The deterioration of visibility due to air pollutants and relative humidity has been a serious environmental problem in eastern Asia. In most previous studies, chemical compositions of atmospheric ...particles were provided using filter-based offline analyses, which were unable to provide long-term and in-situ measurements that resolve sufficient temporal variations of air pollution and meteorology, hindering the resolution of the relationship between air quality and visibility. Here, we present a year-long continuously measured data from a comprehensive suite of online instruments to investigate diurnal and seasonal impacts of the aerosol chemical compositions in PM2.5 on visibility seasonally and diurnally. The measured dry aerosol extinction at λ = 550 nm reached a closure with that predicted by aerosol compositions within 12%. However, the hygroscopic growth of particles under ambient RH could enhance the aerosol extinction by a factor of 2–6, matching the perceptive visibility of the public. Particulate ammonium nitrate was most sensitive to reducing visibility, while ammonium sulfate contributed the most to the light extinction. In spring and winter, the monsoon and stagnant air masses reduced the visibility and increased PM2.5 (>35 μg m−3). The moisture was found to substantially enhance the light extinction under RH = 60–90%, reducing visibility by approximately 15 km, largely attributed to hygroscopic inorganic salts. This study serves as a metric to highlight the need to consider the influence of RH, and aqueous reactions in producing secondary inorganic aerosols on atmospheric visibility, underpinning the more accurate mitigation strategies of air pollution.
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•The measured visibility differed from that of naked eye observation due to RH effect.•Ammonium nitrate was found to be most sensitive to visibility impairment.•Seasonality in the impact of hygroscopic aerosols on visibility was investigated.•Transmission of air pollutants by the northeast monsoon contributed to low visibility.•Stagnant air masses coupled with low PBLH resulted in low visibility.
This paper provides a synthesis of available in situ primary production (PP) measurements from the Pacific Arctic Region (PAR), collected between 1950 and 2012. Seasonal integrated primary production ...(IPP) across the PAR was calculated from 524 profiles, 340 of which were also analyzed to determine the average vertical distribution of PP rates for spring, summer and fall months. The Chirikov Basin and Chukchi Shelf were the most productive areas, with the East Siberian Sea, Chukchi Plateau and Canada Basin the lowest. Decadal-scale changes were indicated in the southern Chukchi Sea, and across Hanna Shoal. In the southern Chukchi Sea in August, IPP increased significantly from 113±35mgCm-2 d-1 in 1959 and 1960 to 833±307mgCm-2 d-1 in the 2000s. Increases in the magnitude of IPP were accompanied by variations in the vertical distribution, the subsurface peak observed in the 1959/60 was not present in the 2000s. The mechanism behind this change was undetermined but could have included changes in stratification, mixing or surface distribution of water masses as well as methodological differences. Over Hanna Shoal, the phytoplankton surface bloom now occurs earlier by several weeks compared to 1993, linked to increases in light due to earlier sea- ice retreat. In 1993 with sea ice still present in the region the surface bloom occurred in August, in 2002 and 2004 this same period was characterized by open water and low surface PP and strong subsurface production. This dataset provides a region-wide quantification of IPP and decadal trends and highlights the need for a cooperative monitoring program to observe the long-term impacts of climate change in the Arctic ecosystem.
Understanding how electrocatalysts function in a nucleophile oxidation reaction (NOR) on anode, replacing the oxygen evolution reaction (OER) of water splitting, is vital to the development of ...hydrogen generation and organic electrosynthesis. Here, we propose that for β-Ni(OH)2 and NiO, the NOR activity origins are β-Ni(OH)O containing electrophilic lattice oxygen and NiO(OH)ads containing electrophilic adsorption oxygen, respectively. For β-Ni(OH)2, NOR is a two-step, one-electron reaction, including an electrogenerated catalyst dehydrogenation reaction and a spontaneous nucleophile dehydrogenation reaction. Therefore, the NOR activity of β-Ni(OH)2 can be markedly regulated by tuning the lattice oxygen ligand environment. For β-Co0.1Ni0.9(OH)2, the onset potential of NOR with different nucleophiles is ∼1.29 V (1 M KOH), which breaks the bottleneck of ∼1.35 V for most nickel-based catalysts. Overall, we identify the activity origins and propose the design principles of nickel-based catalysts for NOR. These provide theoretical guidance for the development of NOR and organic electrosynthesis in practical industrial applications.
