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Investigating the sources of ammonia (NH3) in the atmosphere and the contribution of each source is essential for environmental pollution control. The presented dataset aims to provide 15N natural abundance (δ15N) data collected from different controlled treatments to fill the knowledge gap between insufficient data of soil δ15N-NH3 and accurately identifying atmospheric NH3 source apportionments. Our results showed that the overall δ15N-NH3 values emitted from soil ranged from −46.09 to 10.22‰, with an average of −26.81 ± 11.17‰. The mean δ15N-NH3 values under different nitrogen (N) application rates, N fertilizer types, air temperatures, soil moisture, soil pH, soil types, and land use types were −29.41 ± 10.91, −32.43 ± 6.86, −29.10 ± 10.04, −30.31 ± 6.18, −24.84 ± 13.76, −23.53 ± 7.66, and −14.57 ± 12.54‰, respectively. Significant correlations were observed between δ15N-NH3 values and soil pH, soil NO3−-N concentration, and NH3 volatilization. This unique database provides basic data and evidence for the qualification of atmospheric NH3 source apportionments under different study area conditions. [ABSTRACT FROM AUTHOR]

A passive double triangular damping (DTD) device with equivalent negative stiffness is proposed in this study. The DTD device consists of transmission systems and triangular damping systems. A mechanical model was developed to describe the force–displacement relationship of a triangular damping system, while the feasibility of both the system and model was evaluated using experimental tests. The theoretical analysis demonstrated that DTD was a form of damping with equivalent negative stiffness, and the equivalent expressions were generated. Finally, the prospect of application in the DTD-controlled isolation system was explored using numerical simulation. The results revealed that DTD was more effective than a lead–rubber bearing in reducing isolator displacement and rooftop acceleration when subjected to ground motions. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) volatilized from cropland significantly impacts the ecological environment and human health. The identification and quantification of atmospheric sources of NH3 from cropland are therefore important for NH3 emission reduction and air pollution control. Choosing appropriate nitrogen (N) fertilizer types is one of the key ways to reduce NH3 emissions from agricultural systems due to different N fertilizers with different emission factors. The natural abundance isotope of N (δ15N) values can well identify the source of NH3 volatilization, although there is rare research on δ15N-NH3 values volatilized when applying different types of N fertilizers. Here, we conducted an incubation experiment to study the characteristics of δ15N-NH3 values during the whole volatilization process after different N fertilizers were applied to the soil. The results show that the cumulative NH3 volatilization from urea (U), urease inhibitor fertilizer (UI), compound fertilizer (CF) and ammonium nitrate phosphate fertilizer (AP) treatment was 5.25 ± 0.00, 3.11 ± 0.00, 3.22 ± 0.19 and 1.38 ± 0.12 kg N ha−1 at the end of the 15-day incubation period, respectively. The average δ15N value of NH3 volatilized from the U, UI, CF and AP treatments was −36.02 ± 4.95, −29.08 ± 9.70, −35.18 ± 4.98 and −29.42 ± 4.33‰, respectively. Generally, the δ15N-NH3 values ranged from −41.33 to −6.30‰ during the NH3 volatilization process. The δ15N-NH3 value was lower in the U treatment than in the UI and AP treatments (p < 0.05), which suggests that N forms and the slow-release additions of different fertilizers, such as NO3−-N and urease inhibitors, can delay or slow down NH3 volatilization, resulting in relative isotopic enrichment. Therefore, the basic properties of different N fertilizers, the changes in soil NH4+-N and cumulative NH3 during the volatilization process significantly impacted the δ15N-NH3 values. [ABSTRACT FROM AUTHOR]

A structure supplemented with dampers may be over-critical damped as a result of more deformations in higher modes. Over-critical modal damping can significantly decrease structural displacements but also increase absolute accelerations and consequently the seismic forces. In dynamic analyses, undamped and complex mode superposition approaches are always employed due to their efficiency. However, the critical and over-critical damping issues are normally ignored because of more complexities introduced in the calculation of mode vectors. Particularly, the critical damping can result in the defectiveness of non-classically damped systems such that the analysis methods aforementioned become invalid. In this paper, a generalized complex mode superposition method is developed without the limit of modal damping. Orthogonality conditions among under-critical, critical, and over-critical damped modes are firstly constructed based on the linear algebra theory and the generalized complex mode superposition method is derived in time domain. Then, this approach is further extended to frequency domain and associating with the response spectra. The implementation and effectiveness of the proposed methods are presented in numerical examples. The results show that the over-critical damped modes have a remarkable effect on the structural response, particularly for the low stories. [ABSTRACT FROM AUTHOR]

