中国主要粮食作物农药过量使用程度的时空分析

基于2001～2016年的全国农产品成本收益数据,利用DEA模型测算了我国水稻、小麦、玉米三种主要粮食作物的农药过量使用程度,并对农药过量使用程度的时空差异特征进行了分析。研究结果表明:(1)从时序变化来看,2001～2016年,我国水稻和玉米的农药过量使用程度呈下降趋势,小麦的农药过量使用程度呈上升趋势。(2)从空间格局来看,广东、广西和河北是我国水稻农药过量使用程度较为严重的省份;江苏、湖北、河南、山西、陕西、甘肃和宁夏是我国小麦农药过量使用程度较为严重的省份;河南、湖北和山东是我国玉米农药过量使用程度较为严重的省份。

我国油菜生产中化肥投入的经济分析与评价

为了解我国油菜生产受化肥过量投入的影响,基于1991-2019年全国15个油菜主产省(市)的成本收益数据,通过比较化肥在油菜生产中的边际产品价值与化肥价格的比值,从油菜种植户利润最大化视角出发,对我国油菜生产的过量施肥程度进行评价,估计我国油菜生产的化肥减量任务与潜力,以期为促进我国油菜产业绿色高效发展提供数据支撑。研究结果表明:我国油菜生产的化肥产出弹性为0.1255。1991-2019年我国油菜生产平均过量施肥程度为25.5%。“十三五”期间,我国油菜生产的化肥投入虽然超过了经济意义上的最优施用水平,但尚且处于历史低位。若实现经济意义上最优化肥投入,1991-2019年我国油菜生产可累计减少化肥施用1090万吨。基于上述结果,本文从政策层面得出如下启示:(1)明确油菜生产的化肥减量任务,优化油菜化肥施用顶层设计方案;(2)完善有机肥、配方肥专项补贴制度,扩大有机肥、配方肥在油菜生产中的推广应用范围;(3)加强基层施肥技术指导与培训服务,提高油菜种植户认知水平和科学施肥能力。

2002—2015年中国主要粮食作物过量施肥程度的空间关联格局分析

为使全国范围内化肥减量工作的开展更具有针对性,本研究采用C-D生产函数测算2002—2015年水稻、小麦、玉米3种粮食作物主产区的过量施肥程度,并运用空间自相关理论和冷热点分析方法,对中国主要粮食作物过量施肥程度的空间关联格局进行分析。结果显示:1)水稻主产区过量施肥程度的高值区域在黄淮海地区、华南地区呈团块状分布,小麦主产区过量施肥程度的高值区域在北部高原地区、黄淮海地区和长江中下游地区连片分布,玉米主产区过量施肥程度的高值区域在华南地区、长江中下游地区和东北地区呈团块状分布,集聚特征显著。2)水稻、小麦和玉米过量施肥程度均呈现出较强的空间自相关性,小麦集聚程度最强,水稻居中,玉米最弱。3)水稻过量施肥程度的热点区域主要分布在黄淮海地区、长江中下游地区和华南地区,冷点区域主要分布在北部高原地区和东北地区;小麦过量施肥程度的冷热点空间分布特征表现为"中间热周围冷",热点区域集中在黄淮海地区和长江中下游地区,冷点区域集中在西北地区;玉米过量施肥程度的冷热点格局由"南热北冷"转变为"东热西冷",热点区域集中在西南地区、华南地区和长江中下游地区,冷点区域集中在西北地区。

The Pressure Gradient Elastic Wave： Energy Transfer Process for Compressible Fluids with Pressure Gradient

The temperature separation was discovered inside the short vortex chamber （H/D = 0.18）. Experiments revealed that the highest temperature of the periphery was 465 ℃, and the lowest temperature of the central zone was -45 ℃ （the compressed air was pumped into the chamber at room temperature）. The objective of this paper is to proof that this temperature separation effect cannot be explained by conventional heat transfer processes. To explain this phenomenon, the concept of PGEW （Pressure Gradient Elastic Waves） is proposed. PGEW are kind of elastic waves, which operate in compressible fluids with pressure gradients and density fluctuations. The result of PGEW propagation is a heat transfer from area of low pressure to high pressure zone. The physical model of a gas in a strong field of mass forces is proposed to substantiate the PGEW existence. This physical model is intended for the construction of a theory of PGEW. Understanding the processes associated with the PGEW permits the possibility of creating new devices for energy saving and low potential heat utilization, which have unique properties.

