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The warmer-than-present (5–10 °C) climate during the Miocene Climate Optimum (MMCO, approximately 16.9–14.7 Ma) is likely to serve as a reference for future pessimistic warming scenarios. Forced with MMCO boundary conditions, the warming and ocean circulation changes are simulated by the fully coupled climate model FGOALS-g3 with a nominal 1° horizontal resolution ocean component model. Under a 400 ppmv CO 2 concentration, the model generally simulates the MMCO temperature well with small biases at mid and low latitudes compared to the proxy data. Large biases at high latitudes show that FGOALS-g3 fails to reproduce the weak meridional gradient indicated by the proxy record. MMCO surface albedo decreases significantly owing to changes in worldwide forest cover in the boundary condition and the amount of sea ice melt due to the warming climate compared with the PI run. Based on the Energy Balance Model decomposition, warming by the lower surface albedo reaches 1.4–2.7 °C, which is comparable to greenhouse effect warming (∼2.7 °C). Accompanied by MMCO global ocean warming and land–sea distribution changes, both oceanic wind-driven and thermohaline circulations strengthen. The Antarctic Circumpolar Current in the MMCO is stronger due to the enhanced westerly wind stress and the reduced sea ice extent. The intensified MMCO Atlantic Meridional Overturning Cell (AMOC) relative to PI is likely linked to the altered ocean-gateway configuration, particularly at low and middle latitudes. When the MMCO Panama Seaway and Tethys Seaway open, waters from the Pacific and the Indian Ocean converge and mix in the western North Atlantic. Combined with the supplemental water (∼30 Sv), the Gulf Stream is enhanced and flows more poleward, causing the sea ice to retreat, leading to a deeper mixed layer. Consequently, the Subpolar North Atlantic salinification causes stronger convective motion and the appearance of the Atlantic Meridional Overturning Cell. • The model simulates the reconstructed MMCO temperature well in low and mid latitudes. • Intensified greenhouse effect and low surface albedo mainly cause MMCO warmth. • Strengthened AMOC results from the convergence of Pacific and Indian Ocean water. [ABSTRACT FROM AUTHOR]

A super-large ensemble simulation dataset with 110 members has been produced by the fully coupled model FGOALS-g3 developed by researchers at the Institute of Atmospheric Physics, Chinese Academy of Sciences. This is the first dataset of large ensemble simulations with a climate system model developed by a Chinese modeling center. The simulation has the largest realizations up to now worldwide in terms of single-model initial-condition large ensembles. Each member includes a historical experiment (1850–2014) and an experiment (2015–99) under the very high greenhouse gas emissions Shared Socioeconomic Pathway scenario (SSP5-8.5). The dataset includes monthly and daily temperature, precipitation, and other variables, requiring storage of 275 TB. Additionally, the surface air temperature (SAT) and land precipitation simulated by the FGOALS-g3 super-large ensemble have been validated and projected. The ensemble can capture the response of SAT and land precipitation to external forcings well, and the internal variabilities can be quantified. The availability of more than 100 realizations will help researchers to study rare events and improve the understanding of the impact of internal variability on forced climate changes. [ABSTRACT FROM AUTHOR]

The defect classification is investigated by using features-based giant-magnetoresistive pulsed eddy current (GMR-PEC) sensor. The power spectrum density of the intrinsic mode functions (IMFs) is extracted as the classification feature, considering the disadvantage of selecting a wavelet base determined in previous work on spectral analysis combined with wavelet-decomposition. The IMFs are derived through empirical mode decomposition (EMD) and ensemble EMD. Principal component analysis, linear discriminant analysis, and Bayesian classifier are employed for defect classification algorithm. The proposed approach is validated by experiments, and results indicate that the cracks and cavities in the surface and subsurface can be classified satisfactorily. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new PEC feature (spectrum analysis after wavelet decomposition) is investigated. [•] The spectrum of the detail decomposited exceeding 1.7kHz is more effective. [•] The high-frequency components are dominant among the surface and sub-surface defects. [•] The PCA-LDA and Bayesian classifier can correctly classify all kinds of defects. [ABSTRACT FROM AUTHOR]

