The unreasonable application of nitrogen fertilizer poses a threat to agricultural productivity and the environment protection in Northeast China.Therefore,accurately assessing crop nitrogen requirements and optimizin...The unreasonable application of nitrogen fertilizer poses a threat to agricultural productivity and the environment protection in Northeast China.Therefore,accurately assessing crop nitrogen requirements and optimizing fertilization are crucial for sustainable agricultural production.A three-year field experiment was conducted to evaluate the effects of planting density on the critical nitrogen concentration dilution curve(CNDC)for spring maize under drip irrigation and fertilization integration,incorporating two planting densities:D1(60,000 plants ha^(-1))and D2(90,000 plants ha^(-1))and six nitrogen levels:no nitrogen(N0),90(N90),180(N180),270(N270),360(N360),and 450(N450)kg ha^(-1).A Bayesian hierarchical model was used to develop CNDC models based on dry matter(DM)and leaf area index(LAI).The results revealed that the critical nitrogen concentration exhibited a power function relationship with both DM and LAI,while planting density had no significant impact on the CNDC parameters.Based on these findings,we propose unified CNDC equations for maize under drip irrigation and fertilization integration:Nc=4.505DM-0.384(based on DM)and Nc=3.793LAI-0.327(based on LAI).Additionally,the nitrogen nutrition index(NNI),derived from the CNDC,increased with higher nitrogen application rates.The nitrogen nutrition index(NNI)approached 1 with a nitrogen application rate of 180 kg ha^(-1)under the D1 planting density,while it reached 1 at 270 kg ha^(-1)under the D2 planting density.The relationship between NNI and relative yield(RY)followed a“linear+plateau”model,with maximum RY observed when the NNI approached 1.Thus,under the condition of drip irrigation and fertilization integration in Northeast China’s spring maize production,the optimal nitrogen application rates for achieving the highest yields were 180 kg ha^(-1)at a planting density of 60,000 plants ha^(-1),and 270 kg ha^(-1)at a density of 90,000 plants ha^(-1).The CNDC and NNI models developed in this study are valuable tools for diagnosing nitrogen nutrition and guiding precise fertilization practices in maize production under integrated drip irrigation and fertilization systems in Northeast China.展开更多
To provide advanced diagnostic techniques for diagnosing the outlet temperature distribution and species concentrations of future advanced combustors,this study focuses on a dual-swirl single-dome rectangular combusto...To provide advanced diagnostic techniques for diagnosing the outlet temperature distribution and species concentrations of future advanced combustors,this study focuses on a dual-swirl single-dome rectangular combustor.Through the integration of multiple diagnostics,simultaneous measurement of outlet temperature distribution and species concentrations was achieved.The study validates the engineering applicability of these simultaneous measurements using tungsten-rhenium(W-Re)thermocouples and Coherent Anti-Stokes Raman Scattering(CARS),CARS and Tunable Diode Laser Absorption Spectroscopy(TDLAS),as well as Gas Analysis(GA)and Mass Spectrometry(MS).The results demonstrate that measurements by thermocouples and CARS exhibit good consistency and repeatability,with a relative deviation of less than 4%,fully meeting the requirements of engineering experiments.The spatial distribution reconstruction results of TDLAS can reflect the temperature distribution characteristics at the combustor outlet.Temperature comparison between TDLAS and CARS at single-point positions shows consistent results,with a relative deviation of less than 11%and 7%under both conditions,respectively.Simultaneous measurements by integrating GA and MS show high engineering applicability for the first time,meeting the requirements for measuring both inorganic species and free radicals at the combustor outlet.Under C_(1)condition,the relative deviations of four key species(Unburned Hydrocarbon(UHC),NO,O_(2),and CO_(2))remain within 2%,while that of NO_(2)is slightly higher at approximately 8%.Under C_(2)condition,the overall deviations increase for most species,with only O_(2)and CO_(2)maintaining relatively low deviations.The primary species of UHCs at the combustor outlet under both conditions are small molecular hydrocarbons(C_(3)-C_(8))and RO_(2)radicals,accounting for over 90%of total UHC.Specifically,RO_(2)species(R is C_(1)-C_(2)alkyl groups)are the predominant species,accounting for 74.3%and 82.1%of total RO_(2)under both conditions,respectively.These integrated diagnostic methods for temperature and species concentrations at the combustor outlet serve as a crucial reference for its engineering applications.展开更多
Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic ads...Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic adsorption model was established by coupling equations of mass,momentum and energy balance,and solved by finite element analysis.The simulation breakthrough curves fit well with the low-concentration CO_(2) adsorption experimental data,indicating the reliability of the established model.The distributions of concentration and temperature field in the column for CO_(2) adsorption and separation from CO_(2)/N_(2) were obtained.The sensitivity analysis of the adsorption conditions shows that the operation parameters such as feed flow rate,feed concentration,pellet size,and column height-to-diameter ratio produce a significant effect on the dynamic adsorption performance.The multi-physics coupled 2D axisymmetric model could provide a theoretical foundation and guidance for designing CO_(2) fixed-bed adsorption and separation processes,which could be extended to other mixed gases as well.展开更多
Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includ...Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimizationbased ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salinity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by timeseries data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency(NSE),Kling–Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R^(2)).Example analysis demonstrates that:①The proposed model can obtain excellent DO forecasting results;②the proposed model is superior to other comparison models;and③the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.展开更多
This paper presents the analysis of two-layer cilia induced flow of Phan-Thien-Tanner(PTT) fluid with thermal and concentration effect.The Phan-Thien-Tanner fluid model has been used in the analogy of mucus present in...This paper presents the analysis of two-layer cilia induced flow of Phan-Thien-Tanner(PTT) fluid with thermal and concentration effect.The Phan-Thien-Tanner fluid model has been used in the analogy of mucus present in the respiratory tract.The two-layer model approach was used due to the Peri Ciliary liquid Layer(PCL) and Airway Ciliary Layer(ACL) present on the epithelium cell in respiratory tract.The mathematical modelling of two-layer flow problem was simplified using long wavelength and small Reynold ’ s number approximation.The resulting differential equation with moving boundary gives exact solution for velocity,temperature and concentration profiles in two layers.The change in pressure has calculated by the results of velocity profile,also the pressure rise was evaluated by the numerical integration of pressure gradient along the channel wall.The impact of physical parameters on pressure rise,velocity,temperature and concentration profile was explained by the graphs.It can be seen from graphs that velocity and temperature profile are maximum in the inner layer of fluid(PCL) and concentration profile is maximum at outer layers of fluid(ACL).展开更多
A modified shear-lag model accounting for the effect of the tensile stiffness of the ma, trix is proposed for solving the stress redistribution due to the failure of fibers and matrix in unidirectionally fibre-reinfor...A modified shear-lag model accounting for the effect of the tensile stiffness of the ma, trix is proposed for solving the stress redistribution due to the failure of fibers and matrix in unidirectionally fibre-reinforced composites. The advantages of this model are simple, reasonable and accurate by comparison with the other similar modified shear-lag models. It can be further extended to study the stress redistribution with interfacial damage between fibres and matrix This paper quantitatively dis cusses the influence of the tensile stiffness ratio of matrix to fibre and of the fibre volume fraction on the stress concentration in the fibres and ma trix adjacent to cut fibres and matrix, and suggests that the influence of the matrix stiffness on the stress concentration can be neglected when the matrix stiffness is low, such as polymer matrix composites, and the fibre volume fraction is high. For other cases such as ceramic and metal matrix composites, the tensile load of the matrix cannot be neglected in the shear-lag analysis.展开更多
The TSI-3321 APS was used to measure concentration of atmospheric particulates in Ranjiaba region of Yubei District in Chongqing City during March 21- 29,2014,and the temporal variations in the hourly average mass and...The TSI-3321 APS was used to measure concentration of atmospheric particulates in Ranjiaba region of Yubei District in Chongqing City during March 21- 29,2014,and the temporal variations in the hourly average mass and number concentration and median particle diameter of PM10 and PM2.5 as well as their correlation with relative humidity were analyzed. The results showed that the three indicators of PM10 and PM2.5 except for the mass concentration correlated with relative humidity,of which the correlation between the mass median particle diameter and relative humidity was the best. The correlation coefficient R^2 between the mass median particle diameter of PM10（ PM2.5） and relative humidity was up to 0. 943（ 0. 832）. Therefore,relative humidity and pressure are key impact factors of indicators of particles.展开更多
Conventionally,soil cadmium(Cd)measurements in the laboratory are expensive and timeconsuming,involving complex processes of sample preparation and chemical analysis.This study aimed to identify the feasibility of usi...Conventionally,soil cadmium(Cd)measurements in the laboratory are expensive and timeconsuming,involving complex processes of sample preparation and chemical analysis.This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance(Vis-NIR)spectroscopy and portable X-ray fluorescence spectrometry(PXRF)to estimate regional soil Cd concentration in a time-and cost-savingmanner.The sensor data of Vis-NIR and PXRF,and Cd concentrations of 128 surface soils from Yunnan Province,China,were measured.Outer-product analysis(OPA)was used for synthesizing the sensor data and Granger-Ramanathan averaging(GRA)was applied to fuse the model results.Artificial neural network(ANN)models were built using Vis-NIR data,PXRF data,and OPA data,respectively.Results showed that:(1)ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation;(2)Fusion methods of both OPA and GRA had higher predictive power(R^(2))=0.89,ratios of performance to interquartile range(RPIQ)=4.14,and lower root mean squared error(RMSE)=0.06,in ANN model based on OPA fusion;R^(2)=0.88,RMSE=0.06,and RPIQ=3.53 in GRA model)than those based on either Vis-NIR data or PXRF data.In conclusion,there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.展开更多