In recent years, China has adopted numerous policies and regulations to control NO x emissions to further alleviate the adverse impacts of NO 3 −-N deposition. However, the variation in wet NO 3 −-N deposition under such policies is not clear. In this study, the southeastern area, with highly developed industries and traditional agriculture, was selected to explore the variation in NO 3 −-N deposition and its sources changes after such air pollution control through field observation and isotope tracing. Results showed that the annual mean concentrations of NO 3 −-N in precipitation were 0.67 mg L−1 and 0.54 mg L−1 in 2014–2015 and 2021–2022, respectively. The average wet NO 3 −-N depositions in 2014–2015 and 2021–2022 was 7.76 kg N ha−1 yr−1 and 5.03 kg N ha−1 yr−1, respectively, indicating a 35% decrease. The δ15N–NO 3 − and δ18O–NO 3 − values were lower in warm seasons and higher in cold seasons, and both showed a lower trend in 2021–2022 compared with 2014–2015. The Bayesian model results showed that the NO x emitted from coal-powered plants contributed 53.6% to wet NO 3 −-N deposition, followed by vehicle exhaust (22.9%), other sources (17.1%), and soil emissions (6.4%) during 2014–2015. However, the contribution of vehicle exhaust (33.3%) overpassed the coal combustion (32.3%) and followed by other sources (25.4%) and soil emissions (9.0%) in 2021–2022. Apart from the control of air pollution, meteorological factors such as temperature, precipitation, and solar radiation are closely related to the changes in atmospheric N transformation and deposition. The results suggest phased achievements in air pollution control and that more attention should be paid to the control of motor vehicle exhaust pollution in the future, at the same time maintaining current actions and supervision of coal-powered plants. [Display omitted] • Air pollution control reduced wet NO 3 −-N deposition in a southeast area of China. • Changes of δ15N–NO 3 - and δ18O–NO 3 - were found during long-term observations. • Current contribution of vehicle exhaust was higher than that of coal-powered plants. [ABSTRACT FROM AUTHOR]

In accordance with current codes, a single-story single-bay reinforced concrete frame structure in municipal engineering in eight degree fortification area shall be designed as the first grade. This requirement is so rigorous that the designed cross-sectional area is too large. In order to coordinate the revision work of 'Code for seismic design of outdoor water supply, sewerage, gas and heating engineering', experiments have been carried out on six 1-2 scaled single-story single-bay concrete frame models under cyclic loading, the influence of different seismic grades on the seismic performance of structural model was investigated. Simulations using ABAQUS was done under the same loading. The results show that the seismic performance of the fourth grade models meets the seismic standard performance requirements, and the safety margin under second grade is enough. The lateral deformation ability of the single-story single-bay concrete frame is better than the first story in a multi-story structure because its axial compression ratio is small and its columns are all exterior. Seismic grade two is suggested for single-story single-bay concrete frame in municipal engineering in degree eight seismic fortification zone. [ABSTRACT FROM AUTHOR]

In order to study the seismic performance of the staircase in the cast-in-place reinforced concrete frame, a 1/2 scaled specimen of the structural unit composed of concrete frame and staircase was tested quasi-statically. The test demonstrated the failure mode and mechanism of the structural unit as a whole and those of its various components, and the load-carrying capacity, displacements and other aspects related to seismic behavior were also measured. The test shows that, when fully connected to the main structure with the conventional manner of construction, the staircase works as asymmetrically inclined bracings in the structure, resulting in its early cracking and fast damaging, and consequently, its functions, such as seismic rescue and evacuation, could not be ensured; meanwhile, it also causes irregular forces of the frame members, leading to the brittle failure of the column in one side of frame and then the complete failure of the specimen. The enclosed area of hysteretic loop of the specimen is relatively small and its peak value of load reaches high but, after that, the capacity decreases fast. The rigid connection between the frame column and the supporting beam of the stair platform on the half story makes some frame columns, which are already in complex state of loading, the short columns, leading to the local collapse of such column and failure in other parts of the frame suddenly. Therefore, the staircase connected to the concrete frame with such a conventional manner as mentioned above is adverse to seismic resistance of the structure. [ABSTRACT FROM AUTHOR]

Employing geostatistical methods and GIS technology, this paper studied the spatial distribution characteristics of pH, organic matter, CEC, total nitrogen, available phosphorus and slowly available potassium in cultivated soils of Xinhui District, Jiangmen City. All the test variables were normally or log normally distributed. Semivariogram analysis showed that soil nutrients were moderately spatially-dependent in a given spatial range, except that soil total nitrogen was strongly spatially-dependent. It was shown from Kriging analysis that soil pH and CEC was the highest in the northeast, and soil organic matter content was higher in the middle and northeast investigation region. The area with 1.5-2.0 g x kg(-1) soil total nitrogen content accounted for 75.7% of the investigated region, mainly distributed in the west and east, that with > 40 mg x kg(-1) soil available phosphorus content was accounted for 48.7%, mainly distributed in the west and northeast, and the area that slowly available potassium content was 160-350 mg x kg(-1) accounted for 48.1%, mainly distributed in the east, northeast and the middle.