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A sensor operating at room temperature has low power consumption and is beneficial for the detection of environmental pollutants such as ammonia and benzene vapor. In this study, polyaniline (PANI) ... is made from aniline under acidic conditions by chemical oxidative polymerization and doped with tin dioxide (SnO2) at a specific percentage. The PANI/SnO2 hybrid material obtained is then ground at room temperature. The results of scanning electron microscopy show that the prepared powder comprises nanoscale particles and has good dispersibility, which is conducive to gas adsorption. The thermal decomposition temperature of the powder and its stability are measured using a differential thermo gravimetric analyzer. At 20 °C, the ammonia gas and benzene vapor gas sensing of the PANI/SnO2 hybrid material was tested at concentrations of between 1 and 7 ppm of ammonia and between 0.4 and 90 ppm of benzene vapor. The tests show that the response sensitivities to ammonia and benzene vapor are essentially linear. The sensing mechanisms of the PANI/SnO2 hybrid material to ammonia and benzene vapors were analyzed. The results demonstrate that doped SnO2 significantly affects the sensitivity, response time, and recovery time of the PANI material. več

To improve the performance of wind sensors in the high velocity range, this paper proposes a wind measurement strategy for thermal wind velocity sensors that combines the constant power and constant ... temperature difference driving modes of the heating element. Based on the airflow distribution characteristics from fluid dynamics, sequential measurement and correction is proposed as a method of measuring wind direction. In addition, a wind velocity and direction measurement instrument was developed using the above-mentioned approaches. The test results showed that the proposed instrument can obtain large dynamic wind velocity measurements from 0 to 60 m/s. The wind velocity measurement accuracy was ±0.5 m/s in the common velocity range of 0–20 m/s and ±1 m/s in the high velocity range of 20–60 m/s. The wind direction accuracy was ±3° throughout the 360° range. The proposed approaches and instrument are not only practical but also capable of meeting the requirements of wide-range and large dynamic wind vector measurement applications. več

Vehicular pollutant exposure of residents and pedestrians in high-rise deep street canyons with viaducts and noise barriers requires special concerns because the ventilation capacity is weak and the ... literature reported inconsistent findings on flow patterns as aspect ratios (building height/street width, H/W) are larger than 2. By conducting computational fluid dynamics (CFD) simulations coupled with the intake fraction iF and the daily pollutant exposure Et, this paper investigates the impact of street aspect ratios, viaducts and noise barriers on the flow and vehicular passive pollutant exposure in full-scale street canyons (H/W=1–6, W=24m). iF represents the fraction of total emissions inhaled by a population (1ppm=10−6), while Et means the extent of human beings’ contact with pollutants within one day. CFD methodologies of passive pollutant dispersion modeling are successfully validated by wind tunnel data in Meroney et al. (1996). As a novelty, the two-main-vortex pattern start appearing in full-scale street canyons as H/W changes from 4 to 5, however previous studies using wind-tunnel-scale models (H=6cm) reported two to five vortexes as H/W=2–5. This finding is validated by both smoke visualization in scale-model outdoor field experiments (H=1.2m, W=0.6m) and CFD simulations of Reynolds number independence. Cases with two main vortexes (H/W=5–6) experience much larger daily pollutant exposure (~103–104mg/m3/day) than those with single main vortex as H/W=1–4 (~101–102mg/m3/day). Moreover leeward-side pollutant exposures are much larger than windward-side as H/W=1–4 while oppositely as H/W=5–6. Assuming a general population density, the total iF is 485–803ppm as H/W=1, 2020–12051ppm as H/W=2–4, and 51112–794026ppm as H/W=5–6. With a single elevated pollutant source, cases with viaducts experience significantly smaller pollutant exposures than cases without viaducts. Road barriers slightly increase pollutant exposure in near-road buildings with H/W=1 while reduce a little as H/W=3 and 5. Two-source cases can experience 2.60–5.52 times pollutant exposure as great as single-source cases. •Intake fraction (iF) and daily CO exposure (Et) are used for exposure assessment.•Effects of aspect ratios (H/W=1–6), viaduct/noise barriers are studied by CFD.•iF=102–104ppm as H/W=1–4 (one vortex) but iF=105–106ppm as H/W=5–6 (two vortexes).•Viaducts produce less CO exposure if only a viaduct-level CO source is fixed.•Noise barriers slightly reduce vehicular indoor CO exposure as H/W=3–6. več

