanism causing the vibration is alleviated.
Applying Physiologically Relevant Strains to Tenocytes in an In Vitro Cell Device Induces In Vivo Like Behaviors
Authors: Joo Kim Jung , Musson David S. , Matthews Brya G. , Cornish Jillian , Anderson Iain A. , Shim Vickie B.
Published: July 2016

We have developed a novel cell stretching device (called Cell Gym) capable of applying physiologically relevant low magnitude strains to tenocytes on a collagen type I coated membrane. We validated our device thoroughly on two levels: (1) substrate strains, (2) cell level strains. Our cell level strain results showed that the applied stretches were transferred to cells accurately (∼90%). Our gene expression data showed that mechanically stimulated tenocytes (4%) expressed a lower level of COL I gene. COX2 gene was increased but did not reach statistical significance. Our device was then tested to see if it could reproduce results from an in vivo study that measured time-dependent changes in collagen synthesis. Our results showed that collagen synthesis peaked at 24 hrs after exercise and then decreased, which matched the results from the in vivo study. Our study demonstrated that it is important to incorporate physiologically relevant low strain magnitudes in in vitro cell mechanical studies and the need to validate the device thoroughly to operate the device at small strains. This device will be used in designing novel tendon tissue engineering scaffolds in the future.
Characterization of Creeping and Shape Memory Effect in Laser Sintered Thermoplastic Polyurethane
Authors: Yuan Shangqin , Bai Jiaming , Kai Chua Chee , Zhou Kun , Wei Jun
Published: July 2016

Thermoplastic polyurethane (TPU) powders were successfully processed in a selective laser sintering (SLS) system. The laser-sintered polyurethane products with viscoelastic behaviors exhibit high flexibility and elongation at break at room temperature. Moreover, the creeping and the thermoresponsive shape-memory effects (SME) were also characterized. The influences of the time-temperature relevant parameters on the shape-fixity and shape-recovery ratios were investigated quantitatively. The creeping and SME were time–temperature dependent phenomena, and the shape recovery mechanism is associated to the microsegments thermal transitions within the polymer matrix.
Dynamic Computation of Time-Varying Spatial Contexts
Authors: Horváth Imre , Li Yongzhe , Rusák Zoltán , van der Vegte Wilhelm Frederik , Zhang Guangjun
Published: July 2016

There are many real-life processes whose smart control requires processing context information. Though processing time-varied context information is addressed in the literature, domain-independent solutions for reasoning about time-varying process scenarios are scarce. This paper proposes a method for dynamic context computation concerning spatial and attributive information. Context is interpreted as a body of information dynamically created by a pattern of entities and relationships over a history of situations. Time is conceived as a causative force capable of changing situations and acting on people and objects. The invariant and variant spatial information is captured by a two-dimensional spatial feature representation matrix (SFR-matrix). The time-dependent changes in the context information are computed based on a dynamic context information (DCI) management hyper-matrix. This humble but powerful representation lends itself to a quasi-real time computing and is able to provide information about foreseeable happenings over multiple situations. Based on this, the reasoning mechanism proposed in this paper is able to provide informative instructions for users who needed to be informed in a dynamically changing situation. This paper uses the practical case of evacuation of a building in fire both as an explorative case for conceptualization of the functionality of the computational mechanism and as a demonstrative and testing application. Our intention is to use the dynamic context computation mechanism as a kernel component of a reasoning platform for informing cyber-physical systems (I-CPSs). Our future research will address the issue of context information management for multiple interrelated spaces.
Multi-Objective Optimization With Multiple Spatially Distributed Surrogates
Authors: Shankar Bhattacharjee Kalyan , Kumar Singh Hemant , Ray Tapabrata
Published: July 2016

