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Performance of various commercial TiO <sub/>2</sub> in photocatalytic degradation of a mixture of indoor air pollutants: Effect of photocatalyst and operating parameters
摘要： Photocatalytic oxidation (PCO) air cleaners can be installed in air handling units to reduce occupants’ exposure to hazardous gases, boost indoor air quality, and concomitantly lower HVAC energy consumption by lowering the required ventilation rate. In this work, photocatalytic activity of four commercialized titanium dioxide photocatalysts (P25, PC500, UV100, and S5-300A) for treating a mixture of seven prevalent volatile organic compounds (VOCs) were assessed in a continuous flow reactor. The impacts of major experimental factors namely concentration (15-100 ppb), relative humidity level (0-60% at 23?C), and residence time (0.012-0.05 s) on the removal efficiency and by-products generation were examined. Photocatalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). UV100 possessed the highest values for total VOC removal efficiency, which could be attributed to its large surface area, high porosity, good crystallinity, and large population of surface hydroxyls. Regarding relative humidity, two dominant trends were found: i) increasing the humidity resulted in lower removal efficiencies, or ii) existence of an optimum humidity level in some cases. The treatment efficiency followed the order: alcohols > ketones > aromatics > alkanes. The main by-products in the gas phase were formaldehyde, acetaldehyde, acetone, and propionaldehyde.
关键词： titanium dioxide,volatile organic compounds,indoor air quality,photocatalytic oxidation,relative humidity,residence time,by-products
更新于2025-09-23 15:22:29
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Agar-coated fiber Bragg grating sensor for relative humidity measurements: influence of coating thickness and polymer concentration nm
摘要： The importance of humidity control is spreading through a broad spectrum of applications, from food and pharmaceutical industries to biomedical and chemical fields. During the last decades, the growing interest in fiber Bragg gratings (FBG) led to new approaches and applications for the humidity measurement by means of the deposition of hygroscopic materials on gratings. The influence of the coating material and its features such us coating thickness (tk) and concentration (wt%) on static and dynamic metrological properties have been investigated in the literature. In this study, four agar-coated FBG sensors for humidity measurements have been fabricated, and the influence of tk and wt% on the sensors’ sensitivity and response time has been experimentally assessed. Sensitivity increases with tk and wt%: for instance, at 1 wt% it was 0.0024 nm·%-1 and 0.0052 nm·%-1 for tk=87 μm and tk=212 μm, respectively. Results showed that also the response time increased with tk and wt%: for instance, at 1 wt% it was 56.7 s and 107.6 s for tk=87 μm and tk=212 μm, respectively.
关键词： Moisture sensitive polymers,Hygroscopic materials,Relative humidity sensing,Fiber Bragg grating sensors,Fiber optic sensors
更新于2025-09-23 15:22:29
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Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes
摘要： The properties of multi-wall carbon nanotubes decorated with iridium oxide nanoparticles (IrOx-MWCNTs) are studied to detect harmful gases such as nitrogen dioxide and ammonia. IrOx nanoparticles were synthetized using a two-step method, based on a hydrolysis and acid condensation growth mechanism. The metal oxide nanoparticles obtained were employed for decorating the sidewalls of carbon nanotubes. Iridium-oxide nanoparticle decorated carbon nanotube material showed higher and more stable responses towards NH3 and NO2 than bare carbon nanotubes under different experimental conditions, establishing the optimal operating temperatures and estimating the limits of detection and quantification. Furthermore, the nanomaterials employed were studied using different morphological and compositional characterization techniques and a gas sensing mechanism is proposed.
