The comparative transient prediction on hydrodynamic characteristics and flow field properties of pump-jets with accelerating and decelerating ducts.

Pump-jet holds a pivotal position in various marine applications, underscoring the need for comprehending their transient behavior for the purpose of design enhancement and performance refinement. This paper employs Reynolds-averaged Navier-Stokes equations method in conjunction with Detached Eddy Simulation model. The study delves into the ramifications of accelerating and decelerating ducts, distinguished by camber f and attack angles α, on transient hydrodynamic characteristics. The hydrodynamic characteristics are investigated numerically, after the validation of the numerical methodology by comparing simulation outcomes against experimental results. Subsequently, the study delves into propulsion characteristics, followed by an exploration of time-domain and frequency-domain data transformed through fast Fourier transform to analyze thrust fluctuations and pulsating pressures. Additionally, a detailed examination of pressure distribution and velocity field is provided, aiming to dissect the mechanisms through the variations in f and α influence the flow field. Findings suggest that the outlet velocity of accelerating ducts significantly surpasses the inlet velocity, a behavior contrasted by decelerating ducts. Notably, the patterns of accelerating and decelerating ducts resulting from alterations in f exhibit consistent characteristics with those brought about by changes in α. However, several opposite characteristics surface in transient flow field due to the distinct modifications in the duct profile. Furthermore, by considering vorticity magnitude distribution and vortices, a comparative analysis elucidates the effects of varying f and α on rotor and stator trailing vortices. This contributes to understanding the flow instability mechanism under differing duct configurations. It is evident that changes in f and α exert significant influence on both performance and flow field.

[Nutrients and Ecological Stoichiometry Characteristics of Typical Wetland Soils in the Lower Yellow River].

Carbon, nitrogen, phosphorus, and potassium in the soil are the necessary nutrient elements for plant growth, and their contents and ecological stoichiometry can reflect the status of soil quality and nutrient limitation. The Huayuankou Yellow River Floating Bridge Wetland in the lower Yellow River was selected as the research object. The methods of ANOVA, redundancy analysis, and linear regression fitting were used to study the contents of organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), and their ecological stoichiometric ratios as well as the limiting elements of soil nutrients, and the key physicochemical properties that affect soil nutrients and their ecological stoichiometry in the wetland were revealed. The results showed that the mean values of ω(SOC), ω(TN), ω(TP), ω(TK), ω(AN), ω(AP), and ω(AK) in wetland soil were 5.46 g·kg-1, 0.60 g·kg-1, 0.28 g·kg-1, 17.06 g·kg-1, 13.75 mg·kg-1, 6.54 mg·kg-1, and 158.56 mg·kg-1, respectively, which showed an increasing trend from the river bank to the shoaly land and were generally higher at the high vegetation coverage areas than at the low vegetation coverage areas. There were significant correlations among SOC, TN, TP, and TK. Soil C/P, C/K, N/P, and N/K showed a consistent trend with soil nutrients, whereas C/N showed the opposite. The coefficients of variation of SOC, TN, AN, N/P, and N/K in the soil exceeded 50.00%, with significant spatial differences. The average value of C/N in wetland soil was 11.882, which was close to the average level of soils in China, whereas the average values of C/P and N/P were 49.119 and 4.516, respectively, both of which were lower than the average level of soils in China, and the N/P of soil was far less than 14, which indicated that N was limited in the soil. The proportion of clay and electrical conductivity combined to explain 61.4% and 43.9% of the variation in the soil nutrients and their ecological stoichiometry, respectively, which were the dominant soil physicochemical properties affecting the soil nutrients and their ecological stoichiometry of Huayuankou Yellow River Floating Bridge Wetland. The research results are helpful to improve our knowledge of nutrients and their influencing factors in the wetland soil of the lower Yellow River and provide an important scientific basis for the ecological restoration and management of the wetland in the lower Yellow River.

Can Green-Technology Innovation Reduce Atmospheric Environmental Pollution?