A 61-year (1958–2018) global eddy-resolving dataset for phase 2 of the Ocean Model Intercomparison Project has been produced by the version 3 of Chinese Academy of Science, the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP) Climate system Ocean Model (CAS-LICOM3). The monthly and a part of the surface daily data in this study can be accessed on the Earth System Grid Federation (ESGF) node. Besides the details of the model and experiments, the evolutions and spatial patterns of large-scale and mesoscale features are also presented. The mesoscale features are reproduced well in the high-resolution simulation, as the mesoscale activities can contribute up to 50% of the total SST variability in eddy-rich regions. Also, the large-scale circulations are remarkably improved compared with the low-resolution simulation, such as the climatological annual mean SST (the RMSE is reduced from 0.59°C to 0.47°C, globally) and the evolution of Atlantic Meridional Overturning Circulation. The preliminary evaluation also indicates that there are systematic biases in the salinity, the separation location of the western boundary currents, and the magnitude of eddy kinetic energy. All these biases are worthy of further investigation. [ABSTRACT FROM AUTHOR]

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) is an endorsed Model Intercomparison Project in phase 6 of the Coupled Model Intercomparison Project (CMIP6). The goal of FAFMIP is to investigate the spread in the atmosphere-ocean general circulation model projections of ocean climate change forced by increased CO2, including the uncertainties in the simulations of ocean heat uptake, global mean sea level rise due to ocean thermal expansion and dynamic sea level change due to ocean circulation and density changes. The FAFMIP experiments have already been conducted with the Flexible Global Ocean-Atmosphere-Land System Model, gridpoint version 3.0 (FGOALS-g3). The model datasets have been submitted to the Earth System Grid Federation (ESGF) node. Here, the details of the experiments, the output variables and some baseline results are presented. Compared with the preliminary results of other models, the evolutions of global mean variables can be reproduced well by FGOALS-g3. The simulations of spatial patterns are also consistent with those of other models in most regions except the North Atlantic and the Southern Ocean, indicating large uncertainties in the regional sea level projections of these two regions. [ABSTRACT FROM AUTHOR]

The datasets of two Ocean Model Intercomparison Project (OMIP) simulation experiments from the LASG/IAP Climate Ocean Model, version 3 (LICOM3), forced by two different sets of atmospheric surface data, are described in this paper. The experiment forced by CORE-II (Co-ordinated Ocean–Ice Reference Experiments, Phase II) data (1948–2009) is called OMIP1, and that forced by JRA55-do (surface dataset for driving ocean–sea-ice models based on Japanese 55-year atmospheric reanalysis) data (1958–2018) is called OMIP2. First, the improvement of LICOM from CMIP5 to CMIP6 and the configurations of the two experiments are described. Second, the basic performances of the two experiments are validated using the climatological-mean and interannual time scales from observation. We find that the mean states, interannual variabilities, and long-term linear trends can be reproduced well by the two experiments. The differences between the two datasets are also discussed. Finally, the usage of these data is described. These datasets are helpful toward understanding the origin system bias of the fully coupled model. [ABSTRACT FROM AUTHOR]

Highlights • A portable laser sensor for trace NH3 is developed based on FPGA. • WMS-2 f /1 f is employed to reduce the random fluctuations. • The adsorption of NH3 is studied and minimized in measurements. • The sensor is deployed for in-situ measurement of NH3 slip in SCR. Abstract A portable laser sensor for trace ammonia (NH 3) is developed based on near-infrared laser absorption spectroscopy. Tunable diode laser absorption spectroscopy in conjunction with wavelength modulation spectroscopy is implemented by a system-on-chip based on field-programmable gate array. A variable temperature multipass cell with a 15 m optical path length is adopted to enhance the absorption path length and avoid the NH 3 adsorption. The physical dimension of the sensor is minimized into 43 × 18 × 16 cm3 on the benefit of home-made electronic system and compact optical design. A unique absorption line of NH 3 around 1.51 µm covered by a distributed feedback diode laser is selected to reduce the influence from carbon dioxide, vapor and other trace gases. Calibration-free modulation spectroscopy is employed to avoid the random fluctuations due to laser noise and non-absorption transmission losses. The performance of sensor including adsorption of NH 3 , stability and flow of gas are examined and discussed in detail. For removing the adsorption of NH 3 , the temperature-dependent curve is obtained by the direct absorption spectroscopy, and it shows that the adsorption is significantly suppressed at (or higher than) 415 K. According to Allan deviation analysis, the minimum detection limit is 0.16 ppm at 184 s, and the rise time and the fall time of system are about 4.5 s and 3.7 s, respectively. The feasibility of the sensor is validated and deployed to monitor the NH 3 slip in selective catalytic reduction (SCR) of coke oven flue gas. The work provides a potentially valuable control sensor for SCR. [ABSTRACT FROM AUTHOR]