A genetic Gaussian process regression model based on memetic algorithm

Gaussian process(GP)has fewer parameters,simple model and output of probabilistic sense,when compared with the methods such as support vector machines.Selection of the hyper-parameters is critical to the performance of Gaussian process model.However,the common-used algorithm has the disadvantages of difficult determination of iteration steps,over-dependence of optimization effect on initial values,and easily falling into local optimum.To solve this problem,a method combining the Gaussian process with memetic algorithm was proposed.Based on this method,memetic algorithm was used to search the optimal hyper parameters of Gaussian process regression(GPR)model in the training process and form MA-GPR algorithms,and then the model was used to predict and test the results.When used in the marine long-range precision strike system(LPSS)battle effectiveness evaluation,the proposed MA-GPR model significantly improved the prediction accuracy,compared with the conjugate gradient method and the genetic algorithm optimization process.

Non-complete relief method for measuring surface stresses in surrounding rocks

The measurement of surface stresses in surrounding rocks with the use of a relief method of annular hole-drilling was studied by numerical analysis. The stress relief process by hole-drilling was then simulated with the use of finite element method. The influences of the borehole diameter(d), the initial stresses and the ratio of the initial principle stresses on the variations of the remained stress and the released stress in function of the relief depth(h) were discussed. The relation between the non-dimensional ratio of the released principle strains and that of the initial principle stresses, and the effect of the elastic modulus and the Poisson ratio of the rock mass on the stress relief curves were studied. The results show that the stress relief behavior formulated with the non-dimensional ratio of the released stress and the ratio of h/d is only sensitive to the ratio of the initial principle stresses and the Poisson ratio. The stresses are completely released when h equals 1.6d, and the tensile stresses take place on the bore core surface in the relief measurement process. Finally, a non-complete relief method of annular hole-drilling for measuring surface stress in surrounding rocks is proposed and the procedure is presented.

Thermal deformation analysis of the composite material satellite antenna

Controlling the thermal deformation is a crucial index for the design of the satellite antenna. To calculate and measure the satellite antenna’s thermal deformation is also an important step for the design of satellite antenna. Based on the foundation of equivalent assumption, the thermal deformation of the parabolic satellite antenna was analyzed by the finite element method for different design project. The best design project that had the minimum of the thermal deformation could be obtained through changing the lay-angle, lay-layers and lay-thickness of each layer. Results show the asymmetry structure has the minimum of thermal deformation. This paper may provide useful information for the further investigation on the coupling of thermal-stress structure.

Variation characteristics of temperature and moisture content of seasonal frozen soil during freezing process in Changchun,China

In China, seasonal frozen soil is widely distributed. The freezing damage of subgrade soil in Jilin Province has been one of major engineering geological problems troubling the safety of road, in which some common damage phenomena, such as frost heave, subsidence deformation and frost boiling, are all caused by water translocation. Aiming at the phenomenon, the changes of moisture content of seasonal frozen soil in Changchun City are mainly studied by long-term field observation and indoor testing of physical properties under different conditions, and then the variation characteristics of moisture content in soil under different compactness and temperature conditions are realized. The results show that the increasing section of moisture content and negative temperature section all lie in O. 0 - 1.0 m of subgrade. Both lowest air and earth temperature occur in January to February, and the most negative temperature ranges from -7℃ to -10℃.

Blood micronutrient, oxidative stress, and viral load in patients with chronic hepatitis C

