588 research outputs found
Helping children think: Gaze aversion and teaching
No full textLooking away from an interlocutor's face during demanding cognitive activity can help adults answer challenging arithmetic and verbal-reasoning questions (Glenberg, Schroeder, & Robertson, 1998). However, such `gaze aversion' (GA) is poorly applied by 5-year-old school children (Doherty-Sneddon, Bruce, Bonner, Longbotham, & Doyle, 2002). In Experiment 1 we trained ten 5-year-old children to use GA while thinking about answers to questions. This trained group performed significantly better on challenging questions compared with 10 controls given no GA training. In Experiment 2 we found significant and monotonic age-related increments in spontaneous use of GA across three cohorts of ten 5-year-old school children (mean ages: 5;02, 5;06 and 5;08). Teaching and encouraging GA during challenging cognitive activity promises to be invaluable in promoting learning, particularly during early primary years
Compact N-Way Doherty Power Combiners for mm-wave 5G Transmitters
No full textThis paper presents a design procedure for compact lumped-element 3-/4-/5-way Doherty power combiners suitable for mm-wave 5G transmitters. Among them, the 3-way Doherty power combiner is favored due to its low complexity, compact layout, and average drain efficiency at 12 dB power back-off (PBO) when implemented using lossy lumped elements. Based on the metal stack of a 40nm CMOS process, a 3-way Doherty power combiner can provide a simulated passive efficiency of more than 60% at 12 dB PBO and a 10% drain-efficiency bandwidth power bandwidth of 8/15 GHz at 30 GHz
A Millimeter-Wave CMOS Series-Doherty Power Amplifier With Post-Silicon Inter-Stage Passive Validation
No full textThis article presents a wideband series-Doherty power amplifier (SDPA) for millimeter-wave (mm-wave) fifth-generation (5G) applications. It features a compact two-step impedance inverting-based series-Doherty power combiner that provides broadband close-to-perfect power back-off (PBO) efficiency enhancement. The amplitude-to-amplitude (AM-AM)/amplitude-to-phase (AM-PM) performance of the load-modulated Doherty power amplifier for broadband operation is analyzed. We also devise a post-silicon inter-stage passive validation (PSIV) approach to evaluate the mm-wave chip prototype utilizing the embedded voltage root mean square detectors. The proposed SDPA is realized in a 40-nm bulk CMOS, and it delivers 20.4 dBm PSAT with 39.1%/34% PAE at 0-/6-dB PBO. Over a 23.5-30 GHz band, its PAE is >24% at 6-dB PBO. At 27 GHz, applying a '2 GHz 16-quadratic-amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM)' signal, the proposed SDPA generates 10.2 dBm average power with 18.9% average PAE. The average error vector magnitude is better than -24.5 dB without digital predistortion for a '400-MHz 64-QAM OFDM' signal while generating an average output power of 8.8 dBm with 15% PAE. The AM-AM/AM-PM of the realized SDPA is investigated by employing a '50-MHz 64-QAM OFDM' signal, validating our analysis and showing that the linearity limitation of DPAs is systematic and predictable. Utilizing the proposed PSIV approach, the frequency response of the input/inter-stage passive circuits is measured, indicating an excellent agreement with 3-D electromagnetic (EM) simulation results.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
A Wideband Four-Way Doherty Bits-In RF-Out CMOS Transmitter
No full textWe present a wideband, 12-bit four-way Doherty Cartesian digital transmitter (DTX) featuring an innovative 50%-LO signed I/Q interleaved up-conversion technique that enables close to perfect orthogonal I/Q summation. The DTX incorporates a compact four-way lumped-element Doherty power combining network to enhance its average efficiency at deep power back-off (DPBO). It comprises a signed second-order hold (SOH) interpolation filter to suppress the sampling spectral replicas significantly. The proposed DTX is realized in a 40-nm bulk CMOS and delivers a peak output power of 27.54 dBm with drain and system efficiencies of 46.35% and 30.77%, respectively, at 5.3 GHz. At 12 dB DPBO, the realized DTX demonstrates a drain efficiency (DE) of 41.74%-39.27% in a 5.2-5.5 GHz band, respectively. Its intrinsic I/Q image, LO leakage, and C-IMD3/H 3BB for a 200 MHz tone spacing over a 4.8-6.2 GHz band are-64,-65, and-69 dBc, respectively, without calibration. Applying a simple memoryless 2× 1-D digital pre-distortion, its error vector magnitude and adjacent channel leakage ratio are lower than-31 dB and-39 dBc, respectively, for a six-carrier '40 MHz 256-QAM OFDM' signal with 18 dBm average output power and a 41% average DE. The signed SOH functionality is verified employing a four-carrier '80 MHz 512-QAM OFDM' signal with spectral purity of better than-35 dBc, while its baseband sampling frequency is 675 MHz.Accepted author manuscriptElectronic
Annotated record of the detailed examination of Mn deposits recovered from dredges and cores from VEMA 16 Expedition stations
No full textThe cores and dredges described in this report were taken during the Vema 16 Expedition from October 1959 until September 1960 by the Lamont Geological Observatory, Columbia University from the R/V Vema. An approximate total of 300 cores, dredges and camera stations were recovered and are available at Lamont-Doherty Earth Observatory for sampling and study
The modernist angel: Art at the Limits of the Human in D. H. Lawrence, H. D. and Mina Loy
No full textPhDThe subject of this thesis is a figure that might provisionally be called the *modemist
angel'. Focusing on modernist literature, and more particularly on the work of D. H.
