A Full-Scale Optimization of a Crop Spatial Planting Structure and its Associated Effects

Driven by the concept of agricultural sustainable development,crop planting structure optimization(CPSO)has become an effective measure to reduce regional crop water demand,ensure food security,and protect the environment.However,traditional optimization of crop planting structures often ignores the impact on regional food supply–demand relations and interprovincial food trading.Therefore,using a system analysis concept and taking virtual water output as the connecting point,this study proposes a theoretical CPSO framework based on a multi-aspect and full-scale evaluation index system.To this end,a water footprint(WF)simulation module denoted as soil and water assessment tool–water footprint(SWAT-WF)is constructed to simulate the amount and components of regional crop WFs.A multi-objective spatial CPSO model with the objectives of maximizing the regional economic water productivity(EWP),minimizing the blue water dependency(BWFrate),and minimizing the grey water footprint(GWFgrey)is established to achieve an optimal planting layout.Considering various benefits,a fullscale evaluation index system based on region,province,and country scales is constructed.Through an entropy weight technique for order preference by similarity to an ideal solution(TOPSIS)comprehensive evaluation model,the optimal plan is selected from a variety of CPSO plans.The proposed framework is then verified through a case study of the upper–middle reaches of the Heihe River Basin in Gansu province,China.By combining the theory of virtual water trading with system analysis,the optimal planting structure is found.While sacrificing reasonable regional economic benefits,the optimization of the planting structure significantly improves the regional water resource benefits and ecological benefits at different scales.

The Experimental Investigation of Recirculation of Air-Cooled System for a Large Power Plant

The paper introduces thermal buoyancy effects to experimental investigation of wind tunnel simulation on direct air-cooled condenser for a large power plant. In order to get thermal flow field of air-cooled tower, PIV experiments are carried out and recirculation ratio of each condition is calculated. Results show that the thermal flow field of the cooling tower has great influence on the recirculation under the cooling tower. Ameliorating the thermal flow field of the cooling tower can reduce the recirculation under the cooling tower and improve the efficiency of air-cooled condenser also.

Efficiency of white lupin in the removal of mercury from contaminated soils: Soil and hydroponic experiments

This study examined the ability of the white lupin to remove mercury （Hg） from a hydroponic system （Hg concentrations 0, 1.25, 2.5, 5 and 10 μmol/L） and from soil in pots and lysimeters （total Hg concentration （19.2 ± 1.9） mg/kg availability 0.07%, and （28.9 ± 0.4） mg/kg availability 0.09%, respectively）, and investigated the accumulation and distribution of Hg in different parts of the plant. White lupin roots efficiently took up Hg, but its translocation to the harvestable parts of the plant was low. The Hg concentration in the seeds posed no risk to human health according to the recommendations of the World Health Organization, but the shoots should not be used as fodder for livestock, at least when unmixed with other fodder crops. The accumulation of Hg in the hydroponically-grown plants was linear over the concentration range tested. The amount of Hg retained in the roots, relative to the shoots, was almost constant irrespective of Hg dose （90%）. In the soil experiments, Hg accumulation increased with exposure time and was the greater in the lysimeter than in the pot experiments. Although Hg removal was the greater in the hydroponic system, revealing the potential of the white lupin to extract Hg, bioaccumulation was the greatest in the lysimeter-grown plants; the latter system more likely reflects the true behaviour of white lupin in the field when Hg availability is a factor that limits Hg removal. The present results suggest that the white lupin could be used in long-term soil reclamation strategies that include the goal of profitable land use in Hg-polluted areas.

Experimental and Numerical Study on the Gas Explosion in Urban Regulator Station

Regulator station is an important part in the urban gas transmission and distribution system.Once gas explosion occurs,the real explosion process and consequences of methane gas explosion in the regulator station were not revealed systematically.In this study,a full-scale experiment was carried out to simulate the regulator station explosion process,and some numerical simulations with a commercial CFD software called FLACS were conducted to analyze the effect of ignition and vent conditions on the blast overpressure and flame propagation.The experimental results demonstrated that the peak overpressure increased as the distance from the vent increased within a certain distance.And the maximum overpressure appeared 3 m away from the door,which was about 36.6 kPa.It was found that the pressure-time rising curves obtained from the simulation are basically the same as the ones from the experiment,however,the time of reaching the peak pressure was much shorter.The numerical simulation results show that the peak overpressures show an increase trend as the ignition height decreased and the vent relief pressure increased.It indicates that the damage and peak overpressure of gas explosion could be well predicted by FLACS in different styles of regulator station.In addition,the results help us to understand the internal mechanism and development process of gas explosion better.It also offers technical support for the safety protection of the urban regulator station.

