基于CWSI的贵州省干旱时空变化特征及影响因素分析

为了促进贵州省农业和生态环境可持续发展,基于作物缺水指数(Crop Water Stress Index,CWSI),结合气象、植被指数等数据,采用Theil-Sen Median趋势分析、Mann-Kendall检验、变异系数和相关性分析等方法,对贵州省2000—2019年的干旱时空变化特征、趋势及影响因素进行了分析。研究表明:(1)贵州省CWSI多年均值为0.43,整体处于轻旱等级,空间分布为东南湿润,西北干旱,多年旱情变化呈缓解趋势;(2)从地貌类型来看,非喀斯特地貌CWSI多年均值为0.37,整体处于无旱等级,喀斯特地貌均值为0.47,处于轻旱状态;(3)从植被类型来看,除针叶林整体处于无旱状态外,其他植被类型都处于轻旱等级,且针叶林的变异系数(CV)值较其他林地高,说明其对气候因子的敏感性高,抗旱能力强;(4)贵州省CWSI与降水和气温均呈负相关,负相关面积占比为95%和54%,说明降水对CWSI的影响较大。综合分析得出,贵州省东南部湿润,西北地区干旱,全省干旱受喀斯特地貌、降水的影响较大。

基于贵州省土地变化的碳储量演变及其脆弱性特征分析

[目的]分析贵州省生态系统碳储量时空分布格局、演变特征及其对土地利用转移的响应,研究各县域生态系统碳储量服务的脆弱性,为贵州省区域土地利用管理决策及“双碳”目标的实现提供科学依据和参考。[方法]运用InVEST模型和潜在影响指数(PI)分析贵州省2000—2020年碳储量变化特征和生态系统碳储存服务的脆弱性。[结果]①近20 a间贵州省土地利用结构发生显著变化,前10 a和后10 a分别有14.10%,17.29%的土地发生转移,耕地是建设用地扩张的主要来源。②贵州省20 a间生态系统碳储量减少2.40×10^(7)t,林地的缩减和建设用地的扩张是碳储量减少的主要原因。③贵州省碳储量Moran’s I指数均大于0,空间分布具有显著的空间正相关性和集聚性。冷热点分析显示碳储量热点分布较为分散,冷点分布集中稳定。④贵州省前10 a和后10 a PI指数分别为-1.27和-0.15,脆弱性有所改善。县域间脆弱性存在空间差异,边缘县域负向影响显著,20 a间81.82%的县脆弱性降低。[结论]贵州省林地的转出和建设用地的扩张对碳储量和碳储量服务脆弱性影响显著,未来应优化土地利用结构,加强规划管理。

基于土地利用和景观格局的高原山区湖库水质变化主要贡献因子分析

[目的]准确分析与识别高原山区湖库水质变化的主要贡献因子,为高原山区乃至全国水环境污染防治和管理工作提供科学参考。[方法]解译贵阳市“两湖一库”流域2013,2016和2019年3期土地利用数据,采集丰—枯水期总氮和总磷水质数据,通过Pearson相关分析揭示3期土地利用/景观指数与水质的相关性,冗余分析识别土地利用/景观指数对水质的贡献。[结果]①2013—2019年,林地、建设用地和草地分别增加11.72%,9.96%和3.18%,水田、旱地分别减少8.77%,12.07%。林地与建设用地均表现为结合度增强,斑块数量比例增加。②红枫湖水质达到国家Ⅰ—Ⅲ类水质标准,百花湖和阿哈水库的总磷、总氮浓度波动较大,水质状况劣于红枫湖。③林地面积比例和景观指数与水质指标整体表现为负相关,建设用地面积比例和景观指数与水质指标整体表现为正相关。④2013和2016年林地斑块数量比例的贡献度分别达到54.0%和52.5%,2019年建设用地面积比例的贡献度达到68.7%。[结论]林地表现出“汇”的效果,建设用地则是“源”的效果,增加流域“汇”效应,抑制污染“源”的输出,是缓解“两湖一库”流域水质恶化的有效手段。