Highlights • The sensor utilized a DFB laser around 2.33 μm as source. • The sensor was developed by using a high performance microcontroller and simple DLIA algorithm. • The LoD of 0.45 ppm is achieved while a precision of 0.0875 ppm is observed with an optimal time of ∼24 s. • The response times were significantly shorted with the detectable threshold being set at 5 ppm instead of 100 ppm. Abstract A distributed feedback laser-based carbon monoxide (CO) sensor has been developed for early warning detection of fire. The sensor, based on a system-on-chip with high-performance 32-bit microcontroller (MCU), features a digital lock-in amplifier (DLIA) for wavelength modulation spectroscopy (WMS) to improve detection sensitivity. The ramp scanning signal and a sinusoidally modulated signal were generated and superimposed by the MCU, and converted by a digital-to-analog converter to scan the absorption line of CO around 2.327 μm. The n -harmonic components obtained through multiplication of the n- th cosine wave data of the spectral signal, were then processed by integration and filter algorithms. The Allan-Werle deviation was used to evaluate the long-term performance of the sensor. The limit of detection (LoD) for CO was calculated to be 0.0875 ppm based on an optimal integration time of ∼24 s. In field tests, five small-scale standard fires were investigated in accord with EN54 and the results for the test substances – cotton rope (smoldering fire), polyurethane foam (smoldering fire), beech wood, a sheet of A4 paper and polyvinylchloride – verified the reliability and robustness of the developed sensor. Relatively fast response times (110 s for foam and A4 paper; 250 s for PVC, beech wood and cotton rope) were realized based on a threshold of 5 ppm CO. The CO sensor is considered suitable for integration into portable devices for industrial application, particularly for in-situ early warning fire detection. [ABSTRACT FROM AUTHOR]

Fire poses a significant risk to the safety, health, and property of people around the world. However, traditional ‘‘point sensor’’ fire detection techniques for indoor buildings based on air particles, air temperatures, and smoke have a low sensitivity, long response time, and poor stability. Therefore, video-based fire detection has become a particularly efficient and important method for detecting the early signs of a fire. Due to image blur, low illumination, flame-like interference and other factors, there is a certain error rate of fire recognition using video flame recognition methods. According to our previous study of a multi-feature flame recognition algorithm, a novel flame recognition algorithm based on free radical emission spectroscopy during combustion is investigated in this paper. First, multiple features are extracted from the video images by employing our proposed processing scheme. Then, the features are post-processed by a temporal smoothing algorithm to eliminate the error recognition rate, which is caused by the similar characteristics of objects between flame-like and real flame areas. In the temporal smoothing experiments, the proposed method achieves the true positive rates of 0.965 and 0.937 for butane flames and forest fire, respectively. Additionally, the spectral signals of OH, CH, C2 and other free radicals in the combustion objects were acquired by the spectrometer. The vibrational temperature and rotational temperature are calculated after identification of the A2Δ → X2Π transition of the CH (410-440 nm). The flames-like are completely rejected by the proposed method in the validation experiment. In the subsequent butane combustion experiment, the vibrational temperature of the butane was 4896 K, and the rotational temperature was 2290 K. The experimental results show that real fires can be precisely recognized and that the combustion temperature can be determined from the CH emission spectroscopy. This novel method provides a new viewpoint for fire detection and recognition. [ABSTRACT FROM AUTHOR]

A resolved line pair was selected for simultaneous measurement of carbon monoxide (CO) and carbon dioxide (CO2) in the near-infrared (NIR) region. The spectral lines of CO and CO2 at 1.578 µm were measured by wavelength modulation spectroscopy (WMS)-2f and the absorption was enhanced with a multipass absorption cell. The white noise was further reduced by averaging technology. The detection sensitivity (1σ) for the system is estimated at 2.63 × 10−7 cm−1 for direct absorption spectroscopy. The ultimate detection limits of CO2 and CO mixed with pure N2 at 75 Torr are 29 parts per million (ppm) and 47 ppm, respectively. It is demonstrated that the signal is highly linear with the concentration in the range of 100–800 ppm. Based on an Allan variation analysis, the minimum detectable limit of CO2 and CO is 7.5 and 14 ppm, respectively. The response time of the system is about 30 s and a relationship of temperature dependence was obtained. As an example, an in situ measurement of exhaust of alkane combustion emission is presented. [ABSTRACT FROM AUTHOR]

