bluuebunny/crossref_metadata_2025 huggingface dataset:
Cohomology rings of almost-direct products of free groups
Authors: Cohen Daniel C.
Published: January 2010

An almost-direct product of free groups is an iterated semidirect product of finitely generated free groups in which the action of the constituent free groups on the homology of one another is trivial. We determine the structure of the cohomology ring of such a group. This is used to analyze the topological complexity of the associated Eilenberg–MacLane space.
Improving Efficiency of a High Work Turbine Using Nonaxisymmetric Endwalls—Part II: Time-Resolved Flow Physics
Authors: Schüpbach P. , Abhari R. S. , Rose M. G. , Germain T. , Raab I. , Gier J.
Published: January 2010

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one and a half stage high work axial flow turbine. The first part covered the design of the endwall profiling, as well as a comparison with steady probe data; this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that leads to a total-to-total stage efficiency improvement of 1.0%±0.4%. The investigated geometry is a model of a high work (Δh/U2=2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a fast response aerodynamic probe (FRAP). This paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the nonaxisymmetric endwall profiling cases. The flowfield at the exit of the first stator is improved considerably due to the nonaxisymmetric endwall profiling and results in reduced secondary flow and a reduction in loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction in secondary flows mainly at the hub. At the rotor exit, the flow field with nonaxisymmetric endwalls is more homogenous due to the reduction in secondary flows in the two rows upstream of the measurement plane. This confirms that nonaxisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption, the time-resolved data are used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The nonaxisymmetric endwall profiling of the first nozzle guide vane show reductions in dissipation and streamwise vorticity due to the reduced trailing shed vorticity. This smaller vorticity explains the reduction in loss at midspan, which is shown in the first part of the two part paper. This leads to the conclusion that nonaxisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.
Experiments and Computations on Large Tip Clearance Effects in a Linear Cascade
Authors: Williams Richard , Gregory-Smith David , He Li , Ingram Grant
Published: January 2010

Large tip clearances typically in the region of 6% exist in the high pressure (HP) stages of compressors of industrial gas turbines. Due to the relatively short annulus height and significant blockage, the tip clearance flow accounts for the largest proportion of loss in the HP. Therefore increasing the understanding of such flows will allow for improvements in design of such compressors, increasing efficiency, stability, and the operating range. Experimental and computational techniques have been used to increase the physical understanding of the tip clearance flows through varying clearances in a linear cascade of controlled-diffusion blades. This paper shows two unexpected results. First the loss does not increase with clearances greater than 4% and second there is an increase in blade loading toward the tip above 2% clearance. It appears that the loss production mechanisms of the pressure driven tip clearance jet do not increase as the clearance is increased to large values. The increase in blade force is attributed to the effect of the strong tip clearance vortex, which does not move across the blade passage to the pressure surface, as is often observed for high stagger blading. These results may be significant for the design of HP compressors for industrial gas turbines.
Design and Optimization of the Internal Cooling Channels of a High Pressure Turbine Blade—Part I: Methodology
Authors: Amaral Sergio , Verstraete Tom , Van den Braembussche René , Arts Tony
Published: January 2010

This first paper describes the conjugate heat transfer (CHT) method and its application to the performance and lifetime prediction of a high pressure turbine blade operating at a very high inlet temperature. It is the analysis tool for the aerothermal optimization described in a second paper. The CHT method uses three separate solvers: a Navier–Stokes solver to predict the nonadiabatic external flow and heat flux, a finite element analysis (FEA) to compute the heat conduction and stress within the solid, and a 1D aerothermal model based on friction and heat transfer correlations for smooth and rib-roughened cooling channels. Special attention is given to the boundary conditions linking these solvers and to the stability of the complete CHT calculation procedure. The Larson–Miller parameter model is used to determine the creep-to-rupture failure lifetime of the blade. This model requires both the temperature and thermal stress inside the blade, calculated by the CHT and FEA. The CHT method is validated on two test cases: a gas turbine rotor blade without cooling and one with five cooling channels evenly distributed along the camber line. The metal temperature and thermal stress distribution in both blades are presented and the impact of the cooling channel geometry on lifetime is discussed.
Design and Optimization of the Internal Cooling Channels of a High Pressure Turbine Blade—Part II: Optimization
Authors: Verstraete Tom , Amaral Sergio , Van den Braembussche René , Arts Tony
Published: January 2010

This second paper presents the aerothermal optimization of the first stage rotor blade of an axial high pressure (HP) turbine by means of the conjugate heat transfer (CHT) method and lifetime model described in Paper I. The optimization system defines the position and diameter of the cooling channels leading to the maximum lifetime of the blade while limiting the amount of cooling flow. It is driven by the results of a CHT and subsequent stress analysis of each newly designed geometry. Both temperature and stress distributions are the input for the Larson–Miller material model to predict the lifetime of the blade. The optimization procedure makes use of a genetic algorithm (GA) and requires the aerothermal analysis of a large number of geometries. Because of the large computational cost of each CHT analysis, this results in a prohibitive computational effort. The latter has been remediated by using a more elaborate optimization system, in which a large part of the CHT analyzes is replaced by approximated predictions by means of a metamodel. Two metamodels, an artificial neural network and a radial basis function network, have been tested and their merits have been discussed. It is shown how this optimization procedure based on CHT calculations, a GA, and a metamodel can lead to a considerable extension of the blade lifetime without an increase in the amount of cooling flow or the complexity of the cooling geometry.
Investigation of Sand Blocking Within Impingement and Film-Cooling Holes
Authors: Cardwell N. D. , Thole K. A. , Burd S. W.
Published: January 2010