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•NOR activity origins of β-Ni(OH)2 and NiO are β-Ni(OH)O and NiO(OH)ads, respectively•First step for NOR of β-Ni(OH)2 is the electrogenerated catalyst dehydrogenation reaction•Second step for NOR of β-Ni(OH)2 is the spontaneous nucleophile dehydrogenation reaction•Explicit electrocatalyst design principle of β-Ni(OH)2 for NOR is proposed
Nucleophile oxidation reaction (NOR) is an emerging field to replace oxygen evolution reaction (OER) in overall water splitting. For β-Ni(OH)2, NOR is a two-step, one-electron reaction, including an electrogenerated catalyst dehydrogenation reaction from lattice hydroxyl to electrophilic lattice oxygen (β-Ni(OH)2 + OH− = β-Ni(OH)O + H2O + e−) and a spontaneous nucleophile dehydrogenation reaction (β-Ni(OH)O + HNu + e−Nu = β-Ni(OH)2). Based on this detailed mechanism, we propose the design principle of electrocatalysts for NOR such that the dehydrogenation potential of lattice hydroxyl can be regulated by tuning the lattice oxygen ligand environment of β-Ni(OH)2, thereby resulting in a steerable NOR performance.
Owing to low energy consumption and high-value-added products, the nucleophile oxidation reaction (NOR), as a rising half-reaction to replace the sluggish oxygen evolution reaction (OER) in overall water splitting, has been researched widely based on nickel-based electrocatalysts; however, the indeterminate nature of the NOR mechanism limits the development of this emerging field. Here, focusing on model catalysts, including β-Ni(OH)2 and NiO, we discover that their NOR activity origins are β-Ni(OH)O containing electrophilic lattice oxygen and NiO(OH)ads containing electrophilic adsorption oxygen, respectively. For β-Ni(OH)2, NOR is a two-step, one-electron reaction including an electrogenerated catalyst dehydrogenation reaction from lattice hydroxyl to electron-deficient lattice oxygen (β-Ni(OH)2 + OH− = β-Ni(OH)O + H2O + e−) and a spontaneous nucleophile dehydrogenation reaction (β-Ni(OH)O + HNu + e−Nu = β-Ni(OH)2). Hence, we report a general design principle of electrocatalysts for NOR that involves tuning of the lattice oxygen ligand environment to effectively change the dehydrogenation potential of β-Ni(OH)2, thus regulating NOR performance.
A thermo-mechanical model of directed energy deposition additive manufacturing of Ti–6Al–4V is developed using measurements of the surface convection generated by gasses flowing during the ...deposition. In directed energy deposition, material is injected into a melt pool that is traversed to fill in a cross-section of a part, building it layer-by-layer. This creates large thermal gradients that generate plastic deformation and residual stresses. Finite element analysis (FEA) is often used to study these phenomena using simple assumptions of the surface convection. This work proposes that a detailed knowledge of the surface heat transfer is required to produce more accurate FEA results. The surface convection generated by the deposition process is measured and implemented in the thermo-mechanical model. Three depositions with different geometries and dwell times are used to validate the model using in situ measurements of the temperature and deflection as well as post-process measurements of the residual stress. An additional model is developed using the assumption of free convection on all surfaces. The results show that a measurement-based convection model is required to produce accurate simulation results.
•Conditions were refined for using the heat flow meter (HFM) method in low U-value façades.•The variables were temperature difference, test duration and equipment accuracy.•An insufficient ...temperature difference led to deviations above 7%.•The test duration should be extended, as the temperature differences were low.•The accuracy of the temperature sensors had a considerable impact on the initial cycles of the test.
