Showing papers by "Lehigh University published in 2007"
TL;DR: Results indicate that tensile strained n-type Ge is a good candidate for Si integrated lasers, despite of the free carrier absorption loss.
Abstract: We analyze the optical gain of tensile-strained, n-type Ge material for Si-compatible laser applications. The band structure of unstrained Ge exhibits indirect conduction band valleys (L) lower than the direct valley (Γ) by 136 meV. Adequate strain and n-type doping engineering can effectively provide population inversion in the direct bandgap of Ge. The tensile strain decreases the difference between the L valleys and the Γ valley, while the extrinsic electrons from n-type doping fill the L valleys to the level of the Γ valley to compensate for the remaining energy difference. Our modeling shows that with a combination of 0.25% tensile strain and an extrinsic electron density of 7.6×1019/cm3 by n-type doping, a net material gain of ~400 cm-1 can be obtained from the direct gap transition of Ge despite of the free carrier absorption loss. The threshold current density for lasing is estimated to be ~6kA cm-2 for a typical edge-emitting double heterojunction structure. These results indicate that tensile strained n-type Ge is a good candidate for Si integrated lasers.
603 citations
TL;DR: This paper addresses the problem of radar waveform design for target identification and classification and presents an asymptotic formulation which requires less knowledge of the statistical model of the target.
Abstract: This paper addresses the problem of radar waveform design for target identification and classification. Both the ordinary radar with a single transmitter and receiver and the recently proposed multiple-input multiple-output (MIMO) radar are considered. A random target impulse response is used to model the scattering characteristics of the extended (nonpoint) target, and two radar waveform design problems with constraints on waveform power have been investigated. The first one is to design waveforms that maximize the conditional mutual information (MI) between the random target impulse response and the reflected waveforms given the knowledge of transmitted waveforms. The second one is to find transmitted waveforms that minimize the mean-square error (MSE) in estimating the target impulse response. Our analysis indicates that under the same total power constraint, these two criteria lead to the same solution for a matrix which specifies the essential part of the optimum waveform design. The solution employs water-filling to allocate the limited power appropriately. We also present an asymptotic formulation which requires less knowledge of the statistical model of the target
518 citations
TL;DR: Lab studies show that HAIX selectively removes phosphate from the background of much higher concentrations of competing sulfate, chloride and bicarbonate anions due to the combined presence of Coulombic and Lewis acid-base interactions.
400 citations
TL;DR: The authors examined the emotional and behavioral consequences of making functional versus hedonic trade-offs and found that consumers attach greater importance to the hedonics attribute than the functional attribute in choice tasks.
Abstract: This article examines the emotional and behavioral consequences of making functional versus hedonic trade-offs. Building on the proposed correspondence between functionality and a prevention focus and between hedonics and a promotion focus, the authors predict that contexts involving functional versus hedonic trade-offs evoke a variety of both negative and positive emotions, including guilt/anxiety, sadness/disappointment, cheerfulness/excitement, and confidence/security. These predictions are confirmed. Furthermore, an analysis of the intensities of these specific emotions reveals the following additional insights: (1) Under conditions in which the options in a choice set meet or exceed both functional and hedonic cutoffs, consumers attach greater importance to the hedonic attribute, and (2) whereas the functionally superior option is preferred in choice tasks, the hedonically superior one is preferred in willingness-to-pay tasks.
397 citations
TL;DR: Until they are certain that outsourcing IT management is the best possible option, firms would do well to maintain and invest in their own in-house IT assets.
Abstract: Until they are certain that outsourcing IT management is the best possible option, firms would do well to maintain and invest in their own in-house IT assets.
370 citations
TL;DR: In this article, a detailed study of high-pressure and ultra-high-pressure metamorphic suites incorporating knowledge of mineral chemistry and reactions, kinetics and disequilibrium, prograde and exhumation-related P-T paths, fluid flow and fluid-rock interactions, and experimental evidence for the physical and chemical properties of fluids at the pressures and temperatures experienced by subducting slabs.
365 citations
TL;DR: In this paper, the electronic and molecular structures of well-defined W(VI) bulk mixed oxide reference compounds consisting of isolated WO4 or WO6 monomers, dimeric O3W−O−WO3, polymeric chain of alternating WO 4/WO6 units, and WO 6-coordinated W9−W18 clusters were examined.
