bluuebunny/crossref_metadata_2025 huggingface dataset:
Hot-Wire Measurements in a Plane Turbulent Jet
Authors: Heskestad Gunnar
Published: October 2011

Results from hot-wire measurements in a plane turbulent jet of air are reported. The jet was found to be approximately self-preserving sufficiently far downstream where measurements of intermittency and data for calculating the energy balance of the turbulent motion were obtained. Measurements were also made of the effect of the jet speed (assumed equivalent to a Reynolds-number effect for the low Mach numbers used) on the centerline development of turbulent intensity and the flatness factor of the velocity derivative at a fixed downstream centerline location.
Laminar Pressure Drop Associated With the Continuum Entrance Region and for Slip Flow in a Circular Tube
Authors: McComas S. T. , Eckert E. R. G.
Published: October 2011

The pressure drop in the entrance region of an abrupt inlet circular tube was determined experimentally. Local values of K, the dimensionless factor for laminar flow which expresses the excess of pressure drop over that of fully developed flow, were determined for the Reynolds range from 200 to 600. Variations in absolute pressure were used at each Reynolds number in order to produce different bulk velocities. The results for this Reynolds number range agreed with the analyses for smooth entrance tubes, and no dependency on bulk velocity was observed. The absolute pressure of the test section was also reduced sufficiently to obtain a large mean free path for air, thus producing a slip effect at the tube wall. Pressure-drop measurements were made for a Knudsen number range of 0.001 to 0.07, and the slip-flow correction was determined in this range. The data agreed well with Kennard’s prediction for slip flow in a tube if a value of 0.9 was used for the diffuse factor.
Experimental Investigation of Rolling Contact
Authors: Spengos Aris C.
Published: October 2011

A particular case of rolling contact, that for cylinders having different elastic constants and transmitting a tangential force in the direction of rolling, was experimentally investigated. A steel cylinder, driving a rubber-covered cylinder, was instrumented for the quantitative, as well as qualitative, investigation of the action taking place in the contact area. The results indicate the extent of the locked region at the leading edge of the contact area, the development of the slip region, and the magnitude of the constant-rate slip at the trailing edge of the contact area.
A Method of Analysis of Transient Thermal Stresses in Thermorheologically Simple Viscoelastic Solids
Authors: Valanis K. C. , Lianis George
Published: October 2011

This paper is concerned with a perturbation technique suitable for the stress analysis of viscoelastic solids with temperature-dependent properties in the presence of nonuniform transient temperature fields. The problems of the infinite slab, solid sphere, and infinitely long viscoelastic cylinder are given solutions in the form of infinite series. Sufficient conditions for the convergence of the series are established.
Steady Gravity Flow of Frictional-Cohesive Solids in Converging Channels
Authors: Jenike A. W.
Published: October 2011

Frictional-cohesive solids such as soil, ores, chemicals, sugar, flour are regarded as plastic and represented by the Jenike-Shield yield function [1] during steady flow. The stress-strain rate relations are based on isotropy, continuity, and a one-to-one dependence of density on the major pressure. In plane strain and in axial symmetry the stress field requires the solution of a system of two hyperbolic partial differential equations. The velocity field can then be computed by solving another system of two linear homogeneous partial differential equations of the hyperbolic type. In straight conical channels, a particular stress field called the “radial stress field” assumes a special importance because evidence has been presented elsewhere that all general fields tend to approach the radial stress fields in the vicinity of the vertex. Examples of numerical solutions of radial stress fields are given.
On a Nonlinear Vibrating System Having Infinitely Many Limit Cycles
Authors: Klotter K. , Kreyszig E.
Published: October 2011

This investigation is concerned with a nonlinear differential equation that governs oscillations having infinitely many limit cycles. Bounds and approximations for the corresponding limit amplitudes are obtained from suitable estimates of first integrals.
Torsion of Bars With Isosceles Triangular and Diamond Sections
Authors: Gloumakoff N. A. , Yu Yi-Yuan
Published: October 2011

Torsional problems of prismatical bars with cross sections in the shape of isosceles triangles and diamonds are solved by means of a stress function used previously by Saint-Venant for a circular sector. Complete information on the magnitude and location of the maximum shearing stress and on the twisting moment is presented.
Lift, Drag, and Added-Mass Coefficients for a Circular Cylinder Immersed in a Time-Dependent Flow
Authors: Sarpkaya Turgut
Published: October 2011

Lagally’s theorem is extended to a number m of moving and growing vortices arbitrarily situated behind a circular cylinder immersed in a time-dependent ambient flow. Lift, drag, and added-mass coefficients are presented in terms of the characteristics of vortices.
Transients in Certain Autonomous Multiple-Degree-of-Freedom Nonlinear Vibrating Systems
Authors: Sethna P. R.
Published: October 2011

Oscillations of weakly nonlinear autonomous multiple-degree-of-freedom dynamical systems are studied. The analysis includes nonlinear effects arising from the potential as well as the kinetic energies of the systems and the systems include elements that produce nonlinear dissipative forces. The method of averaging is applied to a suitably transformed set of equations. In several important cases nonperiodic solutions for arbitrary initial conditions are obtained by quadratures.
The Elastic Moduli of Heterogeneous Materials
Authors: Hashin Zvi
Published: October 2011

