1,102 research outputs found
Synthesis and properties of oligomeric poly(glycidyl ether)s with a carbazole-based multifunctional photorefractive chromophore
No full textNovel photorefractive poly(glycidyl ether) oligomers of a carbazole-based multifunctional chromophore were synthesized via ring-opening cationic polymerization. This new class of materials showed good solubility in various organic solvents and thermal stability up to 400 degrees C. Optical quality films of excellent transparency at the light wavelength above 430 nm were obtained by spin-coating or casting. Photoconductive sensitivity of the film was as high as 10(-13) S cm(-1)/mW cm(-2) at 532 nm. Electrooptic coefficients (r(33)) of 5-7 pm V-1 were easily achieved by the contact poling of spin-coated films. As evidence of photonfractivity, an asymmetric two-beam coupling gain of 3.2 cm(-1) was demonstrated at an electric field of 30 V mu m(-1) with a low-T-g polymer blend of multifunctional poly(glycidyl ether). (C) 2000 Elsevier Science B.V. All rights reserved
Bayesian probabilistic damage detection of a reinforced-concrete bridge column
No full textA Bayesian probabilistic approach for damage detection has been proposed for the continuous monitoring of civil structures (Sohn H, Law KH. Bayesian probabilistic approach for structure damage detection. Earthquake Engineering and Structural Dynamics 1997; 26: 1259-1281). This paper describes the application of the Bayesian approach to predict the location of plastic hinge deformation using the experimental data obtained from the vibration tests of a reinforced-concrete bridge column. The column was statically pushed incrementally with lateral displacements until a plastic hinge is fully formed at the bottom portion of the column. Vibration tests were performed at different damage stages. The proposed damage detection method was able to locate the damaged region using a simplified analytical model and the modal parameters estimated from the vibration tests, although (1) only the first bending and first torsional modes were estimated from the experimental test data, (2) the locations where the accelerations were measured did not coincide with the degrees of freedom of the analytical model, and (3) there existed discrepancies between the undamaged test structure and the analytical model. The Bayesian framework was able to systematically update the damage probabilities when new test data became available. Better diagnosis was obtained by employing multiple data sets than just by using each test data set separately. Copyright (C) 2000 John Wiley & Sons, Ltd.The "rst author wishes to express his sincere thanks to Professor Gerard C. Pardoen and his students at the
University of California at Irvine for providing an opportunity to observe the bridge column test. Also, the
authors are indebted to Dr Charles R. Farrar and Dr Scott W. Doebling of the Los Alamos National
Laboratory for providing the vibration test data. This research was partially sponsored by the National
Science Foundation under Grant No. CMS-95261-2
Patania brevipennis
No full textPatania brevipennis (Inoue, 1982) Pleuroptya brevipennis Inoue, 1982: vol. 1: 342, vol. 2: 234, 454, pl. 228, fig. 24, pl. 306, fig. 3, Pl. 307, fig. 3. TL: Akita prefecture, Honjô-shi. Host plants. Unknown. Distribution. Korea, Japan (Inoue, 1982; Yamanaka & Sasaki, 2013; Sohn et al., 2020). Remarks. This species was first recorded in Korea by Sohn et al. (2020).Published as part of Lee, Tak-Gi, Heo, Un-Hong & Bae, Yang-Seop, 2022, Status of Patania harutai (Inoue, 1955) in Korea, with a new species (Lepidoptera, Crambidae, Spilomelinae), and clarification of their host plants, pp. 407-419 in Zootaxa 5196 (3) on page 408, DOI: 10.11646/zootaxa.5196.3.5, http://zenodo.org/record/723551
Current status of Clonorchis sinensis and clonorchiasis in Korea: epidemiological perspectives integrating the data from human and intermediate hosts
No full textClonorchis sinensis is a carcinogenic liver fluke that causes clonorchiasis in humans. Clonorchiasis is prevalent in East Asian countries, and approximately 15-20 million individuals are estimated to be infected with this fluke globally. This review highlights the current status of C. sinensis and clonorchiasis in Korea from the epidemiological perspective involving the analysis of humans and intermediate hosts. Despite the recent decline in C. sinensis infection rate in Korea, C. sinensis infections remain endemic in 5 major river basins (Han-gang, Geum-gang, Seomjin-gang, Yeongsan-gang and Nakdong-gang; gang means river) with a high incidence of cholangiocarcinoma. A noticeable pattern involves increasing mild infections among patients diagnosed positive for C. sinensis eggs. The infection rate of C. sinensis metacercariae in the second intermediate host, freshwater fish, is also maintained at a substantial level. Thus, the One Health approach integrating different sectors and disciplines is recommended to accelerate and sustain control of C. sinensis, thereby leading to successful eradication. Health promotion via information dissemination and health education should be extended to prevent the consumption of raw freshwater fish by residents living in high-risk areas.Y
Dense Cross-Modal Correspondence Estimation With the Deep Self-Correlation Descriptor