Abstract: Combined UV−vis diffuse reflectance spectroscopy (DRS) and Raman spectroscopy were applied to examine the electronic and molecular structures, respectively, of well-defined W(VI) bulk mixed oxide reference compounds consisting of (i) isolated WO4 or WO6 monomers, (ii) dimeric O3W−O−WO3, (iii) polymeric chain of alternating WO4/WO6 units, and (iv) WO6-coordinated W9−W18 clusters. Raman spectroscopy was employed to confirm the identity and phase purity of the different tungsten oxide structures. UV−vis DRS provided the corresponding electronic edge energy (Eg) of the ligand-to-metal charge transfer (LMCT) transitions of the W(VI) cations. A correlation between the edge energy and the number of covalent bridging W−O−W bonds around the central W(VI) cation was found with Eg linearly decreasing with increasing number of bridging W−O−W bonds. However, a direct relationship between Eg and the domain size, NW, for finite WOx clusters does not exist. Subsequently, UV−vis and Raman spectroscopy information were app...
352 citations
01 Mar 2007
TL;DR: An analytical model develops an analytical model that explores how important supply chain parameters affect the cost savings to be realized from collaborative initiatives such as vendor-managed inventory (VMI) and shows that benefits, in the form of inventory cost reductions, may be generated from integration.
Abstract: This paper develops an analytical model that explores how important supply chain parameters affect the cost savings to be realized from collaborative initiatives such as vendor-managed inventory (VMI). Results from the model show that benefits, in the form of inventory cost reductions, may be generated from integration depending upon the ratio of the order costs of the supplier to the buyer and the ratio of the carrying charges of the supplier to the buyer. Results also show that these benefits are disproportionally distributed between buyers and suppliers.
347 citations
TL;DR: This article summarizes the findings of research studies designed to improve the comprehension of expository text for students with learning disabilities and discusses treatment outcomes.
Abstract: This article summarizes the findings of research studies designed to improve the comprehension of expository text for students with learning disabilities. Twenty-nine studies were located that met the inclusion criteria. Interventions gleaned from the review were categorized as content enhancement (i.e., advance and graphic organizers, visual displays, mnemonic illustrations, and computer-assisted instruction) or cognitive strategy instruction (i.e., text structure, main idea identification, summarization, questioning, cognitive mapping, reciprocal teaching). Treatment outcomes are discussed in relation to the various instructional approaches, student characteristics (e.g., grade, IQ), instructional features (e.g., materials, treatment length), methodological features, strategy maintenance, and generalization components. Implications for classroom practice and future research directions are provided.
336 citations
TL;DR: In this paper, the energy and distribution of surface plasmons excited by fast electrons was measured using Electron Energy-Loss Spectroscopy (EELS) combined with spectrum imaging and data processing.
Abstract: The optical response from metal nanoparticles and nanostructures is dominated by surface plasmon generation and is critically dependent on the local structure and geometry. Electron energy-loss spectroscopy (EELS), combined with recent developments in spectrum imaging and data processing, has been used to observe the energy and distribution of surface plasmons excited by fast electrons. The energy of the plasmon responses is consistent with the optical response and with calculations. For gold and silver rods and ellipsoids, longitudinal, transverse and distinct cluster modes were readily identified and mapped. The spatial resolution of the presented maps is one order of magnitude better than that achievable with scanning near-field optical microscopy (SNOM)-based techniques.
302 citations
TL;DR: In this article, a study on the catalytic properties of palladium for hydrodechlorination using nanoscale zero-valent iron particles is presented. But the results of the study were limited to the case of chlorinated ethylenes.
Abstract: Reported herein is a study on the catalytic properties of palladium for hydrodechlorination using nanoscale zero-valent iron particles. Temperature-dependent experiments and X-ray diffraction (XRD) are conducted to characterize reactions of chlorinated ethylenes with nanoscale Fe and Pd/Fe particles. XRD results suggest bimetallic structures are created as a result of Pd(II) reduction by zero-valent iron and the degree of surface palladium loading is proportional to the initial amount of palladium applied. The optimal content of palladium in the bimetallic particles for dechlorination is in the range of 1–5% by weight. XRD analyses further suggest that oxidation of iron produces mainly iron oxides. No oxidized species of palladium (e.g., PdO) is found before or after the reactions. Activation energies of the dechlorination reactions with the nanoscale Pd/Fe and Fe particles are estimated to be 31.1 and 44.9 kJ/mol, respectively. A conceptual model for the catalytic hydrodechlorination by the nanoscale Pd/Fe particles is presented.
