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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Signal and noise analysis in resonant photoacoustic spectroscopy using fast Fourier transform
摘要： A simple method based on fast Fourier transform (FFT) is used to analyze the signal and noise in resonant photoacoustic spectroscopy. Varying the sampling time, the photoacoustic signal and noise are analyzed using FFT method, and compared with lock-in amplifier method. A detection limit of 1 ppm of methane has been achieved in pure nitrogen using a 1653 nm laser with an average power of 3.6 mW.
关键词： climate control,research,gas absorption,methane,FFT,PAS
更新于2025-09-16 10:30:52
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Investigation of hydrogen production potential of the LASER inertial confinement fusion fission energy (LIFE) engine
摘要： The main purpose of this paper is to research of the time-dependent hydrogen production possibility of the Laser Inertial Con?nement Fusion Fission Energy (LIFE) engine using steam methane reforming (SMR), sulfureiodine (SeI) thermochemical water splitting and high temperature electrolysis (HTE) cycles. The fuel zone of the LIFE engine contains 90 vol % Flibe coolant and 10 vol% TRISO coated minor actinides. Firstly, to examine the time-dependent hydrogen generation potential of this reactor, the time-dependent neutronic performance of the reactor has been performed with using the MCNP neutron transport code. As a result of neutronic calculations, tritium production (TBR), energy multiplication factor (M) and fuel burnup (BU) values have been computed. Secondly, the total power required for SMR, SeI and HTE cycle process have been calculated by using the time dependent energy multiplication factor obtained from the neutronic results. Depending on this total power, the change of hydrogen production with operation time in the LIFE engine has been investigated. As a result of the calculations, it has been found that the LIFE engine has a good both neutronic performance and hydrogen production by SMR, SeI and HTE cycle process.
关键词： Minor actinides,SeI cycle,LIFE engine,Steam methane reforming,Hydrogen,High temperature electrolysis
更新于2025-09-16 10:30:52
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Near-infrared methane sensor system using off-axis integrated cavity output spectroscopy with novel dual-input dual-output coupling scheme for mode noise suppression
摘要： Mode noise suppression in o?-axis integrated cavity output spectroscopy (OA-ICOS) is a key for improving the signal-to-noise ratio (SNR) of a sensor system, which basically depends on the ability to smooth out the cavity mode structure and to reduce the cavity mode linewidth. We demonstrated a novel dual-input dual-output (DIDO) coupling scheme of OA-ICOS for mode noise suppression. The in?uences of beam splitting ratio and light re?ection number to the output intensity and cavity mode linewidth were theoretically studied. Experimental investigation on the suppression of cavity mode noise was carried out in terms of detection sensitivity and SNR through methane (CH4) measurements. A SNR of 221 and a detection sensitivity of 1.73 × 10-8 cm-1 Hz-1/2 was obtained for the DIDO-based OA-ICOS sensor system. The SNR was improved by a factor of ～ 2.5 and the sensitivity was improved by a factor of ～ 2.2 compared to the regular single-input single-output (R-SISO) approach. Multi-input multi-output (MIMO) con?guration was further numerically studied to verify the noise suppression ability of this detection concept. This work reveals a new laser-to-cavity coupling method and provides a novel way to exploit OA-ICOS sensors with improved SNR and sensitivity.
关键词： Methane detection,O?-axis integrated cavity output spectroscopy,Wavelength modulation spectroscopy,Dual-input dual-output,Chemical gas sensor
更新于2025-09-16 10:30:52
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Precise measurements of 12CH2D2 by tunable infrared laser direct absorption spectroscopy
摘要： We present precise measurements of doubly-deuterated methane (12CH2D2) in natural methane samples using tunable infrared laser direct absorption spectroscopy (TILDAS). Using a 413 m optical path length astigmatic Herriott cell and two quantum cascade lasers (QCLs) scanning the spectral regions of 1090.46 ± 0.1 cm-1 and 1200.23 ± 0.1 cm-1, the instrument simultaneously measures the five main isotopologues of methane. The ratios 13CH3D/12CH4 and 12CH2D2/12CH4 are measured at 0.01‰ and 0.5‰ (1σ) instrumental precision, respectively. The instrumental accuracy was assessed by measuring a series of methane gases with a range of δ13C and δD values but with the abundances of all isotopologues driven to thermal equilibrium at 250 °C. The estimated accuracy of Δ12CH2D2 is 1‰ (1σ) based on the results of the heated methane samples. This new TILDAS instrument provides a simple and rapid technique to explore the sources of methane in the environment.
