Scienceand Engineering Research Articles

Recent progress on synthesis of ceramics core/shell nanostructures

Thin surface layers on fine particles were found to substantially change their functionalities and properties, such as chemical reactivity, thermal stability, catalytic activity, dispersibility, or optical, magnetic and electronic properties. Because of that, the core/shell nanostructures have opened up research opportunities in almost all areas of science and engineering, including medicine, catalysis, biotechnology, chemistry, optics, electronics, energy storage, etc. Immense efforts have been implied to produce and investigate different core/ shell systems, and thereby, various synthesis techniques have been developed. In this review, we report a detailed overview of different synthesis techniques used for preparation of various ceramics core/shell nanostructures with tunable size and tailored structure.

Temperature Jump Phenomenon During Plasmatron Testing of ZrB2-SiC Ultrahigh-Temperature Ceramics

U LTRAHIGH temperature ceramic (UHTC) materials containing hafnium diboride (HfB2) and zirconium diboride (ZrB2) with a silica former, most commonly silicon carbide (SiC), have been studied extensively over the last decade as materials for leading-edge and control surface components on hypersonic vehicles [1–3]. Such components experience extreme aerothermal heating in chemically aggressive, partially dissociated air environments. Promising aspects of diboride-based UHTC materials include the very high melting points of HfB2 and ZrB2 and their refractory oxides hafnia (HfO2) and zirconia (ZrO2), as well as the high thermal conductivities of HfB2 and ZrB2, which enables efficient heat conduction away from stagnation point regions [4]. Zirconium diboride has some advantages over hafnium diboride as an aerospace material, because it is lighter and less expensive. The oxidation of ZrB2 produces both zirconia and boron oxide (B2O3). Significant oxidation of ZrB2 in atmospheric air begins at about 1050 K. The softening temperature for amorphous B2O3 is in the range of 830–900 K [5]; below about 1500 K, the oxide scale consists of a porousZrO2 network filled with liquidB2O3 that acts as an effective oxygen diffusion barrier [6,7]. However, the vapor pressure of B2O3 increases rapidly with temperature [8], resulting in rapid loss of B2O3 above 1500 K. The residual porous zirconia scale provides little resistance to inward oxygen transport and further oxidation [9,10], making the oxidation resistance of pure ZrB2 insufficient for high-temperature hypersonic vehicle applications. The addition of a silica former to ZrB2 improves its oxidation resistance [11–14]. Compositions containing from 10 to 30% (by volume) SiC have generally been found to be optimal in this regard. The virgin ZrB2-SiC surfaces oxidize through parallel reactions that generate ZrO2,B2O3, and SiO2. LiquidB2O3 mixes with amorphous SiO2 to form a borosilicate glass that seals the ZrO2 scale [15]. With increasing temperature, boron oxide evaporates preferentially from Received 10 August 2011; revision received 13 February 2012; accepted for publication 19 February 2012. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0887-8722/12 and $10.00 in correspondence with the CCC. ∗Senior Research Scientist, Molecular Physics Laboratory, 333 Ravenswood Avenue; jochen.marschall@sri.com. Senior Member AIAA (Corresponding Author). Research Physicist, Molecular Physics Laboratory, 333 Ravenswood Avenue. Member AIAA. Professor, Department ofMaterials Science andEngineering, 223McNutt Hall; billf@mst.edu. Professor, Department ofMaterials Science andEngineering, 223McNutt Hall; ghilmas@mst.edu. Ph.D. Candidate, Aeronautics and Aerospace Department. Chaussee De Waterloo 72; panerai@vki.ac.be. ∗∗Associate Professor, Aeronautics and Aerospace Department, Chaussee De Waterloo 72; olivier.chazot@vki.ac.be. JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER Vol. 26, No. 4, October–December 2012

Employment Patterns and Job Satisfaction of Foreign-Born Science and Engineering Doctorate Recipients in the United States