TL;DR: The five industrial software architecture design methods are compared and it is found that the five approaches have a lot in common and match more or less the ''ideal'' pattern that can be used for further method comparisons.
TL;DR: In this article, a large-scale BRBF with improved connection details was tested at the ATLSS Center, Lehigh University, which demonstrated that a properly detailed BRBF can withstand severe seismic input and maintain its full load-carrying capacity.
Abstract: As buckling-restrained braced frames (BRBFs) have been used increasingly in the United States, the need for knowledge about BRBF behavior has grown. In particular, large-scale experimental evaluations of BRBFs are necessary to demonstrate the seismic performance of the system. Although tests of buckling-restrained braces (BRBs) have demonstrated their ability to withstand significant ductility demands, large-scale BRBF tests have exhibited poor performance at story drifts between 0.02 and 0.025 rad. These tests indicate that the large stiffness of the typical beam-column-brace connection detail leads to large flexural demands that cause undesirable failure modes. As part of a research program composed of numerical and experimental simulations, a large-scale BRBF with improved connection details was tested at the ATLSS Center, Lehigh University. During multiple earthquake simulations, which were conducted using a hybrid pseudodynamic testing method, the test frame sustained story drifts of close to 0.05 rad and BRB maximum ductility demands of over 25 with minimal damage and no stiffness or strength degradation. The testing program demonstrated that a properly detailed BRBF can withstand severe seismic input and maintain its full load-carrying capacity.
TL;DR: In this paper, a rationale for the use of antecedent strategies and literature-based examples of applications within school settings at both the class-wide and individual levels are discussed.
Abstract: In response to ongoing concerns with student academic and behavior problems, antecedent strategies have garnered increasing attention. Antecedent intervention approaches focus on structuring the environment to prevent problems and enhance motivation. At the class-wide level, implementation of these strategies can create a structured and orderly environment to which most students are responsive. In the case of persistent behavior problems, specific events that precede problem behavior can be removed or modified to create individualized antecedent interventions. The empirical literature base supporting the value of this approach has witnessed rapid growth. In this article, we offer a rationale for the use of antecedent strategies and provide literature-based examples of applications within school settings at both the class-wide and individual levels. In addition, we discuss practical considerations for implementing antecedent interventions. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 65–75, 2007.
TL;DR: In this article, the molecular and electronic structures of the dehydrated supported metal oxides and the SiO2 support were determined by combined in situ Raman, IR, and UV−vis spectroscopy under dehydrated conditions.
Abstract: Groups 5−7 transition metal oxides (V2O5, Nb2O5, Ta2O5, CrO3, MoO3, WO3, Re2O7) were anchored on a SiO2 support via incipient wetness impregnation and calcination. The molecular and electronic structures of the dehydrated supported metal oxides and the SiO2 support were determined by combined in situ Raman, IR, and UV−vis spectroscopy under dehydrated conditions. In situ Raman characterization reveals that the supported metal oxides are only present as surface species below the maximum dispersion limit (where crystalline metal oxide nanoparticles are absent). In situ IR analysis shows that the surface metal oxides anchor to the SiO2 support at Si−OH and adjacent Si−O−Si sites. The corresponding in situ UV−vis diffuse reflectance spectroscopy indicates that the dehydrated surface metal oxide species are present as isolated structures. Isotopic D2O−H2O exchange demonstrates that the dehydrated surface MOx species possess the MO oxo functionality but no MOH bonds. The number of MO oxo bonds was found to be r...
TL;DR: This paper explores how transmit diversity can improve the direction finding performance of a radar utilizing an antenna array at the receiver with multiple-input multiple-output antenna systems.