A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlo...A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.展开更多
This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical ...This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.展开更多
In order to fill up the deficiency of the theoretical basis about fluoride formation during Bayan Obo iron concentrate roasting process, the thermodynamic conditions of the interactivity between the components of the ...In order to fill up the deficiency of the theoretical basis about fluoride formation during Bayan Obo iron concentrate roasting process, the thermodynamic conditions of the interactivity between the components of the gangue and calcium fluorite were studied by means of thermodynamic calculation, DTA-TG thermal analysis and XRD characterization. The results revealed that KF, NaF and SiF4 （gaseous） could he,formed during the roasting process, and the tendency of the generation of KF is greater than that of NaF or SiF4 in standard state. Besides, the results of roasting experiments showed that the products of KCaCO3 F and KCaF3 formed in the temperature range of 800-1250 ℃and KF appears when the roasting temperature was higher than 1250 ℃ in K2O-CaF2 system. For the Na2O-CaF2 system, the product of NaF appears at temperature higher than 1050 ℃. The formation reaction of gaseous SiF4 with solid phase CaO · SiO2 in SiO2-CaF2 system took place＂only＇at temperature higher than 1 150 ℃. In the natural potash feldspar-CaF2-CaO system, the fluorination reaction products involved KF at temperature higher than 1 270 ℃ , while in the natural aegirine-CaF2-CaO system, NaF formed at terhperature higher than 980 ℃ during roasting process.展开更多
Understanding metal accumulation at organ level in roots, leaves and seeds in O. glaberrima (OG) is crucial for improving physiological and metabolic aspects in growing Asian and African rice in salted areas. The micr...Understanding metal accumulation at organ level in roots, leaves and seeds in O. glaberrima (OG) is crucial for improving physiological and metabolic aspects in growing Asian and African rice in salted areas. The micro-analytical imaging techniques are required to reveal its accumulation and distribution within plant tissues. PIXE studies have been performed to determine different elements in rice plants. The existing microbeam analytical technique at the iThemba LABS will be applied for the 2D image mapping of fresh rice tissues to perform a concentration of low atomic mass elements (such as Al, Si, P, S, Cl, Ca, Ti, Mn, Fe, Cu, Br, Zn and K) with detection limits of typically 1-10 μg/g. Comparison of the distribution of the elements between leaves, root and seed samples using uptake and distribution of elements in particular environmental conditions with potential amount of salt in water have been performed. We are also expecting to indicate metal exclusion as salt tolerance strategies from leaves, root, and seed compartments using matrix correlation between samples and between elements on rice species.展开更多
A new small concentrating solar power plant which is suitable for urban area is presented, and a theoretical framework for the energy and exergy analysis in the overall power plant is also constructed. The framework c...A new small concentrating solar power plant which is suitable for urban area is presented, and a theoretical framework for the energy and exergy analysis in the overall power plant is also constructed. The framework can be used to evaluate the energy and exergy losses in each component. Furthermore, the energy and exergy efficiencies have also been computed and compared for the individual components as well as for the overall plant.展开更多
In present paper application of Endurance Time Analysis （ETA） method in nonlinear seismic assessment of steel concentrically braced frames is studied. In this method structure is subjected to a set of predesigned in...In present paper application of Endurance Time Analysis （ETA） method in nonlinear seismic assessment of steel concentrically braced frames is studied. In this method structure is subjected to a set of predesigned increasing acceleration functions and various responses of the structure are recorded during synthetic seismic excitation. The averages of maximum values for various responses in Nonlinear Time-History Analyses （NTHA） extracted from real ground motions are expected to be close to those obtained from ETA up to equivalent target time. For this purpose a set of 9, 11, 13 and 15 stories steel frames were designed and plastic hinge method was selected as source of nonlinearity in all cases. Responses were compared based on interstory drift ratio and story shear in two methods and results show satisfactory consistency between two methods. Finally, it was concluded that the ETA method can be used as alternative method in nonlinear seismic analysis of concentrically braced steel frames.展开更多
This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilizat...This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.展开更多
Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite eleme...Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.展开更多