Bounds and expressions for the elastic moduli of two or many phase nonhomogeneous materials are obtained by an approximate method based on the variational theorems of the theory of elasticity and on a concentric-spheres model. Theoretical results are in good agreement with experimental results for a two-phase alloy.
Application of Moire Methods to the Determination of Transient Stress and Strain Distributions
Authors: Riley W. F. , Durelli A. J.
Published: October 2011

When two arrays of lines are superimposed an optical phenomenon known as the moire effect is observed under certain conditions. This moire effect is used by the authors to determine the distribution of transient strains on the surface of two-dimensional bodies. The method can be used to solve completely the strain-distribution problem or it can be used in combination with photoelasticity to separate the principal stresses. The methods used in interpreting the moire fringe patterns and the techniques used to produce the patterns are described in the paper. Two applications are discussed.
Torsional Creep Buckling of Thin-Walled Open Tubes With a Cross Section Having an Axis of Symmetry
Authors: Lianis George
Published: October 2011

The variational theorem by Sanders, McComb, and Schlechte [1] is applied to find the critical collapse time of an open thin-walled tube with a cross section having an axis of symmetry subjected to torsional creep buckling. Large deformation strains are considered. It is shown that small deformation strains yield inaccurate results in predicting the critical time. A simplified stress distribution is introduced which gives a closed-form solution. More accurate stress patterns present considerable difficulties and a tedious numerical integration is needed. In examining most cases, however, the simplified stress configuration predicts the critical time very accurately.
On the Vibration of Beams or Rods Carrying a Concentrated Mass
Authors: Chen Yu
Published: October 2011

A new formulation is given to the problem of vibration of beams or rods carrying a concentrated mass in which the Dirac δ-function is used in the differential equation to describe the effect of a concentrated mass. The homogeneous differential equation which describes the free vibration is solved first by separation of variables and the resulting ordinary differential equation is then solved by Laplace transform to yield the eigenfunctions of the problem. Orthogonality relation, derived by treating the beam as a variable-density beam, is used to solve the general initial-value problem as well as the forced-vibration problem.
Extension of a Method of Solution for Poisson’s Equation
Authors: Cobble M. H. , Ames W. F.
Published: October 2011

A classical substitution procedure for solving Poisson’s equation ∇2φ = −K is extended by application of certain coordinate transformations suggested by the functional form of K. The method is applied to the determination of fluid-velocity fields in two curvilinear geometries.
Taylor Instability of a Liquid Film Around a Long, Horizontal, Circular Cylindrical Body in Still Air
Authors: Lee Shao-Lin
Published: October 2011

A combined theoretical and experimental investigation is made of the instability of a liquid film around a long, horizontal, circular cylindrical body in still air. In the theoretical investigation, a modified Taylor-type analysis is applied to a simplified physical model. Due to the curvilinear nature of the liquid-air interface, the surface tension as well as the radius of the cylinder are found to play important roles in the establishment of a criterion of instability of the problem. A critical wave length along the length of the cylinder is also found for which the instability will be amplified most rapidly. Such a critical wave length, then, naturally suggests the critical interval distance at which droplets formed as a direct consequence of the instability will break away from the liquid film. In the experimental investigation, measurements were made of a visually observable critical distance of the liquid film around each of several cylinders of different sizes. For two liquids of considerably different surface tension, the results in all cases agree closely with the suggestions made by the theoretical critical wave length.
Cavitation in Valve-Controlled Hydraulic Actuators
Authors: Wang P. K. C. , Ma J. T. S.
Published: October 2011

Results of analytical and experimental studies of cavitation in valve-controlled hydraulic actuators under various dynamic conditions are presented. The analytical work consists of deriving approximate critical cavitation conditions for various operating modes. The experimental investigation includes both a high-speed photographic study of cavity formation and tests to check the validity of the derived cavitation conditions. Close agreement between analytical and experimental results was obtained. The mechanisms governing cavity formation and cavitation effects are discussed qualitatively.
An Axisymmetric Nonlinear Vibration of Circular Plates
Authors: Bulkeley P. Z.
Published: October 2011

The response of a simple oscillator to elliptic forcing has been treated by Hsu. This note gives a solution for axisymmetric elliptic arcing of a circular elastic plate by edge moment around its circumference, the plate being otherwise free.
Some Gyroscopic Oscillations
Authors: Thorne C. J.
Published: October 2011

Consideration is given to the nonlinear terms in the differential equations governing the motion of gyroscopes under constant acceleration and a “correcting” torque. Unstable oscillations are noted when a correcting torque is present and the nonlinear terms are included.
Non-Newtonian Flow in Annuli
Authors: Rotem Zeev
Published: October 2011

Equations for the calculation of velocity profiles and flow rate for the steady, isothermal and laminar flow of an incompressible, inelastic, non-Newtonian fluid in annuli are presented. A solution for the Rabinowitsch equation type of pseudoplastic behavior is obtained as a special case. Solutions presented should prove of interest in viscosity pump and screw extruder design.
Dynamics of a Vehicle Containing Moving Parts
Authors: Grubin Carl
Published: October 2011

The dynamical equations determining the linear and angular motions of a rigid carrier vehicle which houses a number of rigid moving parts are derived. The motions of the parts either are prescribed time functions or are themselves to be determined. For the latter case, the equations given here become part of a system of coupled equations for determining simultaneously the vehicle’s motion and that of the moving parts. Two simple applications illustrating the use of the equations are presented.
An Extension of Duhamel’s Analogy to Plasticity
Authors: Murch S. A.
Published: October 2011

