Abstract
Although indoor environmental monitoring data are increasingly available, they often fail to accurately capture personal environmental perception, comfort, and satisfaction. This ...disconnection has led to a growing interest in using real-time feedback from building users to improve the control of heating, ventilation, and air-conditioning systems and reduce energy waste. However, traditional questionnaire-based surveys only provide a snapshot at the time of investigation and suffer from a variety of bias sources. To address this, this paper proposes a novel camera-based method for estimating perceived indoor air quality and environmental satisfaction by analysing facial expressions. We conducted indoor air pollution exposure experiments on 24 healthy adults in twin environmental chambers. Their changes in facial expressions were compared between different exposure conditions and the potential correlation between facial expressions and perceived air quality, environmental satisfaction, and self-reported sick building syndrome symptoms was explored. Preliminary results indicate that a common RGB camera can repeatably detect facial expressions from the same subject. Also, results from a subset of five subjects suggest moderate differences in concentration, calmness, contemplation, and tiredness expressions between the two air quality conditions.
To evaluate a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and compare it with RT-PCR.
...We designed primers specific to the orf1ab and S genes of SARS-CoV-2. Total viral RNA was extracted using the QIAamp Viral RNA Mini Kit. We optimized the RT-LAMP assay, and evaluated it for its sensitivity and specificity of detection using real-time turbidity monitoring and visual observation.
The primer sets orf1ab-4 and S-123 amplified the genes in the shortest times, the mean (±SD) times were 18 ± 1.32 min and 20 ± 1.80 min, respectively, and 63°C was the optimum reaction temperature. The sensitivities were 2 × 101 copies and 2 × 102 copies per reaction with primer sets orf1ab-4 and S-123, respectively. This assay showed no cross-reactivity with 60 other respiratory pathogens. To describe the availability of this method in clinical diagnosis, we collected 130 specimens from patients with clinically suspected SARS-CoV-2 infection. Among them, 58 were confirmed to be positive and 72 were negative by RT-LAMP. The sensitivity was 100% (95% CI 92.3%–100%), specificity 100% (95% CI 93.7%–100%). This assay detected SARS-CoV-2 in a mean (±SD) time of 26.28 ± 4.48 min and the results can be identified with visual observation.
These results demonstrate that we developed a rapid, simple, specific and sensitive RT-LAMP assay for SARS-CoV-2 detection among clinical samples. It will be a powerful tool for SARS-CoV-2 identification, and for monitoring suspected patients, close contacts and high-risk groups.
DC transmission helps to solve the decentralization of distributed wind power generation and other renewable power sources to enhance system performance. But the existence of surface charges by the ...corona makes earlier insulation failure and plays an important role during the development of the surface flashover. The influences of the ambient temperature and the polarity reversal voltage on the surface charge and the flashover of the heat-shrinkable polymer are not completely clear. In this paper, the carrier mobility and the volume conductivity were employed to explain the temperature dependent surface charge decay results. The initial surface charge density and decay rates served for analyzing the effects of polarity reversal voltage. Furthermore, the flashover experiments of the samples charged by the polarity reversal voltage at different ambient temperatures were conducted. Obtained results show that the descending speed of the surface charge becomes faster at higher temperature. An obvious temperature dependence of the carrier mobility and the volume conductivity is observed. Moreover, the surface charges of the samples charged by the voltage with shorter reversal time decay more rapidly. The flashover voltage increases with the increasing ambient temperature because of less accumulated surface charges in this condition. Considering the accelerated surface charge decay by the increasing temperature and easier charge accumulation during the steady negative period, attentions should be paid to the design of DC insulation and the security of operation.
Silicone rubber (SiR), as a basic insulating material, is widely used in insulators for HVDC transmission lines. Incorporation of nanoparticles could not only improve the insulating properties, but ...also alter surface charge behavior as a consequence. In HVDC transmission lines, corona discharge could even occur on well-designed insulators, which can inject charge into the insulator surface and influence dc flashover voltage. Direct fluorination is a method to change the surface chemical component of polymers, which could induce the corresponding changes in electrical properties of the surface layer, thus influencing surface charge behavior and dc flashover voltage. This paper tries to study the effects of fluorination time and mass fraction of nanoparticles on surface charge behavior and dc flashover voltage of SiR/SiO 2 nanocomposites. Samples were prepared by dispersing nano-SiO 2 into SiR matrix with the fraction of 0, 1, 3 and 5 wt% respectively. Then the direct fluorination of the samples were conducted in a stainless reaction vessel at 25 °C using a F 2 /N 2 mixture gas with 12% F 2 by volume at 0.05 MPa for 5, 10, 15 and 20 minutes. After corona discharge tests performed at room temperature with a relative humidity of ~ 40%, the decay curves of the surface potential were measured using an electrostatic voltmeter, and flashover tests were carried out under dc stress, of which the polarity was identical with the corona discharge. Obtained results show that the dc flashover voltage is affected by the surface charge, which varies with the fluorination time and mass fraction of nanoparticles. It is indicated that the direct fluorination can markedly improve the decay rate of surface charge, and raise the dc flashover voltage of SiR/SiO 2 nanocomposites.