Gas turbines are not generally designed for operation with a particle laden inlet flow but, in fact, are commonly operated in unclean environments resulting in dirt, sand, and other debris ingestion. In addition to the negative effects within the main gas path, for aeroengines these particles are pulled into the coolant system where they can clog cooling passages and erode internal surfaces. Unlike previous research that focused on deposition and erosion within the main gas path, this study evaluated blocking in a double wall liner whereby both impingement and film-cooling holes were simulated. Double wall liners are commonly used in the combustor and turbine for combined internal and external cooling of metal components. Specifically, sand blockages were evaluated through comparisons of measured flowrates for a particular pressure ratio across the liner. Four liner geometries were tested whereby the coolant hole size and orientation were varied in test coupons. At ambient temperature, blocking was shown to be a function of the impingement flow area. A significant rise in blocking was observed as sand and metal temperatures were increased. The overlap between the impingement and film-cooling holes was also found to have a significant effect.
Enhancement of Impingement Cooling in a High Cross Flow Channel Using Shaped Impingement Cooling Holes
Authors: Chambers Andrew C. , Gillespie David R. H. , Ireland Peter T. , Kingston Robert
Published: January 2010

Impingement systems are common place in many turbine cooling applications. Generally these systems consist of a target plate that is cooled by the impingement of multiple orthogonal jets. While it is possible to achieve high target surface heat transfer with this configuration, the associated pressure drop is generally high and the cooling efficiency low. Furthermore, especially in large impingement arrays, the buildup of cross flow from upstream jets can be significant and results in deflection of downstream impingement jets reducing the resultant heat transfer coefficient distribution. This paper presents a computational and experimental investigation into the use of shaped elliptical or elongated circular impingement holes designed to improve the penetration of the impinging jet across the coolant passage. This is of particular interest where there is significant cross flow. Literature review and computational investigations are used to determine the optimum aspect ratio of the impingement jet. The improved heat transfer performance of the modified design is then tested in an experimental rig with varying degrees of cross flow at engine representative conditions. In all cases, a 16% increase in the Nusselt number on the impingement target surface in the downstream half of the cooling passage was achieved. Under the first four impingement holes, a Nusselt number enhancement of 28–77% was achieved, provided no additional cross flow was present in the passage. When appropriately aligned, a significant reduction in the stress concentration factor caused by the addition of a hole can be achieved using this design.
Predictions of Turbulent Flow for the Impeller of a NASA Low-Speed Centrifugal Compressor
Authors: Guleren K. M. , Afgan I. , Turan A.
Published: January 2010

The turbulent flow inside a low-speed centrifugal compressor at design condition is investigated using large-eddy simulation (LES) comprising of up to 26×106 computational volume cells. Unlike in the past, the current study’s special emphasis is placed on the turbulence field evolution inside the impeller. LES predictions suggest that the Boussinesq hypothesis does not seem to be valid, especially near the exit of the impeller where the blade unloading takes place. Reynolds stress variations show a tendency toward an “axisymmetric expansion” type of turbulence after the impeller exit for which the subgrid-scale stress contribution shows a monotonic decrease. Probability density function analysis for the leakage flow show that instantaneous velocities in the wake region are less intermittent as compared with those in the jet. Time spectra analysis display also another feature that the energy cascade proceeds at a higher rate and lasts longer in the wake region than in the tip jet region.
Aerothermal Impact of Stator-Rim Purge Flow and Rotor-Platform Film Cooling on a Transonic Turbine Stage
Authors: Pau M. , Paniagua G. , Delhaye D. , de la Loma A. , Ginibre P.
Published: January 2010

The sealing of the stator-rotor gap and rotor-platform cooling are vital to the safe operation of the high-pressure turbine. Contrary to the experience in subsonic turbines, this paper demonstrates the potential to improve the efficiency in transonic turbines at certain rim seal rates. Two types of cooling techniques were investigated: purge gas ejected out of the cavity between the stator rim and the rotor disk, and cooling at the rotor-platform. The tests were carried out in a full annular stage fed by a compression tube at M2is=1.1, Re=1.1×106, and at temperature ratios reproducing engine conditions. The stator outlet was instrumented to allow the aerothermal characterization of the purge flow. The rotor blade was heavily instrumented with fast-response pressure sensors and double-layer thin film gauges. The tests are coupled with numerical calculations performed using the ONERA’s code ELSA. The results indicate that the stator-rotor interaction is significantly affected by the stator-rim seal, both in terms of heat transfer and pressure fluctuations. The flow exchange between the rotor disk cavity and the mainstream passage is mainly governed by the vane trailing edge shock patterns. The purge flow leads to the appearance of a large coherent vortex structure on the suction side of the blade, which enhances the overall heat transfer coefficient due to the blockage effect created. The impact of the platform cooling is observed to be restricted to the platform, with negligible effects on the blade suction side. The platform cooling results in a clear attenuation of pressure pulsations at some specific locations. The experimental and computational fluid dynamics results show an increase in the turbine performance compared with the no rim seal case. A detailed loss breakdown analysis helped to identify the shock loss as the major loss source. The presented results should help designers improve the protection of the rotor platform while minimizing the amount of coolant used.
Optimal Design of Hybrid Electric Fuel Cell Vehicles Under Uncertainty and Enterprise Considerations
Authors: Han Jeongwoo , Papalambros Panos Y.
Published: January 2010

