- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Measurement of Photosynthesis Using PAM Technology in a Purple Sulfur Bacterium <i>Thermochromatium tepidum</i> (Chromatiaceae)
摘要： We demonstrate that Blue-diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance curves fitted the waiting-in-line model (ETR = (ETRmax * E/Eopt) * exp (1-E/Eopt)). Yield (Y) was only 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m?2 s?1 or ~15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m?3) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m?3) but not sulfide and is only marginally increased by the presence of Fe2?. Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo-organisms or Rhodopseudomonads.
关键词： photosynthesis,PAM technology,photoinhibition,absorptance,Thermochromatium tepidum,purple sulfur bacteria,electron transport rate
更新于2025-09-23 15:22:29
-
Absorption Coefficient Dispersion in Flash Thermography of Semitransparent Solids
摘要： Pulse and flash thermography are experimental techniques which are widely used in the field of non-destructive testing for materials characterization and defect detection. We recently showed that it is possible to determine quantitatively the thickness of semitransparent polymeric solids by fitting of results of an analytical model to experimental flash thermography data, for both transmission and reflection configuration. However, depending on the chosen experimental configuration, different effective optical absorption coefficients had to be used in the model to properly fit the respective experimental data, although the material was always the same. Here, we show that this effect can be explained by the wavelength dependency of the absorption coefficient of the sample material if a polychromatic light source, such as a flash lamp, is used. We present an extension of the analytical model to describe the decay of the heating irradiance by two instead of only one effective absorption coefficient, greatly extending its applicability. We show that using this extended model, the experimental results from both measurement configurations and for different sample thicknesses can be fitted by a single set of parameters. Additionally, the deviations between experimental and modeled surface temperatures are reduced compared to a single optimized effective absorption coefficient.
关键词： Dispersion,Flash thermography,NDT,Absorptance,Infrared thermography,Semitransparency
更新于2025-09-23 15:22:29
-
Dynamic Laser Absorptance Measured in a Geometrically Characterized Stainless-Steel Powder Layer
摘要： The relationship between real powder distributions and optical coupling is a critical building block for developing a deeper physical understanding of laser-additive manufacturing and for creating more reliable and accurate models for predictable manufacturing. Laser-light absorption by a metal powder is distinctly different from that of a solid material, as it is impacted by additional parameters, such as particle size, shape distribution, and packing. Here, we use x-ray computed tomography to experimentally determine these parameters in a thinly spread austenitic stainless-steel powder on a metal substrate, and we combine these results with optical absorptance measurements during a 1 ms stationary laser-light exposure to simulate the additive-manufacturing process. Within the thinly spread powder layer, the particle volume fraction changes continuously from near zero at the powder surface to a peak value of 0.72 at a depth of 235 μm, with the most rapid increase taking place in the first 100 μm. The relationship between this particle volume fraction gradient and optical absorptance is investigated using an analytical model, which shows that depth-averaged absorptance measurements can measure the predicted average value, but will fail to capture local effects that result from a changing powder density. The time-averaged absorptance remains at levels between 0.67 and 0.80 across a two orders of magnitude range in laser power, which is significantly higher than that observed in solid stainless-steel experiments. The dynamic behavior of the absorptance, however, reveals physical phenomena, including oxidation, melting, and vapor cavity (keyhole) formation, as well as quantifying the effect of these on the absorbed energy.
关键词： keyhole formation,laser-additive manufacturing,stainless-steel powder,x-ray computed tomography,optical coupling,optical absorptance,particle volume fraction
更新于2025-09-23 15:21:01
-
Perfect Dual-Band Absorber Based on Plasmonic Effect with the Cross-Hair/Nanorod Combination
摘要： Plasmonic e?ect using a cross-hair can convey strongly localized surface plasmon modes among the separated composite nanostructures. Compared to its counterpart without the cross-hair, this characteristic has the remarkable merit of enhancing absorptance at resonance and can make the structure carry out a dual-band plasmonic perfect absorber (PPA). In this paper, we propose and design a novel dual-band PPA with a gathering of four metal-shell nanorods using a cross-hair operating at visible and near-infrared regions. Two absorptance peaks at 1050 nm and 750 nm with maximal absorptance of 99.59% and 99.89% for modes 1 and 2, respectively, are detected. High sensitivity of 1200 nm refractive unit (1/RIU), ?gure of merit of 26.67 and Q factor of 23.33 are acquired, which are very remarkable compared with the other PPAs. In addition, the absorptance in mode 1 is about nine times compared to its counterpart without the cross-hair. The proposed structure gives a novel inspiration for the design of a tunable dual-band PPA, which can be exploited for plasmonic sensor and other nanophotonic devices.
