Showing papers by "Lehigh University published in 2009"
TL;DR: In this paper, a method was proposed to identify and purify all 12 major single-chirality semiconducting species from a synthetic mixture of carbon nanotubes, with sufficient yield for both fundamental studies and application development.
Abstract: Single-walled carbon nanotubes (SWNTs) are a family of molecules that have the same cylindrical shape but different chiralities. Many fundamental studies and technological applications of SWNTs require a population of tubes with identical chirality that current syntheses cannot provide. The SWNT sorting problem-that is, separation of a synthetic mixture of tubes into individual single-chirality components-has attracted considerable attention in recent years. Intense efforts so far have focused largely on, and resulted in solutions for, a weaker version of the sorting problem: metal/semiconductor separation. A systematic and general method to purify each and every single-chirality species of the same electronic type from the synthetic mixture of SWNTs is highly desirable, but the task has proven to be insurmountable to date. Here we report such a method, which allows purification of all 12 major single-chirality semiconducting species from a synthetic mixture, with sufficient yield for both fundamental studies and application development. We have designed an effective search of a DNA library of approximately 10(60) in size, and have identified more than 20 short DNA sequences, each of which recognizes and enables chromatographic purification of a particular nanotube species from the synthetic mixture. Recognition sequences exhibit a periodic purine-pyrimidines pattern, which can undergo hydrogen-bonding to form a two-dimensional sheet, and fold selectively on nanotubes into a well-ordered three-dimensional barrel. We propose that the ordered two-dimensional sheet and three-dimensional barrel provide the structural basis for the observed DNA recognition of SWNTs.
1,031 citations
TL;DR: In this paper, a silicon-organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams.
Abstract: Integrated optical circuits based on silicon-on-insulator technology are likely to become the mainstay of the photonics industry. Over recent years an impressive range of silicon-on-insulator devices has been realized, including waveguides1,2, filters3,4 and photonic-crystal devices5. However, silicon-based all-optical switching is still challenging owing to the slow dynamics of two-photon generated free carriers. Here we show that silicon–organic hybrid integration overcomes such intrinsic limitations by combining the best of two worlds, using mature CMOS processing to fabricate the waveguide, and molecular beam deposition to cover it with organic molecules that efficiently mediate all-optical interaction without introducing significant absorption. We fabricate a 4-mm-long silicon–organic hybrid waveguide with a record nonlinearity coefficient of γ ≈ 1 × 105 W−1 km−1 and perform all-optical demultiplexing of 170.8 Gb s−1 to 42.7 Gb s−1. This is—to the best of our knowledge—the fastest silicon photonic optical signal processing demonstrated. A silicon–organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams. The approach could form the basis of compact high-speed optical processing units for future communication networks.
821 citations
TL;DR: An sBB software package named couenne (Convex Over- and Under-ENvelopes for Non-linear Estimation) is developed and used for extensive tests on several combinations of BT and branching techniques on a set of publicly available and real-world MINLP instances and is compared with a state-of-the-art MINLP solver.
Abstract: Many industrial problems can be naturally formulated using mixed integer non-linear programming (MINLP) models and can be solved by spatial Branch&Bound (sBB) techniques. We study the impact of two important parts of sBB methods: bounds tightening (BT) and branching strategies. We extend a branching technique originally developed for MILP, reliability branching, to the MINLP case. Motivated by the demand for open-source solvers for real-world MINLP problems, we have developed an sBB software package named couenne (Convex Over-and Under-ENvelopes for Non-linear Estimation) and used it for extensive tests on several combinations of BT and branching techniques on a set of publicly available and real-world MINLP instances. We also compare the performance of couenne with a state-of-the-art MINLP solver.
629 citations
TL;DR: Direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21st century are examined using linked economic and terrestrial biogeochemistry models.