Rapid economic growth leads to such problems as resource scarcity and environmental degradation. Local governments successively take measures such as technological innovation to solve atmospheric environmental pollution; however, technological innovation fails to fundamentally alleviate atmospheric environmental pollution. Therefore, local governments come to realize the importance of green-technology innovation, which means an inevitable choice for various countries in the world to seek long-term development and win competitive advantage. Under such circumstances, this paper chooses the panel data of 30 provinces and regions in China from 2005 to 2018, takes environmental regulation as the threshold variable, and empirically analyzes the relationship between green-technology innovation and atmospheric environmental pollution by constructing a Spatial Measurement Model and Panel Regression Model. As evinced, green-technology innovation has a significant inhibitory effect and a spatial spillover effect on atmospheric environmental pollution. When environmental regulation reaches a level of intensity, green-technology innovation can effectively curb atmospheric environmental pollution. Accordingly, relevant parties should strengthen green-technology innovation, coordinate the development of the governance system of green-technology innovation, establish a joint prevention and control mechanism, increase the investment in green technology research and development, and augment the role of green-technology innovation.

Effects of heavy rain on the concentrations and forms of carbon, nitrogen and phosphorus in urban rivers of northern China.

Non-point source pollution caused by rainfall runoff is an important pollution source for river water. To explore the impact of heavy rain on urban river water environments, this paper studied the changes in carbon, nitrogen, and phosphorus levels, composition, and structure in the river water of Kaifeng, China, during the heavy rain in July 2021. The results showed that the concentrations of different forms of carbon, nitrogen, and phosphorus all increased under the effect of the heavy rain. The increase of phosphorus in the river was the largest, and that of carbon was the smallest. The most significant pollution from carbon, nitrogen, and phosphorus occurred in the HJ River. Colored dissolved organic matter (CDOM) was present in the form of macromolecules after the rain, and the degree of humification was deeper compared with before the rain. But heavy rain did not affect the CDOM composition in urban rivers. The spectral slope (SR) and the absorption coefficient at 240 nm to 420 nm (E2/E4) values showed that the CDOM was dominated by exogenous input after the rain, with endogenous pollution again becoming the main factor one week after the rain.

Effect of algal blooms outbreak and decline on phosphorus migration in Lake Taihu, China.

Algal blooms (ABs) can affect the migration of phosphorus (P) among sediments, interstitial water and overlying water. It is important to analyze the characteristics of P and their interactions in the three media during ABs. A 5-month field study (June to October in 2016) was conducted in Zhushan Bay of Lake Taihu. P fractions, P adsorption characteristics and P diffusion fluxes at the sediment-water interface (SWI) were investigated. During the outbreak period of ABs from June to August, labile P concentrations in the sediment measured by diffusive gradients in thin films (DGT-labile P) and its diffusion fluxes across the SWI increased significantly. The equilibrium P concentration (EPC0) of the sediment was higher than the PO43--P concentration in the overlying water. During the period of decline of ABs from September to October, the concentrations and diffusion fluxes of DGT-labile P sharply decreased. However, the sediment total P (TP), overlying water TP, total dissolved P (TDP) and PO43--P concentrations increased. These results show that the ability of sediment solids to supplement interstitial water labile P was significantly enhanced by the outbreak of ABs. Labile P was then intensively released into the overlying water by interstitial water. Degraded algae became a crucial P source during the period of decline of ABs. P from the degraded algae was re-released to the sediment and overlying water. The observed DGT-labile P and DGT-labile Fe coupling in June, September and October confirmed the Fe redox-driven P release mechanism in sediment during these periods. The decoupling of DGT-labile P and DGT-labile Fe was observed in July and August and was probably caused by algal decomposition, labile organic P degradation and/or sulfate reduction in sediment stimulated by the ABs outbreak.

A novel method for quantifying human disturbances: A case study of Huaihe River Basin, China.