近30年贵阳市土地利用冲突时空变化分析

[目的]科学识别和掌握土地利用冲突的时空演变特征是区域寻求可持续发展的基础。[方法]基于相对生态风险评价概念模型和景观生态学理论构建土地利用空间冲突测度模型,定量分析了贵阳市1990—2020年的空间冲突水平及时空演变特征。[结果]1990—2020年贵阳市土地利用冲突整体处于可控级别且变化明显,稳定可控占比由24.76%上升到61.10%,严重失控占比由2.24%波动上升到2.43%,有增长趋势。贵阳市土地利用冲突呈“南高北低”的空间格局,稳定可控和基本可控向息烽县、开阳县、乌当区等山地丘陵聚集;基本失控和严重失控趋于向城市市区及其周边区域集中。贵阳市土地利用冲突具有明显的空间聚集效应,整体呈“南高北低”相对的分布特征;热点区由清镇市、修文县、花溪区向城市中心迁移,冷点区主要聚集在乌当区、开阳县。[结论]贵阳市近30年土地利用冲突时空变化显著,基本可控向稳定可控转变,失控地区向城市中心聚集,未来要重视城市中心生态建设,协调生态与经济的平衡发展。

中药解酒机制研究进展

在我国大多数民族的文化和习俗中,饮酒是一种常见的社会行为。饮酒在社会交往、婚丧嫁娶和庆贺活动中不可缺少,但过量饮酒给社会和个人带来的健康问题却日益严重。长期大量饮酒可导致人体多器官的损伤,其中以肝、脑、胃黏膜受损最为严重。当前中药解酒的效果日趋显著,本文分别从四个方面阐述了中药解酒的作用机制:通过降低体内乙醇含量,减轻酒精对机体的损害;提高机体抗氧化活性,免受自由基的损伤;降低炎症因子的表达,减轻慢性炎症对机体的损害;抑制NF-κB通路,激活Nrf-2/Keap-1通路,防止酒精性肝病形成。

商用车SMC材质件常见涂装质量缺陷及提升措施

文章简要介绍了SMC材质件涂装过程常见的质量缺陷及提升措施。着重讲述发生几率较高的针眼、鼓包、气泡、层间附着力差、咬底等缺陷现象,查找出设备、工装、参数、底漆面污染、不干等真因过程,制定改造设备、调整参数、清洁漆面、控制干燥度等提升措施,使得此类问题得到有效解决和控制。

涂装工艺技术管理的研究探讨

结合车间管理经验,从管理框架、工艺技术人员配置、控制计划、标准作业、流程、记录等几个方面,介绍了涂装工艺技术管理的相关知识。

Numerical simulation of underwater explosion bubble with a refined interface treatment

With the intermediate flow states predicted by local two phase Riemann problem,the modified ghost fluid method(MGFM)and its variant(r GFM)have been widely employed to resolve the interface condition in the simulation of compressible multi-medium flows.In this work,the drawback of the construction procedure of local two phase Riemann problem in r GFM was investigated in detail,and a refined version of the construction procedure was specially developed to make the simulation of underwater explosion bubbles more accurate and robust.Beside the refined r GFM,the fast and accurate particle level set method was also adopted to achieve a more effective and computationally efficient capture of the evolving multi-medium interfaces during the simulation.To demonstrate the improvement brought by current refinement,several typical numerical examples of underwater explosion bubbles were performed with original r GFM and refined r GFM,respectively.The results indicate that,when compared with original r GFM,numerical oscillations were effectively removed with the proposed refinement.Accordingly,with present refined treatment of interface condition,a more accurate and robust simulation of underwater explosion bubbles was accomplished in this work.