Hybrid electric fuel cell vehicles are studied using a system perspective that explores the tradeoffs among fuel economy, acceleration, and other vehicle attributes. Design decisions are derived from an enterprise decision-making model that seeks to maximize profit. Uncertainties stemming from manufacturing variability, customer preferences, and market response to fuel price fluctuations are also included. The system is hierarchically partitioned into three levels that comprise enterprise, powertrain, fuel cell, and battery subsystem models. Analytical target cascading, a decomposition-based multidisciplinary design optimization strategy, is used to solve the resulting problem. Results indicate a strong interaction between enterprise and engineering considerations, and a significant impact of uncertainty on the optimal system design.
Shrinkage Control of the Sealing Layer for the Cube-Type Solid Oxide Fuel Cell Bundle
Authors: Sakuragi S. , Funahashi Y. , Suzuki T. , Fujishiro Y. , Awano M.
Published: January 2010

Currently, microtubular solid oxide fuel cells (SOFC) bundles are under development, which consist of microtubular SOFCs (diameter=0.8–2 mm) and porous cathode matrix where the SOFCs are integrated. In this study, a new fabrication process of the sealing layer for the microtubular SOFC bundles was examined using MgO-magnesium boro-silicate glass composites. A sheet and paste of these composites were prepared, and the microstructure and shrinkage behavior of the composite glass layers were investigated to minimize the deformation of the layer during fabrication process. The results indicated that using 100% glass sheet with the composite glass pastes appeared to be effective in reducing the shrinkage of the glass layer. In addition, the effect of sheet thickness on the shrinkage behavior was investigated and showed that the shrinkage ratio reduced as the sheet thickness decreased, and the shrinkage of about 0.2% was achieved at the sheet thickness of about 200 μm without defects or shape deformations. Thus, this fabrication method turned out to be effective for constructing a sealing layer for the microtubular SOFC bundles.
Development of molecular simulation methods to accurately represent protein-surface interactions: Method assessment for the calculation of electrostatic effects
Authors: Collier Galen , Vellore Nadeem A. , Latour Robert A. , Stuart Steven J.
Published: January 2010

The simulation of the interactions of proteins with charged surfaces in a condensed-phase aqueous solution containing electrolytes using empirical force field based methods is predominantly governed by nonbonded interactions between the atoms of the protein, surface, and the solvent. Electrostatic effects represent the strongest type of these interactions and the type that is most difficult to accurately represent because of their long-range influence. While many different methods have been developed to represent electrostatic interactions, the particle mesh Ewald summation (PME) method is generally considered to be the most accurate one for calculating these effects. However, the PME method was designed for systems with three-dimensional (3D) periodicity, and not for interfacial systems such as the case of protein adsorption to a charged surface. Interfacial systems such as these have only two-dimensional periodicity, which may not be appropriate for treatment with PME due to the possibility that the presence of multiple charged image surfaces parallel to the primary simulation cell’s surface, may introduce nonphysical effects on the behavior of the charged molecules in the system. In an effort to address this issue, the authors have conducted a set of nanosecond-scale molecular dynamics simulations to calculate the equilibrium distribution of Na+ and Cl− ions near a charged surface using PME and a range of radial cutoff methods for treating electrostatic interactions, where the cutoffs prevent interaction with the periodic images of the system. The resulting ion concentration profiles were compared to one another and to a continuum analytical solution of the theoretical ion distribution obtained from the Poisson—Boltzmann equation. Their results show that the PME method does not introduce the suspected nonphysical effects in the ion distributions due to the 3D periodic images of the system, thus indicating that it is appropriate for use for this type of molecular simulation. Although their interest is motivated by protein-surface interactions, the conclusions are applicable for the treatment of electrostatics in other aqueous systems with two-dimensional periodicity.
Novel application of imaging surface plasmon resonance for in situ studies of the surface exploration of marine organisms
Authors: Andersson Olof , Ekblad Tobias , Aldred Nick , Clare Anthony S. , Liedberg Bo
Published: January 2010

The surface interactions of exploring cyprids of the barnacle Semibalanus balanoides were studied in situ using imaging surface plasmon resonance. It was demonstrated how the deposition of a proteinaceous adhesive could be followed in real time as the cyprids explored and temporarily attached to a surface. Furthermore, the amount of protein left on the surface when the cyprids moved on could be quantified. Clear differences were demonstrated between an oligo(ethyleneglycol) coated surface and a bare gold substrate. It is anticipated that this technique will be a valuable tool in the development of novel surface chemistries that can prevent biofouling.
Etch mechanism of In2O3 and SnO2 thin films in HBr-based inductively coupled plasmas
Authors: Kwon Kwang-Ho , Efremov Alexander , Kim Moonkeun , Min Nam Ki , Jeong Jaehwa , Hong MunPyo , Kim Kwangsoo
Published: January 2010