The combination of CM-β-CD-P and CA-DA-P can significantly improve the scale inhibition performance of CM-β-CD-P/CA-DA-P. [Display omitted] • The L-CM-β-CD-EP/CA-DA-EP composite scale inhibitor were designed and constructed. • The L-CM-β-CD-EP/CA-DA-EP composite scale inhibitor exhibits excellent scale inhibition performance. • The host–guest synergistic effects can significantly improve the scale inhibition performance of L-CM-β-CD-EP/CA-DA-EP. • The L-CM-β-CD-EP/CA-DA-EP has excellent biodegradability, low bioaccumulation, and ecotoxicity. • The L-CM-β-CD-EP/CA-DA-EP can potentially serve as an eco-friendly inhibitor in seawater. Currently, reducing the formation of calcium scale is an important challenge for seawater utilization in the cooling water system of offshore oil and gas platforms. The combination of linear carboxymethyl β-cyclodextrin-epichlorohydrin polymer (L-CM-β-CD-EP) and citric acid-dopamine-epichlorohydrin polymer (CA-DA-EP) as an eco-friendly scale inhibitor was studied by the static experiments. We observed that L-CM-β-CD-EP/CA-DA-EP displayed excellent scale inhibition efficiency of 94.6 % and 92.5 % against CaCO 3 and CaSO 4 , respectively, at the 19.2 mg/L inhibitor (Ca2+ = C O 3 2 - = 2400 mg/L, Ca2+ = S O 4 2 - = 800 mg/L). XRD and SEM images of scale crystal exhibited that CaCO 3 and CaSO 4 crystals were deformed and transformed by L-CM-β-CD-EP/CA-DA-EP, which was attributed to multiple inhibition effects, including lattice distortion, chelation, and host–guest synergistic effects. More importantly, the host–guest synergistic effects of L-CM-β-CD-EP and CA-DA-EP can significantly improve the scale inhibition performance of L-CM-β-CD-EP/CA-DA-EP. Besides, the TOC results analysis showed that L-CM-β-CD-EP/CA-DA-EP possessed excellent biodegradability, low bioaccumulation, and ecotoxicity. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) radicals in the a 4 Π state were produced by discharging the mixture of NO gas and helium at the audio frequency. In the near infrared region, the spectra of the b 4 Σ − - a 4 Π system of the NO radical were studied by optical heterodyne - concentration modulation laser absorption spectroscopy. More than one hundred and thirty lines and eleven branches were recorded for the first time and assigned to the (3, 0) band. A global fitting was carried out to extract the molecular constants. In particular, the parameters D , p , γ and A D were precisely determined. [ABSTRACT FROM AUTHOR]

Based on the non-Kolmogorov spectrum, using the extended Huygens–Fresnel principle, the analytical expressions for the spectrum of the coherent and incoherent superpositions of rectangular array Gaussian Schell-model (RAGSM) beams propagating through non-Kolmogorov atmospheric turbulence are derived, and are used to study the influence of non-Kolmogorov atmospheric turbulence on spectral changes of coherent and incoherent superpositions RAGSM beams. It is shown that, with the increment of the general exponent α and the inner scale of turbulence l 0 , as well as the decrement of the general structure constant C ˜ n 2 , the magnitude of the spectral shift will increase, the magnitude of spectral transition will decrease and the critical position of spectral transition will decrease. The outer scale of turbulence L 0 has little effect on the spectral shift and spectral transition. [ABSTRACT FROM AUTHOR]

Both the software and hardware of a pulsed eddy current (PEC) real-time testing device are designed to pre-process the noise from continuous casting slabs (CCS) during in situ defect detection. An algorithm based on a sliding window with a fixed length is developed in the process of denoising. The root mean square error (RMSE) and the signal-to- noise ratio (SNR) of the denoised PEC response are given with the combination of Daubechies4, Symlet4 and three threshold denoising algorithms. The results of the simulation and experiment indicate that the best real-time denoising condition is with the wavelet transform of three or four layers. Herein, the SNR obtained is above 19 dB and the average throughput rate is 51 kHz when the moving speed of the casting slabs is about 2 m/s. Our system highlights real-time processing, stability, high accuracy and strong anti-interference, so it is suitable for automatic testing in a production situation. [ABSTRACT FROM AUTHOR]