Abstract: A global biofuels program will lead to intense pressures on land supply and can increase greenhouse gas emissions from land-use changes. Using linked economic and terrestrial biogeochemistry models, we examined direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21st century. Our model predicts that indirect land use will be responsible for substantially more carbon loss (up to twice as much) than direct land use; however, because of predicted increases in fertilizer use, nitrous oxide emissions will be more important than carbon losses themselves in terms of warming potential. A global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production.
576 citations
TL;DR: As work in Web page classification is reviewed, the importance of these Web-specific features and algorithms are noted, state-of-the-art practices are described, and the underlying assumptions behind the use of information from neighboring pages are tracked.
Abstract: Classification of Web page content is essential to many tasks in Web information retrieval such as maintaining Web directories and focused crawling. The uncontrolled nature of Web content presents additional challenges to Web page classification as compared to traditional text classification, but the interconnected nature of hypertext also provides features that can assist the process.As we review work in Web page classification, we note the importance of these Web-specific features and algorithms, describe state-of-the-art practices, and track the underlying assumptions behind the use of information from neighboring pages.
502 citations
TL;DR: Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics.
Abstract: Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics.
470 citations
TL;DR: In this article, the authors adopt a multi-dimensional view of absorptive capacity and focus specifically on the application of external knowledge that has been obtained via university-firm collaborations and examine various organizational conditions that influence a firm's ability to apply external knowledge for explorative and exploitative innovations.
Abstract: A firm's ability to acquire and exploit external knowledge is often critical to achieving and sustaining a competitive advantage. In this study, we adopt a multi-dimensional view of absorptive capacity and focus specifically on the application of external knowledge that has been obtained via university-firm collaborations. We examine various organizational conditions that we propose influence a firm's ability to apply external knowledge for explorative and exploitative innovations. We collected data by a survey of firms in industries that frequently work with university research centres (URCs) and from publicly available sources. Results show that predictors of exploration and exploitation of the application of external knowledge differ. Surprisingly, technological relatedness, a common measure of absorptive capacity, is negatively associated with the application of external knowledge to explorative innovations, indicating that knowledge from more distant sources is applied more to exploration. Results also indicate that the effects of two external learning capabilities (prior experience with URCs and technological capability) on knowledge application are moderated in such a way by the tacitness of the knowledge transferred that experience is a stronger predictor when the knowledge is more explicit and technological capability is a stronger predictor when the knowledge is more tacit. We discuss the implications of these findings for research on the application of external knowledge.
397 citations
Posted Content•
TL;DR: The authors decompose information in the IPO prospectus into its standard and informative components, and suggest that pre-market due diligence and disclosure by underwriters and issuers can serve as a substitute for costly bookbuilding.
Abstract: Using word content analysis, we decompose information in the IPO prospectus into its standard and informative components. Greater informative content, as a proxy for pre-market due diligence, results in more accurate offer prices and less underpricing because it decreases the issuing firm’s reliance on bookbuilding to price the issue. The opposite is true for standard content. Greater content from high reputation underwriters and issuing firm managers, through Management’s Discussion and Analysis, contribute to the informativeness of the prospectus. Our results suggest that pre-market due diligence and disclosure by underwriters and issuers can serve as a substitute for costly bookbuilding.
359 citations
TL;DR: A critical review of the field focusing on the important parameters affecting rubber-toughening is presented in this paper, which is classified in five categories including roles of matrix ductility, rubber concentration, blend morphology, particle cavitation, and particle/matrix interface.
Abstract: Epoxy resins have been used as structural materials since the late 1940s. Despite their desirable properties such as high strength, excellent creep resistance, and good adhesion, they suffer from low fracture energy. Rubber modification as a major toughening approach to overcome the inherent brittleness of epoxy polymers was introduced during the early 1970s. Since then, a large number of investigations have been conducted to elucidate different aspects of rubber-toughened epoxies. The present work is a critical review of the field focusing on the important parameters affecting rubber-toughening. The studies reviewed are classified in five categories including roles of matrix ductility, rubber concentration, blend morphology, particle cavitation, and particle/matrix interface. It has been tried to provide an in-depth view of the state-of-the-art knowledge in the field and to direct future studies towards exploring new approaches for toughening of epoxy polymers.