Large scale sand saltation over hard surface:a controlled experiment in still air

Saltation is the major particle movement type in wind erosion process.Saltating sand grains can rebound up to tens of times larger in length and height over hard surface(such as gravel surface)than over loose sand surface.Gravels usually have different faces,causing distinct response of the impacting grains,but the effects of the grain and gravel-surface contact angle on grain rebound are not yet well quantified.We performed full-range controlled experiments of grain saltation using different contact angles,grain sizes and impact speeds in still air,to show that contact angle increases the height of representative saltation path but decreases particle travel length.The results were compared with outputs from the COMprehensive numerical model of SALTation(COMSALT).Large saltation height of 4.8 m and length of 9.0 m were recorded.The maximum and representative saltation height over the gravel surface were found to be about 4.9 times and 12.8 times those over the loose sandy surface,respectively.The maximum saltation length may be reduced by 58%and the representative saltation height may be increased by 77%as contact angle increases from 20°to 40°.We further showed that the collision inertia contributes 60%of the saltation length,and wind contributes to the other 40%.These quantitative findings have important implications for modeling saltation trajectory over gravel surface.

Full-scale experiment for segmental linings of deep-buried shield tunnels bearing high inner water pressure:Comparison of mechanical behaviors of continuous-and stagger-jointed structures

Full-scale loading tests were performed on shield segmental linings bearing a high earth pressure and high inner water pressure,focus-ing on the effects of the inner water load and assembly manner on the mechanical properties of the segmental linings.The test results indicate that the deep-buried segmental linings without inner pressure have a high safety reserve.After the action of high inner water pressure,the lining deformation will increase with the reduction of the safety reserve,caused by the significant decrease in the axial force in the linings.Because the bending moment at the segmental joints is transferred to the segment sections in the adjacent ling rings,the convergence deformation,openings of segmental joints,and bolt strains are smaller for the stagger-jointed lining than those for the continuous-jointed lining;however,dislocations appear in the circumferential joints owing to the stagger-jointed assembly.Although it significantly improves the mechanical performance of the segmental lining,stagger-jointed assembly results in compromising the water-proofing safety of circumferential joints.The stagger-jointed assembly manner can be considered to improve the service performance of shield tunnels bearing high inner water pressure on the premise that circumferential joint waterproofing is satisfied.

Experimental Study on Working Performance of Rice Rope Direct Seeding Machine

Structure and sowing principles of rice rope direct seeding machine are introduced. In order to test the machine＇ s working performance, such as compacting effect, sowing depth, influence of sowing device to rice rope, etc., field experiments were conducted. It is concluded that mean slip ratio of compacting wheel 1 is 4.44%, wheel 2 is 5.58%, wheel 3 is 7.81%, and wheel 4 is 6.96%; mean depth of planting is 29.72 mm, and mean variability coefficient of planting depth is 6.39%. Maximum variability coefficient of planting depth is 8.40%. Rice rope＇s snapping is closely related with the machine＇s speed and guide thread wheel by sowing device orthogonal experiments. Test results show that the machine has a rational design, safe work and meets to the requirements of planting. This study has laid the foundation for further studying the project.