In situ measurements of low thermal transmittance façades are required to ensure compliance with energy performance strategies for new nearly zero-energy buildings (nZEB) and with energy policies for the transition of existing building stock to nZEB. The aim of this paper was to enhance the accuracy of the in situ measurement of low U-value façades, employing the widely used ISO 9869-1:2014 HFM method and exploring the limits of its conditions. To refine the testing conditions, three variables were analysed and compared with indications of ISO 9869-1:2014 and the existing literature: the temperature difference, the test duration and the accuracy of equipment. A continuous experimental campaign was conducted in a building mock-up. The findings showed that to accurately measure in situ low U-value façades, the temperature differences must be greater than those indicated in the existing literature. Temperature differences above 19 °C required a test duration of 72 h, while for lower temperature differences the test duration must be prolonged. The accuracy of temperature sensors had a greater impact on the accuracy of measurement in the initial cycles of the test. Likewise, the accuracy of ambient temperature sensors was found to have a considerable influence on the uncertainty of measurements.
Rainfall and soil moisture, SM, are two important quantities for modeling the interaction between the land surface and the atmosphere. Usually, rainfall observations are used as input data for ...modeling the time evolution of SM within hydrological and land surface models. In this study, by inverting the soil‐water balance equation, a simple analytical relationship for estimating rainfall accumulations from the knowledge of SM time series is obtained. In situ and satellite SM observations from three different sites in Italy, Spain, and France are used to test the reliability of the proposed approach in contrasting climatic conditions. The results show that the model is able to satisfactorily reproduce daily rainfall data when in situ SM observations are employed (correlation coefficient, R, nearly equal to 0.9). Furthermore, also by using satellite data reasonable results are obtained in reproducing 4 day rainfall accumulations with R‐values close to 0.8. Based on these preliminary results, the proposed approach can be adopted conveniently to improve rainfall estimation at a catchment scale and as a supplementary source of data to estimate rainfall at a global scale.
Key Points
A new method for estimating rainfall from soil moisture observations is proposed
The method provides reasonable results using both in situ ans satellite data
New possibilities for rainfall estimation at basin and global scale
Li-ion batteries experience mechanical stress evolution due in part to Li intercalation into and de-intercalation out of the electrodes, ultimately resulting in performance degradation. In situ ...measurements of electrode stress can be used to analyze stress generation factors, verify mechanical deformation models, and validate degradation mechanisms. They can also be embedded in Li-ion battery management systems when stress sensors are either implanted in electrodes or attached on battery surfaces. This paper reviews in situ measurement methods of electrode stress based on optical principles, including digital image correlation, curvature measurement, and fiber optical sensors. Their experimental setups, principles, and applications are described and contrasted. This literature review summarizes the current status of these stress measurement methods for battery electrodes and discusses recent developments and trends.
This paper presents a simulation tool chain for the prediction of thermal comfort in passive urban buildings during summer and under heat wave conditions. The tool chain encompasses EnergyPlus ...building energy model and the Urban Weather Generator and UrbaWind tools to consider the impacts of the urban environment on building loads. This chain of tools is computationally efficient and does not require notable expertise for the simulations. To assess its accuracy, this simulation results are compared to in situ measurements. This paper describes the measurement setup, analyzes the measurement results and reveals a satisfactory model accuracy through a comparison to the measurement data. The average nighttime urban heat island between July and September 2020 reached 2.31 °C in the city of Lyon. Not considering the urban heat island effect (employing rural weather files) in urban thermal simulations could induce a 1 °C bias in indoor air temperature predictions. This could also result in overpredicting the cooling potential of natural ventilation during summer. Key parameters of the simulation accuracy are identified. These are the action schedule of occupants in regard to opening devices (shutters, windows and doors) and the urban boundary layer height at night.