In engineering design optimization, evaluation of a single solution (design) often requires running one or more computationally expensive simulations. Surrogate assisted optimization (SAO) approaches have long been used for solving such problems, in which approximations/surrogates are used in lieu of computationally expensive simulations during the course of search. Existing SAO approaches often use the same type of approximation model to represent all objectives and constraints in all regions of the search space. The selection of a type of surrogate model over another is nontrivial and an a priori choice limits flexibility in representation. In this paper, we introduce a multi-objective evolutionary algorithm (EA) with multiple adaptive spatially distributed surrogates. Instead of a single global surrogate, local surrogates of multiple types are constructed in the neighborhood of each offspring solution and a multi-objective search is conducted using the best surrogate for each objective and constraint function. The proposed approach offers flexibility of representation by capitalizing on the benefits offered by various types of surrogates in different regions of the search space. The approach is also immune to illvalidation since approximated and truly evaluated solutions are not ranked together. The performance of the proposed surrogate assisted multi-objective algorithm (SAMO) is compared with baseline nondominated sorting genetic algorithm II (NSGA-II) and NSGA-II embedded with global and local surrogates of various types. The performance of the proposed approach is quantitatively assessed using several engineering design optimization problems. The numerical experiments demonstrate competence and consistency of SAMO.
Influence of Single Point Incremental Forming on Mechanical Properties and Chain Orientation in Thermoplastic Polymers
Authors: Davarpanah Mohammad Ali , Bansal Shalu , Malhotra Rajiv
Published: July 2016

Incremental forming of thermoplastic surfaces has recently received significant interest due to the potential for simultaneous reduction in thermal energy consumption and in part-shape specific tooling. This paper examines the mechanical properties and the chain orientation of the formed material in single point incremental forming (SPIF) of amorphous polyvinyl chloride (PVC) and semicrystalline polyamide sheets. Tensile and stress relaxation properties of the formed polymers are compared to those of the unformed polymer. The effect of incremental depth and tool rotation speed on the above properties, and on the temperature rise of the sheet during SPIF, is quantified. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) are used to compare the chain orientation and crystallinity of the formed and the unformed polymers. It is observed that the formed material has greater toughness and ductility, but lower yield stress and reduced Young's modulus, as compared to the unformed material. We also observe deformation-induced chain reorientation in the formed polymer, with minimal change in the degree of crystallinity. The link between the SPIF process parameters, temperature rise of the polymer during SPIF, change in chain orientation, and change in mechanical properties of the polymer is discussed.
LPCVD SiNx thin film on c-Si wafer by spectroscopic ellipsometry
Authors: Gautam Laxmi Karki , Ye Ligang , Podraza Nikolas J.
Published: July 2016

Infrared to ultraviolet range ellipsometric spectra of thin film silicon nitride (SiNx) collected from rotating compensator instruments have been analyzed simultaneously. A common complex dielectric function (ε = ε1 + iε2) parameterization from 0.08 to 5.89 eV for amorphous 490 Å thick low pressure chemical vapor deposition SiNx, nominally x = 1.33 Si3N4, on a single crystal silicon (c-Si) wafer is determined. Visible to ultraviolet range electronic transitions at high photon energies and infrared active vibrational modes at low energies are identified.
Eagle XG® glass, optical constants from 230 to 1690 nm (0.73 - 5.39 eV) by spectroscopic ellipsometry
Authors: Cushman Cody V. , Sturgell Brandon A. , Martin Andrew C. , Lunt Barry M. , Smith Nicholas J. , Linford Matthew R.
Published: July 2016

Eagle XG® glass is widely used in the manufacture of electronic displays. Spectroscopic ellipsometry and transmission data for this material were obtained from 193 to 1690 nm. The optical constants of the material were then modeled from 230 to 1690 nm. The data were initially fit with a basis spline (B-spline), and these results were used as the starting point for either a two-Gaussian oscillator model or a Tauc-Lorentz (T-L) + Gaussian oscillator model. Both models gave good fits, with unweighted mean squared error values of ca. 1.1. Samples were provided by Corning Incorporated directly from their production facility.
Adhesion kinetics of human primary monocytes, dendritic cells, and macrophages: Dynamic cell adhesion measurements with a label-free optical biosensor and their comparison with end-point assays
Authors: Orgovan Norbert , Ungai-Salánki Rita , Lukácsi Szilvia , Sándor Noémi , Bajtay Zsuzsa , Erdei Anna , Szabó Bálint , Horvath Robert
Published: July 2016