The investigations of etch characteristics and mechanisms for both In2O3 and SnO2 thin films in the HBr-based inductively coupled plasmas were carried out. The etch rates were measured as functions of gas mixing ratio (0%–100% Ar), input power (400–700 W), and gas pressure (4–10 mTorr) at fixed bias power (200 W) and gas flow rate [40 SCCM (SCCM denotes cubic centimeter per minute at STP)]. Plasma parameters and composition were determined using a combination of plasma diagnostics by double Langmuir probe and global (zero-dimensional) plasma model. The correlations between the behaviors of etch rates and fluxes of plasma active species allow one to infer both In2O3 and SnO2 etch mechanisms as the transitional regime of ion-assisted chemical reaction, which is controlled by neutral and charged fluxes together.
Obtaining and Investigating Unconventional Sources of Radioactivity
Authors: Lapp David R.
Published: January 2010

This paper provides examples of naturally radioactive items that are likely to be found in most communities. Additionally, there is information provided on how to acquire many of these items inexpensively. I have found that the presence of these materials in the classroom is not only useful for teaching about nuclear radiation and debunking the “nuclear free” myth, but also for helping students to understand the history of some of the commercial uses of radioactive materials since the early 20th century. Finally, the activity of each source (relative to background radiation) is provided.
The Ekman Layer and Why Tea Leaves Go to the Center of the Cup
Authors: Heavers Richard M. , Dapp Rachel M.
Published: January 2010

Consider a transparent, cylindrical container filled with water and sitting in the center of a record player turntable. When the turntable is started suddenly, the container rotates with the turntable, but the bulk of the fluid initially remains at rest. A thin (∼1 mm) viscous boundary layer (Ekman layer) forms almost immediately at the bottom and top (if there is a lid) of the fluid. Here we describe a laboratory or demonstration exercise in which we use dye crystals1 and fine particles2 as tracers to study the flow in the Ekman layer. We also give a general method for using fine particles to measure the time it takes for the bulk of the fluid to rotate with the turntable (spin-up time) for different rates of rotation and fluid depths.
Measuring the Flight Speed of Fire Bombers from Photos: An In-Class Exercise in Introductory Kinematics
Authors: Lowe Greg W. , Ayars Eric
Published: January 2010

In the western half of the United States, fire bombers are not an uncommon sight. During the “fire season,” which can extend from June through November, these specially modified aircraft are used to drop fire retardant chemicals or water on wildfires. It can be an entertaining and instructive classroom exercise to use pictures of these planes in action to calculate the speed of the plane during a drop run.
Interactive Engagement: How Much Is Enough?
Authors: Keiner Louis E. , Burns Teresa E.
Published: January 2010

It is now widely known that interactive engagement (IE) teaching methods are the most effective methods of teaching physics.1–6 As physics instructors, we now have a variety of methods and models to choose from to make courses interactive.7,8 Included in these are methods that function as interactive adaptations to the traditional structure of physics classes, such as Peer Instruction (PI)2, and those that modify the entire structure of the course, such as the “studio” or “workshop” format.9–11 These possibilities raise the question: Is it worth the effort and expense to completely modify classrooms and instructional time by going to a studio model, or is a simpler IE method such as PI adequate by itself? What method will most easily help your students meet the course learning goals?
Invariability of Mass
Authors: Bartlett Albert A.
Published: January 2010

The following is a petition written over 36 years ago by University of Colorado students to the seven members of Colorado's delegation to the United States Congress. I was advisor to the student groups and found this when cleaning up my university office. It strikes me as being amazingly farsighted.
Bell's Theorem and Einstein's ‘Spooky Actions’ from a Simple Thought Experiment
Authors: Kuttner Fred , Rosenblum Bruce
Published: January 2010

In 1964 John Bell proved a theorem2 allowing the experimental test of whether what Einstein derided as “spooky actions at a distance” actually exist. We will see that they do. Bell's theorem can be displayed with a simple, nonmathematical thought experiment suitable for a physics course at any level. And a simple, semi-classical derivation of the quantum theory result can be given for physics students. These entanglement phenomena are today applied in industrial laboratories and are increasingly discussed in the popular literature. Unfortunately, they are also misappropriated by the purveyors of pseudoscience, something physicists have a responsibility to address.3 Students can be intrigued by the quantum strangeness physics has encountered at a boundary of our discipline.
Repulsion of Superinfecting Virions: A Mechanism for Rapid Virus Spread
Authors: Doceul Virginie , Hollinshead Michael , van der Linden Lonneke , Smith Geoffrey L.
Published: January 2010

Viral Superspreaders

Viruses are thought to spread across a lawn of cells by an iterative process of infection, replication, and release. If this were the case, the rate of spread would be limited by the viral replication kinetics. Now,

Doceul
et al.