•An Urban Thermal Tool Chain simulates the thermal behaviour of urban buildings.•The developed UTTC is devoted to passive buildings under summer conditions.•The UTTC includes EnergyPlus, Urban Weather Generator, and UrbaWind.•In-situ measurements were carried out on four types of buildings in Lyon.•Remarkable correspondence between simulations and measurements.
•The two only blended SM products are assessed synchronously for the first time.•CCI has better errors statistics than SMOPS across most of the regions worldwide.•SMOPS can provide SM with acceptable ...accuracy over the gaps remaining by CCI.•The two SM products reveal potential to complement each other in applications.
Multiple soil moisture (SM) products have been produced based on observations from microwave satellite sensors nowadays, allowing for the acquisition of global SM dynamics in a timely manner. Currently, only two blended microwave SM products, namely the Climate Change Initiative (CCI) from the European Space Agency and the Soil Moisture Operational Product System (SMOPS) from the National Oceanic and Atmospheric Administration, are available with either better temporal or better spatial coverage than those of other SM products derived from a single sensor. However, an assessment and especially a synchronous comparison of these two products are still lacking, making it difficult to determine a better alternative in actual applications. In the present study, a comprehensive assessment of the two blended products was conducted with reanalysis SM data from the European Centre for Medium-Range Weather Forecasts and in-situ measurements from the International Soil Moisture Network. The scaling strategy of cumulative distribution function matching was used to remove the systematic differences in spatial mismatch between the satellite pixels and ground in-situ observations. The results indicated that CCI reveals overall better accuracy than that of SMOPS with both in-situ measurements and reanalysis data under different climate patterns. Specifically, the overall root mean square error (RMSE) with the in-situ measurements were 0.042 m3/m3 and 0.046 m3/m3 for CCI and SMOPS, respectively. Further investigation also confirmed that SMOPS could be a potential alternative over the regions where CCI is not available, since SMOPS has better spatial coverage than CCI.
•A new method (SHB-HFM) is used to measure a traditional wall R-value in situ.•The SHB-HFM is successfully used in a heterogeneous wall.•The method revealed to be in situ effective and ...expeditious.•The introduction of a baffle in the apparatus is presented and discussed.•A R-value of 0.56 m2 °C W−1 was measured for the tabique wall.
Improving the thermal performance of the historic building stock has the potential to revitalise these buildings and reduce the operational energy share. To achieve that, the first requirement should be to identify and clearly characterise the building stock. However, currently, there is a lack of knowledge regarding the thermal behaviour of traditional wall solutions, and, consequently, energy auditors often use assumptions and simplifications to predict it. Wrong estimations or excessive simplifications may have a severe impact on the thermal behaviour assessment and consequently on the effectiveness of the retrofitting measures. In the scope of buildings thermal comfort and energy efficiency, the thermal resistance of both the external and internal envelope is one of the most relevant parameters for the characterisation of building elements. This work investigates the in situ thermal resistance of a traditional wall solution (“tabique” wall) of a historic building located in the north region of Portugal. The Simple Hot Box - Heat Flow Meter Method (SHB-HFM), based on the procedure described in the standard ISO 9869, is considered in the present study and its applicability to heterogeneous traditional wall solutions is discussed. The importance of controlling the radiative part of the heat transfer onto the measuring sensors is highlighted, and new development to the method is proposed in this paper via the introduction of a baffle inside the SHB. Furthermore, a finite element computer model of the case study was developed in order to ensure that some important premises allowing improving the accuracy of the final results were achieved during the measurement period as well as to enhance the robustness of the obtained conclusions. The achieved results contribute to explore the applicability of the SHB-HFM to highly heterogeneous constructive solutions present in historic buildings, where the traditional HFM method may not be applicable. In addition, this research also aims to better understand the thermal behaviour of “tabique” walls, upon which the available information is scarce. The experimental measurements and numerical simulation results present a good agreement, and an R-value of 0.56 m2 °C W−1 is measured and computed.
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