Monocytes, dendritic cells (DCs), and macrophages (MFs) are closely related immune cells that differ in their main functions. These specific functions are, to a considerable degree, determined by the differences in the adhesion behavior of the cells. To study the inherently and essentially dynamic aspects of the adhesion of monocytes, DCs, and MFs, dynamic cell adhesion assays were performed with a high-throughput label-free optical biosensor [Epic BenchTop (BT)] on surfaces coated with either fibrinogen (Fgn) or the biomimetic copolymer PLL-g-PEG-RGD. Cell adhesion profiles typically reached their maximum at ∼60 min after cell seeding, which was followed by a monotonic signal decrease, indicating gradually weakening cell adhesion. According to the biosensor response, cell types could be ordered by increasing adherence as monocytes, MFs, and DCs. Notably, all three cell types induced a larger biosensor signal on Fgn than on PLL-g-PEG-RGD. To interpret this result, the molecular layers were characterized by further exploiting the potentials of the biosensor: by measuring the adsorption signal induced during the surface coating procedure, the authors could estimate the surface density of adsorbed molecules and, thus, the number of binding sites potentially presented for the adhesion receptors. Surfaces coated with PLL-g-PEG-RGD presented less RGD sites, but was less efficient in promoting cell spreading than those coated with Fgn; hence, other binding sites in Fgn played a more decisive role in determining cell adherence. To support the cell adhesion data obtained with the biosensor, cell adherence on Fgn-coated surfaces 30–60 min after cell seeding was measured with three complementary techniques, i.e., with (1) a fluorescence-based classical adherence assay, (2) a shear flow chamber applying hydrodynamic shear stress to wash cells away, and (3) an automated micropipette using vacuum-generated fluid flow to lift cells up. These techniques confirmed the results obtained with the high-temporal-resolution Epic BT, but could only provide end-point data. In contrast, complex, nonmonotonic cell adhesion kinetics measured by the high-throughput optical biosensor is expected to open a window on the hidden background of the immune cell–extracellular matrix interactions.
Structural and strain anisotropies of N-polar GaN epilayers on offcut sapphire substrates
Authors: Li Chengguo , Wang Hongli , Liu Hongfei , Chua Soo Jin
Published: July 2016

The dependence of the structure and strain upon the crystal direction (anisotropies) of N-polar GaN films grown on offcut c-plane sapphire substrates was examined by varying the degree of substrate offcut and the V/III ratio. On offcut substrates, the broadening of GaN (0002¯) rocking curves was found to depend upon the x-ray incidence azimuth, whereby the maxima and minima of the broadening, respectively, occurred parallel and perpendicular to the offcut direction. In contrast, no such structural anisotropies were observed for samples grown on the on-axis substrates. Mosaic tilt was suggested as the determining factor for the structural anisotropy, which was further aided by the different island coalescence rates in the two orthogonal directions during the initial nucleation stage. In addition, the off-axis samples exhibited larger in-plane strains occurring in the direction perpendicular to the substrate offcut than in other directions, which was significantly different from the uniform in-plane strain found in the on-axis sample. The in-plane strain anisotropy was attributed to preferential strain relaxation along the substrate offcut direction via the formation of geometrical partial misfit dislocations along the orthogonal direction. Moreover, the structural (strain) anisotropy decreased (increased) as the substrate offcut increased, and both anisotropies were affected only marginally by the V/III ratio.
A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements
Authors: Titovich Alexey S. , Norris Andrew N. , Haberman Michael R.
Published: July 2016

The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics of a circular region to a square dictate that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed by Titovich and Norris [J. Acoust. Soc. Am. 136(4), 1601–1609 (2014)]. The sizes of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation pattern in the four plane wave directions.
A nonlinear acoustic metamaterial: Realization of a backwards-traveling second-harmonic sound wave
Authors: Quan Li , Qian Feng , Liu Xiaozhou , Gong Xiufen
Published: July 2016

An ordinary waveguide with periodic vibration plates and side holes can realize an acoustic metamaterial that simultaneously possesses a negative bulk modulus and a negative mass density. The study is further extended to a nonlinear case and it is predicted that a backwards-traveling second-harmonic sound wave can be obtained through the nonlinear propagation of a sound wave in such a metamaterial.
Exploiting the leaky-wave properties of transmission-line metamaterials for single-microphone direction finding
Authors: Esfahlani Hussein , Karkar Sami , Lissek Hervé , Mosig Juan R.
Published: July 2016