(p.
873
, published online 21 January; see the Perspective by
Pickup
) describe a spreading mechanism used by vaccinia virus that is not restricted by viral replication kinetics and that causes a dramatic acceleration of spread. Early after infection, vaccinia virus proteins A33 and A36 are expressed as a complex on the cell surface. This marks the cell as infected and causes superinfecting virions to be repelled by the formation of actin projections beneath the virus particle. Virions are repelled from infected cells repeatedly until an uninfected cell is reached and are thus pushed further away from the origin of infection to accelerate dissemination.
STANDARD-FREE METHOD FOR HOOF SAMPLES TAKEN FROM DOMESTIC ANIMALS SUCH AS COW, CALF, PONY AND SHEEP
Authors: SERA K. , SUZUKI K. , TAGUCHI K. , ITOH J. , GOTO S. , SAITOH Y.
Published: January 2010

A standard-free method for hoof samples taken from cattle such as cow, calf, pony and sheep has been developed in order to estimate the state of health of these animals. The standard-free method developed for human nails was confirmed to be applicable to quantitative analysis of hoof samples since the shape of continuous X-rays is almost the same for nail and hoof taken from these ungulate animals. Accuracy and sensitivity of the present standard method were examined by comparing the results with those obtained by an internal-standard method combined with a chemical-ashing method, and it is confirmed that the method is applicable to hoof samples taken from domestic animals of many species. The method allows us to quantitatively analyze untreated hoof samples and to prepare the targets without complicated preparation technique which often brings ambiguous factors such as elemental loss from the sample and contamination of the sample during preparation procedure. It is also confirmed that halogens, which are important elements for estimating the state of health and are mostly lost during chemical-ashing, can be analyzed without problem by the present method. It is found that elemental concentration of more than twenty elements can be constantly analyzed and it is expected to be quite useful in order to estimate the state of health and to make diagnosis of domestic animals. It is also confirmed that elemental concentration of essential elements in hoof is not so changed depending on the positions in the sliced sample along both horizontal and vertical axis.
INVESTIGATION OF TUMOR CELL TOXICITY FROM PARTICLE INDUCED X-RAY EMISSION FROM A 45-MeV PROTON BEAM IRRADIATED FERRITE NANOPARTICLE
Authors: KIM KI-HONG , KIM HONG-TAE , KIM JONG-HEE , SEO SEUNG-JUN , CHUNG DUCK-SOO , KIM JONG-KI
Published: January 2010

In order to investigate the potential cytotoxic effects of particle-induced x-ray emission (PIXE) on tumor cells, 45 MeV proton beam was irradiated on C6 glioma cell lines that had taken up alginate-coated ferrite nanoparticles (Alg-SNP). Cells were anchored in vertical 96-well dishes facing a horizontal beam where the Bragg peak was placed on the upper part of the 96-well dish. Experimental groups included cells without SNP as a control (No-SNP), and cells incubated with SNP for 6 hours (6hr-SNP) or overnight (ON-SNP).

A 0 to 200 Gy proton beam from an MC50 cyclotron (Scanditronix, Sweden) at the Korea Cancer Center Hospital (Seoul, Korea) was used to irradiate each experimental group. Perinuclear Alg-SNP nanoparticle distribution was observed in glioma cells. The test groups (6hr-SNP or ON-SNP) showed an estimated 20-28% (ANOVA, P < 0.05) less cell survival compared to the control group based on MTT assay. Nuclear damage, indicating apoptosis, was present at a higher frequency in the 6hr-SNP and ON-SNP groups up to relatively low radiation dose of 100 Gy by fluorescence microscopy upon Hoechst 33342 and Acridine Orange staining. Ferrite nanoparticles alone were not cytotoxic at the experimental concentration of 0.15 mg/ml. Therefore ferrite nanoparticles may induce additional cytotoxicity from X-ray emission from potential PIXE effects. PIXE and metal nanoparticles may be developed as a therapeutic factor and prodrug for localized proton beam therapy without side effects of solid or disseminate tumors on the surrounding normal tissue.
FIRST STUDY OF AIRBORNE PARTICULATE POLLUTION USING PIXE ANALYSIS IN HAVANA CITY, CUBA
Authors: PÉREZ G. , PIÑERA I. , ALDAPE F. , FLORES J. M. , MARTÍNEZ M. , MOLINA E. , FERNÁNDEZ A. , RAMOS M. , GUIBERT R.
Published: January 2010

The present work reports the results of a first study of elemental composition in airborne particulate matter (fine and coarse) collected at the Municipality of Centro Habana, Havana City, Cuba, using the PIXE technique. At present, there is not any information available about element contents in airborne particulate matter from this region. A five months sampling campaign was carried out, collecting the samples under an air flux of 20 l/min with a Gent SFU Sampler equipped with a system which allows the aerosol collection in both size fractions simultaneously. A total of 144 aerosol samples were collected. For the PIXE analysis, the samples were irradiated by 2.0 MeV energy protons from a 2MV Tandetron Accelerator. A total of 14 elements ( S , Cl , K , Ca , Ti , V , Cr , Mn , Fe , Ni , Cu , Zn , Br and Pb ) were consistently detected with minimum detection limits from 1 ng/m3 to 10 ng/m3 for most of the elements. Enrichment factors were also calculated for both fractions in order to identify the natural and anthropogenic group of elements. The quantitative results obtained have revealed important information that has been used in a first attempt to understand and to characterize the atmospheric pollution of this area.
TWO-MACHINE FLOW-SHOP MINIMUM-LENGTH SCHEDULING WITH INTERVAL PROCESSING TIMES
Authors: NG C. T. , MATSVEICHUK NATALJA M. , SOTSKOV YURI N. , CHENG T. C. EDWIN
Published: January 2010