352 citations
TL;DR: This work frames the challenges of DNA sequencing-by-synthesis in a manner accessible to a broad community of scientists and engineers, and hopes to solicit input from the broader research community on means of accelerating the advancement of genome sequencing technology.
Abstract: DNA sequencing-by-synthesis (SBS) technology, using a polymerase or ligase enzyme as its core biochemistry, has already been incorporated in several second-generation DNA sequencing systems with significant performance. Notwithstanding the substantial success of these SBS platforms, challenges continue to limit the ability to reduce the cost of sequencing a human genome to $100,000 or less. Achieving dramatically reduced cost with enhanced throughput and quality will require the seamless integration of scientific and technological effort across disciplines within biochemistry, chemistry, physics and engineering. The challenges include sample preparation, surface chemistry, fluorescent labels, optimizing the enzyme-substrate system, optics, instrumentation, understanding tradeoffs of throughput versus accuracy, and read-length/phasing limitations. By framing these challenges in a manner accessible to a broad community of scientists and engineers, we hope to solicit input from the broader research community on means of accelerating the advancement of genome sequencing technology.
322 citations
TL;DR: This paper proposes a perceptual quality evaluation method for image fusion which is based on human visual system (HVS) models and finds the algorithm provides better predictions, which are more closely matched to human perceptual evaluations, than the existing algorithms.
TL;DR: Rapid thermal processing can improve the separation performance of thick columnar films of a certain zeolite (silicalite-1) by eliminating grain boundary defects, possibly by strengthening grain bonding at the grain boundaries.
Abstract: Microporous molecular sieve catalysts and adsorbents discriminate molecules on the basis of size and shape. Interest in molecular sieve films stems from their potential for energy-efficient membrane separations. However, grain boundary defects, formed in response to stresses induced by heat treatment, compromise their selectivity by creating nonselective transport pathways for permeating molecules. We show that rapid thermal processing can improve the separation performance of thick columnar films of a certain zeolite (silicalite-1) by eliminating grain boundary defects, possibly by strengthening grain bonding at the grain boundaries. This methodology enables the preparation of silicalite-1 membranes with high separation performance for aromatic and linear versus branched hydrocarbon isomers and holds promise for realizing high-throughput and scalable production of these zeolite membranes with improved energy efficiency.
TL;DR: Results show that Monte Carlo cost-to-go estimation reduces computation time 65% in large instances with little or no loss in solution quality, and compares results to the perfect information case from solving exact a posteriori solutions for sampled vehicle routing problems.
TL;DR: By incorporating the frequency-dependent dielectric properties of the metal, the graded grating structures developed for "trapped rainbow" storage of THz light in mum level can be scaled to nm level for telecommunication waves for applications in optical communication and various nanophotonic circuits.
Abstract: The reported "trapped rainbow" storage of THz light in metamaterials and plasmonic graded structures has opened an attractive new method to control electromagnetic radiation Here, we show how, by incorporating the frequency-dependent dielectric properties of the metal, the graded grating structures developed for "trapped rainbow" storage of THz light in mum level can be scaled to nm level for telecommunication waves for applications in optical communication and various nanophotonic circuits
Posted Content•
TL;DR: In this paper, first-order alternating linearization algorithms based on an alternating direction augmented Lagrangian approach for minimizing the sum of two convex functions are presented, with little change in the computational effort required at each iteration.
Abstract: We present in this paper first-order alternating linearization algorithms based on an alternating direction augmented Lagrangian approach for minimizing the sum of two convex functions. Our basic methods require at most $O(1/\epsilon)$ iterations to obtain an $\epsilon$-optimal solution, while our accelerated (i.e., fast) versions of them require at most $O(1/\sqrt{\epsilon})$ iterations, with little change in the computational effort required at each iteration. For both types of methods, we present one algorithm that requires both functions to be smooth with Lipschitz continuous gradients and one algorithm that needs only one of the functions to be so. Algorithms in this paper are Gauss-Seidel type methods, in contrast to the ones proposed by Goldfarb and Ma in [21] where the algorithms are Jacobi type methods. Numerical results are reported to support our theoretical conclusions and demonstrate the practical potential of our algorithms.