The over-parameterisation, as a common issue in numerical models, may be unavoidable in the TOUGH + Hydrate (T + H) model. Therefore, a global sensitivity analysis of the influence of main or ... uneasily-measured 26 input parameters on five model outputs, i.e. cumulative gas production, gas production rate, hydrate saturation, gas saturation and aqueous saturation, under depressurization and brine-inhibitor injection was performed using the LH-OAT sampling method. The 26 parameters were classified as ‘Very important’, ‘Important’, ‘Slightly important’, and ‘Unimportant’ by analyzing their sensitivity indices at different sampling times and sampling positions in the modeling area, using the TSPAC segmentation package. The sensitivity of an input parameter to a model output was dependent on sampling time, sampling position and the identity of the model output in question. Cumulative gas production and gas production rate were governed by four permeability-related parameters (parameter n and residual aqueous saturation (in the relative permeability-saturation model), permeability reduction exponent and critical mobile phase saturation) and four inhibitor-related parameters (inhibitor density, the specific enthalpy of the dissolution of the inhibitor in water, reference inhibitor mole fraction in the aqueous phase and inhibitor-induced reference temperature depression). Hydrate saturation was governed by two hydrate dissociation-related parameters (temperature-dependent hydrate specific heat and hydrate density) and two parameters related to the flow of released fluids in the pore network (permeability and pore structure expansion). Gas saturation was governed by several types of input parameters: six parameters related to the flow of pore gas (parameter n and residual aqueous saturation (in the relative permeability-saturation model), critical mobile phase saturation, intrinsic permeability, permeability reduction exponent and pore compressibility), three inhibitor-related parameters (the specific enthalpy of the dissolution of the inhibitor in water, reference inhibitor mole fraction in the aqueous phase and inhibitor-induced reference temperature depression) and two hydrate dissociation-related parameters (temperature-dependent hydrate density polynomial and temperature-dependent hydrate specific heat polynomial). Finally, aqueous saturation was governed by five permeability-related parameters (parameter λ and residual aqueous saturation (in the saturation-capillary pressure function model), pore expansion, grain specific heat and the tortuosity factor model). Overall, the most influential parameter for all five model outputs was the parameter n in the relative permeability-saturation function model. •We perform a global sensitivity analysis for T + H model with spatio-temporal sampling.•Parameter sensitivity is dependent on sampling time, position and model outputs.•Influential parameters are associated with the processes which causes the output.•The overall most important parameter is n in the S-p relationship function.•Informative sensitivity analysis requires rigorous spatial and temporal sampling. več

Based on atmospheric circulation reanalysis, global gridded precipitation, and outgoing longwave radiation datasets, this study reveals the physical process through which the land–sea thermal ... contrast over East Asia interrelates with the variability of the interface between the Indian summer monsoon and East Asian summer monsoon (IIE). The results indicate that the release of latent heating exerted by the low-frequency variability of anomalous land–sea thermal contrast is one of the most important physical processes correlating with the zonal movement of the IIE, in which the release of latent heating over eastern East Asia makes the greatest contribution. When a lower apparent moisture sink occurs over the South China Sea but a higher one over southern China, an anomalously positive land–sea thermal contrast is formed. An anomalous convergent zone in relation to the positive land–sea thermal contrast, located in the eastern part of the IIE, will favor the IIE to move more eastward than normal, and vice versa. An anomalous divergent zone located in the eastern part of the IIE will benefit the IIE to shift more westward than normal. Experiments using a linear baroclinic model confirm the physical processes revealed by the observational analysis. več

•Human activities exert more influence on the HONO formation after the holidays.•The average HONO concentration was considerably higher after than during the holidays.•Daytime homogenous HONO ... formation was greatly enhanced under high NO conditions.•A primary emission was likely contributed to the large fractional unknown source. Nitrous acid (HONO) is an important source of hydrogen oxides (HOx), which affects air quality, the atmospheric oxidation capacity, and human health. Here, we present ambient measurements of the HONO concentrations in Zhuhai, a coastal city in Southern China, from February 7 to March 15, 2021. The campaign was classified into two periods during (P1) and after (P2) the Spring Festival holidays. The average HONO mixing ratio during P2 (1.19 ± 0.85 ppbv) was much higher than that during P1 (0.24 ± 0.18 ppbv), likely due to the contribution of homogeneous HONO formation. During nighttime, the heterogeneous conversion rate during P2 (0.0089/hr) was considerably higher than that during P1 (0.0057/hr), suggesting a higher heterogeneous NO2 conversion potential. However, the heterogeneous NO2 conversion was the dominant way during P1 with a high percentage of 88%, while comparable ratios of heterogeneous and homogeneous formation were found (54% vs. 46%) during P2, indicating that the homogeneous formation was also important during P2. During daytime, homogeneous reaction was the major known pathway, with a contribution of 16% during P1 and 27% during P2, leaving large unknown HONO sources which reasonably correlated with the photo-enhanced NO2 conversion. Two case scenarios were additionally explored, showing that there might be a primary emission source during one scenario (February 17-18) and vehicle emissions might be the major unknown HONO source for another scenario (March 3–5). The results suggest that large unknown daytime sources still exist which need more future ambient and laboratory studies. Display omitted več