The flow-shop minimum-length scheduling problem with n jobs processed on two machines is addressed where processing times are uncertain: only lower and upper bounds of the random processing times are given before scheduling, but their probability distributions are unknown. For such a problem, there may not exist a dominant schedule that remains optimal for all possible realizations of the processing times and so we look for a minimal set of schedules that are dominant. We obtain necessary and sufficient conditions for the case when it is possible to fix the order of two jobs in a minimal set of dominant schedules. The necessary and sufficient conditions are proven for the case when one schedule dominates all the others. We characterize also the case where there does not exist non-trivial schedule domination. All the conditions proven may be tested in polynomial time of n.
A DECOMPOSITION-COORDINATION METHOD FOR COMPLEX MULTI-OBJECTIVE SYSTEMS
Authors: MIGUEL F. , GÓMEZ T. , LUQUE M. , RUIZ F. , CABALLERO R.
Published: January 2010

The generation of Pareto optimal solutions for complex systems with multiple conflicting objectives can be easier if the problem can be decomposed and solved as a set of smaller coordinated subproblems. In this paper, a new decomposition-coordination method is proposed, where the global problem is partitioned into subsystems on the basis of the connection structure of the mathematical model, assigning a relative importance to each of them. In order to obtain Pareto optimal solutions for the global system, the aforementioned subproblems are coordinated taking into account their relative importance. The scheme that has been developed is an iterative one, and the global efficient solutions are found through a continuous information exchange process between the coordination level (upper level) and the subsystem level (lower level). Computational experiments on several randomly generated problem instances show that the suggested algorithm produces efficient solutions within reasonable computational times.
CONVEX HULL PRESENTATION OF A QUADRATICALLY CONSTRAINED SET AND ITS APPLICATION IN SOLVING QUADRATIC PROGRAMMING PROBLEMS
Authors: XIA YONG
Published: January 2010

In this article, we study the convex hull presentation of a quadratically constrained set. Applying the new result, we solve a kind of quadratically constrained quadratic programming problems, which generalizes many well-studied problems.
ROBUST DYNAMIC PRICING OVER INFINITE HORIZON IN THE PRESENCE OF MODEL UNCERTAINTY
Authors: LI GENDAO , XIONG YU , XIONG ZHONGKAI
Published: January 2010

This paper studies a problem of dynamic pricing faced by a retailer with limited inventory, uncertain about the demand rate model, aiming to maximize expected discounted revenue over an infinite time horizon. The retailer doubts his demand model which is generated by historical data and views it as an approximation. Uncertainty in the demand rate model is represented by a notion of generalized relative entropy process, and the robust pricing problem is formulated as a two-player zero-sum stochastic differential game. The pricing policy is obtained through the Hamilton-Jacobi-Isaacs (HJI) equation. The existence and uniqueness of the solution of the HJI equation is shown and a verification theorem is proved to show that the solution of the HJI equation is indeed the value function of the pricing problem. The results are illustrated by an example with exponential nominal demand rate.
A TABU SEARCH ALGORITHM FOR A PIPE-PROCESSING FLOWSHOP SCHEDULING PROBLEM MINIMIZING TOTAL TARDINESS IN A SHIPYARD
Authors: HU XIAOFENG , BAO JINGSONG , JIN YE
Published: January 2010

This paper focuses on scheduling problem of a pipe-processing flowshop in a shipyard. The flowshop composes of five stages, including cutting, bending, welding preprocessing, argon-welding and CO2-welding, and each stage consists of identical parallel machines. Since thousands of pipes are mounted on the hull block before erection, the pipe-processing scheduling is a critical task for shipbuilding to meet the due date of the block erection. A tabu search algorithm is developed for the scheduling problem with the objective of minimizing total tardiness. Computational experiments are performed on the collected real data. Results show that the proposed algorithm is efficient for this problem.
AN OPTIMAL BLOCK PREVENTIVE MAINTENANCE POLICY FOR A MULTI-UNIT SYSTEM CONSIDERING IMPERFECT MAINTENANCE
Authors: PARK J. H. , LEE S. C. , HONG J. W. , LIE C. H.
Published: January 2010

A block preventive maintenance (PM) policy for a multi-unit system composed of identical units is investigated in this paper. The block PM model of this paper considers periodic inspection and periodic imperfect maintenance. The imperfect maintenance effects are formulated using improvement factor and age reduction model. We define variables of maintenance policy as the inspection period and the PM period and obtain an optimal maintenance policy which minimizes the average total cost. A numerical example is presented, and some sensitivity analyses for model parameters are also investigated.
PHASE TRANSITIONS IN HIGHER DIMENSIONAL COSMOLOGY
Authors: UL HAQ ANSARI RIZWAN , SURESH P. K.
Published: January 2010