关键词： methane,spectroscopy,isotopologues
更新于2025-09-12 10:27:22
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Lean combustion analysis using a corona discharge igniter in an optical engine fueled with methane and a hydrogen-methane blend
摘要： The robustness of combustion initiation is one of the main issues of actual spark-ignition engines, especially for highly-diluted or lean mixtures. In this work, the effects on combustion stabilization obtained by the usage of a radio-frequency corona igniter were evaluated on a single-cylinder optical engine. The comparison with a conventional spark igniter was carried out using pure methane fuel and a blend of hydrogen and methane. For each combination of fuel and igniter, the combustion stability was explored at different air–fuel ratios, from stoichiometric conditions to the lean stable limit (up to λ = 2.0 with the corona igniter and the hydrogen-methane mixture). The combustion analysis was carried out by using the synchronized indicating and imaging data. The latter is essential to estimate the contribution of the corona igniter, which was found to be considerable only before the 5% of mass fraction burned. The corona effect igniter, with respect to a conventional spark igniter, was able to extend the lean stable limit of about 0.15 λ units with methane fuel, and about 0.10 λ units with the hydrogen-methane blend in the tested engine point. Early flame analysis confirmed the capability of corona igniter to improve combustion onset speed and to obtain a more stable and repeatable flame kernel. The findings of this study can help for a better implementation of corona ignition with gaseous low-carbon fuels, and in particular to achieve a higher lean limit extension without the drawback of a performance decay given by a substantial hydrogen enrichment.
关键词： Hydrogen,Lean combustion,Corona ignition,Methane,Optical engine
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Tunable All-Fiber Laser for Remote Sensing of Methane Near 3.4 μm
摘要： The mid-infrared (MIR) region of the optical spectrum has drawn considerable scientific interest in the past few years. Indeed, several molecules relevant to medical or environmental conundrums exhibit strong absorption lines in this region: for instance, methane lines in the MIR are up to 100 times stronger than in the near-infrared [1]. In turn, fiber lasers have long stood as prime candidates for remote gas detection in outdoor environments, given their exemplary robustness, power scaling and beam quality. However, while several previous contributions have targeted methane bands under 3.3 μm in wavelength [2], little work has been done to push fiber laser detection tools past 3.4 μm, where methane absorption lines are mostly decoupled from the absorption spectra of water and other atmospheric constituents. This is especially relevant when probing CH4 through a gas mixture with relatively high water content, such as when studying gas emission from methane-rich thermokarst lakes in northern regions. To this end, we present a tunable all-fiber laser emitting near 3.43 μm and operating at high average power. The laser design (Fig. 1) is based on an all-fiber dual-pumping scheme [3], which combines core-pumping at 1976 nm with clad-pumping at 976 nm in a single-mode erbium-doped fluoride glass fiber to reach, in the present case, up to 3 W of output power at the desired wavelength. The laser cavity itself is delimited by two fiber Bragg gratings (FBG): a highly-reflective (HR) FBG at the input, which has a narrow bandwidth to dictate the laser wavelength, and a lowly-reflective (LR) FBG at the output, which has a large bandwidth to accommodate shifts of the HR FBG. Tuning of the laser cavity is achieved by mechanically stretching (i.e. lengthening) the HR FBG via the beam bending technique [4]. The HR FBG is nested within an Invar-based metallic groove and fixed using a polymer of sufficient elasticity, the groove is then deformed using a piezoelectric actuator (PA), allowing for rapid and precise wavelength tuning over a wavelength range of a few nanometers. Figure 2 compares normalized spectra of the laser emission at various commanding voltages for the PA along with the absorption spectrum of methane as given by the HITRAN database [1]. As can be seen on Fig.2, the presence of consecutive extrema (min-max) allows for quick referencing of the measurement during each tuning cycle. Early gas cell experiments and further engineering refinement show good promise for future deployment in northern regions by climate scientists.
关键词： methane,remote sensing,mid-infrared,piezoelectric actuator,fiber Bragg gratings,tunable all-fiber laser
更新于2025-09-12 10:27:22
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Prediction of sunlight-driven CO2 conversion: Producing methane from photovoltaics, and full system design for single-house application
摘要： CO2 capture and utilization (CCU) technologies are being immensely researched as means to close the anthropogenic carbon cycle. One approach known as artificial photosynthesis uses solar energy from photovoltaics (PV), carbon dioxide and water to generate hydrocarbon fuels, being methane (CH4) a preferential target due to the already in place infrastructures for its storage, distribution and consumption. Here, a model is developed to simulate a direct (1-step) solar methane production approach, which is studied in two scenarios: first, we compare it against a more conventional 2-step methane production route, and second, we apply it to address the energetic needs of concept buildings with usual space and domestic hot water heating requirements. The analysed 2-step process consists in the PV-powered synthesis of an intermediate fuel e syngas e followed by its conversion to CH4 via a Fischer eTropsch (methanation) process. It was found that the 1-step route could be adequate to a domestic, small scale use, potentially providing energy for a single-family house, whilst the 2-step can be used in both small and large scale applications, from domestic to industrial uses. In terms of overall solar-to-CH4 energy efficiency, the 2-step method reaches 13.26% against the 9.18% reached by the 1-step method. Next, the application of the direct solar methane technology is analysed for domestic buildings, in different European locations, equipped with a combination of solar thermal collectors (STCs) and PV panels, in which the heating needs that cannot be fulfilled by the STCs are satisfied by the combustion of methane synthesized by the PV-powered electrolyzers. Various combinations of situations for a whole year were studied and it was found that this auxiliary system can produce, per m2 of PV area, in the worst case scenario 23.6 g/day (0.328 kWh/day) of methane in Stockholm, and in the best case scenario 47.4 g/day (0.658 kWh/day) in Lisbon.
