5,114 research outputs found
Polymer-silica hybrid 1 x 2 thermooptic switch with low crosstalk
No full textA new polymer-silica hybrid I x 2 thermooptic switch with significantly low crosstalk is demonstrated. The top cladding and the core layers are composed of polymer, while the bottom cladding layer is made of silica. Since polymer and silica have algebraic signs of their thermooptic coefficients that are opposite to each other, the refractive index of the core changes in the opposite direction to that of the bottom cladding as the temperature is increased. Thus, switching operation is initially done through adiabatic mode evolution in the Y-branch, and then a heated waveguide arm in the Y-branch can enter into the optical cut-off region if the temperature is sufficiently high. Using this phenomenon, low crosstalk performance is achieved. The proposed device has a crosstalk of -35 dB, while most integrated-optic switches with a single stage have a relatively high crosstalk in the region of -20 dB. The switching power of the proposed device is about 70 mW. (c) 2006 Elsevier B.V. All rights reserved
Low optical loss perfluorinated methacrylates for a single-mode polymer waveguide
No full textPerfluoroalkyleneoxy methacrylate containing polar functional carbonate (-O-C(= O)-O-) or carbamate (-NH-C(= O)-O-) groups were synthesized to improve optical and adhesion properties of optical waveguide materials. Transparent polymer films were prepared by photocuring of a solution containing methacryloyl perfluoroalkyleneoxy carbonate and a photoinitiator. Optical loss of 0.35 dB/ cm at 1550 nm was determined from the photocured film, for TE polarization by measuring the transmitted power along the slab waveguide length. The refractive indices at 1550 rim were determined as 1.4337 and 1.4334 for TE and TM modes, respectively, indicating low birefringence of Deltan = 0.0003 +/- 0.0002. Adhesion between the substrate and the polymer layer was enhanced by introducing carbonates and carbamates as determined from a SEM cross section and low surface energy of the photocured polymer film. Low-loss optical waveguides have been fabricated from a solution containing methacryloyl perfluoroalkyleneoxy carbonate by photo-cross-linking and then reactive ion etching to produce high-quality channel waveguides with very smooth surfaces. The propagation loss of the channel waveguides was 0.50 and 0.70 dB/cm at the monitoring light of 1550 nm for TE and TM polarizations, respectively
GLS Detrending-Based Unit Root Tests in Nonlinear STAR and SETAR Frameworks.
No full textThis paper consider the GLS detrending procedure advanced by Elliott et al. (1996) for unit root tests against alternative hypotheses where the time series data under investigation follow either globally stationary SETAR or STAR processes with deterministic components being present. It is found that the proposed testing procedures have considerable power gains against both the standard Dickey-Fuller unit root tests and existing nonlinear unit root tests recently proposed by Kapetanios and Shin (2002) and Kapetanios et al. (2003). The empirical application to DM and Yen bilateral real exchange rates against a number of other currencies also confirms that nonlinear unit root tests based on GLS detrending will be more powerful than linear ones. Interestingly, we find that the DM dataset seems to produce more rejections of the null using the GLS detrending-based SETAR tests than using the GLS detrending-based STAR tests, whereas the number of rejections of both tests are similar for the Yen dataset. The different results may arise from the respective liquidity of the DM and Yen Forex markets.Unit Root Tests, Nonlinear STAR and SETAR Models, GLS Detrending, Real Exchange Rates.
Gravitational-Wave Fringes at LIGO: Detecting Compact Dark Matter by Gravitational Lensing
No full text© 2019 American Physical Society. Utilizing gravitational-wave (GW) lensing opens a new way to understand the small-scale structure of the Universe. We show that, in spite of its coarse angular resolution and short duration of observation, LIGO can detect the GW lensing induced by small structures, in particular by compact dark matter (DM) or the primordial black hole of 10-10(5) M-circle dot, which remains an interesting DM candidate. The lensing is detected through GW frequency chirping, creating the natural and rapid change of lensing patterns: frequency-dependent amplification and modulation of GW waveforms. As a highest-frequency GW detector, LIGO is a unique GW lab to probe such light compact DM. With the design sensitivity of Advanced LIGO, one-year observation by three detectors can optimistically constrain the compact DM density fraction f(DM) to the level of a few percent.11Nsciescopu
Deformation of axion potentials: Implications for spontaneous baryogenesis, dark matter, and isocurvature perturbations
No full text© 2019 authors. Published by the American Physical Society.We show that both the baryon asymmetry of the universe and dark matter (DM) can be accounted for by the dynamics of a single axionlike field. In this scenario, the observed baryon asymmetry is produced through spontaneous baryogenesis - driven by the early evolution of the axion - while its late-time coherent oscillations explain the observed DM abundance. Typically, spontaneous baryogenesis via axions is only successful in regions of parameter space where the axion is relatively heavy, rendering it highly unstable and unfit as a dark matter candidate. However, we show that a field-dependent wave function renormalization can arise which effectively deforms the axion potential, allowing for efficient generation of baryon asymmetry while maintaining a light and stable axion. Meanwhile, such deformations of the potential induce nontrivial axion dynamics, including a tracking behavior during its intermediate phase of evolution. This attractorlike dynamics dramatically reduces the sensitivity of the axion relic abundance to initial conditions and naturally suppresses DM isocurvature perturbations. Finally, we construct an explicit model realization, using a continuum-clockwork axion, and survey the details of its phenomenological viability. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP 311Nsciescopu
Diabetic polyneuropathy and the risk of developing carpal tunnel syndrome: A nationwide, population‐based study
No full textBACKGROUND: We investigated the risk of carpal tunnel syndrome (CTS) in diabetic polyneuropathy (DPN).
METHODS: This study was conducted using records from the National Health Insurance System (NHIS). We divided patients diagnosed with diabetes mellitus (DM) into those with and without DPN. We assessed the effect of DPN on the risk of CTS using Cox proportional hazards regression analyses.
RESULTS: DPN was associated with an increased risk of CTS (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.12-1.58). In sub-analyses, female gender (HR, 1.45; 95% CI, 1.20-1.76), presence of type 2 DM (HR, 1.36; 95% CI, 1.11-1.64), and age 35 to 64 years (HR 1.35; 95% CI, 1.11-1.64) were significantly associated with an increased risk of CTS.
CONCLUSIONS: Patients with DPN had an increased risk of CTS compared with the non-DPN group, particularly females, those with type 2 DM, and those aged 35 to 64 years
Characteristics of the DM group (n = 3,478) and non-DM group (n = 10,820).
No full textCharacteristics of the DM group (n = 3,478) and non-DM group (n = 10,820).</p
Development of High-Yielding and Early-Maturing Korean Hairy Vetch
No full textThere are a number of forage cultivars recommended by the government, but only a few winter-spring legumes are available for the farmers in Korea. Hairy vetch has superior winter hardiness and produces high dry matter (DM) yield compared with crimson clover, Persian clover, rose clover, common vetch and Chinese milk vetch in Korea. However, under a double cropping forage production system an early maturing vetch cultivar was more productive than a late maturing one (Shin et al., 2000). The objective of this research was to develop a high yielding and early flowering new hairy vetch cultivar derived from an accession in Korea
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