TL;DR: Wang et al. as discussed by the authors synthesized pollen records from 31 sites with reliable chronologies and high-resolution data in the monsoonal region of China were synthesized to document Holocene vegetation and climate change and to understand the large-scale controls on these changes.
TL;DR: In this article, the authors conduct a comprehensive study of commonality in liquidity using intraday spread and depth data from 47 stock exchanges and find that commonality is a widespread, global phenomenon.
Abstract: We conduct the first comprehensive study of commonality in liquidity using intraday spread and depth data from 47 stock exchanges. We show that commonality is a widespread, global phenomenon. Firm-level changes in spreads and depths are significantly influenced by exchange-wide changes in liquidity on the majority of the world’s stock exchanges. Emerging Asian exchanges have exceptionally strong commonality, while those of Latin America exhibit little if any commonality. In contrast to previous NYSE-based results, we find that commonality in bid-ask spreads is most prevalent among small firms while commonality in depths increases monotonically with firm size. After documenting the pervasive role of commonality within individual exchanges, we examine commonality across exchanges. We extend the empirical model of Chordia, Roll, and Subrahmanyam (2000) and find the first empirical evidence of a distinct, global component in bid-ask spreads and depths. Changes in global spreads and depths have a significant effect on changes in liquidity at the exchange level. We show that while exchange size (total market capitalization) plays an influential role in the liquidity transmission process, global commonality is not driven by a subset of large exchanges.
TL;DR: In this article, the authors examined how operational outcomes, relational outcomes and business performance are affected by a collaboration project between buyers and suppliers in a supply chain and found that higher levels of collaboration led to improvements in operational and relational outcomes.
Abstract: This research examined how operational outcomes, relational outcomes and business performance are affected by a collaboration project between buyers and suppliers in a supply chain. It is hypothesized that interdependence of knowledge and process, supply chain partner insight, and the level of collaboration between the firms affect the outcomes of a collaboration project. Survey data from buyers and suppliers from a wide range of industries and organizations were used in this analysis. Among these participants, higher levels of collaboration led to improvements in operational and relational outcomes, which together led to improvements in asset utilization, competitive position, organizational performance, and profitability.
TL;DR: In this article, a strain-compensated InGaN-AlGaN quantum well (QW) structure consisting of thin tensile-strained AlGaN barriers surrounding the QW was investigated as improved active regions for lasers and light emitting diodes.
Abstract: Strain-compensated InGaN-AlGaN quantum wells (QW) are investigated as improved active regions for lasers and light emitting diodes. The strain-compensated QW structure consists of thin tensile-strained AlGaN barriers surrounding the InGaN QW. The band structure was calculated by using a self-consistent 6-band kmiddotp formalism, taking into account valence band mixing, strain effect, spontaneous and piezoelectric polarizations, as well as the carrier screening effect. The spontaneous emission and gain properties were analyzed for strain-compensated InGaN-AlGaN QW structures with indium contents of 28%, 22%, and 15% for lasers (light-emitting diodes) emitting at 480 (500), 440 (450), and 405 nm (415 nm) spectral regimes, respectively. The spontaneous emission spectra show significant improvement of the radiative emission for strain-compensated QW for all three structures compared to the corresponding conventional InGaN QW, which indicates the enhanced radiative efficiency for light emitting diodes. Our studies show the improvement of the optical gain and reduction of the threshold current density from the use of strain-compensated InGaN-AlGaN QW as active regions for diode lasers.
TL;DR: In this article, the authors extend the theory of bundles of corporate governance mechanisms to address agency issues within the Anglo-Saxon system of Corporate Governance and propose that it is best to look at these mechanisms as a bundle of mechanisms to protect shareholder interests, and that firm performance is a key determinant of the composition of this bundle.