Science and engineering fields are important to a nation’s economy, especially in the areas ofinnovation and technology development (Committee on Science, Engineering, and Public Policy,2007). The demand for scientists and engineers is increasing globally, making it more difficult fororganizations to attract and retain qualified professionals in these fields as schools and industriescompete on a global level for top talent (Committee on Science, Engineering, and Public Policy, 2005).It is not surprising, then, that academia and industry are increasing their focus on the science andengineering workforce. Indeed, a recent National Academies report stated that "identifying the best,brightest, and the most innovative science and engineering talent will be crucial" to maintaining acompetitive advantage (Committee on Maximizing the Potential of Women in Academic Science andEngineering, 2006, p. 1-1).Foreign-born workers comprise

The Supply Side of Innovation: H‐1B Visa Reforms and U.S. Ethnic Invention

This study evaluates the impact of high‐skilled immigrants on U.S. technology formation. We use reduced‐form specifications that exploit large changes in the H‐1B visa program. Higher H‐1B admissions increase immigrant science and engineering (SE) employment and patenting by inventors with Indian and Chinese names in cities and firms dependent upon the program relative to their peers. Most specifications find limited effects for native SE employment or patenting. We are able to rule out displacement effects, and small crowding‐in effects may exist. Total SE employment and invention increases with higher admissions primarily through direct contributions of immigrants.

Improved Computational Efficiency of Unsteady Flow Problems via the Modified Wavelet Method

The authors gratefully acknowledge that this research was supported by the Brain Korea 21 program for the Mechanical and Aerospace Engineering Research at Seoul National University, by the Center of Innovative Design Optimization Technology, Korea Science and Engineering Foundation and by grant R01-2006-000- 10034-0 from the Basic Research Program of the Korea Science and Engineering Foundation. Also the authors gratefully acknowledge the financial support by the Agency for Defense Development and by the Flight Vehicle Research Center (FVRC), Seoul National University.

Semi-Automatic Measurement of the Airway Dimension by Computed Tomography Using the Full-With-Half-Maximum Method: a Study of the Measurement Accuracy according to the Orientation of an Artificial Airway

ObjectiveTo develop an algorithm to measure the dimensions of an airway oriented obliquely on a volumetric CT, as well as assess the effect of the imaging parameters on the correct measurement of the airway dimension.Materials and MethodsAn airway phantom with 11 poly-acryl tubes of various lumen diameters and wall thicknesses was scanned using a 16-MDCT (multidetector CT) at various tilt angles (0, 30, 45, and 60°). The CT images were reconstructed at various reconstruction kernels and thicknesses. The axis of each airway was determined using the 3D thinning algorithm, with images perpendicular to the axis being reconstructed. The luminal radius and wall thickness was measured by the full-width-half-maximum method. The influence of the CT parameters (the size of the airways, obliquity on the radius and wall thickness) was assessed by comparing the actual dimension of each tube with the estimated values.ResultsThe 3D thinning algorithm correctly determined the axis of the oblique airway in all tubes (mean error: 0.91 ± 0.82°). A sharper reconstruction kernel, thicker image thickness and larger tilt angle of the airway axis resulted in a significant decrease of the measured wall thickness and an increase of the measured luminal radius. Use of a standard kernel and a 0.75-mm slice thickness resulted in the most accurate measurement of airway dimension, which was independent of obliquity.ConclusionThe airway obliquity and imaging parameters have a strong influence on the accuracy of the airway wall measurement. For the accurate measurement of airway thickness, the CT images should be reconstructed with a standard kernel and a 0.75 mm slice thickness.