Abstract: The spectra of d 3Δ–a 3П (7,1) band of CS radical were measured by optical heterodyne–concentration modulation spectroscopy in the region from 11640 to 12230cm−1. In total, we assigned three hundred and four lines, of which Ree and Rff branches in the d 3Δ1–a 3П0 subsystem and more than a hundred lines were first observed and identified. The anomalous lambda-doubling of the d 3Δ1 (υ =7) level reveals a local perturbation interaction from the 1Σ− state. The perturbation parameter between 1Σ− and a 3П0 (υ =13), and molecular constants of the d 3Δ1 (υ =7) as well as 1Σ− were derived through fitting all assigned lines to the effective Hamiltonian. [Copyright &y& Elsevier]

In the original version of this article, the second author's first name was misspelled as Zhipeng. The correct spelling is Zipeng. The sixth author's first name was misspelled as Jirong. The correct spelling is Jinrong. The correct version is as follows: LICOM Model Datasets for the CMIP6 Ocean Model Intercomparison Project Pengfei LIN1,4, Zipeng YU1,4, Hailong LIU1,4, Yongqiang YU1,4, Yiwen LI1,4, Jinrong JIANG2, Wei XUE3, Kangjun CHEN1, Qian YANG1,4, Bowen ZHAO1,4, Jilin WEI1,4, Mengrong DING1,4, Zhikuo SUN1,4, Yaqi WANG1,4, Yao MENG1,4, Weipeng ZHENG1,4, and Jinfeng MA11LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2Computer Network Information Center, Chinese Academy of Sciences, Beijing 100190, China 3Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China 4College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China In the section "Data availability statement" on page 248 of the original version of this article, the URL of the data should be https://esgf-node.llnl.gov/projects/cmip6. [ABSTRACT FROM AUTHOR]

• A dual-species sensor was constructed based on two-channel ALIA. • A Herriott cell and normalized technique were adopted to improve sensitivity. • A sensitivity for CO and CH 4 was about 0.20 ppm with a 2.5 s sampling time. • The CO emission satisfied the exponential growth tendency during CSC. • Two CTs were recognized and were able to precisely forecast CSC. As a common hazard, coal spontaneous combustion (CSC) causes the loss of coal in piles and mines. To rapidly and reliably forecast CSC, a portable and powerful detection system based on a laser spectroscopic technique is proposed, to precisely measure gaseous inhibitors; the technique uses a single, distributed-feedback diode laser emitting at 2.33 μm as a sensing light source for dual species. The detection system carries out wavelength-modulation spectroscopy to suppress detection noise by using a two-channel analogue lock-in amplifier (ALIA) and a complex programmable logic device (CPLD) controller. To improve detection sensitivity, a Herriott cell is adopted to increase the interaction length between the laser and the target species. The embedded system on a chip (SoC) of STM32F103 is the charge of the current driver and temperature control of the laser. Deployment of the SoC of STM32H743 acquires and digitally filters the original demodulated absorption signal, after which communication with a personal computer takes place. The second demodulation component, normalized by the first demodulation component, is used to improve the signal-to-noise ratio. The sensor-calibration experiment reveals the square of the correlation coefficients R2 to be 0.99718 and 0.99905 for carbon monoxide (CO) and methane (CH 4), respectively, over the concentration range of 5–200 ppm. Using Allan-Werle deviation analysis, the detection sensitivity for CO and CH 4 are 0.27 ppm and 0.20 ppm with a 2.5 s sampling time, and 0.05 ppm and 0.03 ppm with ~125 and 95 s integration times, respectively. Finally, the detection system is used for the online measurement and analysis of the growth pattern of gaseous products which are released during the CSC process, the temperature varying from 30 to 200 °C. Two critical temperatures were correctly determined to further forecast CSC status. On beginning a vigorous oxidation process, the exponential-evolution trends of the CH 4 and CO gases agree with each other. Compared with CH 4 , CO may be more suitable for online, early detection of CSC. [ABSTRACT FROM AUTHOR]