关键词： carbon nanotubes,relative humidity effect,metal nanoparticles,iridium oxide,chemoresistive gas sensor
更新于2025-09-23 15:22:29
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Investigation of photovoltaic thermoelectric air-conditioning system for room application under tropical climate
摘要： Photovoltaic thermoelectric air-conditioning system (PT A/C) system could be a greater option compared to conventional A/C system as it is Freon-free and absence of moving parts. This study investigated the cooling and dehumidification performance of a PT A/C that is solely powered by solar energy under tropical climate conditions. The system is built with 9 pieces of thermoelectric to provide cooling for a test chamber of 3.6 m3 volume. The effect of input current on the system’s cooling and moisture removal rate were investigated and results showed that 5 A is the optimum current level, providing an average of 181 W cooling capacity and 0.14 ltr/hour of moisture removal rate at the given ambient conditions. During the operation, indoor temperature of the test chamber was 4 °C lower than the unconditioned chamber and 7.7 °C compared to the ambient temperature. Whereas the indoor relative humidity varies between 58~83 %. Furthermore, for a 12 hours operation, the system consumes 1.45 kWh of energy, and delivered temperature between 23.8 to 27.8 oC at 5 A.
关键词： Air-conditioning,Cooling,Relative humidity,Thermoelectric
更新于2025-09-23 15:21:01
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Effect of relative humidity during the preparation of perovskite solar cells: Performance and stability
摘要： Humidity is one of the main environmental factors that limits performance and stability of perovskite solar cells (PSC); it plays a critical role during the preparation of the perovskite film, influencing the crystal growth. In this work, it is investigated the effect of the relative humidity (RH) and type of atmosphere (nitrogen vs air) used during the deposition of both perovskite layer and hole extraction layer (HEL). While humidity and oxygen seem not to affect the HEL deposition step, the perovskite layer is notoriously influenced by the RH and by the presence of oxygen during its deposition. Until 10% of RH, the performance of devices prepared with a triple-cation perovskite layer deposited under a nitrogen environment was mostly unaffected, whilst for devices deposited in air that limit is lower. On the other hand, for high RH values (above 30%), devices prepared with a triple-cation perovskite layer deposited under N2 presented slightly better stability over time than the ones prepared under air. The best-performing device was prepared with a triple-cation perovskite layer deposited under dry air, presenting a power conversion efficiency of 16.7%. These results are of critical value when designing a plant for fabricating PSC showing that the perovskite layer may be deposited under a simple dry air atmosphere (RH < 1%).
关键词： Stability,Perovskite solar cells,Relative humidity effect,Crystal growth,Energy conversion
更新于2025-09-23 15:19:57
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High-performance optical fiber humidity sensor based on lossy mode resonance using a nanostructured polyethylenimine and graphene oxide coating
摘要： In this study, a rapid optical fiber sensor for humidity with high sensitivity and wide detection range has been constructed, based on lossy mode resonance (LMR). A thin film made of alternating polyethylenimine (PEI) and graphene oxide (GO) layers was selected as sensitive coating. It was deposited on a SnO2-sputtered fiber core in a dip-assisted layer-by-layer assembly. The structure and surface chemistry of the raw materials were investigated by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Key properties such as sensitivity, linearity, hysteresis, stability and response and recovery times were characterized. The sensor exhibited excellent sensitivity, especially at high relative humidity (RH) levels, and short reaction and retrieval periods. This research provides a viable and practical way to fabricate high performance humidity optical fiber sensors with GO-based nanostructured coatings.
关键词： relative humidity sensor,layer-by-layer,breathing monitoring,graphene oxide,lossy mode resonance,Optical fiber sensor
更新于2025-09-19 17:15:36
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Simultaneous in situ temperature and relative humidity monitoring in mechanical ventilators using an array of functionalised optical fibre long period grating sensors
摘要： An array of optical fibre long period gratings (LPGs) has been demonstrated for biomedical application to monitor temperature and relative humidity (RH) changes in the air delivered by a mechanical ventilator operating in different modes. The LPG array consists of two gratings, where one was kept bare to monitor the temperature change and the second was modified with 10 layers of silica nanoparticles to measure relative humidity. A mesoporous film was deposited on the surface of an optical fibre LPG using the layer-by-layer method. The sensor was calibrated in a bench model against a commercially available temperature and relative humidity sensor and sensitivity of the sensor was 0.46±0.01 nm/ oC and 0.53 nm/RH%, respectively. The tip of the sensor array was modified with reflection mirror and placed inside an endotracheal tube (ETT) and tested in typical clinical equipment to enable the in-situ real-time monitoring of humidity and temperature. Temperature and RH changes associated with the breathing frequency of 8 and 15 breaths per minute were successfully monitored using developed sensor array.