Accurate semen analysis is critical for decisions about patient care, as well as for studies addressing overall changes in semen quality, contraceptive efficacy and effects of toxicant exposure. The standardization of...Accurate semen analysis is critical for decisions about patient care, as well as for studies addressing overall changes in semen quality, contraceptive efficacy and effects of toxicant exposure. The standardization of semen analysis is very difficult for many reasons, including the use of subjective techniques with no standards for comparison, poor technician training, problems with proficiency testing and a reluctance to change techniques. The World Health Organization （WHO） Semen handbook （2010） offers a vastly improved set of standardized procedures, all at a level of detail that will preclude most misinterpretations. However, there is a limit to what can be learned from words and pictures alone. A WHO- produced DVD that offers complete demonstrations of each technique along with quality assurance standards for motility, morphology and concentration assessments would enhance the effectiveness of the manual. However, neither the manual nor a DVD will help unless there is general acknowledgement of the critical need to standardize techniques and rigorously pursue quality control to ensure that laboratories actually perform techniques ＇according to WHO＇ instead of merely reporting that they have done so. Unless improvements are made, patient results will continue to be compromised and comparison between studies and laboratories will have limited merit.展开更多
Despite controversy regarding the clinical value of semen analysis, male fertility investigation still relies on a standardized analysis of the semen parameters. This is especially true for infertility clinics in both...Despite controversy regarding the clinical value of semen analysis, male fertility investigation still relies on a standardized analysis of the semen parameters. This is especially true for infertility clinics in both developing and developed countries. Other optional tests or sophisticated technologies have not been widely applied. The current review addresses important changes in the analysis of semen as described in the new World Health Organization （WHO） manual for semen analysis. The most important change in the manual is the use of evidence-based publications as references to determine cutoff values for normality. Apart from the above mentioned changes, the initial evaluation and handling methods remain, in most instances, the same as in previous editions. Furthermore, the review evaluates the importance of quality control in andrology with emphasis on the evaluation of sperm morphology. WHO sperm morphology training programmes for Sub-Saharan countries were initiated at Tygerberg Hospital in 1995. The external qualitY control programme has ensured that the majority of participants have maintained their morphological reading skills acquired during initial training. This review reports on current sperm functional tests, such as the induced acrosome reaction, and sperm-zona pellucida binding assays, as well as the impact of sperm quality in terms of DNA integrity, and the relationship of sperm function tests to sperm morphology.展开更多
Since the impoundment of the Three Gorges Reservoir in 2003, algal blooms have frequently been observed in it. The chlorophyll a concentration is an important parameter for evaluating algal blooms. In this study, the ...Since the impoundment of the Three Gorges Reservoir in 2003, algal blooms have frequently been observed in it. The chlorophyll a concentration is an important parameter for evaluating algal blooms. In this study, the chlorophyll a concentration in Xiangxi Bay, in the Three Gorges Reservoir, was predicted using HJ-1 satellite imagery. Several models were established based on a correlation analysis between in situ measurements of the chlorophyll a concentration and the values obtained from satellite images of the study area from January 2010 to December 2011. Chlorophyll a concentrations in Xiangxi Bay were predicted based on the established models. The results show that the maximum correlation is between the reflectance of the band combination of B4/（B2＋B3） and in situ measurements of chlorophyll a concentration. The root mean square errors of the predicted values using the linear and quadratic models are 18.49 mg/m3 and 18.52 mg/m3, respectively, and the average relative errors are 37.79% and 36.79%, respectively. The results provide a reference for water bloom prediction in typical tributaries of the Three Gorges Reservoir and contribute to large-scale remote sensing monitoring and water quality management.展开更多
The mechanical properties of cemented paste backfill(CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteri...The mechanical properties of cemented paste backfill(CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteristics and micro-structure of CPB. CPB specimens with different mass concentrations prepared from the full tailings of Xianglushan Tungsten Ore were micro-tests. Moreover, acquired pore digital images were processed by using the pores(particles) and cracks analysis system(PCAS), and a sensitivity analysis was performed. The results show that as the mass concentration of CPB increases from 70% to 78%, the porosity, the average pore area and the number of pores drop overall, leading to a decline in the pores opening degree and enhancing the mechanical characteristics. As the mass concentration of CPB increases, the trend of fractal dimension, probability entropy and roundness is reduced, constant and increased, which can result in an enhancement of the uniformity, an unchanged directionality and more round pores. According to the definition of sensitivity, the sensitivities of various micro-parameters were calculated and can be ranked as porosity > average pore area > number of pores > roundness > fractal dimension > probability entropy.展开更多
基金supported by the grants from National Key Research and Development Program of China(2023YFD2303300)China Agriculture Research System(CARS-02-15)the Agricultural Science and Technology Innovation Program(CAAS-ZDRW202004).