It is shown that the Duhamel analogy of classical elasticity theory may be extended without modification to the incremental theory of plasticity, when the loading function is temperature independent. For a class of temperature-dependent loading functions the analogy of the Duhamel type is shown to hold: (a) When the temperature field is stationary; (b) for problems in which the elastic and plastic components of strain individually satisfy compatibility; or (c) when the material is rigid plastic, provided the medium is interpreted as nonhomogeneous. Examples of particular correspondences are discussed. It is also noted that for linear viscoelastic materials in which volume changes are purely thermoelastic the transformations in the analogy are identical to those for elasticity.
Theoretical Pressure Distribution in Journal Bearings
Authors: Habata Kichiye
Published: October 2011

By assuming oil viscosity constant, Reynolds’ equation for journal bearings has been solved in a manner similar to Hill’s method. Two approximate solutions using E. O. Waters’ method and Ritz’s method have been added. Numerical computations have been carried out for a centrally supported 120-deg bearing with a unity slenderness ratio. Isobarriers have been determined from the pressure distributions. In order to show a justification for assuming the viscosity constant, the Reynolds equation was solved for the infinitely long bearing with variable viscosity, and the solution compared with that of Sommerfeld.
Permanent Periodic Surface Deformations Due to a Traveling Jet
Authors: Abrahamson G. R.
Published: October 2011

A steel bullet in the form of a right circular cylinder which strikes a 10-mil-thick plane lead target at 45 deg incidence and at 2700 fps acquires on its front surface a series of corrugations, or waves, approximately 10 mils in amplitude and 40 mils in wave length. This phenomenon is investigated from a hydrodynamic point of view and it is found that similar waves develop at much lower velocities with materials which are viscous liquids under ordinary conditions. A mechanism of wave formation based on a hydrodynamic instability is presented.
Gas-Lubricated Cylindrical Journal Bearings of the Finite Length: Static Loading
Authors: Sternlicht B.
Published: October 2011

This paper presents numerical solutions of the Reynolds equation for finite length, gas-lubricated cylindrical journal bearings under static loading (this corresponds to a load of constant magnitude and direction with respect to the bearing). It is shown that the incompressible results are but only limiting cases to the more general compressible solutions. The results of the two solutions are dovetailed together through the use of two dimensionless parameters: the inverse of the Sommerfeld number and the compressibility number. Comparisons of the iterative solutions and the first-order perturbation and the “linearized ph” methods are made. The advantages and disadvantages of these methods of analysis are discussed.
The Rolling Contact of a Rigid Cylinder With a Viscoelastic Half Space
Authors: Hunter S. C.
Published: October 2011

The problem of a rigid cylinder rolling on the surface of a viscoelastic solid is solved in an approximation in which inertial forces are neglected. With the introduction of viscoelastic effects, the symmetry associated with the corresponding elastic problem is destroyed, and in particular the cylinder motion is impeded by a resistive force. For a standard linear solid, the resulting coefficient of friction, a function of the rolling velocity V, tends to zero for small and large values of V, and attains a single maximum at an intermediate value.
Probabilistic Models for Wind Turbine and Wind Farm Performance
Authors: Arwade Sanjay R. , Lackner Matthew A. , Grigoriu Mircea D.
Published: October 2011

A Markov model for the performance of wind turbines is developed that accounts for component reliability and the effect of wind speed and turbine capacity on component reliability. The model is calibrated to the observed performance of offshore turbines in the north of Europe, and uses wind records obtained from the coast of the state of Maine in the northeast United States in simulation. Simulation results indicate availability of 0.91, with mean residence time in the operating state that is nearly exponential and has a mean of 42 days. Using a power curve typical for a 2.5 MW turbine, the capacity factor is found to be beta distributed and highly non-Gaussian. Noticeable seasonal variation in turbine and farm performance metrics are observed and result from seasonal fluctuations in the characteristics of the wind record. The input parameters to the Markov model, as defined in this paper, are limited to those for which field data are available for calibration. Nevertheless, the framework of the model is readily adaptable to include, for example: site specific conditions; turbine details; wake induced loading effects; component redundancies; and dependencies. An on-off model is introduced as an approximation to the stochastic process describing the operating state of a wind turbine, and from this on-off process an Ornstein–Uhlenbeck (O–U) process is developed as a model for the availability of a wind farm. The O–U model agrees well with Monte Carlo (MC) simulation of the Markov model and is accepted as a valid approximation. Using the O–U model in design and management of large wind farms will be advantageous because it can provide statistics of wind farm performance without resort to intensive large scale MC simulation.
De-AMPylation Unmasked: Modulation of Host Membrane Trafficking
Authors: Ham Hyeilin , Orth Kim
Published: October 2011

The reversible modification of a protein that regulates membrane trafficking promotes the replication of a bacterial pathogen.
Localizing LPA Production
Authors: Gough Nancy R.
Published: October 2011

Binding of the enzyme that synthesizes lysophosphatidic acid to integrins allows the production of this signaling molecule at its site of action.
Nerves and T Cells Connect
Authors: Mueller Kristen L.
Published: October 2011