Lawrence, H. D. and Mina Loy, it aims to isolate from the many angels found in all periods
and all types of art a historically specific and intellectually coherent paradigm: an angel of
and for its modernist times. A figure of precisely this type could be said to exist in the
form of Walter Benjamin's 'angel of history'. Critics who address the question of the
modern angel in texts by Franz Kafka and Rainer Maria Rilke often do so in conjunction
with the problem posed by the angel of history. Beginning with a chapter on Benjamin,
this thesis nevertheless follows a different trajectory. Over five chapters, it explores a
modernist landscape formed not only by Lawrence, H. D. and Loy, but also by European
and American writers such as A. R. Orage, Allen Upward, Ezra Pound, Wallace Stevens,
Havelock Ellis, Edward Carpenter, Sigmund Freud and Friedrich Nietzsche. Although the
angel that emerges from this investigation might, in some respects, be said to anticipate
Benjamin's later version, this figure is also very different, standing for a project that is
distinctively, and recognisably, modernist in nature. He/she (the sex of the modernist
angel is often open to question) represents an attempt to reconcile the divine
responsibilities of the artist with the material and gendered conditions of being,
specifically of being human, in the modem world. This thesis looks again at the clash of
intellectual paradigms in the early-twentieth century - notably, the confrontation of the
Romantic view of art as a superhuman or sacred undertaking with the psychoanalytical or
evolutionary idea that all human endeavour is underpinned by sub-human motives - and
suggests the angel as a new and instructive figure through which to think the perilous
limits between the human and the divine in modernist literature
Sentrin/SUMO Specific Proteases as Novel Tissue-Selective Modulators of Vitamin D Receptor-Mediated Signaling
No full textabstract: Vitamin D receptor (VDR) is a substrate for modification with small ubiquitin-like modifier (SUMO). To further assess the role of reversible SUMOylation within the vitamin D hormonal response, we evaluated the effects of sentrin/SUMO-specific proteases (SENPs) that can function to remove small ubiquitin-like modifier (SUMO) from target proteins upon the activities of VDR and related receptors. We report that SENP1 and SENP2 strikingly potentiate ligand-mediated transactivation of VDR and also its heterodimeric partner, retinoid X receptor (RXRα) with depletion of cellular SENP1 significantly diminishing the hormonal responsiveness of the endogenous vitamin D target gene CYP24A1. We find that SENP-directed modulation of VDR activity is cell line-dependent, achieving potent modulatory effects in Caco-2 and HEK-293 cells, while in MCF-7 cells the vitamin D signal is unaffected by any tested SENP. In support of their function as novel modulators of the vitamin D hormonal pathway we demonstrate that both SENP1 and SENP2 can interact with VDR and reverse its modification with SUMO2. In a preliminary analysis we identify lysine 91, a residue known to be critical for formation and DNA binding of the VDR-RXR heterodimer, as a minor SUMO acceptor site within VDR. In combination, our results support a repressor function for SUMOylation of VDR and reveal SENPs as a novel class of VDR/RXR co-regulatory protein that significantly modulate the vitamin D response and which could also have important impact upon the functionality of both RXR-containing homo and heterodimers.The article is published at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.008950
Financial Innovation in the Management of Catastrophe Risk
No full textCatastrophic events such as hurricane and earthquakes are the dominant source of risk for many property casualty insurers. Primary insurers usually limit the scale and geographic scope of their operations in order to focus on core competencies such as marketing, underwriting and loss control. But his often leaves them without sufficient geographic spread to diversify catastrophe risk. The traditional hedge for the primary insurer is reinsurance. Specialist reinsurers achieve a spacial spread of risk and can therefore bear catastrophe risk that is undiversifiable to the primary. But the transaction costs associated with reinsurance, and therefore premiums, are high. High premiums, coupled with the fact that catastrophe losses exhibit little correlation with capital market indices, has attracted considerable activity in Wall Street in searching for new instruments that securitize catastrophe