A laser-based spectrometer with a physical size of 60× 30 ×25 cm3 has been developed to continuously monitor CO and CH 4 in atmosphere based on tunable diode laser absorption spectroscopy (TDLAS). Two neighboring lines of CO and CH 4 around 2.3 μ m were selected as candidates for simultaneous measurement by a single diode distributed feedback (DFB) laser. A special Herriott-type multipass absorption cell, with a 72 m optical path length, was designed and used to enhance the absorption signals of sample gases. Normalized wavelength modulation spectroscopy was applied to improve the sensitivity and robustness of the spectrometer and it was implemented on a home-made electronic system based on field programmable gate array (FPGA). Meanwhile, the electronic system controlled the temperature and current of DFB laser with the precision of 0.01 °C and 40 ppm. The 2nd-harmonic signals normalized by the corresponding 1st-harmonic signals for both CO and CH 4 are of high linear response to their concentrations in the range of 0.046–4.6 ppm and 0.487–48.7 ppm, respectively. According to the Allan variance, respective minimum detection limits for CO and CH 4 are 0.73 ppb and 36 ppb at 122 s and 137 s. As an application example, the spectrometer has been validated through real-time and in-situ measurement of atmospheric CO and CH 4 for 48 h. Unlabelled Image • A compact laser-based spectrometer has been developed to monitor atmospheric CO and CH 4 using a single DFB laser emitting at 2.33 μm. • A special Herriott-type multipass cell combined with FPGA system was designed and used to improve the sensitivity and compactness of the system. • The normalized WMS-(2 f /1 f) technique was employed to achieve high robustness of spectrometer. • The spectrometer has been validated for real-time and in-situ measurement of atmospheric CO and CH 4 for 48 h. [ABSTRACT FROM AUTHOR]

In Traditional Chinese Medicine (TCM), moisture content (MC) inspection using voltage level or a lock-in amplifier, with a features-based near-infrared light-emitting diode sensor is possible. Abundant absorption response in a wide frequency range and information in both the time-domain and frequency-domain can be obtained, with the square excitation method. However, planeness, heterogeneous particle sizes, and measurement noise negatively affect the time-domain feature during MC inspection. In this work, spectrum analysis (SA) for feature extraction is investigated, to precisely measure the MC of Dutong pills. The principal components for low and high frequencies, are aimed at counteracting the dimensional methods, which are used for supplying the lower dimensional features. The SA experimental results demonstrate that the low frequency components, ranging from the base to the 3rd harmonic components, have a high linear correlation with the MC. The calibration and validation experimental results reveal that the MC can be a monotonic function about the SA amplitudes or first principal component (PC1), with the proposed sensor. This method has the potential to be used for gauging automatic, in situ MCs, particularly for quality control and Process Analytical Technology in TCM. Future research opportunities include improving accuracy and application of the method under field conditions. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction and non-selective catalytic reduction (SCR/SNCR) are the most popular de-NOx processes for coal-fired power plant, where the real-time temperature is a significant parameter. A new developed tunable diode laser spectroscopy used for measuring the temperature of ammonia (NH3) in the process of SCR/SNCR influenced by strong exhaust gas matrices CO2 and H2O was presented in this paper. Two lines near 6605 cm−1 were selected, with rather weak temperature dependency and minimal interface from CO2 and H2O according to HITRAN12 database. A homemade heating equipment for high temperature laser spectroscopy measurement was developed based on an ARM microcontroller. The temperature calibration experiments of absorption lines were carried out at variable concentrations under different temperatures. The spectral signals of 2.5%, 3.5% and 4.5% NH3 were observed for validation of the generalization and robustness of the sensor. The calibration and validation experimental results show that the maximum measurement error and global average error of the temperature sensor with the temperature ranging from 453 to 653 K are less than 2% and 1.38%, respectively. It demonstrates that our proposed sensor with high accuracy and linearity, and can be utilized to measure the temperature in SNCR/SCR process. [ABSTRACT FROM AUTHOR]

Tunable diode laser absorption spectroscopy (TDLAS) is an important technique for trace gas detection. The sensitivity of TDLAS system, especially for multi-pass absorption, is usually limited by optical fringes. It is an effective approach to suppressing optical fringes of spectral lines using digital filtering. The parameters derived from filtering simulations are key factors and they are related to the noise characteristic. In the paper, the precise Airy functions were used to simulate optical interference and the interference signal was effectively minimized by the wavelet transforms. The root-mean-square error and the residual standard deviation are introduced to quantify the suppression ratio of etalon fringes. It is demonstrated that the optimum wavelet function in denoising the observed CO2 lines is fk18, in comparison with haar, db02, coif1 etc. In addition, the absorption signals recorded by direct absorption spectroscopy and wavelength modulation spectroscopy at second-harmonic (WMS-2f) with a 10 m White-type cell were subjected to low-pass, averaging and fk18 wavelet filtering, respectively. The results show that only wavelet transform is capable of suppressing optical interference noise. The detection limit of WMS-2f can reach 7 ppm and the perfect calibration curves between signal intensity and gas concentration are obtained after wavelet filtering. To further demonstrate the feasibility of the approach, spectral signals at different pressures and temperatures were acquired and the etalon interference is substantially eliminated by fk18 wavelet at 13th level of decomposition. [ABSTRACT FROM AUTHOR]