Neurotransmitters relay immunosuppressive signals to T cells under pathological conditions.
Pharmacokinetics of Tenofovir following Intravaginal and Intrarectal Administration of Tenofovir Gel to Rhesus Macaques
Authors: Nuttall Jeremy , Kashuba Angela , Wang Ruili , White Nicole , Allen Philip , Roberts Jeffrey , Romano Joseph
Published: October 2011

Tenofovir gel (1%) is being developed as a microbicide for the prevention of human immunodeficiency virus (HIV) infection and has been shown to reduce transmission to women by 39%. The gel also prevents infection in macaques when applied intravaginally or intrarectally prior to challenge with simian-human immunodeficiency virus (SHIV), but very little pharmacokinetic information for macaques is available to help extrapolate the data to humans and thus inform future development activities. We have determined the pharmacokinetics of tenofovir in macaques following intravaginal and intrarectal administration of 0.2, 1, and 5% gels. Plasma and vaginal and rectal fluid samples were collected up to 24 h after dosing, and at 24 h postdosing biopsy specimens were taken from the vaginal wall, cervix, and rectum. Following vaginal and rectal administration, tenofovir rapidly distributed to the matrices distal to the site of administration. In all matrices, exposure increased with increasing dose, and with the 1% and 5% formulations, concentrations remained detectable in most animals 24 h after dosing. At all doses, concentrations at the dosing site were typically 1 to 2 log units higher than those in the opposite compartment and 4 to 5 log units higher than those in plasma. Exposure in vaginal fluid after vaginal dosing was 58 to 82% lower than that in rectal fluid after rectal dosing, but plasma exposure was 1- to 2-fold greater after vaginal dosing than after rectal dosing. These data suggest that a tenofovir-based microbicide may have the potential to protect when exposure is via vaginal or anal intercourse, regardless of whether the microbicide is applied vaginally or rectally.
The association of two invasive shrubs, common buckthorn (Rhamnus cathartica) and Tartarian honeysuckle (Lonicera tatarica), with oak communities in the midwestern United States
Authors: Schulte Lisa A. , Mottl Erik C. , Palik Brian J.
Published: October 2011

Oak forests throughout North America are declining due to changes in disturbance regimes that have led to increased competition from other tree and shrub species. We evaluated associations between oak regeneration, the occurrence of two common invasive shrubs (common buckthorn ( Rhamnus cathartica L.) and Tartarian honeysuckle ( Lonicera tatarica L.)), and forest edges in oak forests in a portion of the midwestern United States where bur ( Quercus macrocarpa Michx.), red ( Quercus rubra L.), and white oak ( Quercus alba L.) were historically dominant. We found poor recruitment of oaks in comparison to other, more shade-tolerant tree species. Results further revealed a strong stand-scale association between bur oak, open canopy conditions, high soil nutrient levels, and the presence of common buckthorn and Tartarian honeysuckle; these same site characteristics were disassociated with red and white oak. Within red and white oak stands, however, the presence of the invasive shrubs was more pronounced near forest edges. While oak recruitment is hampered throughout stands, our research suggests that predominant constraints may vary based on soil and light gradients found along forest edges.
Highly heritable heartwood properties of Scots pine: possibilities for selective seed harvest in seed orchards
Authors: Partanen Jouni , Harju Anni M. , Venäläinen Martti , Kärkkäinen Katri
Published: October 2011

The stilbenes pinosylvin (PS) and its monomethyl ether (PSM) provide natural decay resistance to Scots pine ( Pinus sylvestris L.) heartwood timber. For growing trees, the inducible stilbene production serves as a defence against biotic and abiotic stresses. To improve the potential of reforestation material to produce stilbenes, we assessed the possibilities of selective harvesting from seed orchards. Half-sib progenies growing in a field trial and their grafted mothers in seed orchards were surveyed for several chemical and dimensional heartwood characteristics. The correlations between the clonal means of grafted mothers and the family means of their progenies were high for concentration of PS (r = 0.83, p = 0.000) and PSM (r = 0.60, p = 0.010) and for heartwood density (r = 0.72, p = 0.001). For these traits, the narrow-sense heritabilities (h2) estimated from the progeny trial and the broad-sense heritabilities (H2) in seed orchards were high as well. For the concentration of PS, both h2 (0.67) and H2 (0.81) showed the highest values of any trait. The selective collection of Scots pine seed from seed orchards is a promising way to obtain seedlings that possess genetic potential for active defence and to produce high-quality heartwood as mature trees.
Influence of forest management on pre- and post-fledging productivity of a Neotropical migratory songbird in a highly fragmented landscape
Authors: Eng Margaret L. , Stutchbury Bridget J. M. , Burke Dawn M. , Elliott Ken A.
Published: October 2011