A transmission-line acoustic metamaterial is an engineered, periodic arrangement of relatively small unit-cells, the acoustic properties of which can be manipulated to achieve anomalous physical behaviours. These exotic properties open the door to practical applications, such as an acoustic leaky-wave antenna, through the implementation of radiating channels along the metamaterial. In the transmitting mode, such a leaky-wave antenna is capable of steering sound waves in frequency-dependent directions. Used in reverse, the antenna presents a well defined direction-frequency behaviour. In this paper, an acoustic leaky-wave structure is presented in the receiving mode. It is shown that it behaves as a sound source direction-finding device using only one sensor. After a general introduction of the acoustic leaky-wave antenna concept, its radiation pattern and radiation efficiency are expressed in closed form. Then, numerical simulations and experimental assessments of the proposed transmission-line based structure, implementing only one sensor at one termination, are presented. It is shown that such a structure is capable of finding the direction of an incoming sound wave, from backward to forward, based on received sound power spectra. This introduces the concept of sound source localization without resorting to beam-steering techniques based on multiple sensors.
Generalized metamaterials: Definitions and taxonomy
Authors: Kim Noori , Yoon Yong-Jin , Allen Jont B.
Published: July 2016

This article reviews the development of metamaterials (MM), starting from Newton's discovery of the wave equation, and ends with a discussion of the need for a technical taxonomy (classification) of these materials, along with a better defined definition of metamaterials. It is intended to be a technical definition of metamaterials, based on a historical perspective. The evolution of MMs began with the discovery of the wave equation, traceable back to Newton's calculation of the speed of sound. The theory of sound evolved to include quasi-statics (Helmholtz) and the circuit equations of Kirchhoff's circuit laws, leading to the ultimate development of Maxwell's equations and the equation for the speed of light. Be it light, or sound, the speed of the wave-front travel defines the wavelength, and thus the quasi-static (QS) approximation. But there is much more at stake than QSs. Taxonomy requires a proper statement of the laws of physics, which includes at least the six basic network postulates: (P1) causality (non-causal/acausal), (P2) linearity (non-linear), (P3) real (complex) time response, (P4) passive (active), (P5) time-invariant (time varying), and (P6) reciprocal (non-reciprocal). These six postulates are extended to include MMs.
A single-phase elastic hyperbolic metamaterial with anisotropic mass density
Authors: Zhu R. , Chen Y. Y. , Wang Y. S. , Hu G. K. , Huang G. L.
Published: July 2016

Wave propagation can be manipulated at a deep subwavelength scale through the locally resonant metamaterial that possesses unusual effective material properties. Hyperlens due to metamaterial's anomalous anisotropy can lead to superior-resolution imaging. In this paper, a single-phase elastic metamaterial with strongly anisotropic effective mass density has been designed. The proposed metamaterial utilizes the independently adjustable locally resonant motions of the subwavelength-scale microstructures along the two principal directions. High anisotropy in the effective mass densities obtained by the numerical-based effective medium theory can be found and even have opposite signs. For practical applications, shunted piezoelectric elements are introduced into the microstructure to tailor the effective mass density in a broad frequency range. Finally, to validate the design, an elastic hyperlens made of the single-phase hyperbolic metamaterial is proposed with subwavelength longitudinal wave imaging illustrated numerically. The proposed single-phase hyperbolic metamaterial has many promising applications for high resolution damage imaging in nondestructive evaluation and structural health monitoring.
Validation of low frequency noise attenuation using locally resonant patches
Authors: Farooqui Maaz , Elnady Tamer , Akl Wael
Published: July 2016

Since conventional silencers in acoustic ducts have problems of size limitations at low frequencies and being prone to high backpressure, locally resonant aluminum patches are introduced in acoustic duct walls aiming at creating frequency stop bands in the low frequency region (below 1 KHz). With these flush mounted patches, promising noise reductions, with no such drawbacks, can be obtained, building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to experimentally validate the performance of an array of flexible side-wall-mounted patches inside ducts. The experimental results are compared with Analytical Green's function method as well as Numerical Finite Element Method and a close agreement was found. The results show that the presence of the patches singly or periodically can play a prominent role in designing any acoustic bandgap materials. The effect of the arrays of patches on the effective dynamic density and bulk modulus has also been investigated.