3,049 research outputs found
Waveguide-based single-pixel up-conversion infrared spectrometer
A periodically poled lithium niobate (PPLN) waveguide-based single-pixel
up-conversion infrared spectrometer was demonstrated. Sum-frequency generation
between a 1.5 micrometer band scanning pump laser and a 1.3 micrometer band
signal generated visible radiation which was detected by a silicon
single-photon detector. The noise equivalent power of the upconversion
spectrometer was two-orders-of-magnitude lower than that of a commercial
optical spectrum analyzer.Comment: 5 pages, 3 figure
The test-retest reliability of centre of pressure measures in bipedal static task conditions - A systematic review of the literature
Summary of background data: The analysis of centre of pressure (COP) excursions is used as an index of postural stability in standing. Conflicting data have been reported over the past 20 years regarding the reliability of COP measures and no standard procedure for COP measure use in study design has been established. Search methods: Six online databases (January 1980 to February 2009) were systematically searched followed by a manual search of retrieved papers. Results: Thirty-two papers met the inclusion criteria. The majority of the papers (26/32, 81.3%) demonstrated acceptable reliability. While COP mean velocity (mVel) demonstrated variable but generally good reliability throughout the different studies (r= 0.32-0.94), no single measurement of COP appeared significantly more reliable than the others. Regarding data acquisition duration, a minimum of 90 s is required to reach acceptable reliability for most COP parameters. This review further suggests that while eyes closed readings may show slightly higher reliability coefficients, both eyes open and closed setups allow acceptable readings under the described conditions (r≥0.75). Also averaging the results of three to five repetitions on firm surface is necessary to obtain acceptable reliability. A sampling frequency of 100. Hz with a cut-off frequency of 10. Hz is also recommended. No final conclusion regarding the feet position could be reached. Conclusions: The studies reviewed show that bipedal static COP measures may be used as a reliable tool for investigating general postural stability and balance performance under specific conditions. Recommendations for maximizing the reliability of COP data are provided
Excitation of plasma resonances by a small pulsed dipole
Resonant oscillation decay excited by pulsed dipole in collisionless plasm
Design principles for Bernal spirals and helices with tunable pitch
Using the framework of potential energy landscape theory, we describe two in
silico designs for self-assembling helical colloidal superstructures based upon
dipolar dumbbells and Janus-type building blocks, respectively. Helical
superstructures with controllable pitch length are obtained using external
magnetic field driven assembly of asymmetric dumbbells involving screened
electrostatic as well as magnetic dipolar interactions. The pitch of the helix
is tuned by modulating the Debye screening length over an experimentally
accessible range. The second design is based on building blocks composed of
rigidly linked spheres with short-range anisotropic interactions, which are
predicted to self-assemble into Bernal spirals. These spirals are quite
flexible, and longer helices undergo rearrangements via cooperative, hinge-like
moves, in agreement with experiment
Measurement of Birefringence of Low-Loss, High-Reflectance Coating of M-Axis Sapphire
The birefringence of a low-loss, high-reflectance coating applied to an 8-cm-diameter sapphire crystal grown in the m-axis direction has been mapped. By monitoring the transmission of a high-finesse Fabry-Perot cavity as a function of the polarization of the input light, we find an upper limit for the magnitude of the birefringence of 2.5 x 10^-4 rad and an upper limit in the variation in direction of the birefringence of 10 deg. These values are sufficiently small to allow consideration of m-axis sapphire as a substrate material for the optics of the advanced detector at the Laser Interferometer Gravitational Wave Observatory
Comparison of rocket-borne probes for electron density measurements Quarterly status report no. 5, Aug. 1 - Oct. 31, 1965
Impedance, resonance, capacitance, electrostatic, and Langmuir probe performance for ionospheric electron density profil
100 km secure differential phase shift quantum key distribution with low jitter up-conversion detectors
We present a quantum key distribution experiment in which keys that were
secure against all individual eavesdropping attacks allowed by quantum
mechanics were distributed over 100 km of optical fiber. We implemented the
differential phase shift quantum key distribution protocol and used low timing
jitter 1.55 um single-photon detectors based on frequency up-conversion in
periodically poled lithium niobate waveguides and silicon avalanche
photodiodes. Based on the security analysis of the protocol against general
individual attacks, we generated secure keys at a practical rate of 166 bit/s
over 100 km of fiber. The use of the low jitter detectors also increased the
sifted key generation rate to 2 Mbit/s over 10 km of fiber.Comment: 10 pages, 5 figure
Reading Proficiency Level of Grade 12 Students in English for Academic and Professional Purposes: Basis for Developing and Evaluating Reading Intervention Materials in English
This study attempted to determine the Reading Proficiency Level in English for Academic and Professional Purposes of grade 12 students as basis for developing and evaluating reading intervention materials in English during the school year 2022-2023. The descriptive method of research was used with the survey questionnaire as the instrument to gather pertinent data. The teacher respondents were grouped into two categories according to qualifications: twenty (20) experts who and twenty (20) English language teachers. Based on the findings, the experts and the teacher respondents rated the developed reading materials in terms of objectives, springboard, lesson content, activities, reflection, and assessment with grand weighted mean ratings of 3.90 and 3.91, respectively, verbally interpreted as Very Highly Acceptable (VHA). The experts also claimed that the material caters for the new generation and can be a great help for teachers who have difficulties with various teaching strategies. On the other hand, the teacher respondents recommended the improvement of the materials by adding more colors to entice students to answer the exercises and to add topics for reading about Philippine setting, society, and culture
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