关键词： relative humidity (RH),Long period grating (LPG),healthcare monitoring,mechanical ventilation,endotracheal tube,temperature,optical fibre sensor,multiplexing
更新于2025-09-19 17:15:36
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Physics of Electrostatic Projection Revealed by High-Speed Video Imaging
摘要： Processes based on electrostatic projection are used extensively in industry, e.g., for mineral separations, electrophotography, or manufacturing of coated abrasives, such as sandpaper. Despite decades of engineering practice, there are still unanswered questions. In this paper, we present a comprehensive experimental study of the projection process of more than 1500 individual spherical alumina particles with a nominal size of 500 μm, captured by high-speed video imaging and digital image analysis. Based on flight trajectories of approximately 1100 projected particles, we determine the acquired charge and dynamics as a function of the relative humidity (RH) and the electric field intensity and compare the results with classical theories. For RH levels of 50% and above, more than 85% of distributed particles are projected, even when the electric field intensity is at its minimum level. This suggests that, beyond a critical value of the electric field intensity, the RH plays a more critical role in the projection process. We also observe that the charging time is reduced dramatically for RH levels of 50% and above, possibly due to the buildup of thin water films around the distributed particles, which can facilitate charge transfer. In contrast, projected particles at the 30% RH level exhibit excessive amounts of electric charge, between 2 and 4 times than that of the saturation value, which might be attributed to triboelectric charging effects. Finally, the physics of electrostatic projection is compared and contrasted with those of induced-charge electrokinetic phenomena, which share similar field-square scaling, as the applied electric field acts on its own induced charge to cause particle motion.
关键词： electric field intensity,high-speed video imaging,alumina particles,charge transfer,electrostatic projection,triboelectric charging,relative humidity
更新于2025-09-19 17:13:59
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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) - Optical fiber relative humidity sensor based on FBG embedded in SMS fiber structure
摘要： A novel optical fiber humidity sensor based on fiber Bragg grating (FBG) embedded in single-mode-multimode-single-mode (SMS) fiber structure is proposed. With relative humidity (RH) changing, the transmission spectrum of the SMS fiber structure shifts while the central wavelength of FBG remains unchanged. Numerical simulations of light distribution of the SMS structure have been carried out, analyzing the effects of different wavelengths of the input light, lengths and core diameters of the multimode fiber (MMF). The cross-sensitive problem of temperature has also been solved.
关键词： relative humidity measurement,FBG,Single-mode-multimode-single-mode fiber structure
更新于2025-09-16 10:30:52
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Elaboration of microporous CeO2 thin layers having nanocrystallites network controlled by Pluronic P123: Impact of key experimental parameters
摘要： Microporous ceria thin ?lms having nanocrystallites network were synthesized by evaporation-induced self-assembly process, using P123 amphiphilic copolymer as structure-directing agent. The impact of key experimental parameters, i.e., the sol ageing, the relative humidity (RH), the thermal treatment, on the thin layer elaboration were investigated. The results show that the organization of the nanoparticles is possible for a sol ageing time lower than 16 days and that the size of the mesophase within the thin layer increases with the relative humidity ?xed during the ?lm deposition. Finally, an increase of the thermal treatment temperature from 300 to 1000 °C leads to the formation of ?uorite-like dioxide material coupled with a loss of nanocrystallites organization and porosity due to the increase of the size of the crystallites. This loss of nanocrystallites organization is more drastic in the direction perpendicular to the surface and less pronounced along the surface. Thus, a compromise between the crystallization and the preservation of the porosity needs to be found.
关键词： relative humidity,P123 amphiphilic copolymer,evaporation-induced self-assembly,nanocrystallites network,thin films,thermal treatment,Microporous ceria,sol ageing
更新于2025-09-16 10:30:52