关键词： Artificial photosynthesis,Fischer-Tropsch synthesis,Photovoltaic-powered electrochemical conversion,Building-integrated solar methane,CO2 electrolysis
更新于2025-09-11 14:15:04
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8.78% Efficient All‐Polymer Solar Cells Enabled by Polymer Acceptors Based on a B←N Embedded Electron‐Deficient Unit
摘要： Mono-cardboard waste digestion in batch tests associated with different impact factors was investigated. The maximum methane generation was 394 mL/gVSadd with the best F/M of 0.5 at mesophilic conditions. The highest methane content reached 75% in the dynamic water bath feeding with an average particle size of 1?3 mm. Hydrolysis and methanogenesis were significantly different between static and dynamic states, especially at particle size over 3 mm. The modified Gompertz model (R2 > 0.98) and the modified Aiba model (R2 > 0.88) were the most appropriate models for methane generation among the six kinds of models. At different TS, the variation of dissolved organic matters reflects the metabolic rate of the microbial community. The soluble microbial product-like and protein-like components half split by excitation?emission factors significantly negatively corresponded to biomethane production. Moreover, a rapid loss of matrix-parallel methanogenesis was observed with high organics concentration. A strong correlation between the F/M ratio and the CH4 generation ability was observed with an optimized F/M of 0.5. The maximum energy production was also investigated based on the optimized particle size of 2?5 mm and F/M of 0.5, in which long-term stability was maintained.
关键词： dissolved organic matter,kinetic models,methane production,EEM-PARAFAC,Mono-cardboard digestion
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Sensitivity All-Fibre Methane Sensor with Gas Permeable Teflon/Cryptophane-A Membrane
摘要： We demonstrate a simple, cheap and compact all fibre methane sensor, with record sensitivity of 0.16 nm/ppm, composed of a D-shaped cross section optical fibre in between two fibre Bragg gratings. The flat side of the fibre is coated with a unique membrane used to solely detect methane, made by a gas permeable Teflon layer and doped with cryptophane-A molecules.
关键词： Teflon,high sensitivity,methane sensor,Cryptophane-A,all-fibre
更新于2025-09-11 14:15:04
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Van der Waals Integration of Bismuth Quantum Dots–Decorated Tellurium Nanotubes (Te@Bi) Heterojunctions and Plasma‐Enhanced Optoelectronic Applications
摘要： Crystallization is relevant to many disciplines, and the control of crystallization of molecules is of importance to a great range of technological applications. It has been well established that a variety of surfaces can serve as possible nucleation sites for heterogeneous crystallization. However, it is still unknown what features of such system may be crucial and whether just a single molecule might serve as a nucleation site for crystallization. Therefore, to probe this question, we have investigated the nucleation of a prototypical multicomponent crystal, clathrate hydrates. As multicomponent crystalline compounds, clathrate hydrates have drawn considerable attention because of their scientific and industrial importance. Clathrate hydrates can occur in several possible structures, where the size of guest molecules and their ability to fit into water cages is a crucial factor. Despite the fact that in most applications, for example in oil?gas pipelines, clathrate hydrates form from gas mixtures that feature a variety of sizes of guest molecules, the possible roles of these species in hydrate formation has remained essentially unexplored. Herein, we investigate the impact of the presence of 2,2-dimethylbutane (DMB) on the nucleation of methane hydrate. Our simulation results provide clear evidence that DMB can serve as a nucleation site and can promote the formation of methane hydrates. The low mobility of the DMB molecule, and the longer residence time and hydrate-like structure of water molecules in its hydration shell appear as important contributors to its behavior. These results demonstrate that the presence of a somewhat larger hydrocarbon in low concentration can significantly impact hydrate nucleation and hence have immediate impact in, for example, flow assurance in oil?gas pipelines. More generally, the results presented herein indicate that single molecules in an otherwise homogeneous solution can promote crystal nucleation by stabilizing early stage structural fluctuations in the liquid.
关键词： crystallization,clathrate hydrates,molecular dynamics simulations,methane hydrate,2,2-dimethylbutane,nucleation
更新于2025-09-11 14:15:04