Human disturbances have become the main factors affecting the ecological environment. Therefore, evaluating the intensity of human disturbances is of great significance for ensuring effective regional conservation and ecosystem management. In this study, we constructed a novel method to quantify human disturbances based on three components of human disturbances into three types, namely naturalness transformation, natural resource consumption, and pollutant emissions. These components were quantified using the land use naturalness index (LNI), resource consumption index (RCI), and pollution emission index (PEI). Based on these three indicators, the human disturbances index (HDI) was calculated to reflect the intensity of human disturbances. In addition, remote sensing (RS), geographic information system (GIS), and multisource data were combined in the HDI method, taking into account the temporal variability of input parameters to achieve more convenient and comprehensive dynamic monitoring and evaluation of human disturbances. The applicability and effectiveness of the HDI method were assessed in the Huaihe River Basin, China. The obtained results revealed an increase and decrease in the intensities of human disturbances in the Huaihe River Basin from 1990 to 2005 and from 2010 to 2018, respectively. In addition, areas with a high level of human disturbances in the 1990-2005 period were mainly concentrated in the agricultural and industrial areas, while those in the 2010-2018 period were mainly observed in urban areas. This change was mainly due to a decrease in the pollutant emission amounts from agricultural and industrial lands and a marked increase in resource consumption in urban areas. This study provides theoretical guidance for regional conservation in the Huaihe River Basin and a new method for quantifying human disturbances.

Response of organic phosphorus in lake water to environmental factors: A simulative study.

Transformation of organic phosphorus (P) is directly related to a range of environmental factors, therefore exploring their relationships is vital to understanding the biogeochemical cycling of P and its significance in eutrophication of lake waters. In this study, a series of experiments were conducted to simulate the organic P transformation in the water under the influence of dissolved oxygen (DO), temperature and phytoplankton growth. Results showed that the transformation rate of total organic P increased with temperature, ranging from 0.02 to 0.25 mg L-1 day-1 at 5 °C, and from 0.04 to 0.72 mg L-1 day-1at 30 °C. The transformation rate of total organic P was significantly higher under anaerobic conditions than that under aerobic conditions at 20 °C and 30 °C, indicating that DO is a more important factor for the transformation of total organic P at the high temperature. However, different compounds of organic P responded differently to environmental factors. The change of orthophosphate monoester (Mono-P) content was consistent with that of total organic P when the temperature and DO were the same, but the transformation rates of phosphonate and DNA in the water were less affected by changes of temperature and DO. Additionally, the transformation rate of Mono-P was increased by the growth of phytoplankton when it was used as a P source. Although the relationships between alkaline phosphatase (ALP) activity and organic P are complex, ALP may be the main factor affecting the transformation of organic P at lower temperatures.

Algorithms for the electronic and vibrational properties of nanocrystals.

Solving the electronic structure problem for nanoscale systems remains a computationally challenging problem. The numerous degrees of freedom, both electronic and nuclear, make the problem impossible to solve without some effective approximations. Here we illustrate some advances in algorithm developments to solve the Kohn-Sham eigenvalue problem, i.e. we solve the electronic structure problem within density functional theory using pseudopotentials expressed in real space. Our algorithms are based on a nonlinear Chebyshev filtered subspace iteration method, which avoids computing explicit eigenvectors except at the first self-consistent-field iteration. Our method may be viewed as an approach to solve the original nonlinear Kohn-Sham equation by a nonlinear subspace iteration technique, without emphasizing the intermediate linearized Kohn-Sham eigenvalue problems. Replacing the standard iterative diagonalization at each self-consistent-field iteration by a Chebyshev subspace filtering step results in a significant speed-up, often an order of magnitude or more, over methods based on standard diagonalization. We illustrate this method by predicting the electronic and vibrational states for silicon nanocrystals.

[Cloning and sequence analysis of full-length cDNA of secoisolariciresinol dehydrogenase of Dysosma versipellis].

OBJECTIVES: To obtain the full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene from Dysosma versipellis by RACE PCR,then investigate the character of Secoisolariciresinol Dehydrogenase gene. METHODS: The full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene was obtained by 3'-RACE and 5'-RACE from Dysosma versipellis. RESULTS: We first reported the full cDNA sequences of Secoisolariciresinol Dehydrogenase in Dysosma versipellis. The acquired gene was 991bp in full length, including 5' untranslated region of 42bp, 3' untranslated region of 112bp with Poly (A). The open reading frame (ORF) encoding 278 amino acid with molecular weight 29253.3 Daltons and isolectric point 6.328. The gene accession nucleotide sequence number in GeneBank was EU573789. Semi-quantitative RT-PCR analysis revealed that the Secoisolariciresinol Dehydrogenase gene was highly expressed in stem. Alignment of the amino acid sequence of Secoisolariciresinol Dehydrogenase indicated there may be some significant amino acid sequence difference among different species. CONCLUSION: Obtain the full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene from Dysosma versipellis.