•A cardiac-sound-detection system with acoustic-pressure sensor array is proposed.•Field-programmable gate array and microcontroller are used for signal processing.•The system shows reduced noise and ... comparable performance to conventional system.•Low cost and thin structure allow integration with wearable electronics. This paper presents a cardiac-sound-detection system based on an acoustic-pressure sensor array. The traditional cardiac-sound probe has the disadvantages of high cost and thick structure, which makes embedding difficult. Therefore, a methodology for cardiac-sound detection, comprising a sound-pressure sensor array, is proposed to achieve a low cost, very thin, and wearable cardiac-sound probe, which can be embedded in furniture or clothes for long-term heart sound monitoring. By introducing several miniature electret-condenser-microphone-based acoustic-pressure sensors, a sensor array for picking up cardiac sound was designed. The data-processing platform comprised a field-programmable gate array and microcontroller unit. Furthermore, a series of de-noising methods including oversampling, finite impulse response digital filtering, and digital extraction were used, thereby facilitating accurate cardiac-sound signal identification. Test results showed that the average Root Mean Square amplitude of the noise after processing was more than 3 dB lower than that of the signal obtained from a single sensor in the array. The signal-to-noise ratio improved more than 7 dB after processing. Furthermore, actual cardiac sounds were acquired and compared using the proposed sensor array and the dedicated cardiac-sound sensor. The proposed 4 mm thick sensor array could effectively acquire S1- and S2-segments of cardiac sound. The proposed system demonstrates the potential for use in the development of wearable cardiac-sound monitoring systems. več

The mean state and year-to-year variations of the tropospheric temperature fields are analyzed in light of their relationship with the establishment of the East Asian summer monsoon (EASM), and the ... Indian monsoon (INM). Primary data for the analysis include the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis from 1982 to 1996 and the European Center for Medium-Range Weather Forecast (ECMWF) Reanalysis (ERA) from 1979 to 1993. The analysis reveals that, in most of the analyzed years, the meridional temperature gradient in the upper troposphere reverses at, or before the onset time of the summer monsoon in both the EASM region and the INM region. On the average, the reversal time of the meridional temperature gradient in the EASM region (INM region) is concurrent with (one pentad earlier than) the onset time of the summer monsoon. A budget analysis shows that the strong horizontal warm advection and the diabatic heating are the main contributors to the upper tropospheric warming against the strong adiabatic cooling during the pre-onset period over the EASM region. Over the INM region, however, strong adiabatic heating due to subsidence is the major warming process against diabatic cooling, and the strong horizontal cold advection related to the persistent northwestlies to the southwestern periphery of the Tibetan Plateau. The results show that the seasonal shift of the South Asian High in the upper troposphere, and the establishment of the EASM and the INM are closely related to the seasonal warming, which results in the reversal of the meridional temperature gradient in the upper troposphere over the two monsoon regions. več

A sensor operating at room temperature has low power consumption and is beneficial for the detection of environmental pollutants such as ammonia and benzene vapor. In this study, polyaniline (PANI) ... is made from aniline under acidic conditions by chemical oxidative polymerization and doped with tin dioxide (SnO ) at a specific percentage. The PANI/SnO hybrid material obtained is then ground at room temperature. The results of scanning electron microscopy show that the prepared powder comprises nanoscale particles and has good dispersibility, which is conducive to gas adsorption. The thermal decomposition temperature of the powder and its stability are measured using a differential thermo gravimetric analyzer. At 20 °C, the ammonia gas and benzene vapor gas sensing of the PANI/SnO hybrid material was tested at concentrations of between 1 and 7 ppm of ammonia and between 0.4 and 90 ppm of benzene vapor. The tests show that the response sensitivities to ammonia and benzene vapor are essentially linear. The sensing mechanisms of the PANI/SnO hybrid material to ammonia and benzene vapors were analyzed. The results demonstrate that doped SnO significantly affects the sensitivity, response time, and recovery time of the PANI material. več

建立气相色谱快速检测植物性食品中氟啶虫酰胺残留量的方法。对气相色谱检测方法中植物性食品提取溶剂、凝胶渗透色谱净化技术（GPC）收集时间、固相萃取小柱、气相色谱柱等进行了分析，建立了检测植物性食品中氟啶虫酰胺残留量的方法，并对该方法的检测范围、检测低限进行分析，最后用建立的方法测定了7种植物性食品的添加回收率及精密度。建立的检测植物性食品中氟啶虫酰胺残留量的方法为：将样品用乙酸乙酯均质提取，提取液经凝胶渗透色谱仪（净化收集时间为7~14 min）和氨基SPE小柱净化，乙酸乙酯定容，用带DB_1701毛细管柱气相色谱仪进行分析。氟啶虫酰胺质量浓度为10~500 μg/L时，其质量浓度与峰面积呈现良好的线性关系，相关系数为0.999，由此计算得出氟啶虫酰胺的检测低限为10 μg/kg。氟啶虫酰胺添加量为10，20，100，400 μg/kg时，7种植物性食品的添加回收率在82.0%~116.0%，标准偏差为0.06~3.17，精密度较高。建立的氟啶虫酰胺残留量检测方法快速、简便、经济，准确性和灵敏度都非常高。 The study was to establish a rapid method to determine flonicamid residues in seven kinds of plant-based foods by gas chromatography. In this method, experiments on the extraction solvents, gathering time by GPC, solid phase extraction cartridges and columns of GC were carried out. And, a rapid method to determine flonicamid residues in plant-based foods by gas chromatography was established. The detection range and the limit of low detection of the method were also studied, while the recoveries and the precision of flonicamid were analyzed too. The establish