Abstract: It has been recently shown that multiple-input multiple-output (MIMO) antenna systems have the potential to dramatically improve the performance of communication systems over single antenna systems. Unlike beamforming, which presumes a high correlation between signals either transmitted or received by an array, the MIMO concept exploits the independence between signals at the array elements. In conventional radar, the target's radar cross section (RCS) fluctuations are regarded as a nuisance parameter that degrades radar performance. The novelty of MIMO radar is that it provides measures to overcome those degradations or even utilizes the RCS fluctuations for new applications. This paper explores how transmit diversity can improve the direction finding performance of a radar utilizing an antenna array at the receiver. To harness diversity, the transmit antennas have to be widely separated, while for direction finding, the receive antennas have to be closely spaced. The analysis is carried out by evaluating several Cramer-Rao bounds for bearing estimation and the mean square error of the maximum likelihood estimate
TL;DR: A stochastic version of the location model with risk pooling (LMRP) that optimizes location, inventory, and allocation decisions under random parameters described by discrete scenarios is presented.
TL;DR: In this paper, the authors explore the themes of self, culture, collaboration, circularity, trustworthiness, and evidence deconstruction from multiple qualitative methodologies for counseling psychology training and research.
Abstract: This article presents an overview of various strategies and methods of engaging in qualitative data interpretations and analyses in counseling psychology. The authors explore the themes of self, culture, collaboration, circularity, trustworthiness, and evidence deconstruction from multiple qualitative methodologies. Commonalities and differences that span across approaches are explored. Implications for how researchers address qualitative data analysis and interpretation in counseling psychology training and research are discussed.
TL;DR: The relationship between PWC and user satisfaction was negative for goal-directed users and inverted-U for experiential users, and the positive relationship between objective complexity and PWC was moderated by user familiarity.
Abstract: In this study, we propose that perceived website complexity (PWC) is central to understanding how sophisticated features of a website (such as animation, audio, video, and rollover effects) affect a visitor's experience at the site. Although previous research suggests that several elements of perceived complexity (e.g., amount of text, animation, graphics, range and consistency of web pages configuring a website, ease of navigating through it, and clarity of hyperlinks) affect important user outcomes, conflicting results yielded by previous research have created an important debate: does complexity enhance or inhibit user experience at a website. In this study, we draw on the task complexity literature to develop a broad and holistic model that examines the antecedents and consequences of PWC. Our results provide two important insights into the relationship between PWC and user outcomes. First, the positive relationship between objective complexity and PWC was moderated by user familiarity. Second, online task goals (goal-directed search and experiential browsing) moderated the relationship between PWC and user satisfaction. Specifically, the relationship between PWC and user satisfaction was negative for goal-directed users and inverted-U for experiential users. The implications of this finding for the practice of website design are discussed.
TL;DR: Simulation results show that the proposed scheme achieves an outage probability close to that for the optimal scheme obtained by numerical search, and achieves significant performance gain over other schemes in the literature.
Abstract: We study power allocation for the decode-and-forward cooperative diversity protocol in a wireless network under the assumption that only mean channel gains are available at the transmitters. In a Rayleigh fading channel with uniformly distributed node locations, we aim to find the power allocation that minimizes the outage probability under a short-term power constraint, wherein the total power for all nodes is less than a prescribed value during each two-stage transmission. Due to the computational and implementation complexity of the optimal solution, we derived a simple near-optimal solution. In this near-optimal scheme, a fixed fraction of the total power is allocated to the source node in stage I. In stage II, the remaining power is split equally among a set of selected nodes if the selected set is not empty, and otherwise is allocated to the source node. A node is selected if it can decode the message from the source and its mean channel gain to the destination is above a threshold. In this scheme, each node only needs to know its own mean channel gain to the destination and the number of selected nodes. Simulation results show that the proposed scheme achieves an outage probability close to that for the optimal scheme obtained by numerical search, and achieves significant performance gain over other schemes in the literature
TL;DR: This geometry enhances adhesion because of its ability to trap interfacial cracks in highly compliant contact regimes between successive fibril detachments, in a manner analogous to lattice trapping of cracks in crystalline solids.