Abstract: Manuscript Type: Conceptual
Research Question/Issue: This paper extends the theory of bundles of corporate governance mechanisms to address agency issues within the Anglo-Saxon system of corporate governance. The focus of our study is to detail the role of firm performance as a key determinant of how the governance mechanisms of monitoring and incentive alignment serve as complements or substitutes in addressing agency issues. Previous research has looked at these mechanisms in isolation from each other, with limited regard for the contingencies of firm performance and external monitoring. We propose that it is best to look at these mechanisms as a bundle of mechanisms to protect shareholder interests, and that firm performance is a key determinant of the composition of this bundle.
Research Findings/Insights: We introduce firm performance as a critical contingency that heightens shareholders' concerns over governance issues as they seek to retain control over adverse selection and moral hazard problems. We propose that when firms are performing poorly, outside monitoring by institutional investors can complement internal monitoring by boards of directors.
Theoretical/Academic Implications: We examine governance bundles under both agency and stewardship theoretical lenses to tie together previous empirical research and advance theory. In specifying the role of firm performance in determining the mix of mechanisms within the governance bundle, we reconcile prior disparate findings as to whether or not these governance mechanisms act in a complementary or substitutable fashion.
Practitioner/Policy Implications: The conceptualization of these governance mechanisms has practitioner merit in analyzing the challenges that board members face managing agency conflicts through the mix of governance mechanisms, given different levels of firm performance. Our research also shows that, under conditions of poor performance, shareholders can provide effective external monitoring that can improve the overall governance effectiveness of the firm.
TL;DR: Rural parental educational attitudes and practices toward boys and girls are more complicated and less uniformly negative for girls than commonly portrayed, and gender disparities in investments in children, children's performance at school, and children's subsequent attainment are investigated.
TL;DR: In this article, two types of nanosilica (NS) particles with different average particle sizes (20 and 80 nm in diameter) were used to fabricate epoxy-silica nanocomposites (ESNs).
TL;DR: In two experiments using an injustice paradigm or a categorization task, critical situations (specified in the if-component) were subliminally presented and it was tested whether these situations influenced the preparation and initiation of the planned goal-directed behavior as discussed by the authors.
Abstract: Forming implementation intentions (“If I encounter cue X, then I will perform behavior Y!”) is postulated to trigger action initiation without further conscious intent once the specified cue is encountered (Gollwitzer, 1999). In two experiments using an injustice paradigm or a categorization task, critical situations (specified in the if-component) were subliminally presented and it was tested whether these situations influenced the preparation (Study 1) and initiation (Study 2) of the planned goal-directed behavior (specified in the then-component). After the subliminal presentation of the critical situations, implementation intention participants showed stronger action preparation and a faster action initiation, as compared to control participants (Study 1) who had not formed any goal intention at all, and compared to participants (Studies 1 and 2) who had only formed goal intentions. These findings suggest that forming implementation intentions leads to automatic action initiation without further consc...
TL;DR: It is shown how substance assumptions block genuine ontological emergence, especially the emergence of normativity, and how a process framework permits a thermodynamic-based account of normative emergence.
Abstract: A shift from a metaphysical framework of substance to one of process enables an integrated account of the emergence of normative phenomena. I show how substance assumptions block genuine ontological emergence, especially the emergence of normativity, and how a process framework permits a thermodynamic-based account of normative emergence. The focus is on two foundational forms of normativity, that of normative function and of representation as emergent in a particular kind of function. This process model of representation, called interactivism, compels changes in many related domains. The discussion ends with brief attention to three domains in which changes are induced by the representational model: perception, learning, and language.
TL;DR: In this article, the metalorganic vapor phase epitaxial (MOVPE) growth of GaN on nanopatterned AGOG sapphire substrates was performed, and the characteristics of the light-emitting diode (LED) devices grown on patterned SAIs and planar SAIs were compared.