关键词： plasmonic e?ect,localized plasmon modes,plasmonic sensor,dual-band plasmonic perfect absorber,absorptance peaks
更新于2025-09-23 15:19:57
-
Development of two new semi-empirical formulas for estimation of solar absorptance in circular cavity receivers
摘要： In this paper two new semi-empirical formulas for calculating the equivalent absorptance of solar irradiation at the inner surface of cylindrical cavities is proposed. The multiple re?ections that occur at the interior of the cavity were ?rst analyzed considering a two-dimensional geometrical approach and thus the ?rst analytical relationship for the equivalent solar absorptance was revealed. In addition, a three-dimensional ray tracing analysis was conducted through Solidworks Flow Simulation. Several di?erent cavity aperture’s widths as well as solar absorptance coe?cients (α = 0.5–0.9 per 0.1) were examined in both analyses and it was found that the two dimensional analytical approach exceeds the simulation by 1.50–6.83% on average going from the highest to the lowest solar absorptance value. Finally, two new correlations were developed for correcting the analytical approach according to the 3D ray tracing with the optimum between them to provide a mean error at the equivalent solar absorptance calculation of about 0.78%, 0.55%, 0.40%, 0.21% and 0.18% for the ?ve di?erent absorptance coe?cients were examined.
关键词： Solidworks Flow Simulation,Solar absorptance,Cavity receiver,Optical analysis,New correlation
更新于2025-09-19 17:15:36
-
Solar Engineering of Thermal Processes, Photovoltaics and Wind || Radiation Characteristics of Opaque Materials
摘要： This chapter begins with a detailed discussion of radiation characteristics of surfaces. For many solar energy calculations only two quantities are required, the solar absorptance and the long-wave or infrared emittance, usually referred to as just absorptance and emittance. Although values of these two quantities are often quoted, other radiation properties may be the only available information on a particular material. Since relationships exist between the various characteristics, it may be possible to calculate a desired quantity from available data. Consequently, it is necessary to understand exactly what is meant by the radiation terms found in the literature, to be familiar with the type of information available, and to know how to manipulate these data to get the desired information. The most common type of data manipulation is illustrated in the examples, and readers may wish to go directly to Section 4.5.
关键词： selective surfaces,solar energy,infrared emittance,solar absorptance,radiation characteristics
更新于2025-09-16 10:30:52
-
Solar Engineering of Thermal Processes, Photovoltaics and Wind || Radiation Transmission through Glazing
摘要： The transmission, reflection, and absorption of solar radiation by the various parts of a solar collector are important in determining collector performance. The transmittance, reflectance, and absorptance are functions of the incoming radiation, thickness, refractive index, and extinction coefficient of the material. Generally, the refractive index n and the extinction coefficient K of the cover material are functions of the wavelength of the radiation. However, in this chapter, all properties initially will be assumed to be independent of wavelength. This is an excellent assumption for glass, the most common solar collector cover material. Some cover materials have significant optical property variations with wavelength, and spectral dependence of properties is considered in Section 5.7. Incident solar radiation is unpolarized (or only slightly polarized). However, polarization considerations are important as radiation becomes partially polarized as it passes through collector covers.
关键词： absorptance,refractive index,solar radiation,transmittance,extinction coefficient,wavelength,reflectance,collector performance,polarization
更新于2025-09-16 10:30:52
-
Solar active envelope module with an adjustable transmittance/absorptance
摘要： A solar active envelope module with a high ?exibility degree is proposed in this paper. The transparent module controls the day-lighting of the room, improving the indoor environment, while absorbing the super?uous solar energy inside. That energy is used to increase the e?ciency of heating, ventilation, and the air-conditioning (HVAC) system of the building. This is carried out through a ?ne control of the absorptance of the envelope module. The active envelope module consists of three glazed chambers with advanced coatings and frames to assure a minimum thermal transmittance while allowing transparency. A ?uid containing heat-absorbing nanoparticles ?ows inside the central chamber and is heated up due to the impinging solar energy. Unlike other systems proposed in the past, which included transparency control systems based on complex ?lters and chemical processes, the absorption of the module is controlled by the variation of the thickness of the central chamber with a mechanical device. That is, varying the thickness of the central chamber, it allows controlling the absorptance of the whole system and, as a result, indoor day-lighting and thermal loads. Therefore, a new system is proposed that enables to: ? Dynamically control the thermal loads and solar day-lighting. ? Improve the thermal performance of building envelope and reduce the energy demand of the building. ? Increase the solar fraction of the heating and cooling, and reduce the thermal losses improving the e?ciency of the building. The solar active device proposed in this article is protected by a Spanish patent application (Fundaci ′on Tekniker, Fundaci ′on CENER-CIEMAT, 2014).
关键词： indoor comfort,dynamic control,absorptance regulation,Solar collector facade,adaptive envelope,architectural module,thermal loads reduction
更新于2025-09-09 09:28:46