Variations of different dissolved and particulate phosphorus classes during an algae bloom in a eutrophic lake by 31P NMR spectroscopy.

Characterization of phosphorus (P) pools is vital to understanding the contribution of P to water eutrophication. In this study, dissolved and particulate P classes during an algae bloom in Lake Taihu, as well as their relationships with the main environmental factors, were analyzed based on solution 31P NMR. The results showed that dissolved P was dominated by orthophosphate (Ortho-P) in heavily polluted regions and by orthophosphate monoester (Mono-P) and orthophosphate diester (Diester-P) in lightly polluted regions, indicating that the main dissolved P classes varied with the degree of lake pollution. The difference in the temporal variation patterns of dissolved P classes revealed that dissolved Ortho-P is the preferred class, and its concentration may be affected by major primary producers. It also revealed that dissolved Mono-P is prone to accumulation under the effects of algal blooms, especially in heavily polluted regions. The main particulate P classes were similar to those of dissolved P, but their variation trends were the same in different lake regions. There were significant positive correlations between the major particulate P classes and Chl a during the majority of the sampling period, indicating that living algal cells have a major contribution to particulate P. Obvious temporal variations of P classes may affect the bioavailability and dynamics of P in the water of Lake Taihu, but the particle reactivities of the main inorganic and organic P classes were similar. Therefore, they have little effect on P partitioning between the dissolved and particulate phases.

Parallel self-consistent-field calculations via Chebyshev-filtered subspace acceleration.

Solving the Kohn-Sham eigenvalue problem constitutes the most computationally expensive part in self-consistent density functional theory (DFT) calculations. In a previous paper, we have proposed a nonlinear Chebyshev-filtered subspace iteration method, which avoids computing explicit eigenvectors except at the first self-consistent-field (SCF) iteration. The method may be viewed as an approach to solve the original nonlinear Kohn-Sham equation by a nonlinear subspace iteration technique, without emphasizing the intermediate linearized Kohn-Sham eigenvalue problems. It reaches self-consistency within a similar number of SCF iterations as eigensolver-based approaches. However, replacing the standard diagonalization at each SCF iteration by a Chebyshev subspace filtering step results in a significant speedup over methods based on standard diagonalization. Here, we discuss an approach for implementing this method in multi-processor, parallel environment. Numerical results are presented to show that the method enables to perform a class of highly challenging DFT calculations that were not feasible before.

[Refining sample preparation procedures for solution 3P-NMR analysis of organic P in sediment].

Solution phosphorus-31 nuclear magnetic resonance spectroscopy (31P-NMR) is a novel technology in characterization of organic phosphorus (P) composition in sediments. This study was aim to refine sample preparation procedures for 31P-NMR, including determination of sample pretreatment, extraction time, sample to extractant ratio and concentration method. The results showed that recovery of P with air dried sample treatment was higher than that for the fresh samples. Most of the P was extracted within the first 8 hours, and the time could extend to 12 to 16 hours in order to improve the recovery of P. Using the extraction ratio [m(sediment): V(extractant)] of 1:8 received more spectral signals compared to 1:20 when both the extracts were concentrated at the same time. No evident loss of P was found when the extract was concentrated at 28 degrees C followed by centrifugation under low temperature.

Evolution of magnetism in iron from the atom to the bulk.

The evolution of the magnetic moment in iron clusters containing 20-400 atoms is investigated using first-principles numerical calculations based on density-functional theory and real-space pseudopotentials. Three families of clusters are studied, characterized by the arrangement of atoms: icosahedral, body-centered cubic centered on an atom site, and body-centered cubic centered on the bridge between two neighboring atoms. We find an overall decrease of magnetic moment as the clusters grow in size towards the bulk limit. Clusters with faceted surfaces are predicted to have magnetic moment lower than other clusters with similar size. As a result, the magnetic moment is observed to decrease as function of size in a nonmonotonic manner, which explains measurements performed at low temperatures.