We have considered five-dimensional massive scalar field coupled to gravity and evaluated the one-loop effective potential in higher dimensions. It is demonstrated that nonminimally coupled φ4 theory can be regularized in five dimensions. Temperature dependent one-loop correction and critical temperature βc are computed. The phase transitions in the early universe depend on the space–time curvature R and scalar gravitational coupling ξ. A brief discussion of symmetry restoration is also presented and the nature of phase transitions in the early universe is found to be of second order.
AGENT BASED DECISION TREE LEARNING: A NOVEL APPROACH
Authors: RAHMANI MOHSEN , HASHEMI SATTAR , HAMZEH ALI , SAMI ASHKAN
Published: January 2010

Decision trees are one of the most effective and widely used induction methods that have received a great deal of attention over the past twenty years. When decision tree induction algorithms were used with uncertain rather than deterministic data, the result is a complete tree, which can classify most of the unseen samples correctly. This tree would be pruned in order to reduce its classification error and over-fitting. Recently, multi agent researchers concentrated on learning from large databases. In this paper we present a novel multi agent learning method that is able to induce a decision tree from distributed training sets. Our method is based on combination of separate decision trees each provided by one agent. Hence an agent is provided to aggregate results of the other agents and induces the final tree. Our empirical results suggest that the proposed method can provide significant benefits to distributed data classification.
A HOLISTIC SEMANTIC FRAMEWORK FOR THE PROVISION OF SERVICES IN THE DOMAIN OF eGOVERNMENT
Authors: SABUCEDO LUIS ÁLVAREZ , RIFÓN LUIS ANIDO , PÉREZ RUBÉN MÍGUEZ , GAGO JUAN SANTOS
Published: January 2010

Providing support for eGovernment services is currently a high-speed race for public administrations and research institutions. In this process towards a fully transactional platform, several projects have made their contribution. Regretfully, current solutions unveils some drawbacks regarding interoperability and accessibility issues. In this context, this paper proposes a semantic approach to fulfill holistic services in the domain. Semantics is called to play a role of first importance as a tool for interoperability. LifeEvents and AdministrativeServices are artifacts defined within this technology. Using these, an entire software architecture is derived and, eventually implemented by means of a software platform also described in this paper. Finally, some conclusions are presented.
EMPIRICAL MODE DECOMPOSITION AND CORRELATION PROPERTIES OF TRAFFIC FLUCTUATION
Authors: SHANG PENGJIAN , DONG KEQIANG , ZHAO LINGLING , KAMAE SANTI
Published: January 2010

This work describes the application of an important tool which can extract periodic information from the time-series of fluctuating traffic data. Compared to the traditional approach using FFT techniques, the nonlinear empirical mode decomposition (EMD) method has a number of advantages. This method is adaptive and therefore highly efficient at identifying embedded structures, even those with small amplitudes. Using this analysis, the traffic time series can be completely decomposed into five temporal modes including a 24-hour cycle, a 1-week cycle and a trend. Simultaneity, long-range correlations in traffic time series are investigated by detrended fluctuation analysis (DFA). In order to accurately capture the scaling exponents, EMD analysis is performed for DFA of the traffic records. The results of DFA for the data cleaned by subtracting the first intrinsic mode functions (IMF) are apparently improved, although the DFA curves are not entirely straight on the log-log plot.
PROFILES OF SUCCESSFUL CRAFT MICRO-RETAILERS
Authors: PAIGE ROSALIND C.
Published: January 2010

This research sought to provide insight on those strategies and business activities associated with successful micro-retail entrepreneurs, specifically in arts-related firms where minimal research has been conducted. The relationship with gender was also investigated. A series of empirical analyses was conducted, including factor analysis, cluster analysis and correlations. Initially, four diverse groups of micro-retailers were identified from self-definitions of success. More successful micro-retailers were found to value both personal satisfaction and financial success as indicators of success. Each of the four groups of micro-retailers who perceived themselves to be more successful engaged in distinct business strategies and activities. Results drawn from this study reveal that those micro-entrepreneurs seeking greater success should develop a strong customer satisfaction orientation and offer differentiated products that are more unique and of higher quality and priced appropriate to quality. Additionally, one strategy found to be unique to successful craft micro-retailers is to educate consumers about crafts and/or craft artisans and the region's culture.
SOCIAL ENTREPRENEURSHIP AND LEARNING: THE CASE OF THE CENTRAL AMERICA LEARNING ALLIANCE
Authors: FAMINOW MERLE D. , CARTER SIMON E. , LUNDY MARK
Published: January 2010