Abstract: Metalorganic vapor phase epitaxial (MOVPE) growth of GaN on nanopatterned AGOG sapphire substrates was performed, and characteristics of the light-emitting diode (LED) devices grown on patterned sapphire and planar substrates were compared. The nanopatterned sapphire substrates were fabricated by a novel process (AGOG) whereby aluminum nanomesas were epitaxially converted into crystalline Al2O3 via a two-stage annealing process. The GaN template grown on the nanopatterned sapphire substrate was done via an abbreviated growth mode, where a 15-nm thick, low-temperature GaN buffer layer was used, without the use of an etch-back and recovery process during the epitaxy. InGaN quantum wells (QWs) LEDs were grown on the GaN template on the nanopatterned sapphire, employing the abbreviated growth mode. The optimized InGaN QW LEDs grown on the patterned AGOG sapphire substrate exhibited a 24% improvement in output power as compared to LEDs on GaN templates grown using the conventional method. The increase in output power of the LEDs is attributed to improved internal quantum efficiency of the LEDs.
TL;DR: In this article, the effect of external energy on the shape, morphology and structure of antimony and bismuth powders has been investigated, showing that the energy had caused deformation and fracture as if the powders have been subjected to high energy milling.
Abstract: Next to atoms and molecules the powders are the smallest state of matter available in high purities and large quantities. The effect of any external energy on the shape, morphology and structure can thus be studied with relative ease. The present investigation deals with the effect of a non-contact external energy on the powders of antimony and bismuth. The characteristics of powders treated by external energy are compared with the as received powders (control). The average particle sizes, d50 and d99, the sizes below which 99% of the particles are present showed significant increase and decrease indicating that the energy had caused deformation and fracture as if the powders have been subjected to high energy milling.
TL;DR: In this paper, a large database of permeability values for common gases (He, H2, O2, N2, CO2 and CH4) has been employed in the following correlation: P j = k P i n where Pi and Pj are the permeabilities of gases i and j; the indices are chosen such that the value of n is > 1.
TL;DR: The authors synthesize a new fluvial terrace chronostratigraphy of the Bidente and Musone Rivers cast within a broader European framework, which forms the basis of a terrace genesis and river incision model for the northern Apennines, Italy.
TL;DR: In this article, the authors study capacity reservation contracts between a high-tech manufacturer (supplier) and its customer (buyer), where the supplier and the buyer are partners who enter a "design-win" agreement to develop the product, and who share the stochastic demand information.
Abstract: We study capacity reservation contracts between a high-tech manufacturer (supplier) and her oem customer (buyer). The supplier and the buyer are partners who enter a “design-win” agreement to develop the product, and who share the stochastic demand information. To encourage the supplier for more aggressive capacity expansion, the buyer reserves capacity upfront by paying a deductible fee. As capacity expansion demonstrates diseconomy of scale in this context, we assume convex capacity costs. We show that as the buyer’s revenue margin decreases, the supplier faces a sequence of four profit scenarios with decreasing desirability. We examine the effects of market size and demand variability to the contract conditions. We propose two channel coordination contracts, and discuss how such contracts can be tailored for situations where the supplier has the option of not complying with the contract, and when the buyer’s demand information is only partially updated during the supplier’s capacity leadtime.
16 Jun 2009
TL;DR: A cost-effective route to build electrically as well as optically controlled modulators in silicon photonics is reviewed, and two key devices in communications are exemplarily regarded in more detail.
Abstract: A cost-effective route to build electrically as well as optically controlled modulators in silicon photonics is reviewed. The technology enables modulation at bit rates beyond 100 Gbit/s. This platform relies on the well-established silicon-based complementary metal-oxide-semiconductor processing technology for fabricating silicon-on-insulator (SOI) waveguides, while an organic cladding layer adds the required nonlinearity. The strength of this hybrid technology is discussed, and two key devices in communications are exemplarily regarded in more detail. The first device demonstrates demultiplexing of a 120 Gbit/s signal by means of four-wave mixing in a slot-waveguide that has been filled with a highly nonlinear chi(3)-organic material. The second device is a 100 Gbit/s/1 V electrooptic modulator based on a slow-light SOI photonic crystal covered with a chi(2) -nonlinear organic material.