In this study, researchers describe the clinical characteristics of coronavirus disease 2019 in a selected cohort of 1099 patients with laboratory-confirmed disease throughout mainland China during ...the first 2 months of the current outbreak.
Epoxy is widely used in electronic and electrical devices because of its excellent insulation properties. The addition of nanoparticles to epoxy could change the material structure and then charge ...behaviors are altered as a consequence. The accumulation of surface charge may cause electric field distortion, which would lead to surface flashover. In this paper, the samples were made by dispersing nano-scale boron nitride (BN) particles in Epoxy with the weight ratios of 5, 10, 20, 30, 40 wt%. The samples were charged by a dc corona triode system using needle-plate electrodes. The distribution of charges was measured with an electrostatic voltmeter and the effect of nanoparticles on charge accumulation and decay behavior was studied. A flashover test was carried out under a dc stress between two finger-type electrodes. The effect of nanoparticles on flashover characteristics and the relation between surface charging and surface flashover were also investigated. The results showed that the traps between nanoparticles and the polymer, which were introduced by the added nanoparticles, could cause surface charge accumulation. In addition, the flashover occurred at a lower voltage because of the accumulated charge on the sample surface.
Silicone rubber (SiR) is widely employed as an insulating material in transmission lines because of its excellent electrical properties and superior performance under wet and polluted conditions. ...However, the discharges that occur during operation can cause electrical erosion on the surface of silicone rubber insulators. The thermal conductivity of insulators has a correlation with the resistance to tracking and erosion. This study attempts to clarify whether the addition of boron nitride (BN) particles can improve the resistance to tracking and erosion of SiR by increasing its thermal conductivity. Before the tests, specimens were prepared by dispersing nano-BN particles into room temperature vulcanizing (RTV) silicone rubber at different loadings. In this paper, the dc test has been developed from the current IEC 60587 inclined plane tracking and erosion test to compare the phenomena occurring during the tests. Temperature distribution was observed by an infrared thermal imager. The experimental results indicate that the filled specimens have a lower degree of surface damage than the unfilled specimens. In addition, with the increase in content of fillers from 0 to 7 wt%, the thermal dissipation is improved and both the erosion depth and the weight loss show a decreasing trend, which proves the resistance of silicone rubber to tracking and erosion is improved.
GIS spacers made of epoxy resin always suffer from the flashover due to surface charge accumulation. Therefore, it is important to seek a new method to improve the performance of epoxy resin. The ...epoxy/SiC composites have been proven to have nonlinear conductivity and the potential of being used in the spacer manufacture because of their field grading function under DC voltage. A high temperature rise on the central conductor of GIS can cause a large temperature gradient along the spacers. Exploring the effects of temperature on the electrical properties of the epoxy/SiC composites is helpful in the design the space dependent SiC filler content in GIS spacers. In this paper, three temperatures 20, 50 and 70 °C were studed on the temperature dependent surface potential decay (SPD) and flashover characteristics of the epoxy/SiC composites. At 20 °C, the epoxy/SiC composites, especially the 14 vol % samples, have much better SPD performances and higher flashover voltages than the pure epoxy. As the temperature increases, the SPD performances of all samples are greatly improved. The SPD rate of the 0 vol % samples approaches that of the 6 vol % samples at 50 °C and the 14 vol % samples at 70 °C. When the temperature is over 50 °C, flashover of the epoxy/SiC composites occur at lower voltages compared with the pure epoxy resin. With a further increase of temperature from 50 to 70°C, the flashover voltages of all samples have a significant drop, indicating that the temperature effects on flashover fault must be included in the spacer design and manufacture.
In this paper, an advanced surface-grafting method is reported to improve the high-temperature performance of biaxially oriented polypropylene (BOPP) membranes. The leakage conductivity of the ...surface-grafted films decreases by 98% at 85 °C. The decline in the leakage loss contributes to the 99% charge-efficiency at 85 °C. The dielectric constant increases by 7%. The DC breakdown strength grows by 43% at 85 °C. The maximum energy storage density goes up from 1.45 to 2.77 J/cm 3 at 85 °C. The surface-grafted BOPP film exhibits outstanding energy density and charge-discharge efficiency characteristics. This research provides a theoretical reference for improving the performance of capacitor film based on surface modification.
PDF