Electronic structures of the oxygenated diamond (100) surfaces

By means of first principles method on the basis of density functional theory (DFT), the equi- librium geometries and density of states (DOS) of the two oxygenated diamond (100) surfaces, bridging model and on-top model are calculated. The results indicate that there are no surface states located in the band gap of the bridging model of oxygenated dia- mond (100) surface, and the occupied surface states in the valence band are attributed to the non-bonded O 2p orbital, O 2p and C 2p bonding orbitals, and C 2p and H 1s bonding orbitals. By contrast, for the on-top model of oxygenated diamond (100) surface, the unoccupied surface states exist in the band gap, which originate from non-bonded C 2p and O 2p or- bitals. In addition, the occupied surface states in the valence band are induced by non-bonded O 2p or- bital and the C==O π bond.

Affected zone generated around the erosion pit on carbon steel surface at the incipient stage of vibration cavitation

The characteristics of erosion pits on a carbon steel surface were investigated at the incipient stage of cavitation erosion. After a 5-minute experiment performed in an ultrasonic vibration system, needle-like erosion pits appeared on the polished steel surface, and a specially affected zone was formed around the pit. The shape of the pit and the plastic deformation of the affected zone indicate that the me- chanical impaction on the surface is the main reason for the cavitation damage. On the other hand, the iridescent color, the decreased surface hardness and the precipitated carbides on the affected zone prove that the affected zone has experienced a tempering process with the temperature higher than 300°C. The lack of oxygen in the affected zone also proves that it is not a chemical oxygen result. A special phenomenon that a carbon ring forms in the affected zone is explained as a result of the toroidal bubbles' heating effect at the final stage of the bubble collapse.

A prediction of drag reduction by entrapped gases in hydrophobic transverse grooves

The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped gas.In this paper,a hydrophobic transverse grooved surface was designed to sustain gas in valleys.A detail numerical simulation was presented to investigate the flow field near the proposed surface.When water flowed over this surface,the entrapped gas was blocked by the ridges and the solid-liquid interface was replaced by the liquid-gas interface due to the entrapped gas,furthermore the micro-vortex formed in the groove.Because there was an effective slippage between water and solid induced by the entrapped gas,the velocity gradient of boundary layer decreased,which contributed to a remarkable drag reduction effect.Additionally,considering the extra undesired pressure drag reduction which negatively impacted the drag reduction effect of this method,the total drag coefficient including the viscous drag coefficient and the pressure coefficient was analyzed.An effective drag reduction rate of about 15%was achieved and the effect of this method was confirmed by experiments conducted in a high-speed water tunnel when grooves were optimized.

Study on design of the regular concave surface profiles

Regular concave surface profiles are adopted in many friction surfaces. But up to now,this is seldom tutored by the theory of lubrication. To design them, a model of the regular depthoptimization was provided. To determine the other size, two propositions are given. At same time,two main effect factors on lubrication were discussed in detail. A lubrication test for different regu-lar concave surface profiles was performed on a pin and ring tester. On the basis of theory analy-sis and experiment, a principle to design regular concave surface profiles is provided.

Fabrication of a micro-structured surface based on interfacial convection for drag reduction

Based on interfacial convection in the presence of solvent evaporation, a novel method for the fabrication of a micro-structured surface is proposed to facilitate drag reduction. A mixture was coated on a substrate through a specially developed spray-painting system. Micron scale pits formed spontaneously in the coated surface because of interfacial convection and deformation driven by the gradient of the interfacial tension. Experimental results indicated that particles in the mixture played a crucial role in pit for-mation, and with a suitable selection of particle size and dosage, the characteristic parameters of the pitting could be controlled. The drag reduction experiments were first performed in a water tunnel, and the results showed that the micro-structured surface had a remarkable drag reduction performance over a great range of flow speeds.

Relationship between the geometric features of carbon steel cavitation erosion debris and the cavitation erosion stages

The debris produced in vibration cavitation tests of three kinds of carbon steel were collected.Their geometric features were analyzed quantitatively and observed respectively by a profilometer and a scanning electronic microscope(SEM) with reference to the investigation of the cavitation damaged surface by SEM and X-ray diffraction(XRD) .It was found that among the debris produced in all cavitation erosion stages,more than 45%were platelets because of the occurrence of dislocation and cleavage fracture,and only less than 25%were strands.The number of granule was small in the first cavitation erosion stage and increased rapidly to the number comparable with that of platelets in the next stage,and then reduced in the third stage.The sphericity values of the debris varied in accordance with the stages of cavitation damage,which were 0.3―0.4 in the incubation stage,0.5―0.7 in the acceleration stage and not less than 0.5 in the maximum rate stage,although a slight decrease occurred in the third stage.