Little is known about the effects of forest management on fledgling survival in birds, despite the fact that this is a key determinant of overall productivity. In 2005–2006, we compared male density, nesting success, and fledgling survival of Hooded Warblers (Wilsonia citrina Boddaert, 1783) among forest fragments that were reference sites (n = 3; not logged in >21 years) or had received either a standard selection system harvest (n = 3) or a heavy cut (n = 5) within the past 6–10 years. Density tended to be higher in logged sites than reference sites, but cumulative probability of nest survival (0.22 ± 0.02; 21 days) did not differ among treatments. Brown-headed Cowbird (Molothrus ater (Boddaert, 1783)) parasitism was significantly higher in recently logged sites, and reference sites produced significantly more Hooded Warbler young per successful nest than standard selection harvest sites. Logging treatment did not have a strong negative effect on fledgling survival, and overall, 51% (33/65) of fledglings survived until three weeks after fledging. Standard selection harvest sites had the highest Hooded Warbler density (0.2 males/ha) but also the lowest seasonal productivity (0.84 independent fledglings/female), raising the possibility of an ecological trap. The estimated number of daughters produced per female per year that are expected to survive to breeding age was lower for all treatments (reference, 0.26; selection, 0.17; heavy cut, 0.32) than the expected annual mortality probability of adult females (0.4–0.6). Forest fragments in this region appear to be population sinks, regardless of extent of partial harvest within the fragment.
Software fault prediction for object oriented systems
Authors: Malhotra Ruchika , Jain Ankita
Published: October 2011

There always has been a demand to produce efficient and high quality software. There are various object oriented metrics that measure various properties of the software like coupling, cohesion, inheritance etc. which affect the software to a large extent. These metrics can be used in predicting important quality attributes such as fault proneness, maintainability, effort, productivity and reliability. Early prediction of fault proneness will help us to focus on testing resources and use them only on the classes which are predicted to be fault-prone. Thus, this will help in early phases of software development to give a measurement of quality assessment.

This paper provides the review of the previous studies which are related to software metrics and the fault proneness. In other words, it reviews several journals and conference papers on software fault prediction. There is large number of software metrics proposed in the literature. Each study uses a different subset of these metrics and performs the analysis using different datasets. Also, the researchers have used different approaches such as Support vector machines, naive bayes network, random forest, artificial neural network, decision tree, logistic regression etc. Thus, this study focuses on the metrics used, dataset used and the evaluation or analysis method used by various authors. This review will be beneficial for the future studies as various researchers and practitioners can use it for comparative analysis.
Designing a SOA based model
Authors: Seth Ashish , Agarwal Himanshu , Singla Ashim Raj
Published: October 2011

Service Oriented Architecture (SOA) is an architectural approach that can be shared and reused. Shortage of studies, research thrust and limited expertise in the area of SOA keeps the application of SOA in Small and Medium Enterprises (SMEs) limited. Also in a country like India, whose major economy is dependent on the small and medium enterprises, the Indian Government is promoting the growth in this sector. Successful examples of individual automated enterprise services and traditional ERP implementation systems exist but there is a lack of holistic, integrated technical solutions that can be applied in small and medium size enterprises. In this paper we propose a five layered SOA based architecture that can integrate all activities comprising Supply Chain Management (SCM), Customer Relationship Management (CRM), Technical and Enterprise Applications Tools according to SMEs requirement. We also compared our model with traditional ERP systems and other similar approaches and found the proposed model is efficient, cost effective and competent with similar existing solutions.
Finite state machine based approach to prevent format string attacks
Authors: Yadav Seema , Ahamd Khaleel , Shekhar Jayant
Published: October 2011

In the computer field there are many types of input validation attacks that occur, in which "Format String Overflow Attacks" is one of the most important. Format String Overflow Attacks remain the leading reason of software vulnerability or exploits. Format string bugs result in error such as wrong result type, memory access error and crash and security breach. In this paper , we proposed a Finite state machine which prevents Format String Overflow Attacks in a secure way with the help of several states of FSM. Proper checking against format string overflow bugs can avoid consequences due to exploits of format string overflow bugs. The result of our proposed finite state machine is improving the security problem and provides protection to memory access from any unauthorized user.
Functionality-rich versus minimalist platforms
Authors: Sen Soumya , Guerin Roch , Hosanagar Kartik
Published: October 2011

Should a new "platform" target a functionality-rich but complex and expensive design or instead opt for a bare-bone but cheaper one? This is a fundamental question with profound implications for the eventual success of any platform. A general answer is, however, elusive as it involves a complex trade-off between benefits and costs. The intent of this paper is to introduce an approach based on standard tools from the field of economics, which can offer some insight into this difficult question. We demonstrate its applicability by developing and solving a generic model that incorporates key interactions between platform stakeholders. The solution confirms that the "optimal" number of features a platform should offer strongly depends on variations in cost factors. More interestingly, it reveals a high sensitivity to small relative changes in those costs. The paper's contribution and motivation are in establishing the potential of such a cross-disciplinary approach for providing qualitative and quantitative insights into the complex question of platform design.
Ionic Exchanges of Poly-(Azure A) Studied by AC-Electrogravimetry
Authors: Agrisuelas Jerónimo , Gabrielli Claude , García-Jareño José Juan , Perrot Hubert , Vicente Francisco
Published: October 2011

This work is focused on the mechanistic aspects of the redox behavior of the poly-(Azure A) in KNO3:KCl mixed aqueous solutions taking advantage of the controlled modulation of their oxidation states by ac-electrogravimetry. The ac-electrogravimetry measurements is well suited to study and to control the transfer of the ions and solvent during the redox processes in this complex system with two active sites and the simultaneous transfer of two different anions (and). The intensive analysis shows that the anions transfers are dependent on the oxidation state of the PAA in these experimental conditions for the two electroactive sites inside polymer. The solvent play an important role in mass changes of the PAA whose insertion/expulsion transfer is coupled with each kind of anion but in contrary sense.
Performance Improvement of Pentacene-Based Organic Thin-Film Transistor with HfO2 Gate Dielectrics Treated by CF4 Plasma
Authors: Chang Kow-Ming , Huang Sung-Hung , Tseng Yi-Wen
Published: October 2011