An Analysis of the School-to-Work Transition of Scienceand Engineering Graduates- Focusing on the Difference of Length of Transitional Periodbetween the Types of Employment -

An Analysis of the School-to-Work Transition of Scienceand Engineering Graduates- Focusing on the Difference of Length of Transitional Periodbetween the Types of Employment -

Shear-Induced Conformational Ordering in the Melt of Isotactic Polypropylene

College of Polymer Science and Engineering and State KeyLaboratory of Polymer Materials Engineering, SichuanUniVersity, Chengdu, China, and National SynchrotronRadiation Lab and Department of Polymer Science andEngineering, UniVersity of Science and Technology of China,Hefei, ChinaReceiVed May 5, 2007ReVised Manuscript ReceiVed May 23, 2007Introduction. Flow-induced order and crystallization ofpolymers are fundamental (but poorly understood) nonequilib-rium properties of these systems. As moreover flow fields areinevitably applied during polymer processing, the developmentof order under such conditions has attracted considerableinterest.

Choi-Williams transform and atomic functions in digital signal processing

INTRODUCTIONIn recent years, signals of new types are findingever-widening applications in various areas of scienceand engineering [1]. For their analysis, it is expedient toapply, along with the conventional Fourier transform,new mathematical methods based on the wavelet trans-form, the theory of atomic functions (AF), and theWigner transform [2–5]. On the other hand, in actualpractice, signals are always detected and processedagainst the background of noise. External noise is mostoften represented by a random sequence of impulseswith random parameters; moreover, it is not necessarilyGaussian. For such noise, expansion components ofdifferent scales turn out to be correlated and, because ofthis, linear methods of analysis are inefficient. Thequalitative indices for the nonlinear filtering of noisecan be increase by means of applying nonlinear trans-forms. Therefore, it is reasonable to study the appropri-ateness of applying the Choi–Williams transform insignal analysis and to compare it to the Wigner trans-form, to the conventional windowed Fourier transform(WFT), and to AF.BASIC PROPERTIESOF THE CHOI–WILLIAMS TRANSFORMThe Choi–Williams transform [6, 7] of a signal f(t)has the form(1)where the asterisk denotes the operation of complexconjugation and σ > 0 is the scale coefficient. As σ →∞, the Choi–Williams transform reduces to the Wignertransform [6, 7]. Let us mention the basic properties ofthe Choi–Williams transform [6]. The function of spec-tral density (FSD) P

Liquid Crystalline Perfluorocyclobutyl Aryl Ether Polymers Containing Oligophenylene Mesogens

Department of Chemistry, School of Materials Science andEngineering and Center for Optical Materials Science andEngineering Technologies (COMSET), Clemson UniVersity,Clemson, South Carolina 29634-0973, and Department ofPhysics, Kent State UniVersity, Kent, Ohio 44242ReceiVed March 6, 2006ReVised Manuscript ReceiVed May 17, 2006Introduction. Poly(p-phenylene)s (PPP) are highly extendedlinear macromolecules due to their rigid structure, and as a result,unmodified PPP is an insoluble and intractable material.

The Effect of Personality and Precollege Characteristics on First-Year Activities and Academic Performance

The relationship between students' gender, personality traits, predicted first-year grades, and quality of effort put forth in academic and personal/social activities with academic achievement and critical thinking was examined for 265 first-year science and engineering undergraduates enrolled at a selective doctoral-extensive university. Results show that some personality traits influence the quality of effort expended with academic and personal/social activities as well as end-of-first-year grades and a measure of critical thinking.

Factors That Influence Persistence in Science and Engineering Career Aspirations

The author investigated students' persistence regarding career aspirations in science and engineering (SE) professional careers as a function of race and sex. In a nationally representative sample of 8th graders, persistent racial minority and female students were compared with nonpersistent racial minority and male students regarding their self‐concept, parental involvement, socioeconomic status, and academic achievement. Men were more likely than women to persist in SE career aspirations. Persistent students scored higher than did nonpersistent students on all of the variables studied. Academic proficiency and math self‐efficacy were 2 of the strongest predictors of persistence in SE careers.

