Synergistic Impacts of Climate Change and Human Activities on Spatiotemporal Organic Nitrogen Burial Variation in a Plateau Lake in Southwest China

The concentration and sources of organic nitrogen (ON) in lake sediment significantly affect the lake nitrogen cycle. However, the influencing factors and contributors to the ON accumulation rate (ONAR) are unclear. In this study, tree sediment cores from northern, eastern, and southern Dianchi Lake (DC-N, DC-E, and DC-S, respectively), sampled in July 2014, were used to study the effects of autochthonous and allochthonous sources on ON. The results showed that ON and the ONAR increased 2.4–5.1 and 2.6–4.8 times, respectively, from1900 to2000, especially since the 1980s, at which point algal blooms occurred more frequently. The ON contents decreased in the order: DC-S > DC-N > DC-E, whereas the ONAR values followed the order: DC-N > DC-S > DC-E, suggesting that the ONAR was influenced by ON content as well as depositional environmental conditions. The total concentrations of n-alkanes (n-C12 to n-C34) ranged from 4719.4 ng g− 1 to 61,959.6 ng g− 1 in the three sediment cores, each of which exhibited different n-alkanes characteristic variation with vertical depth. The sources of ON were mainly allochthonous (soil erosion and terrestrial plants) and autochthonous (algal and aquatic plants) in DC-S and DC-N, respectively, whereas they were primarily mixed planktonic and terrestrial sources in DC-E. Using the stochastic impacts by regression on population, affluence, and technology model to further examine the ONAR values revealed that 1% increase in temperature and nitrogen fertilizer can increase the ONAR by 73.8–86.2% and 73.2–151.3% in all sediments, especially in DC-S and DC-E. However, a 1% increase in construction area could reduce the ONAR by 2.4–14.2%, especially in DC-N. Overall, climate change and human activities determine the spatial and temporal ONAR variation in Dianchi Lake.

Pre-Jurassic Formation Lithological Composition and Reservoir Characteristic Variation Analysis. Core and Field Tests Analysis in Frolovsky and Shaimsky Petroliferous Regions

Analysis of the lithology of rocks of the pre-Jurassic complex and changes in the reservoir properties of rocks is one of the most important and difficult tasks for the formation of a petrophysical model for the interpretation of well logging data. Despite the long history of geological and geophysical study of deposits of the pre-Jurassic complex, a number of issues related to the reflection in the geophysical parameters of rocks and characteristics of reservoir properties have been studied insufficiently. This is due to the high variability of the lithological composition, textural and structural heterogeneity of the volcanic-sedimentary strata of the Turin Group. At present, the sediments of the pre-Jurassic complex are being actively studied - a representative core is purposefully selected, which is studied using an SCAL, including special methods, modern precision electrical, radioactive and acoustic studies are included in the complex of geophysical studies. The results of new studies are a good information base for refining the petrophysical model of an extraordinary object of study. The aim of this work was to analyze the lithology and reservoir properties of rocks, as well as to identify and classify the main groups of rocks that are possible reservoirs in the sediments of the pre-Jurassic complex within the Frolovsky and Shaimsky petroliferous regions.

Characteristic Variation of Ground Heat Flux and Net Radiation at Tropical Station in Ile-Ife, Osun State, Nigeria

Characteristic variation of ground heat flux and net radiation enhances the understanding of the significance of indicated trends of variability to everyday life and factors that might be responsible for such variations. This research work critically analyses some specific days with field data over grass-covered surface at Ile-Ife, Nigeria between ground heat flux and net radiation. For the field observations, an instrumented meteorological mast was set up at an experimental site (7°33’N, 4°35’E) located at Obafemi Awolowo University campus, Ile-Ife, Nigeria for a period of two weeks (31st May-14th June, 2013). The soil heat flux, net radiation and soil temperature from the soil heat flux plate; an all-wave net radiometer, and soil thermometer were recorded every 10 seconds and averaged over 2 minutes interval. The sampled data was stored in the data logger (Campbell Scientific, Model CR10X) storage module. After the removal of spurious measurement values (Quality Assurance and Quality Control), the data stored was further reduced to 30 minutes averages using the Microcal Origin (version 7.0) data analysis software. The results showed that the measured ground heat flux, HGM during the daytime increases until 1400 hrs with maximum value of about 136.86 Wm-2 and minimum value of about -72.87 Wm-2 at 0830 hrs (DOY 156). The measured net radiation, Rn value of 649.65 Wm-2 observed at 1400 hrs (DOY 156), represented the maximum value for the entire period of the study. -10.75 Wm-2 value observed at1800 hrs (DOY 154), represented the minimum value for the entire period of the study due to the cloudy condition of the sky which reduces the amount of incoming solar radiation reaching the earth surface.

Mechanical characteristic variation of ballastless track in high-speed railway: effect of train–track interaction and environment loads

Due to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from complex environmental loads, the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks. This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways, particularly focusing on the typical interface damage evolution between track layers. To this end, a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load (TGL) followed by the same cycle of the positive TGL. Subsequently, the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model. Finally, the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method. Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage; the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities; the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface, which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

Behind the curve: a comparison of historical sources for the Carnegie curve of the global atmospheric electric circuit

The “Carnegie curve” describes the diurnal variation of the global atmospheric electric circuit. It was originally found from atmospheric electric potential gradient (PG) measurements made on the Carnegie, effectively a floating atmospheric electrical observatory, which undertook global cruises between 1915 and 1929. These measurements confirmed that the single diurnal cycle PG variation, previously obtained in both polar regions, was global in extent. The averaged diurnal PG variation, represented by derived harmonic fits, provides a characteristic variation known as the “Carnegie curve”, against which modern measurements are still compared. The ocean air PG measurements were extensively described in reports of the Carnegie Institution of Washington (CIW) but widely used secondary sources of the Carnegie curve contain small differences, arising through approximations and transcription errors. Investigations using the historical CIW data show that the original harmonic fit coefficients are reproducible. Despite the inconsistencies, the secondary sources nevertheless mostly yield diurnal variations which fall within the variability of the original historical data.

Numerical Investigation on Metrological Fidelity of a Shielded Thermocouple Probe and the Effects of Geometrical Parameters

Proper design optimization and precise error characterization of temperature sensing-elements are rudimentary in the field of high accuracy gas temperature measurements. The intricate flow structures and heat transfer mechanisms related to a shielded thermocouple probe are studied in this paper using computational fluid dynamics and conjugate heat transfer (CFD/CHT) simulation tools. Owing to the probe’s novel geometry, it was a pre-requisite to characterize the metrological fidelity of the probe and the steady-state errors were determined from the simulations. The influence of certain geometrical parameters on the error characteristics of the probe was also investigated. The characteristic variation of the metrological fidelity of the probe with respect to those geometrical parameters should facilitate the optimization of the probe design.