Fluorine incorporation into the HfO2 gate dielectrics by post CF4 plasma treatment in an inductively coupled plasma chamber was proposed to improve gate leakage current and modify surface property for low-temperature fabrication. During the whole process, the temperature is controlled below 150 oC. The low-leakage HfO2 dielectric treated by CF4 plasma was characterized and then utilized in pentacene-based OTFTs. After CF4 plasma treatment, the gate leakage and field effect mobility were effectively improved. By integrating high-k HfO2 by CF4 plasma treatment and HMDS evaporation treatment, a low operating voltage (-4V), low threshold voltage (-1.12V), a low subthreshold swing (266 mV/decade), a field-effect mobility (0.029cm2/Vs) and an on/off current ratio (>104) were obtained.
The Effect of Heat Treatment on Electrodeposited Bi2Te3 Thin Films for Thermoelectric Applications
Authors: Wang Wen-Lin , Wan Chi Chao , Wang Yung-Yun , Lan Chao-Ho
Published: October 2011

The simplest compound semiconductor for thermoelectric refrigeration at room temperature is bismuth telluride (Bi2Te3), with space group . Among all the synthesized methods of this compound, electrochemical deposition is a common and convenient technique to grow polycrystalline Bi2Te3 thin film. In this report, the effect of heat treatment on the thermoelectric properties and electrical characteristics of electrodeposited Bi2Te3 films was studied. Different film compositions from 58.9 at.%Te to 62.9 at.%Te were controlled by the diffusion-controlled method through a rotating electrode. With film composition as parameter, the deposited films with and without heat treatment were characterized by X-ray diffraction, scanning electron microscopy, and Hall effect measurements. The results showed that the Seebeck coefficient has been increased because of the heat treatment The maximum value of 120.9 μV/K occurred at 58.9%Te and then decreased to both Bi-rich and Te-rich sides. However, the diffraction pattern, the morphology, and the grain size did not change significantly by post-deposited annealing. Finally, the overall power factor was improved by a factor of 2 due to post-deposited annealing.
Study of Hydrogen Evolution Reaction on Ni/Co3O4 Composite Electrode in Alkaline Solution
Authors: Mirkova Lidia , Pashova Veselina P. , Monev Milko H.
Published: October 2011

Nickel electrodes are widely used in industrial water electrolysis cells for electrochemical production of hydrogen. The use of Ni/based composites instead of pure Ni is one of the ways for improving the electrocatalytic activity of Ni electrode material. In this work, composite Ni/Co3O4 layers were electrodeposited from a conventional Watts' electrolyte containing Co3O4 powder, and their electrochemical properties towards hydrogen evolution reaction were investigated and compared with pure Ni layers under the same conditions. The composite electrodes are characterized by enhanced electrochemical activity with respect to hydrogen evolution reaction in an alkaline electrolyte: they feature a higher hydrogen evolution rate, as well as a lower overpotential as compared with pure Ni electrodes. The composite Ni/Co3O4 electrodes also show higher catalytic activity towards oxygen evolution reaction, which makes them perspective for application not only in alkaline electrolyzers for hydrogen production, but also for oxygen production or as electrodes in fuel cells.
In Situ Coherent X-ray Scattering and Scanning Tunneling Microscopy Studies of Hexagonally Reconstructed Au(001) in Electrolytes
Authors: Pierce M. , Komanicky V. , Barbour A. , Hennessy D. , Su J-D , Sandy A. , Zhu Chenhui , You Hoydoo
Published: October 2011

We studied dynamics of Au(001) surface in situ in 0.1 M HClO4 electrolyte solution using both coherent x-ray scattering and scanning tunneling microscopy (STM). The surface of Au(001) is known to reconstruct at cathodic potentials; the reconstruction lifts at anodic potentials. In our in-situ STM experiments, the measurements focus on time-dependent progressions of surface morphology during slow potential sweep. In our in-situ coherent x-ray scattering measurements, we demonstrate that the equilibrium surface dynamics are directly measurable and the measured dynamics are consistent with morphological evolution of the STM images. These experiments represent the first successful application of coherent x-ray scattering to the study of electrochemical interfaces in situ.
Computer Modeling of Crystalline Electrolytes - Lithium Thiophosphates and Phosphates
Authors: Lepley Nicholas , Holzwarth Natalie
Published: October 2011

First principles modeling techniques are used to examine the stabilities, structures, and Li ion migration properties of (thio)phosphate electrolyte materials, focusing on the "superionic" electrolyte Li7P3S11. We report on our progress toward understanding both vacancy and interstitial mechanisms for Li ion migration.
Mechanism of Copper and tert-Butyl Alcohol Adsorption on Carbon Materials at Various Open-Circuit Potentials
Authors: Goldin Mikhail , Khubutiya Mogely S. , Grafov Boris M. , Davydov Alexei D. , Goldin Mark M. , Kolesnikov Vladimir A.
Published: October 2011