risk. Indeed many players are now talking of catastrophe risk being a new “asset class” and new instruments such as catastrophe options and catastrophe bonds are starting to appear. The rationale for these new instruments is usually developed as follows. Recent catastrophe events such as Hurricane Andrew and the Northridge earthquake have imposed costs on the insurance industry of an order of magnitude not thought possible only a decade ago. More sophisticated modeling now presents potential losses to the industry of 200 billion. Two such events, or one such event combined with continued mass tort claims (e.g. successful plaintiff claims in tobacco litigation) could cripple the whole industry. However, losses of this size would hardly cause a ripple in capital markets. The U.S. capital market currently currently consists of securities representing some $13 trillion of investor wealth and the loss scenarios cited above amount to less than one standard deviation of daily trading volume. Presentations by merchant bankers, reinsurance brokers and others have echoed this potential for diversifying catastrophe risk within the capital market. The high transactions costs of reinsurance offers potential for hedging instruments to be offered to primary insurers that are both competitive with current reinsurance and which offer investors high rates of return. Moreover, since catastrophe risk is uncorrelated with market indices, the benchmark for such investments is just the risk free rate. Pricing new instruments requires that the expected loss be estimated with some. Until recently, insurers and reinsurers had a comparative advantage in information on catastrophic events. But in the past decade a number of modeling firms have developed models that combine seismic and meteorological information with data on the construction, siting, and value of individual buildings. These models can be used to simulate the economic effects of many thousands of storms and earthquakes. Although such models are used by the insurance firms and reinsurers, mainly for loss estimation and re-balancing their exposure, the same models are now available to other companies and investors. The arrival of the modelers and their models is eroding the comparative information advantage of insurers and reinsurers and opening the door to new players. Insurers will retain their comparative advantage over, say, merchant banks in related insurance services such as marketing, underwriting and loss settlement facilities. But the stage has been set for an unbundling of insurance products with insurers retaining marketing underwriting and settlement services and risk bearing by-passing the reinsurance industry and being provided more directly from the capital market. But the combination of high transaction costs for reinsurance and the vast capacity of the capital market for diversification, is not sufficient to ensure the success of these new instruments. The costs associated with reinsurance do not necessarily reflect monopoly rent. Relationships between primary insurers and reinsurers involve moral hazard; the relationship relaxes the incentive for the insurer to underwrite carefully or to settle claims efficiently. Consequently, the reinsurer will monitor the primary. Moreover, long term relationships are often formed to counter such expropriation. The apparently high transaction costs of reinsurance may simply reflect the resolution of moral hazard. If new instruments such as catastrophe options and bonds are to compete successfully with reinsurance, they must be able resolve incentive conflicts between the primary insurer and the ultimate risk bearer. Indeed, if moral hazard is not resolved, using past insurance loss data to estimate the potential returns for purchasers of catastrophe bonds, etc, is spurious. The purpose of this paper is to examine and categorize new catastrophe hedging instruments. These instruments will then be compared with traditional risk management strategies adopted by primary insurers in order to compare their relative efficiency at resolving incentive conflicts. Each instrument offers a different combination of credit risk, basis risk and moral hazard. For example, catastrophe reinsurance is subject to significant credit risk and moral hazard, but does not encounter significant basis risk. I will argue that the differential performance of the traditional and new instruments offers primary insurers with a richer portfolio of risk management strategies, though no strategy is dominant in its performance on all three criteria.
