5,221 research outputs found
Domain switching characteristics and fabrication of periodically poled potassium niobate for second-harmonic generation
No full textWe report on the 180degrees domain switching characteristics and fabrication of periodically poled KNbO3 for second-harmonic generation. Using a modified triangular pulse, a periodically poled KNbO3 of very high quality was fabricated with dimensions of 3 x 4 x 0.925 (a x b x c) mm(3) and a period of 32.5 mum to utilize the d(31) component of the second-order nonlinear optical coefficient tensor. An efficient second-harmonic generation of a mode-locked Nd:YAG laser, operated at 1064 nm with a pulse width of 35 ps, was achieved with a maximum conversion efficiency of 34.8%. The effective nonlinear coefficient, measured in the limit of undepleted pump approximation, was 5.2 pm/V, which is 68% of the theoretical value. (C) 2002 American Institute of Physics
Microstructure tailoring to enhance strength and ductility in Ti–13Nb–13Zr for biomedical applications
No full textNew microstructures were developed by strong grain refinement and phase control in a Ti-13Nb-13Zr alloy. Ultrafine-grained multiphase alloys were fabricated using a multipass caliber-rolling process at the (alpha + beta) region. Transmission electron microscopy analysis revealed that different types of martensitic transformations occurred depending on the cooling rate. The developed alloys exhibited improved strength and ductility compared with a conventional material, and this enhancement of properties is discussed in terms of microstructural effects on the strain-hardening behavior. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.X1119Nsciescopu
A new monolithic thermal inkjet printhead using single crystalline silicon island as a heating resistor isolated by oxidized porous silicon
No full textA new monolithic thermal inkjet printhead using single crystalline silicon island as a heating resistor is proposed. The n(+) silicon island was fabricated by full isolation by porous oxidized silicon (FIPOS) using double diffusion. The heating resistor is thermally and electrically isolated from the silicon substrate by oxidizing the porous silicon; The fabricated thermal inkjet, printhead has a simple structure because high quality thermal oxide can be used as a passivation layer
Novel sol-gel crosslinked epoxy polymers containing second-order nonlinear optical (NLO) moieties
No full textTwo NLO-functionalized epoxy polymers were synthesized and sol-gel technique was introduced into the polymers to achieve the stable second-order nonlinearity. The obtained polymers were characterized with thermal analyses, FT-IR, UV-visible spectroscopy and scanning electron microscopy. The condensation between silanol groups occurred between 100 degrees C and 200 degrees C so that the curing and poling were performed at 220 degrees C. The crosslinked and poled polymer films showed high nonlinearity (d(33)=41 pm/V) and better thermal stability compared to prepolymer, which maintained its nonlinearity up to 100 degrees C without significant loss of NLO activity
Beam rotation actuator based on dove prism in the optical storage media
No full textA beam rotation actuator, which can be utilized to improve the data transfer rate for optical disk systems, has been developed. The newly developed beam rotation actuator with high-resolution and fast response was assembled for micro positioning of an optical storage media. The beam rotation actuator is utilized to put multi-beam spots on more than one track on an optical disk simultaneously in addition to tracing multi-beam spots on tracks in a radial direction. Multi-beam spots turn on an optical axis by rotating dove prism in the optical path at the end of a cantilever arm. The beam rotation actuator is made of bimorph peizoelectric material. The dove prism is responsible for both high-resolution movement as well as multi-beam spot rotation. The dynamic equation of the beam rotation actuator is derived theoretically. The actuator is designed on the grounds of an analytical equation. It is shown that the beam rotation actuator has a natural frequency of 54 Hz or more, and the actuator has high-resolution. The application performance of the beam rotation actuator is verified as the feedback control is applied. (C) 2000 Published by Elsevier Science Ltd
Domains I and II in the 5 ' nontranslated region of the HCV genome are required for RNA replication
No full textHepatitis C virus (HCV), a hepacivirus member of the Flaviviridae family, has a positive-stranded RNA genome, which consists of a single open reading frame (ORF) and nontranslated regions (NTRs) at the 5' and 3' ends. The 5'NTR was found to contain an internal ribosomal entry site (IRES), which is required for the translation of HCV mRNA. Moreover, the 5'NTR is likely to play a key role in the replication of viral RNA. To identify the cis-acting element required for viral RNA replication, chimeric subgenomic replicons of HCV were generated. Dissection of the replication element from the translation element was accomplished by inserting the polioviral IRES between the serially deleted 5'NTR of HCV and ORF encoding neomycin phosphotransferase. The deletions of the 5'NTR of HCV were performed according to the secondary structure of HCV. Replicons containing domains I and II supported RNA replication and further deletion toward the 5' end abolished replication. The addition of domain III and the pseudoknot structure of the 5'NTR to domains I and II augmented the colony-forming efficiency of replicons by 100-fold. This indicates that domains I and II are necessary and sufficient for replication of RNA and that almost all of the 5'NTR is required for efficient RNA replication. (C) 2002 Elsevier Science.
Usability-based caching of query results in OLAP systems
No full textIn this paper we propose a new cache management scheme for online analytical processing (OLAP) systems based on the usability of query results in rewriting and processing other queries. For effective admission and replacement of OLAP query results, we consider the benefit of query results not only for recently issued queries but for the expected future queries of a current query. We exploit semantic relationships between successive queries in an OLAP session, which are derived from the interactive and navigational nature of OLAP query workloads, in order to classify and predict subsequent future queries. We present a method for estimating the usability of query results for the representative future queries using a probability model for them. Experimental evaluation shows that our caching scheme using the past and future usability of query results can reduce the cost of processing OLAP query workloads effectively only with a small cache size and outperforms the previous caching strategies for OLAP systems. (C) 2002 Elsevier Inc. All rights reserved
PiLa-CS Professional Learning Community - Workshop 2 Resources
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from Workshop 2 of the PLC.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. 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 National Science Foundation
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