To improve the biocompatibility of activated carbon materials used for hemosorption (hemoperfusion) detoxification, it is important to understand the mechanism of interaction of the sorbent with toxic compounds and components of blood. A method of elucidating the mechanism of interaction between carbon and various adsorbates was developed, involving the measurement of change in sorbent open-circuit potentials and adsorption of the adsorbate and calculation of the effective number of electrons transferred in the course of adsorption. Cupric ions and t-butanol were used as model adsorbates. It was shown that the adsorption mechanism (Faradaic vs. non-Faradaic) can vary with open-circuit potential of the adsorbent.
Modification of Carbon Materials by Direct and Indirect Pyrrole Electropolymerization
Authors: Khubutiya Mogely S. , Grafov Boris M. , Garaeva Guzel R. , Stepanov Andrey A. , Goldin Mark M. , Davydov Alexei D.
Published: October 2011

Activated carbons and thermally expanded graphite were modified by pyrrole electropolymerization. Both positive and negative shifts of open circuit potential were observed, depending on the initial potential of the carbon material. Pyrrole electropolymerization on carbon material also occurred when carbon was pre-modified to a potential more positive than +600 mV (vs. Ag/AgCl).
Isolation Trench Etch Process Using Pulsed RF Bias Power in HBr/CF4/O2 Plasma
Authors: Park Inho , Kang Yung Seung , Jeong SangSup , Nam Seok Woo
Published: October 2011

Abrupt changes in sidewall profile were induced in pulsed plasma etch process for high aspect ratio isolation trench structuring. Impacts of operational parameters when applying pulsed RF bias power were investigated. Silicon sidewall chipping problems were removed mainly by increasing bias power level and pulse frequency. The chemical sensitivity of O2 has shown decreased in extremely narrow trench spaces of high pattern density
All-Solid Electrochemical Capacitors Using Proton Conducting Polymer Electrolytes
Authors: Gao Han , Lian Keryn
Published: October 2011

A novel polymer electrolyte, comprised of a heteropoly acid (ionic conductor) and poly(vinyl-alcohol) (polymer matrix), has been developed for all-solid electrochemical capacitors. The proton conductivity of this polymer electrolyte has reached 0.01 S/cm at room temperature and showed good stability. The solid ECs have demonstrated high rate performance (up to 100 V/s in cyclic voltammetry and a time constant of 10 ms), which exceeded their liquid-based counterpart. Material characterization revealed that crystallized water facilitate the proton conductivity of the polymer electrolyte.
EMIHSO4 Based Polymer Electrolyte for Electrochemical Capacitors
Authors: Ketabi Sanaz , Lian Keryn
Published: October 2011

Ionic liquid (IL) was investigated as electrolyte in both liquid and solid states for electrochemical capacitors (ECs). 1 Ethyl 3 methylimidazolium hydrogensulfate (EMIHSO4) is a non fluorinated IL; however, it exhibits high resistivity. This issue could be overcome by employing an EMIHSO4 polymer electrolyte. This polymer IL electrolyte had a slightly better performance compared to liquid IL. The EC with polymer IL had a cell voltage window of 1.5 V. High scan rate response up to 1 V/s in cyclic voltammetry and a time constant of 2 s in impedance analyses was obtained.
The Hysteresis Characteristics of Low Temperature (≤ 200 °) Silicon Nanocrystals Embedded in Silicon-Rich Silicon Nitride Films
Authors: Lee Kyoung-Min , Hwang Jae-Dam , Keum Ki-Su , No Kil-Sun , Hong Wan-Shick
Published: October 2011

The electrical properties of silicon nanocrystals (Si NCs) embedded in silicon-rich silicon nitride (SRSN) films were investigated by fabricating metal-insulator-semiconductor capacitor structures to utilize the Si NCs as charge storage nodes. The Si NCs embedded in SRSN films were prepared by catalytic chemical vapor deposition technique at substrate temperatures below 200 °. The counterclockwise hysteresis loops were observed in capacitance-voltage (C-V) characteristics. A memory window of 13 V was observed in the sweep voltage range of ±12 V.
Surfactant Effects in Cu-Sn Alloy Deposition
Authors: Survila Arvydas , Mockus Zenius , Kanapeckaitė Stasė , Bražinskienė Dalia
Published: October 2011

Adsorption behavior of different polyethers (PE) on copper and tin was studied in combination with kinetic investigations. No pronounced effect of PE was detected in the Cu|Cu(II) system. In contrast, these substances show a high inhibition activity on the tin electrode. Halides enhance adsorp¬tion ability on copper electrode but suppress it on tin; this effect intensifies in the sequence: Cl- < Br- < I-. The inhibi¬tion degree of surfactants increases with the length of hydrocarbon chain. Underpotential deposition of Sn(II) is observed in the region of Cu(II) limiting current. The characteristic current minimum arises in the region where the free Sn phase becomes thermodynamically stable. Cl- ions broaden the range of current densities where yellow bronze can be obtained, but Br- ions show the opposite effect. Iodides retard the reduction of Cu(II) therefore tin prevails in the coatings. The deposits obtained are a mixture of pure copper, α-CuSn phase and hcp phase.
Substrate Dosing with TiCl4 as a Surface Pretreatment for CVD and ALD of Al for Future IC Interconnects
Authors: Phillips Richard , Eisenbraun Eric
Published: October 2011