No full textWe present the deep self-correlation (DSC) descriptor for establishing dense correspondences between images taken under different imaging modalities, such as different spectral ranges or lighting conditions. We encode local self-similar structure in a pyramidal manner that yields both more precise localization ability and greater robustness to non-rigid image deformations. Specifically, DSC first computes multiple self-correlation surfaces with randomly sampled patches over a local support window, and then builds pyramidal self-correlation surfaces through average pooling on the surfaces. The feature responses on the self-correlation surfaces are then encoded through spatial pyramid pooling in a log-polar configuration. To better handle geometric variations such as scale and rotation, we additionally propose the geometry-invariant DSC (GI-DSC) that leverages multi-scale self-correlation computation and canonical orientation estimation. In contrast to descriptors based on deep convolutional neural networks (CNNs), DSC and GI-DSC are training-free (i.e., handcrafted descriptors), are robust to cross-modality, and generalize well to various modality variations. Extensive experiments demonstrate the state-of-the-art performance of DSC and GI-DSC on challenging cases of cross-modal image pairs having photometric and/or geometric variations.
The Research on Molecular Orientation and Characterization of the OLED Emitters
No full textWe analyzed the scattered X-ray intensities of the host and host:dopant emitters, which have the spectra of in-plane and out-of-plane scattering to the plane and azimuthal intensity profiles for a plot of orientation distribution using grazing incidence wide-angle X-ray diffraction (GI-WAXD) measurement for high-efficiency organic light-emitting diodes (OLEDs). In blue fluorescent emitters, we found that a non-doped anthracene derivatives have the highly rigid structure and thermal stability because pnaphthylxylene groups in 9,10-positions were highly twisted to anthracene core with steric hindrance of xylene groups. The OLEDs with non-doped emitter with 2,3-diphenyl groups showed high-efficiency of 5.21 cd/A due to enhanced carrier mobility with well-aligned π-stacking structure toward outof-
plane by the face-on orientation by GI-WAXD analysis. In phosphorescent emitters, we have used the tetrahedral silicon-based host materials with electron transporting (ET) property and investigated on the preferential host orientation. The ET hosts had good morphological stability as well as balanced charge-carrier transport by pyridyl-substituted linker in the devices. The Ir(ppy)3-doped or Firpic-doped devices showed high-efficiency of 53.54 cd/A or 11.08 cd/A, respectively. In thermally activated delayed fluorescence emitters, we found that the molecular orientation of emitting materials with diphenylamine derivative containing malononitrile had different horizontal and/or random orientations as a function of para or meta linker position. It showed 12.5 times difference of the device efficiency. These improved device efficiency was confirmed by the enhanced out-coupling efficiency with wellaligned stacking structure in the emitters with horizontal molecular orientation to in-plane and out-of-plane analysis using GI-WAXD analysis. A study on the relationship between device characteristics and molecular orientation using GI-WAXD analysis for the emitting materials will contribute to basic research on molecular design for high efficiency OLEDs.1
Troca ou produção? Uma introdução crítica à proposta teórica de Alfred Sohn-Rethel
No full textThis paper explores and analyzes the critique of the modern-traditional epistemology of the philosopher Alfred Sohn-Rethel, focusing on the categories of "social synthesis" and "real abstraction" that the author postulated in his magnum opus Manual Work and Intellectual Work (2001) . Sohn-Rethel\u27s perspective seeks to critically adapt Marx\u27s materialist conception of history to the analysis of the emergence of the fundamental categories of scientific knowledge, as formulated in European modernity. However, the author\u27s emphasis on exchange over production ends up being inconsistent with basic postulates derived from the critique of political economy formulated by Marx in Capital. Thus, from the review of Marx\u27s categories and taking into account the position of other authors, the research emphasizes the limitations derived from the Sohn-Rethel proposal when analyzing the social forms of knowledge.El presente artículo explora y analiza la crítica a la epistemología moderna-tradicional del filósofo Alfred Sohn-Rethel centrándose en las categorías de “síntesis social” y “abstracción real” que el autor postuló en su obra magna Trabajo manual y trabajo intelectual (2001). La perspectiva de Sohn-Rethel busca adecuar críticamente la concepción materialista de la historia de Marx al análisis de la emergencia de las categorías fundamentales del conocimiento científico, tal y como se formularon en la modernidad europea. Sin embargo, el énfasis que el autor sostiene del intercambio por encima de la producción termina por ser incongruente con postulados básicos derivados de la crítica de la economía política formulada por Marx en El Capital. Así, a partir de la revisión de las categorías de Marx y tomando en cuenta la posición de