文摘The unreasonable application of nitrogen fertilizer poses a threat to agricultural productivity and the environment protection in Northeast China.Therefore,accurately assessing crop nitrogen requirements and optimizing fertilization are crucial for sustainable agricultural production.A three-year field experiment was conducted to evaluate the effects of planting density on the critical nitrogen concentration dilution curve(CNDC)for spring maize under drip irrigation and fertilization integration,incorporating two planting densities:D1(60,000 plants ha^(-1))and D2(90,000 plants ha^(-1))and six nitrogen levels:no nitrogen(N0),90(N90),180(N180),270(N270),360(N360),and 450(N450)kg ha^(-1).A Bayesian hierarchical model was used to develop CNDC models based on dry matter(DM)and leaf area index(LAI).The results revealed that the critical nitrogen concentration exhibited a power function relationship with both DM and LAI,while planting density had no significant impact on the CNDC parameters.Based on these findings,we propose unified CNDC equations for maize under drip irrigation and fertilization integration:Nc=4.505DM-0.384(based on DM)and Nc=3.793LAI-0.327(based on LAI).Additionally,the nitrogen nutrition index(NNI),derived from the CNDC,increased with higher nitrogen application rates.The nitrogen nutrition index(NNI)approached 1 with a nitrogen application rate of 180 kg ha^(-1)under the D1 planting density,while it reached 1 at 270 kg ha^(-1)under the D2 planting density.The relationship between NNI and relative yield(RY)followed a“linear+plateau”model,with maximum RY observed when the NNI approached 1.Thus,under the condition of drip irrigation and fertilization integration in Northeast China’s spring maize production,the optimal nitrogen application rates for achieving the highest yields were 180 kg ha^(-1)at a planting density of 60,000 plants ha^(-1),and 270 kg ha^(-1)at a density of 90,000 plants ha^(-1).The CNDC and NNI models developed in this study are valuable tools for diagnosing nitrogen nutrition and guiding precise fertilization practices in maize production under integrated drip irrigation and fertilization systems in Northeast China.
基金support of the National Major Science and Technology Projects of China(No.J2019-V-0005-0096)the National Key Research and Development Program of China(No.2020YFA0405700).
文摘To provide advanced diagnostic techniques for diagnosing the outlet temperature distribution and species concentrations of future advanced combustors,this study focuses on a dual-swirl single-dome rectangular combustor.Through the integration of multiple diagnostics,simultaneous measurement of outlet temperature distribution and species concentrations was achieved.The study validates the engineering applicability of these simultaneous measurements using tungsten-rhenium(W-Re)thermocouples and Coherent Anti-Stokes Raman Scattering(CARS),CARS and Tunable Diode Laser Absorption Spectroscopy(TDLAS),as well as Gas Analysis(GA)and Mass Spectrometry(MS).The results demonstrate that measurements by thermocouples and CARS exhibit good consistency and repeatability,with a relative deviation of less than 4%,fully meeting the requirements of engineering experiments.The spatial distribution reconstruction results of TDLAS can reflect the temperature distribution characteristics at the combustor outlet.Temperature comparison between TDLAS and CARS at single-point positions shows consistent results,with a relative deviation of less than 11%and 7%under both conditions,respectively.Simultaneous measurements by integrating GA and MS show high engineering applicability for the first time,meeting the requirements for measuring both inorganic species and free radicals at the combustor outlet.Under C_(1)condition,the relative deviations of four key species(Unburned Hydrocarbon(UHC),NO,O_(2),and CO_(2))remain within 2%,while that of NO_(2)is slightly higher at approximately 8%.Under C_(2)condition,the overall deviations increase for most species,with only O_(2)and CO_(2)maintaining relatively low deviations.The primary species of UHCs at the combustor outlet under both conditions are small molecular hydrocarbons(C_(3)-C_(8))and RO_(2)radicals,accounting for over 90%of total UHC.Specifically,RO_(2)species(R is C_(1)-C_(2)alkyl groups)are the predominant species,accounting for 74.3%and 82.1%of total RO_(2)under both conditions,respectively.These integrated diagnostic methods for temperature and species concentrations at the combustor outlet serve as a crucial reference for its engineering applications.
