Significant impact of the covid-19 pandemic on methane emissions evaluated by comprehensive statistical analysis of satellite data.

The COVID-19 pandemic has significantly influenced various aspects of society, including environmental factors such as methane emissions. This study investigates the changes in methane concentrations in Seoul, South Korea, from 2019 to 2023, using TROPOMI satellite data and rigorous statistical analyses. The normality of the sample data is first assessed using the Shapiro-Wilk (S-W) and Kolmogorov-Smirnov (K-S) tests, indicating that the data can be considered to come from a normal distribution.

Uncertainty evaluation of photoluminescence quantum yield measurement in an integrating hemisphere-based instrument.

We present an integrating hemisphere-based (i.e., a variant of integrating spheres) implementation of the indirect illumination method for absolute photoluminescence quantum yield measurements, which is a recommended method in the international standard IEC 62607-3-1:2014.

Inherently high uncertainty in predicting the time evolution of epidemics.

Objectives: Amid the spread of coronavirus disease 2019 (COVID-19), with its high infectivity, we have relied on mathematical models to predict the temporal evolution of the disease. This paper aims to show that, due to active behavioral changes of individuals and the inherent nature of infectious diseases, it is complicated and challenging to predict the temporal evolution of epidemics.

Methods: A modified susceptible-exposed-infectious-hospitalized-removed (SEIHR) compartment model with a discrete feedback-controlled transmission rate was proposed to incorporate individuals' behavioral changes into the model.

Bright visible light emission from graphene.

Graphene and related two-dimensional materials are promising candidates for atomically thin, flexible and transparent optoelectronics. In particular, the strong light-matter interaction in graphene has allowed for the development of state-of-the-art photodetectors, optical modulators and plasmonic devices. In addition, electrically biased graphene on SiO2 substrates can be used as a low-efficiency emitter in the mid-infrared range.

Measurement of rod and cone effects in mesopic visual sensitivity by varying viewing field.

To investigate the effects of rods and cones in mesopic visual sensitivity, we perform spectral sensitivity experiments by varying viewing fields and adaptation levels. We obtain mesopic spectral sensitivities for 2° and 10° centrally viewing fields and a (10°-20°) peripherally viewing field at adaptation luminance levels of 0.04 cd/m², 0.

Experimental validation of the six-port design for a highly uniform integrating sphere photometer.

We present experimental realization and validation of the six-port design of integrating sphere photometers for total luminous flux measurement, which significantly improves the uniformity of spatial response compared to the conventional single-port design. Construction, measurement procedure, and data acquisition of the realized instrument with a radius of 1 m are described. Measurement of the spatial response distribution function confirms the expected effect of improving the uniformity by averaging the signals from the six detection ports.

Optical injection locking of a singly resonant continuous-wave optical parametric oscillator.

We report on experimental realization of optical injection locking of a singly resonant continuous-wave optical parametric oscillator (OPO) based on a thermally induced waveguide in a magnesium-oxide doped periodically poled lithium niobate. An external cavity diode laser is used to control the frequency of the resonant signal output of the OPO at 795 nm. The key to successful injection locking was the improvement of the OPO spatial modes by a special operating condition with a thermally induced waveguide.

Measurement of normalized spectral responsivity of digital imaging devices by using a LED-based tunable uniform source.

We present an instrumentation solution for measurement of normalized spectral responsivity of digital imaging sensors and cameras. The instrument consists of multiple light-emitting diodes (LEDs), a single-grating monochromator, and a small-size integrating sphere. Wavelength tuning is achieved by a proper selection of LED in accordance with the monochromator setting in a range from 380 to 900 nm.

Spatial uniformity inspection apparatus for solar cells using a projection display.

We demonstrate a measurement apparatus to inspect spatial uniformity of quantum efficiency of solar cells using a beam projector. Deviation of irradiance from the used beam projector over the area of 1.5×0.

Six-port integrating sphere photometer with uniform spatial response.

We propose an integrating sphere photometer with six detection ports for total luminous flux measurement, which significantly improves the uniformity of spatial response compared to the conventional single-port detection design. Numerical simulations based on the geometric radiative transfer equation show that a spatial response distribution function of the new design is uniform within 2% with respect to all spatial directions. The related spatial mismatch error is calculated to be less than 0.

Differential spectral responsivity measurement of photovoltaic detectors with a light-emitting-diode-based integrating sphere source.

We present an experimental realization of differential spectral responsivity measurement by using a light-emitting diode (LED)-based integrating sphere source. The spectral irradiance responsivity is measured by a Lambertian-like radiation field with a diameter of 40 mm at the peak wavelengths of the 35 selectable LEDs covering a range from 280 to 1550 nm. The systematic errors and uncertainties due to lock-in detection, spatial irradiance distribution, and reflection from the test detector are experimentally corrected or considered.

Simultaneous measurement of emittance, transmittance, and reflectance of semitransparent materials at elevated temperature.

A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples.

Correction of self-screening effect in integrating sphere-based measurement of total luminous flux of large-area surface-emitting light sources.

We present a correction method of a systematic error that arises when total luminous flux of a large-area surface-emitting light source (SLS) is measured in an integrating sphere by substitution with a reference lamp. Putting a large-area SLS into an integrating sphere is equivalent to adding a low-reflective baffle to screen the spatial distribution of radiation inside the sphere, which severely changes the sphere responsivity. To compensate this self-screening effect, we propose to use a specially designed auxiliary lamp whose illuminating area is spatially matched to that of the SLS under test.

Measurement uncertainty evaluation for emission color and luminance of displays.

We present a measurement uncertainty evaluation for emission color and luminance of displays. The calibration procedures and the measurement uncertainties of a CCD-based spectroradiometer and a filter-type luminance meter are discussed. As evaluation examples, a Commission Internationale de l' Eclairage illuminant A, a liquid-crystal display with a light-emitting diode backlight, and a liquid-crystal display with a cold-cathode fluorescent lamp backlight are evaluated.

Continuous-wave 532 nm pumped MgO:PPLN optical parametric oscillator with external power regulation and spatial mode filtering.

We report a continuous-wave (CW) optical parametric oscillator (OPO) based on a MgO-doped periodically poled LiNbO(3) (MgO:PPLN) crystal. The 532 nm pump generates coherent radiation that is tunable from 800 to 920 nm for the signal and from 1250 to 1580 nm for the idler, respectively. The OPO output power exhibits a slowly varying instability that we attribute to a thermal effect induced by the pump.

Uncertainty evaluation for the spectroradiometric measurement of the averaged light-emitting diode intensity.

An uncertainty evaluation is presented for the spectroradiometric measurement of the averaged LED intensity (ALI), which is a standardized photometric quantity of LEDs introduced by the Commission Internationale de l'Eclairage. Using a spectral irradiance standard lamp as a calibration source for the spectroradiometer, 12 uncertainty components are sorted out and their propagation formulated with correlations between the components taken into account. The procedure of uncertainty evaluation is demonstrated for four LED samples of different colors; red, green, blue, and white.