The role of deformation twinning on strain hardening and recrystallization in magnesium alloy AZ31
No full textThe quasi-static mechanical response of annealed, highly textured AZ31 rolled plate was measured in simple compression on two sample directions, each promoting a different twin family. A high plastic anisotropy with extreme strain hardening in both directions was observed. New insights on the influence of both twin types to this behavior were derived by correlating changes in the strain hardening rates with the microstructure evolution. Extension twins nucleated at low strains, grew to consume most of the structure, and saturated at strains below the peak hardening rates. Thin contraction twins were initially postulated to be responsible for the peak hardening rates by limiting the hard pyramidal slip length (producing a Hall-Petch type strengthening). However, subsequent experimental investigations raised questions on whether these are not present at the spacing required to account for the peak hardening rate. Thus, neither twin family was deemed responsible for the peak strain hardening rates.The effect of grain size on deformation twinning during strain hardening was also investigated by producing a similarly textured AZ31 plate with a larger grain size. A lower twinning stress was confirmed in this material. An additional change in strain hardening rate was associated with the nucleation of secondary extension twins forming perpendicular to the primary twin, limiting the growth potential of the pre-existing twins.The microstructure evolution during isothermal static annealing was investigated to critically evaluate the contributions of extension and contraction twins to the recrystallized microstructure after room temperature deformation, and establish the potential of these twins to alter the recrystallized texture. Contraction twins were potent sites for recrystallized nuclei producing many favorably oriented orientations for reduction of the strong c-axis fiber texture; while extension twins were not very effective in recrystallization. Recovery before the onset of recrystallization was extensive when the c-axis in most grains was compressed. Incomplete recrystallization within the hardest grains was deemed responsible for the retention of the c-axis fiber texture.These new insights were employed to identify the benefits of laser-roller hemming versus conventional hemming. Hemming is an automotive processing operation used to join inner and outer body panels involving severe forming and design requirements.Ph.D., Materials Science and Engineering -- Drexel University, 201
Microstructural effects on the hydrogen embrittlement of high strength steels
No full textHigh-strength, high-toughness steels are used in critical components of Naval aviation systems. These critical applications include landing gear components in tactical aircraft and rotary components in helicopters where large stresses must be sustained and the probability of failure due to flaws in the part are kept minimal. To prevent corrosion and wear, high strength steels are plated. When parts undergo repair/rework, the plating is stripped in an acidic bath, and the part is re-plated. During stripping and plating, as well as in-service duty, the steel is exposed to hydrogen-rich environments, which have been identified as a potential cause of premature failures in aviation system components. A high strength, precipitation hardened steel, PH 13-8Mo, one of six candidate steels, was examined in three different conditions – solution annealed (SA), H1000 (538oC aged), and H1150 (621oC aged) in order to compare the susceptibility of the different microstructures to hydrogen embrittlement and determine the stress-life curve for PH13-8 Mo in the H1000 condition. The PH 13-8Mo was selected as a result of a recent in-service failure of a reworked component.Fatigue pre-cracked compaction-tension (CT) specimen were loaded in displacement control and seated in a 10% strength hydrochloric acid bath. The load and crack mouth opening displacement (CMOD) were monitored as a function of time. From the load and CMOD versus time behavior, failure criterion were developed to determine points of crack initiation.Fractured samples were examined via scanning electron microscopy (SEM). Polished samples of the H1000, SA and H1150 condition were also analyzed by electron backscatter diffraction (EBSD). EBSD analysis showed that the packets of reverted austenite that grew in the H1150 condition material possessed an orientation that tended towards [111], which may indicate a Kurdjumov-Sachs or Nishiyama-Wasserman orientation relationship. In addition, packets of austenite within a local region also shared a common orientation with one another. An explanation for this behavior is proposed.The hydrogen embrittlement results show that the H1000 condition is highly susceptible to crack initiation over a wide range of applied stress values. A comparison of the different conditions showed that the H1150 and SA conditions possessed similar equal or better resistance to crack initiation in the hydrogen-rich environment at equivalent values of applied stress intensity (K) than the H1000 condition. Comparing equal percentages of applied (apparent) fracture toughness (KQ or KIC), only the SA condition had better resistance to initiation than the H100 condition. Resistance to crack propagation for the H1150 and SA conditions was superior to that of the H1000 condition. Finally, the threshold stress intensity, Kth, below which no cracking occurs for the H1000 condition, is on the order of 10% KIC or less, which is in good agreement with what has been established in literature.M.S., Materials Science and Engineering -- Drexel University, 201
- …