基金supported by the National Natural Science Foundation of China(21776028)Key Research and Development Projects of Liaoning Province(2017308004)。
文摘Accurately predicting distributions of concentration and temperature field in fixed-bed column is essential for designing adsorption processes.In this study,a two-dimensional(2D),axisymmetric,nonisothermal,dynamic adsorption model was established by coupling equations of mass,momentum and energy balance,and solved by finite element analysis.The simulation breakthrough curves fit well with the low-concentration CO_(2) adsorption experimental data,indicating the reliability of the established model.The distributions of concentration and temperature field in the column for CO_(2) adsorption and separation from CO_(2)/N_(2) were obtained.The sensitivity analysis of the adsorption conditions shows that the operation parameters such as feed flow rate,feed concentration,pellet size,and column height-to-diameter ratio produce a significant effect on the dynamic adsorption performance.The multi-physics coupled 2D axisymmetric model could provide a theoretical foundation and guidance for designing CO_(2) fixed-bed adsorption and separation processes,which could be extended to other mixed gases as well.
基金the National Natural Science Foundation of China(61873283)the Changsha Science&Technology Project(KQ1707017)the innovation-driven project of the Central South University(2019CX005).
文摘Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimizationbased ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salinity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by timeseries data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency(NSE),Kling–Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R^(2)).Example analysis demonstrates that:①The proposed model can obtain excellent DO forecasting results;②the proposed model is superior to other comparison models;and③the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.
文摘This paper presents the analysis of two-layer cilia induced flow of Phan-Thien-Tanner(PTT) fluid with thermal and concentration effect.The Phan-Thien-Tanner fluid model has been used in the analogy of mucus present in the respiratory tract.The two-layer model approach was used due to the Peri Ciliary liquid Layer(PCL) and Airway Ciliary Layer(ACL) present on the epithelium cell in respiratory tract.The mathematical modelling of two-layer flow problem was simplified using long wavelength and small Reynold ’ s number approximation.The resulting differential equation with moving boundary gives exact solution for velocity,temperature and concentration profiles in two layers.The change in pressure has calculated by the results of velocity profile,also the pressure rise was evaluated by the numerical integration of pressure gradient along the channel wall.The impact of physical parameters on pressure rise,velocity,temperature and concentration profile was explained by the graphs.It can be seen from graphs that velocity and temperature profile are maximum in the inner layer of fluid(PCL) and concentration profile is maximum at outer layers of fluid(ACL).
基金the Guangdong Provincial Natural Science Foundation of China.
文摘A modified shear-lag model accounting for the effect of the tensile stiffness of the ma, trix is proposed for solving the stress redistribution due to the failure of fibers and matrix in unidirectionally fibre-reinforced composites. The advantages of this model are simple, reasonable and accurate by comparison with the other similar modified shear-lag models. It can be further extended to study the stress redistribution with interfacial damage between fibres and matrix This paper quantitatively dis cusses the influence of the tensile stiffness ratio of matrix to fibre and of the fibre volume fraction on the stress concentration in the fibres and ma trix adjacent to cut fibres and matrix, and suggests that the influence of the matrix stiffness on the stress concentration can be neglected when the matrix stiffness is low, such as polymer matrix composites, and the fibre volume fraction is high. For other cases such as ceramic and metal matrix composites, the tensile load of the matrix cannot be neglected in the shear-lag analysis.
文摘The TSI-3321 APS was used to measure concentration of atmospheric particulates in Ranjiaba region of Yubei District in Chongqing City during March 21- 29,2014,and the temporal variations in the hourly average mass and number concentration and median particle diameter of PM10 and PM2.5 as well as their correlation with relative humidity were analyzed. The results showed that the three indicators of PM10 and PM2.5 except for the mass concentration correlated with relative humidity,of which the correlation between the mass median particle diameter and relative humidity was the best. The correlation coefficient R^2 between the mass median particle diameter of PM10（ PM2.5） and relative humidity was up to 0. 943（ 0. 832）. Therefore,relative humidity and pressure are key impact factors of indicators of particles.
基金supported by the National Key Research and Development Project(No.2020YFC1807405)the China Postdoctoral Science Foundation(No.2021M703301)+1 种基金the Key-Area Research and Development Program of Guangdong Province(No.2020B0202010006)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019312).