Abstract: We present a synthetic adaptation of the fibrillar adhesion surfaces found in nature. The structure consists of protruding fibrils topped by a thin plate and shows an experimentally measured enhancement in adhesion energy of up to a factor of 9 over a flat control. Additionally, this structure solves the robustness problems of previous mimic structures and has preferred contact properties (i.e., a large surface area and a highly compliant structure). We show that this geometry enhances adhesion because of its ability to trap interfacial cracks in highly compliant contact regimes between successive fibril detachments. This results in the requirement that the externally supplied energy release rate for interfacial separation be greater than the intrinsic work of adhesion, in a manner analogous to lattice trapping of cracks in crystalline solids.
TL;DR: This article examined whether the links between attachment security and social behavior in late adolescence were mediated by emotional competence, and found that secure attachment relationships foster appropriate social behavior by promoting high levels of emotional awareness, empathy, positive expressiveness, and low levels of negative dominant expressiveness.
TL;DR: In this article, the fast directions of seismic anisotropy determined using shear-wave splitting analysis correlate with the surfi cial geology including major sutures and shear zones and with the surface strain derived from the global positioning system velocity fi eld.
Abstract: Ongoing plate convergence between India and Eurasia provides a natural laboratory for studying the dynamics of continental collision, a fi rst-order process in the evolution of continents, regional climate, and natural hazards. In southeastern Tibet, the fast directions of seismic anisotropy determined using shear-wave splitting analysis correlate with the surfi cial geology including major sutures and shear zones and with the surface strain derived from the global positioning system velocity fi eld. These observations are consistent with a clockwise rotation of material around the eastern Himalayan syntaxis and suggest coherent distributed lithospheric deformation beneath much of southeastern Tibet. At the southeastern edge of the Tibetan Plateau we observe a sharp transition in mantle anisotropy with a change in fast directions to a consistent E-W direction and a clockwise rotation of the surface velocity, surface strain fi eld, and fault network toward Burma. Around the eastern Himalayan syntaxis, the coincidence between structural crustal features, surface strain, and mantle anisotropy suggests that the deformation in the lithosphere is mechanically coupled across the crust-mantle interface and that the lower crust is suffi ciently strong to transmit stress. At the southeastern margin of the plateau in Yunnan province, a change in orientation between mantle anisotropy and surface strain suggests a change in the relationship between crustal and mantle deformation. Lateral variations in boundary conditions and rheological properties of the lithosphere play an important role in the geodynamic evolution of the Himalayan orogen and Tibetan Plateau and require the development of three-dimensional models that incorporate lateral heterogeneity.
TL;DR: In this article, a 688-cm-long sediment core from Hurleg Lake, a freshwater lake located in the Qaidam Basin on the NE Tibetan Plateau, just beyond the northern limit of the East Asian summer monsoon influence was aided by surface pollen analysis.
TL;DR: In this paper, a performance-based seismic design approach for PT steel frame systems is presented, and the design objectives are outlined, design criteria are given, and a step-by-step design procedure is given.
Abstract: A posttensioned (PT) steel moment resisting frame is a self-centering earthquake resistant steel frame that uses posttensioning steel to compress the beam flanges against the column flanges at the connections. The posttensioning contributes to the moment capacity of the connections and provides an elastic restoring force that returns the frame to its pre-earthquake position. This paper describes the behavior and design of PT frames and PT frame systems, where a PT frame system is a PT frame with the collector elements that connect it to the floor system. The interaction of the floor system with the PT frame produces axial forces in the beams that add to those from the posttensioning. This paper outlines a performance-based seismic design approach for PT steel frame systems. Seismic performance levels, seismic input levels, structural limit states and capacities, and structural demands for PT frame systems are defined. The design objectives are outlined, design criteria are given, and a step-by-step design procedure is given. The design approach is evaluated via comparisons with time-history analysis results.
TL;DR: In this article, the extent of overlap and predictive strength of multiple forms of child maltreatment and stressors internal and external to the family was examined, and it was found that a strong association was found between physical and sexual abuse, neglect, and exposure to domestic violence.
Abstract: Analyses were conducted to examine the extent of overlap and predictive strength of multiple forms of child maltreatment and stressors internal and external to the family. Findings suggest a strong association between child maltreatment (physical and sexual abuse, neglect, and exposure to domestic violence) and stressors (family conflict, personal problems of parents, and external constraints on the family). After controlling for stressors, family socioeconomic status, and child gender, a general construct of child maltreatment was predictive of internalizing and externalizing behaviors in adolescents. Specific effects of child physical and sexual abuse were revealed in these longitudinal structural equation model tests.