AIM: To assess the extent of micronutrient and oxidative stress in blood and to examine their linkages with viral loads in chronic hepatitis C patients.METHODS: Hepatitis C virus (HCV)-RNA levels were quantified in the serum from 37 previously untreated patients with chronic hepatitis C. The plasma and erythrocyte micronutrients (zinc, selenium, copper, and iron) were estimated, and malondialdehyde (MDA)contents were determined as a marker to detect oxidative stress. Antioxidant enzymes, superoxide dismutase (SOD),glutathione peroxidase (GPX) and glutathione reductase (GR) activities in blood were also measured. The control group contained 31 healthy volunteers.RESULTS: The contents of zinc (Zn), and selenium (Se)in plasma and erythrocytes were significantly lower in hepatitis C patients than in the controls. On the contrary,copper (Cu) levels were significantly higher. Furthermore,plasma and erythrocyte MDA levels, and the SOD and GR activities in erythrocytes significantly increased in hepatitis C patients compared to the controls. However, the plasma GPX activity in patients was markedly lower. Plasma Se (r= -0.730, P<0.05), Cu (r = 0.635), and GPX (r = -0.675)demonstrated correlations with HCV-RNA loads. Significant correlation coefficients were also observed between HCV-RNA levels and erythrocyte Zn (r = -0.403), Se (r = -0.544), Cu (r = 0.701) and MDA (r = 0.629) and GR (r = 0.441).CONCLUSION: The levels of Zn, Se, Cu, and oxidative stress (MDA), as well as related anti-oxidative enzymes (GR and GPX) in blood have important impact on the viral factors in chronic hepatitis C. The distribution of these parameters might be significant biomarkers for HCV.

The characteristics of rill development and their effects on runoff and sediment yield under different slope gradients

Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore,total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the variousindices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and-0.98, respectively,indicating that slope gradient is the major factor of affecting the development of rills. Furthermore,runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration,however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.

Effects of the grinding process on the preparation and qualities of CWS

Two different grinding processes were examined to determine the effect grinding has on the quality of a CWS. A series of slurries was prepared from Australian (Au) and Chinese (YZ) coals. Both types of coal were ground by a Chinese (CUMT) and an Australian (JK) grinding process. The performance tests of the prepared CWS showed that fluidity of all slurries was acceptable. The concentration of the CWS from YZ coal ground by the CUMT grinding process was higher than when the JK grinding process was used. The highest concentration was 70.14% in this case. The concentration of the CWS prepared from Au coal by the JK grinding process was higher than when the CUMT grinding process was used. The highest con- centration in this case was 70.97%. These differences are caused by the particle size distribution devel- oped during the different grinding processes.

A back analysis of the temperature field in the combustion volume space during underground coal gasification

The exact shape and size of the gasification channel during underground coal gasification(UGC) are of vital importance for the safety and stability of the upper parts of the geological formation.In practice existing geological measurements are insufficient to obtain such information because the coal seam is typically deeply buried and the geological conditions are often complex.This paper introduces a cylindrical model for the gasification channel.The rock and soil masses are assumed to be homogeneous and isotropic and the effect of seepage on the temperature field was neglected.The theory of heat conduction was used to write the equation predicting the temperature field around the gasification channel.The idea of an excess temperature was introduced to solve the equations.Applying this model to UCG in the field for an influence radius,r,of 70 m gave the model parameters,u1,2,3...,of 2.4,5.5,8.7...By adjusting the radius(2,4,or 6 m) reasonable temperatures of the gasification channel were found for 4 m.The temperature distribution in the vertical direction,and the combustion volume,were also calculated.Comparison to field measurements shows that the results obtained from the proposed model are very close to practice.

A New Model for the Simulation of Distillation Column

A new computational mass transfer model is proposed for simulating the distillation process by solving the fluctuating mass flux u^＇ic^＇ for the closure of turbulent mass transfer equation in order to obtain the concentration profile and the separation efficiency of distillation column. The feather of the proposed model is to abandon the conventional way of introducing the turbulent mass transfer diffusivity （dispersion coefficient） to the turbulent mass transfer equation. To verify the validity of the proposed model, a commercial scale packed column and a sieve tray column were simulated and compared with published experimental data. The simulated results were satisfactorily confirmed in both concentration distribution and senaration efficiency.

Concentration of Vinasse Using Membrane Filtration Processes

The application of single nanofiltration （NF） and sequential filtration of microfiltration （MF） and NF for the concentration of vinasse were studied. Filtration experiments were performed at 60 ℃, 500 rpm and different transmembrane pressures using four commercial membranes： MF, PVDF 0.2 μm; NF, PES 300, 500 and 1000 Da. The process effectiveness was evaluated through the permeate flux and the total solids （TS） concentration in the retentate. Because the retention of TS and permeate fluxes were very similar for MF, PVDF-0.2 membrane at 0.10 MPa was selected because of its lower power consumption. The best conditions tested for NF were the following： PES-1000 at 3.50 MPa with a flux of 183.2 kg/m^2 h at a volume reduction factor （VRF） of 2, under which 68% of solids were retained. For the MF ＋ NF, a PES-1000 at 3.50 MPa was selected because a higher permeate flux was achieved at a VRF of 4, and PES-500 at 3.50 MPa because a higher retention of TS was achieved compared to the other experiments. A single NF resulted in a retentate concentration that was almost twice as high as the hybrid MF and NF process, allowing reduced costs in its transportation from distilleries to distant areas.