Revisit ocean thermal energy conversion system

The earth, covered more than70.8% by the ocean, receives most of itsenergy from the sun. Solar energy istransmitted through the atmosphere andefficiently collected and stored in thesurface layer of the ocean, largely in thetropical zone. Some of the energy isre-emitted to the atmosphere to drive thehydrologic cycle and wind. The wind fieldreturns some of the energy to the ocean inthe form of waves and currents. Themajority of the absorbed solar energy isstored in vertical thermal gradients nearthe surface layer of the ocean, most ofwhich is in the tropical region. Thisthermal energy replenished each day by thesun in the tropical ocean represents atremendous pollution-free energy resourcefor human civilization. Ocean ThermalEnergy Conversion (OTEC) technology refersto a mechanical system that utilizes thenatural temperature gradient that exists inthe tropical ocean between the warm surfacewater and the deep cold water, to generateelectricity and produce other economicallyvaluable by-products. The science andengineering behind OTEC have been studiedin the US since the mid-seventies,supported early by the U.S. Government andlater by State and private industries.There are two general types of OTECdesigns: closed-cycle plants utilize theevaporation of a working fluid, such asammonia or propylene, to drive theturbine-generator, and open-cycle plantsuse steam from evaporated sea water to runthe turbine. Another commonly known design,hybrid plants, is a combination of the two.OTEC requires relatively low operation andmaintenance costs and no fossil fuelconsumption.OTEC system possesses a formidablepotential capacity for renewable energy andoffers a significant elimination ofgreenhouse gases in producing power. Inaddition to electricity and drinking water,an OTEC system can produce many valuableby-products and side-utilizations, such as:hydrogen, air-conditioning, ice,aquaculture, and agriculture, etc. Thepotential of these by-products, especiallydrinking water, aquaculture andmariculture, can easily translate intobillions of dollars in businessopportunities. The current status of theOTEC system definitely deserves to becarefully revisited. This paper willexamine recent major advancements intechnology, evaluate costs andeffectiveness, and assess the overallmarket environment of the OTEC system anddescribe its great renewable energypotential and overall benefits to thenations of the world.

Exploring Ethical Dimensions in Tagore's Muktadhara

This article aims at providing a case study forteaching engineering ethics. It is based on a play byRabindranath Tagore and was used in a technologicalinstitute in India with students of science andengineering. As a case study it can be used withstudents of other disciplines as well.

Defect modes in a two-dimensional square lattice of square rods

This work was supported in part by the Korea Science and Engineering Foundation through the Semiconductor Physics Research Center at Jeonbuk National University and by a grant of time on the Cray computer at the System Engineering Research Institute.

Strategic directions in computer science education

Public support for universities and thetraditional balance between researchand teaching have each come under in-creased scrutiny and criticism. At thesame time, modern society grows evermore dependent on computing technol-ogy and many sectors of science andindustry anticipate ongoing shortages ofwell trained computer scientists and en-gineers.The distance between the foundationsof computing and its research and appli-cation frontiers is considerably shorterthan in many other fields. As a result,the curriculum in computer science andengineering (CS&E) faces constant evo-lutionary pressure to integrate new crit-ical developments. The rapid changes intechnology, however, also affect the pro-cess of educational delivery. Recent ad-vances in networking and graphics, forexample, make it possible to developeffective pedagogical tools and sharethem among many different educationalinstitutions.CS&E educators must play a key rolein responding to these changes. To re-main effective, CS&E education mustevolve in both method and content asour discipline progresses. Educatorsneed to champion new technologies thatincrease the quality of education, pro-vide opportunities to a wider class ofstudents, and prepare graduates to par-ticipate in the development of technolo-gies that ensure the safety, privacy, em-powerment, and competencies of futurecitizens. Meeting this challenge will re-quire fundamental changes in the wayin which faculties represent the princi-ples and practice of CS&E at all educa-tional levels.

Substitutional site of Co2+ ions in single-crystalline AgGaS2:Co2+

This work is supported in part by the Korea Science and Engineering Foundation through the Semiconductor Physics Research Center at Jeonbuk National University.

Advanced courses in scienceand engineering

Advanced courses in scienceand engineering