This paper sets out to analyze social entrepreneurship in the Central America Learning Alliance, in the context of recent literature on entrepreneurship and learning. Drawing on a recent and rapidly growing literature that describes entrepreneurship as a process that is inherently dynamic and experimental, with learning as a core component, we focus on social entrepreneurship in development as a catalyst of social transformation. A case study of a multi-stakeholder network focused on promoting processes of rural enterprise development, known as the Central America Learning Alliance, is used to illustrate social entrepreneurship in the context of the framework for innovation and learning that is developed in the first part of the paper. We conclude that the key concepts underlying entrepreneurial learning have important implications for social entrepreneurship in the context of building dynamic livelihoods for the poor of Central America.
DETERMINANTS OF FAMILY BUSINESS RESILIENCE AFTER A NATURAL DISASTER BY GENDER OF BUSINESS OWNER
Authors: DANES SHARON M. , LEE JINHEE , AMARAPURKAR SAYALI , STAFFORD KATHRYN , HAYNES GEORGE , BREWTON KATHERINE E.
Published: January 2010

Using National Family Business Panel data combined with national natural disaster and federal disaster assistance data, the purpose of the study was to investigate relative contributions of human, social and financial capital; natural disaster exposure; and federal disaster assistance to business-owning family resilience over time for male and female family business owners. With a theoretical foundation of Sustainable Family Business and Conservation of Resources theories, the study examined 311 small family firms from the National Family Business Panel. Federal disaster assistance explained a significant amount of variance in firm-owning resilience. Higher levels of federal disaster assistance were associated with lower family firm resilience for male-owned businesses and higher family firm resilience for female-owned businesses. This study advances knowledge of firm sustainability after natural disasters by adding to the conceptualization and measurement of family firm resilience; by having baseline firm financial data prior to disaster exposure; by utilizing a national, representative, longitudinal family firm sample; by including a range of natural disasters and federal disaster assistance; and by including family resilience over time.
A CAUSE–EFFECT STUDY OF INTER-FIRM NETWORKING AND CORPORATE ENTREPRENEURSHIP: INITIAL EVIDENCE OF SELF-ENFORCING SPIRALS
Authors: THORGREN SARA , WINCENT JOAKIM , ÖRTQVIST DANIEL
Published: January 2010

Participating in inter-firm networks has become increasingly popular to enhance corporate entrepreneurship. Trust, relationship diversity and knowledge transfer are considered some of the prominent cornerstones of well-functioning networks. Using longitudinal survey data covering a population of 41 firms operating in two SME networks, we examine cause–effect relationships between interorganizational trust, relationship diversity and knowledge transfer, and corporate entrepreneurship among networking firms. We found a causal influence of knowledge transfer and relational diversity on corporate entrepreneurship. Our approach also identified self-enforcing spirals between network constructs and corporate entrepreneurship. Firms displaying high corporate entrepreneurship may stimulate the creation of relationships such as those characterized by high knowledge transfer that, in turn, are relationship characteristics that stimulate corporate entrepreneurship.
THE SPEED OF INTERNATIONALIZATION OF ENTREPRENEURIAL START-UPS IN A TRANSITION ENVIRONMENT
Authors: CIESLIK JERZY , KACIAK EUGENE
Published: January 2010

This article examines the speed of internationalization by newly established firms operating in the rapidly changing environment of a country undergoing radical systemic transition, as exemplified by Poland. A longitudinal analysis of the speed of internationalization, measured by the time between the year of establishment and the year of the first export sale, identified three interesting patterns. First, both incumbent state-owned firms and private companies operating under communism played marginal roles in the internationalization process after transition to the market economy system. Second, the entrepreneurial start-ups typically embarked on exports shortly after their establishment. Third, the entrepreneurial start-ups that focused initially on the domestic market were rarely engaging in export operations later on. This aspect of the internationalization process has not been adequately explained by the extant mainstream management theories (new institutional economics, transaction cost and resource-based view). This paper offers an alternative theoretical framework for the internationalization of entrepreneurial start-ups in transition economies by extending Shapero's social psychological model of entrepreneurial events.
SDOCT IMAGE RECONSTRUCTION BY INTERFEROMETRIC SYNTHETIC APERTURE MICROSCOPY
Authors: CHEN XIAODONG , LI QIAO , LEI YONG , WANG YI , YU DAOYIN
Published: January 2010

Spectral domain optical coherence tomography (SDOCT) is a noninvasive, cross-sectional imaging technique that measures depth resolved reflectance of tissue by Fourier transforming the spectral interferogram with the scanning of the reference avoided. Interferometric synthetic aperture microscopy (ISAM) is an optical microscopy computed-imaging technique for measuring the optical properties of biological tissues, which can overcome the compromise between depth of focus and transverse resolution. This paper describes the principle of SDOCT and ISAM, which multiplexes raw acquisitions to provide quantitatively meaningful data with reliable spatially invariant resolution at all depths. A mathematical model for a coherent microscope with a planar scanning geometry and spectral detection was described. The two-dimensional fast Fourier transform (FFT) of spectral data in the transverse directions was calculated. Then the nonuniform ISAM resampling and filtering was implemented to yield the scattering potential within the scalar model. Inverse FFT was used to obtain the ISAM reconstruction. One scatterer, multiple scatterers, and noisy simulations were implemented by use of ISAM to catch spatially invariant resolution. ISAM images were compared to those obtained using standard optical coherence tomography (OCT) methods. The high quality of the results validates the rationality of the founded model and that diffraction limited resolution can be achieved outside the focal plane.