Horizontal roof gap of backfill hydraulic support

For the backfill hydraulic support as the key equipment for achieving integration of backfilling and coal mining simultaneously in the practical process, its characteristics will directly influence the backfill body's compression ratio. Horizontal roof gap, as a key parameter of backfilling characteristics, may impact the backfilling effect from the aspects of control of roof subsidence in advance, support stress, backfilling process and the support design. Firstly, the reason why horizontal roof gap exists was analyzed and its definition, causes and connotation were introduced, then adopting the Pro/E 3D simulation software, three typical 3D entity models of backfill hydraulic supports were built, based on the influence of horizontal roof gap on backfilling effect, and influence rules of four factors, i.e. support height, suspension height, suspension angle and tamping angle, were emphatically analyzed on horizontal roof gap. The results indicate that, the four factors all have significant impacts on horizontal roof gap, but show differences in influence trend and degree, showing negative linear correlation, positive linear correlation, positive semi-parabolic correlation and negative semi-parabolic correlation, respectively. Four legs type is the most adaptive to the four factors, while six legs(II) type has the poorest adaptability, and the horizontal roof gap is small under large support height, small suspension height, small suspension angle and large tamping angle situation. By means of optimizing structure components and their positional relation and suspension height of backfill scrape conveyor in the process of support design and through controlling working face deployment, roof subsidence in advance, mining height and backfilling during engineering application, the horizontal roof gap is optimized. The research results can be served as theoretical basis for support design and guidance for backfill support to have better performance in backfilling.

A review of chemical absorption of carbon dioxide for biogas upgrading

Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide,and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these techniques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.

Influence of Conditions on Reuterin Accumulation by the Resting Cell Biotransformation Process

3-Hydroxypropionaldehyde （3-HPA） is a potential valuable chemical and new broad-spectrum antim-icrobial substance. In order to improve the conversion of 3-HPA/glycerol, our work studied the two-step process from glycerol to 3-HPA, and investigated the influence of cell harvest time, glycerol concentration, biomass con-centration, pH and temperature on the production of 3-HPA by Lactobacillus reuteri CG001, respectively. The re-sults showed that molar conversion yield of 3-HPA/glycerol reached 97.9% under the condition that 200 mmol·L-1 glycerol was converted by 25.3 g·L-1 resting cell for 1 h at 30 ℃. The cells could not be reused directly because the L. reuteri almost lost its bioconversion activity completely, but the ability of glycerol conversion could gradually recover if the fresh medium was added to the deactivated cell for 4 h.

A novel reaching law approach of quasi-sliding-mode control for uncertain discrete-time systems

A novel discrete-time reaching law was proposed for uncertain discrete-time system,which contained process noise and measurement noise.The proposed method reserves all the advantages of discrete-time reaching law,which not only decreases the band width of sliding mode and strengthens the system robustness,but also improves the dynamic performance and stability capability of the system.Moreover,a discrete-time sliding mode control strategy based on Kalman filter method was designed,and Kalman filter was employed to eliminate the influence of system noise.Simulation results show that there is no chattering phenomenon in the output of controller and the state variables of controlled system,and the proposed algorithm is also feasible and has strong robustness to external disturbances.

Characterization of Atomization Processes in Suspension/Emulsion Sprays

The characterization of suspension/emulsion sprays plays a decisive role in many industrial processes. A good example of such a process is the drying of a milk spray to produce milk powder, where the process efficiency and product quality is typically controlled by atomization parameters like flow rate, pressure, etc.. However, these parameters influence directly the droplet size and droplet velocity distributions in a spray, so that optimizing a spray drying process often involves adjusting the spray to a desired droplet size and droplet velocity distribution. This requires a measurement technique capable of characterizing in real time, the droplets in a suspension/emulsion spray. To achieve this aim, we present developments to the well-known time-shift technique for spray measurements.

Laws of Jet Mixing of the Swirled Flows in a Pipe

Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.