文摘Conventionally,soil cadmium(Cd)measurements in the laboratory are expensive and timeconsuming,involving complex processes of sample preparation and chemical analysis.This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance(Vis-NIR)spectroscopy and portable X-ray fluorescence spectrometry(PXRF)to estimate regional soil Cd concentration in a time-and cost-savingmanner.The sensor data of Vis-NIR and PXRF,and Cd concentrations of 128 surface soils from Yunnan Province,China,were measured.Outer-product analysis(OPA)was used for synthesizing the sensor data and Granger-Ramanathan averaging(GRA)was applied to fuse the model results.Artificial neural network(ANN)models were built using Vis-NIR data,PXRF data,and OPA data,respectively.Results showed that:(1)ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation;(2)Fusion methods of both OPA and GRA had higher predictive power(R^(2))=0.89,ratios of performance to interquartile range(RPIQ)=4.14,and lower root mean squared error(RMSE)=0.06,in ANN model based on OPA fusion;R^(2)=0.88,RMSE=0.06,and RPIQ=3.53 in GRA model)than those based on either Vis-NIR data or PXRF data.In conclusion,there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.
基金supported by the National Key Scientific Instrument and Equipment Development Projects(No.2012YQ240121)Liaoning science and technology project(No.2017220010)Changchun Science and Technology Bureau Local Company and College(University,Institution)Cooperation Projects(No.17DY023)
文摘A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.
基金Northeast Electric Power Design Institute of China Under Grant No.K07-T716
文摘This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.
基金Item Sponsored by National Natural Science Foundation of China(51104088)University Science Research Project of Inner Mongolia of China(NJZZ157)
文摘In order to fill up the deficiency of the theoretical basis about fluoride formation during Bayan Obo iron concentrate roasting process, the thermodynamic conditions of the interactivity between the components of the gangue and calcium fluorite were studied by means of thermodynamic calculation, DTA-TG thermal analysis and XRD characterization. The results revealed that KF, NaF and SiF4 （gaseous） could he,formed during the roasting process, and the tendency of the generation of KF is greater than that of NaF or SiF4 in standard state. Besides, the results of roasting experiments showed that the products of KCaCO3 F and KCaF3 formed in the temperature range of 800-1250 ℃and KF appears when the roasting temperature was higher than 1250 ℃ in K2O-CaF2 system. For the Na2O-CaF2 system, the product of NaF appears at temperature higher than 1050 ℃. The formation reaction of gaseous SiF4 with solid phase CaO · SiO2 in SiO2-CaF2 system took place＂only＇at temperature higher than 1 150 ℃. In the natural potash feldspar-CaF2-CaO system, the fluorination reaction products involved KF at temperature higher than 1 270 ℃ , while in the natural aegirine-CaF2-CaO system, NaF formed at terhperature higher than 980 ℃ during roasting process.
文摘Understanding metal accumulation at organ level in roots, leaves and seeds in O. glaberrima (OG) is crucial for improving physiological and metabolic aspects in growing Asian and African rice in salted areas. The micro-analytical imaging techniques are required to reveal its accumulation and distribution within plant tissues. PIXE studies have been performed to determine different elements in rice plants. The existing microbeam analytical technique at the iThemba LABS will be applied for the 2D image mapping of fresh rice tissues to perform a concentration of low atomic mass elements (such as Al, Si, P, S, Cl, Ca, Ti, Mn, Fe, Cu, Br, Zn and K) with detection limits of typically 1-10 μg/g. Comparison of the distribution of the elements between leaves, root and seed samples using uptake and distribution of elements in particular environmental conditions with potential amount of salt in water have been performed. We are also expecting to indicate metal exclusion as salt tolerance strategies from leaves, root, and seed compartments using matrix correlation between samples and between elements on rice species.
文摘A new small concentrating solar power plant which is suitable for urban area is presented, and a theoretical framework for the energy and exergy analysis in the overall power plant is also constructed. The framework can be used to evaluate the energy and exergy losses in each component. Furthermore, the energy and exergy efficiencies have also been computed and compared for the individual components as well as for the overall plant.
文摘In present paper application of Endurance Time Analysis （ETA） method in nonlinear seismic assessment of steel concentrically braced frames is studied. In this method structure is subjected to a set of predesigned increasing acceleration functions and various responses of the structure are recorded during synthetic seismic excitation. The averages of maximum values for various responses in Nonlinear Time-History Analyses （NTHA） extracted from real ground motions are expected to be close to those obtained from ETA up to equivalent target time. For this purpose a set of 9, 11, 13 and 15 stories steel frames were designed and plastic hinge method was selected as source of nonlinearity in all cases. Responses were compared based on interstory drift ratio and story shear in two methods and results show satisfactory consistency between two methods. Finally, it was concluded that the ETA method can be used as alternative method in nonlinear seismic analysis of concentrically braced steel frames.
文摘This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.