otros autores, la investigación enfatiza en los limitantes derivados de la propuesta de Sohn-Rethel al analizar las formas sociales del conocimiento.Este artigo explora e analisa a crítica à epistemologia moderno-tradicional do filósofo Alfred Sohn-Rethel, com foco nas categorias de "síntese social" e "abstração real" que o autor postulou em sua magnum opus Trabalho Manual e Trabalho Intelectual (2001). ). A perspectiva de Sohn-Rethel procura adaptar criticamente a concepção materialista da história de Marx à análise da emergência das categorias fundamentais do conhecimento científico, tal como formuladas na modernidade europeia. No entanto, a ênfase do autor na troca sobre a produção acaba sendo inconsistente com os postulados básicos derivados da crítica da economia política formulada por Marx em O Capital. Assim, a partir da revisão das categorias de Marx e levando em conta a posição de outros autores, a pesquisa enfatiza as limitações derivadas da proposta de Sohn-Rethel ao analisar as formas sociais de conhecimento
Key factors of stretch-flangeability of sheet materials
No full textStretch-flangeability evaluated using hole-expansion testing represents the ability of sheet materials to resist edge fracture during complex shape forming. Despite a property imperative for automotive part applications of advanced high-strength steels, factors governing stretch-flangeability are not yet well understood. In this study, the mechanical properties of a selected group of materials with different microstructures were investigated using tensile, fracture toughness, and hole-expansion tests to find the factor governing the stretch-flangeability that is universally applicable to a variety of metallic materials. It was found that the fracture toughness of materials, measured using the fracture initiation energy, is a universal factor governing stretch-flangeability. We verified that fracture toughness is the key factor governing stretch-flangeability, showing that the hole-expansion ratio could be well predicted using finite element analysis associated with a simple ductile damage model, without explicitly taking into account the microstructural complexity of each specimen. This validates the use of the fracture toughness as a key factor of stretch-flangeability.1
Application of time reversal guided waves to field bridge testing for baseline free damage diagnosis
No full textThis research is partially supported by Pennsylvania Infrastructure Technology Alliance (PITA) Program and Pennsylvania Department of Transportation (PennDOT). The first author would like to acknowledge the graduate fellowship program from Samsung Lee Kun Hee Scholarship Foundation in Seoul, Korea. The authors would like to thank Paul Majoris and James Johnson for granting access to the Buffalo Creek Bridge site. The authors also would like to thank Profs. David W. Greve and Irving J. Oppenheim for providing invaluable comments and making the scaled girder specimen available for our study
Development of Dual PZT Transducers for Reference-Free Crack Detection in Thin Plate Structures
No full textA new Lamb-wave-based nondestructive testing (NDT) technique, which does not rely on previously stored baseline data, is developed for crack monitoring in plate structures. Commonly, the presence of damage is identified by comparing "current data" measured from a potentially damaged stage of a structure with "baseline data" previously obtained at the intact condition of the structure. In practice, structural defects typically take place long after collection of the baseline data, and the baseline data can be also affected by external loading, temperature variations, and changing boundary conditions. To eliminate the dependence on the baseline data comparison, the authors previously developed a reference-free NDT technique using 2 pairs of collocated lead zirconate titanate (PZT) transducers placed on both sides of a plate. This reference-free technique is further advanced in the present study by the necessity of attaching transducers only on a single surface of a structure for certain applications such as aircraft. To achieve this goal, a new design of PZT transducers called dual PZT transducers is proposed. Crack formation creates Lamb wave mode conversion due to a sudden thickness change of the structure. This crack appearance is instantly detected from the measured Lamb wave signals using the dual PZT transducers. This study also suggests a reference-free statistical approach that enables damage classification using only the currently measured data set. Numerical simulations and experiments were conducted using an aluminum plate with uniform thickness and fundamental Lamb waves modes to demonstrate the applicability of the proposed technique to reference-free crack detection.This research is supported by the Radiation Technology Program under
Korea Science and Engineering Foundation (KOSEF) and the Ministry
of Science and Technology (M20703000015-07N0300-01510) and
Korea Research Foundation Grant funded by the Korean Government
(MOEHRD, Basic Research Promotion Fund) (KRF-2007-331-D00462).
Any opinions, findings, and conclusions or recommendations expressed
in this material are those of the author(s) and do not necessarily reflect
the views of the funding agencies
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