Effects of the surface-adsorption of boron-doped diamond electrode on its electrochemical behavior

To elucidate the effects of the hydro- genation and oxygenation of the boron-doped dia- mond (BDD) electrode on its electrochemical behav- iors, the surface morphologies and phases of the two surface-adsorption BDD films have been investigated and the cyclic voltammograms and AC impedance spectra have been measured at these two BDD electrodes. The results indicate that compared with the hydrogen-adsorption BDD film, oxygen-adsor- ption BDD film is less conductive, and has a larger surface roughness and a lower sp3/sp2 ratio. The oxygenated BDD film electrode possesses a wider electrochemical window, larger diamond film resis- tance and capacitance and a larger polarization re- sistance than hydrogenated BDD electrode. In addi- tion, the effect mechanism of the surface-adsorption of BDD electrode on its electrochemical behaviors has been discussed.

Experimental study on the special shear thinning process of a kind of non-Newtonian fluid

To study the effect of long chain molecule and surface active agent on non-Newtonian fluid properties, rheological experiments on two different fluids have been done. The first group of the fluid is the hydroxyethyl cellulose water solution, and the second is the water solution containing the mixture of dodecyl- triethyl ammonium bromide and lauryl sodium sulfate. With the increasing shear rate, shear thinning phenomenon appears in the first group of solution, and a spe- cial shear thickening-shear thinning phenomenon appears in the second group. It is considered that the special rheological phenomenon is caused by the difference between the aggregating and the departing speed of the colloidal particles formed in the fluid. The difference between the two speeds relates with the shear rate. The experiment results indicate that the rheological properties can be designed by choosing proper additives at a certain shear rate, and such a fluid with special vis- cosity variation should be included in the classification of the non-Newtonian fluid.

Effect of microparticle properties on erosion in solid-steam mixtures

Based on a custom-built experimental apparatus, irregular microparticles of different sizes and microparticles of the same size but of different shape were added to wet steam, and erosion experiments were performed on polished medium carbon steel specimens. After the experiments, the eroded surfaces were analyzed by scanning electron microscopy and the degree of damage was evaluated by area loss. The results indicated that microparticle size significantly affects the degree of erosion damage. With an increase in size, variations in the method of damage mainly cause different degrees of damage on an eroded surface. Microparticle shape hardly affects the number of craters. Compared with spherical microparticles, irregular microparticles cause indentations more easily and result in more severe abrasion on the material’s surface.

Application of Navier-Stokes equation to lubrication

Compared with the results of commonly used Reynolds equation, numerical solutions of Navier-Stokes and continuity equations are given for lubricant films in an oil wedge and a Rayleigh bearing. Characteristic length ratio (L_y/L_(xz)), one important parameter in the assumptions of Rey- nolds theory, is discussed in detail to analyse the difference. Some special jumping phenomena appear around Rayleigh step, the increment from average value is up to 28%, which may aggra- vate the wearing of the step tip.

Web-based tribology design repository system

Tribology design is one of the most important parts of mechanical product design as thestrength design. Unfortunately, because tribology design knowledge is often m ulti-disciplinary,complicated and piecemeal, it is therefore difficult for a mechanical designer to capture the neededtribology design knowledge. The concept of tribology design repository is proposed in this paper totry to address this problem. This paper presents an object-oriented knowledge representation lan-guage based on the modeling of tribology design component and it makes the complicated tribol-ogy knowledge represented has such advantages as inheritance, encapsulation, and consistency.A web-based triblogy design repository is then established and it enables the edition, retrieve,sharing and reuse of corporate tribology design knowledge in the repository from the Internet.