基金supported by National Natural Science Foundation of China (Grant No. 50935006)Major Project of High-end CNC Machine Tool and Basic Manufacturing Equipment of China (Grant No.2011ZX04016-031)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2012AA040701)
文摘Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.
文摘Accurate semen analysis is critical for decisions about patient care, as well as for studies addressing overall changes in semen quality, contraceptive efficacy and effects of toxicant exposure. The standardization of semen analysis is very difficult for many reasons, including the use of subjective techniques with no standards for comparison, poor technician training, problems with proficiency testing and a reluctance to change techniques. The World Health Organization （WHO） Semen handbook （2010） offers a vastly improved set of standardized procedures, all at a level of detail that will preclude most misinterpretations. However, there is a limit to what can be learned from words and pictures alone. A WHO- produced DVD that offers complete demonstrations of each technique along with quality assurance standards for motility, morphology and concentration assessments would enhance the effectiveness of the manual. However, neither the manual nor a DVD will help unless there is general acknowledgement of the critical need to standardize techniques and rigorously pursue quality control to ensure that laboratories actually perform techniques ＇according to WHO＇ instead of merely reporting that they have done so. Unless improvements are made, patient results will continue to be compromised and comparison between studies and laboratories will have limited merit.
文摘Despite controversy regarding the clinical value of semen analysis, male fertility investigation still relies on a standardized analysis of the semen parameters. This is especially true for infertility clinics in both developing and developed countries. Other optional tests or sophisticated technologies have not been widely applied. The current review addresses important changes in the analysis of semen as described in the new World Health Organization （WHO） manual for semen analysis. The most important change in the manual is the use of evidence-based publications as references to determine cutoff values for normality. Apart from the above mentioned changes, the initial evaluation and handling methods remain, in most instances, the same as in previous editions. Furthermore, the review evaluates the importance of quality control in andrology with emphasis on the evaluation of sperm morphology. WHO sperm morphology training programmes for Sub-Saharan countries were initiated at Tygerberg Hospital in 1995. The external qualitY control programme has ensured that the majority of participants have maintained their morphological reading skills acquired during initial training. This review reports on current sperm functional tests, such as the induced acrosome reaction, and sperm-zona pellucida binding assays, as well as the impact of sperm quality in terms of DNA integrity, and the relationship of sperm function tests to sperm morphology.
基金supported by the National Natural Science Foundation of China(Grants No.51009080 and 51179095)the Research Innovation Fund for Postgraduates in China Three Gorges University(Grant No.2012CX012)
文摘Since the impoundment of the Three Gorges Reservoir in 2003, algal blooms have frequently been observed in it. The chlorophyll a concentration is an important parameter for evaluating algal blooms. In this study, the chlorophyll a concentration in Xiangxi Bay, in the Three Gorges Reservoir, was predicted using HJ-1 satellite imagery. Several models were established based on a correlation analysis between in situ measurements of the chlorophyll a concentration and the values obtained from satellite images of the study area from January 2010 to December 2011. Chlorophyll a concentrations in Xiangxi Bay were predicted based on the established models. The results show that the maximum correlation is between the reflectance of the band combination of B4/（B2＋B3） and in situ measurements of chlorophyll a concentration. The root mean square errors of the predicted values using the linear and quadratic models are 18.49 mg/m3 and 18.52 mg/m3, respectively, and the average relative errors are 37.79% and 36.79%, respectively. The results provide a reference for water bloom prediction in typical tributaries of the Three Gorges Reservoir and contribute to large-scale remote sensing monitoring and water quality management.
基金Projects(51674188,51874229,51504182)supported by the National Natural Science Foundation of ChinaProject(2018KJXX-083)supported by Shaanxi Innovative Talents Cultivate Program-New-star Plan of Science and Technology,China
文摘The mechanical properties of cemented paste backfill(CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteristics and micro-structure of CPB. CPB specimens with different mass concentrations prepared from the full tailings of Xianglushan Tungsten Ore were micro-tests. Moreover, acquired pore digital images were processed by using the pores(particles) and cracks analysis system(PCAS), and a sensitivity analysis was performed. The results show that as the mass concentration of CPB increases from 70% to 78%, the porosity, the average pore area and the number of pores drop overall, leading to a decline in the pores opening degree and enhancing the mechanical characteristics. As the mass concentration of CPB increases, the trend of fractal dimension, probability entropy and roundness is reduced, constant and increased, which can result in an enhancement of the uniformity, an unchanged directionality and more round pores. According to the definition of sensitivity, the sensitivities of various micro-parameters were calculated and can be ranked as porosity > average pore area > number of pores > roundness > fractal dimension > probability entropy.