Titanium tetrachloride (TiCl4) dosing was evaluated as an in situ surface pretreatment step prior to the CVD and ALD of Al for applications as a potential replacement for copper in nanoscale interconnects. It was found that the dosing step had significant impacts on the subsequent Al nucleation behavior on both insulating and conductive substrates, and could be used to decrease the nucleation temperature on SiO2 surfaces. This dosing step increases the utility of aluminum as a potential nanoscale interconnect material.
BaSnO3 Thick Film as a Carbon Dioxide Sensor
Authors: Cavanagh Leon , Smith Peter , Binions Russell
Published: October 2011

BaSnO3 has been prepared as porous screen-printed thick films gas sensors. The sensor material was characterised by scanning electron microscopy and X-ray diffraction. The sensors gas response was investigated by exposure to varying concentrations of CO2 gas in synthetic air and mixtures of CO and CO2 all at a variety of different operating temperatures. Finally the gas response was examined to potential intereferant gases including humidty. It was found that at an operating temperature of 500 °C and to a 2000 ppm pulse of CO2 the sensors gave a gas response of 3.10, higher than current literature values. It was also found that increasing relative humidity enhanced the gas response in contrast to other approaches.
Development of a Miniaturized Gas Ionization Sensor for Harsh Environments by Using Polyimide Spacer
Authors: Walewyns Thomas , Scheen Gilles , Tooten Ester , Dupuis Pascal , Francis Laurent A.
Published: October 2011

Gas sensing can be performed by fingerprinting their field ionization characteristics. This paper presents the development of a miniaturized ionization sensor using ion-track etched polyimide as structural layer and template for Ni nanowires synthesis. The device consists in two parallel plate electrodes with gaps varying from 5 to 12 µm. The nanowires impact on breakdown voltage has been analyzed during first electrical characterizations and I-V curves measurements. For a 5.5 µm-gap, breakdown voltage is reduced from 320 to 80 V with a corresponding current at least three order of magnitude lower. Using the sensor in harsh environments such as space applications is also discussed. Miniaturized ionization sensors are powerful candidates as integrated universal gas sensor based on pattern recognition for environmental monitoring. Such a system should be easily integrated in picosatellites such as CubeSats dedicated to the physical analysis of low thermosphere composition.
Iridium and Ruthenium Electrodeposition at Platinum Nanopowder Using the Rotating Disc Slurry Electrode Technique
Authors: Rivera-Vélez Nelson E. , Valdez Thomas , González Ileana , Fachini E. , Manzo Michele , Cabrera Carlos R.
Published: October 2011

An (IrRu)/Pt black catalyst was prepared by the Rotating Disc Slurry Electrode technique from the chlorinated precursors at an applied potential of -0.2V vs. Ag|AgCl. XPS and EDS mapping reveal the presence of Ir and Ru on the finished material, while TEM, SEM and XRD suggest that no changes in morphology occurred. A blank sample under the same conditions was prepared without a fixed potential and spontaneously deposited ruthenium was detected in XPS and mappings. Finally, (IrRu)/Pt black was subjected to thermal treatment at 400 åC and the prepared catalysts were painted onto carbon paper and used for potentiodynamic scans to test for their activity for the oxygen evolution reaction. When compared to as-received Pt black our (IrRu)/Pt black performed better due to the Ir and Ru modification and a loss in performance was apparent after the heat treatment, this can be a result of the loss of active sites.
LiCo1-yByO2 as Cathode Materials for Rechargeable Lithium Batteries
Authors: Mauger Alain , Zhang Xiaoyu , Groult Henri , Julien Christian M.
Published: October 2011

LiCo1-yByO2 (0.05≤y≤0.35) samples were synthesized free of any impurity, except residual concentration of Ni present in the commercial products used as the precursors. They were characterized by X-ray powder diffraction, FTIR spectroscopy, and magnetic measurements. Structural data have shown that the limit of solubility of boron is y ~ 0.25. The voltage profiles of electrochemical cells including these compounds as the cathode were monitored against Li anode. The overall capacity of the oxides has been reduced by the sp metal substitution, but more stable cycling performances have been observed, compared to the performances of the native oxides. At 4.4 V cut-off voltage, the Li//LiCo0.75B0.25O2 cell exhibits an almost constant capacity of ca. 127 mAh/g up to the 16th cycle. The origin of the benefit of boron doping is discussed.
MnO2 Nanosheets Thin-Film Electrodes for Electrochemical Capacitors
Authors: Yano Masato , Suzuki Shinya , Miyayama Masaru
Published: October 2011

Electrochemical properties of MnO2 nanosheets thin-film electrode for electrochemical capacitors were examined. MnO2 nanosheets were prepared by exfoliation of birnessite-type MnO2. MnO2 nanosheets with small lateral sizes of 50-100 nm (Small-NS) and large lateral sizes of approximately 1 μm (Large-NS) were obtained by multistep centrifugation. Thin films of MnO2 nanosheets were prepared by electrophoretic deposition. Films of Large-NS had a homogeneous microstructure like a bulk. Small-NS had a heterogeneous microstructure containing micropore. The reversible capacities for the films with thickness of approximately 12 nm were approximately 100 mAh g-1(330 F g-1). Capacities of Large-NS films decreased with increasing amount of nanosheets. Capacities of Small-NS films were almost independent of the amount of nanosheets due to fast ion diffusion in the electrodes. Heterogeneous microstructure containing micropore contributes to the good electrode properties of Small-NS films.