TL;DR: An alternative approach in which morphology arises from the interaction of semantic and phonological codes is investigated, which shows that the magnitude of priming reflects the degree of semanticand phonological overlap between words.
Abstract: A considerable body of empirical and theoretical research suggests that morphological structure governs the representation of words in memory and that many words are decomposed into morphological components in processing. The authors investigated an alternative approach in which morphology arises from the interaction of semantic and phonological codes. A series of cross-modal lexical decision experiments shows that the magnitude of priming reflects the degree of semantic and phonological overlap between words. Crucially, moderately similar items produce intermediate facilitation (e.g., lately-late). This pattern is observed for word pairs exhibiting different types of morphological relationships, including suffixed-stem (e.g., teacher-teach), suffixed-suffixed (e.g., saintly-sainthood), and prefixed-stem pairs (preheat-heat). The results can be understood in terms of connectionist models that use distributed representations rather than discrete morphemes.
TL;DR: In this paper, the intrinsic electrical, elastic, optical, and structural properties of antiparallel domain walls in the trigonal ferroelectrics lithium niobate and lithium tantalate were studied.
Abstract: Domains and domain walls are a fundamental property of interest in ferroelectrics, magnetism, ferroelastics, superconductors, and multiferroic materials. Unlike magnetic Bloch walls, ideal ferroelectric domain walls are well accepted to be only one to two lattice units wide, over which polarization and strain change across the wall. However, walls in real ferroelectrics appear to show unexpected property variations in the vicinity of domain walls that can extend over micrometer length scales. This chapter specifically reviews the local electrical, elastic, optical, and structural properties of antiparallel domain walls in the trigonal ferroelectrics lithium niobate and lithium tantalate. It is shown that extrinsic point defects and their clustering play a key role in the observed local wall structure and influence macroscale properties by orders of magnitude. The review also raises broader and yet unexplored fundamental questions regarding intrinsic widths, defect–domain wall interactions, and static versus dynamic wall structure.
TL;DR: Hill et al. as mentioned in this paper found that ethnic identity retention was influenced by engagement in cultural celebrations and activities, a need to hold onto tradition and upbringing, family ties, social support, and a rejection of perceived Western values.
Abstract: Sixteen 1st-generation Asian Indian mothers and fathers were interviewed about the influence of immigration on retention of their own ethnic identity and their ability to promote a sense of ethnic identity in their 2nd-generation children. Data were analyzed with the consensual qualitative research methodology (C. E. Hill et al., 2005) and revealed ethnic identity retention to be influenced by engagement in cultural celebrations and activities, a need to hold onto tradition and upbringing, family ties, social support, and a rejection of perceived Western values. Ethnic identity retention was challenged by environmental obstacles and barriers within American society, loss of familial support, lack of cultural continuity, and an inability to have the “best of both worlds.” Furthermore, participants identified specific values and strategies relevant to transmitting an ethnic identity to their children as well as specific challenges to this process, including limited familial and communal guidance and modeling, obstacles from Western culture, an inability to apply their own experience or upbringing, a lack of cultural knowledge, and the potential for intermarriage. Implications of the findings are discussed.
TL;DR: In this paper, the electrostatic coupling between single-walled carbon nanotubes (SWCNT) and planar gate electrodes in thin-film transistors (TFTs) is analyzed both in the quantum limit with an analytical model and in the classical limit with finite element modeling.
Abstract: The electrostatic coupling between singled-walled carbon nanotube (SWCNT) networks/arrays and planar gate electrodes in thin-film transistors (TFTs) is analyzed both in the quantum limit with an analytical model and in the classical limit with finite-element modeling. The computed capacitance depends on both the thickness of the gate dielectric and the average spacing between the tubes, with some dependence on the distribution of these spacings. Experiments on transistors that use submonolayer, random networks of SWCNTs verify certain aspects of these calculations. The results are important for the development of networks or arrays of nanotubes as active layers in TFTs and other electronic devices.