Are Invasive Genotypes Superior? An Experimental Approach Using Native and Invasive Genotypes of the Invasive Grass <i>Phalaris Arundinacea</i>

The admixture and recombination of individuals from the native range into a new range may lead to the production of invasive genotypes that have higher fitness and wider climatic tolerances than the native genotypes. In this paper, we compare the survival and growth of native EU and invasive NA genotypes when planted back into the native EU range near where the EU genotypes were collected. We test this hypothesis using the invasive wetland grass Phalaris arundinacea. If invasive genotypes have evolved to have higher survival and growth, then they should outperform the native EU genotypes under field conditions that are better suited to the EU genotypes. Individual plants of the wetland grass, Phalaris arundinacea collected from native Europe (Czech Republic (CZ) and France (FR)) and North America (Vermont (VT) and North Carolina (NC)) were planted into common gardens in Trebon, Czech Republic (49.0042&deg;N, 14.7721&deg;E) and Moussac, France (43.9808&deg;N, 4.2241&deg;E). Invasive genotypes from North Carolina (NC) survived as well or better than native genotypes in both the Trebon and Moussac garden. Additionally, invasive NC genotypes suffered higher herbivore damage than native genotypes but their growth and survival were not significantly different than genotypes from the other re-gions. A companion field experiment that simulated biomass removal through grazing indicated that invasive NC genotypes recovered faster following grazing than genotypes from other regions. Our results suggest that not all invasive genotypes are superior and regional differences in aggressiveness between invasive genotypes are as great as differences between individuals from native and invasive populations. Introduction of genotypes leading to invasion depends upon the environmental conditions and the suitability of the climate for the introduced individuals.

Experiments on Large-Diameter Welded Hollow Spherical Joint

We experimented on welded hollow spherical joint of a stadium steel roof to investigate the stress and strain distributions on the surface of the joint and determine the ultimate bearing capacity. Then, finite element analysis was made to experimental results. When the test load was 140% of the design load, the stress at the bottom of the fourth wimble pipe reached the yield point. The experimental results agree with the analytical results well.

Experimental Research and Finite Element Analysis on Setting Stiffening Rib of Corner Joints in Gabled Frames

In order to clear constructional design of corner joint, it is necessary to further investi-gate mechanical property of corner joint in gabled frames. Through static test and finite element software analysis of comparing the panel zone with and without inclined stiffener. Some conclusions are given in the article. The load displacement curves show that the capacity of oblique nodes installed within stiffening rib components is enhanced i.e. 40% more than those without stiffening rib nodes. The results reveal that in the gabled frames, the corner node with the inclined stiffening rib can improve the bearing capacity of the specimens. When the extraterritorial flange is tension, the erection of the inclined stiffening rib can prevent structural failure and improve effectually the ductility of the structure.

Study on smoke propagation in tunnel construction of a hydropower station: A full-scale fire experiment

In this study,full-scale fire experiments were conducted in a hydropower station to investigate smoke propagation during tunnel construction.The flame height,smoke temperature and stratification,smoke descent and spread velocity were analyzed via measurements and on-site observations.The initial combustion stage was largely affected by ignition source during tunnel construction for diesel pool fire,and the average flame height in the fully developed stage could reach 1.4-2.1 m in experimental fire scenarios.The gradient of the smoke temperature evolution near the fire was the opposite for the upstream and downstream regions.The longitudinal temperature distribution was concentrated in a small range at the heights of the smoke layer,and gradually decreased by air entrainment as the height decreased,while further increasing in the lower half of the tunnel height in the near-fire region under heat radiation from the fire source.Moreover,distinct and stable smoke stratification formed during the fully developed combustion stage,and the smoke layer interface was at approximately half the tunnel height.Smoke descent was aggravated in the decay stage of combustion,and the fire risk remained high after the fully developed period.The smoke front spread velocity was empirically determined for the full-scale tunnel fire scenarios.Conclusions from full-scale experiments can support smoke control design and on-site fire emergency response plans for hydropower stations.

Clonal Transgenerational Effects Transmit for Multiple Generations in a Floating Plant

Environmental conditions of a parent plant can influence the performance of their clonal offspring,and such clonal transgenerational effects may help offspring adapt to different environments.However,it is still unclear how many vegetative generations clonal transgenerational effects can transmit for and whether it depends on the environmental conditions of the offspring.We grew the ancestor ramets of the floating clonal plant Spirodela polyrhiza under a high and a low nutrient level and obtained the so-called 1^(st)-generation offspring ramets of two types(from these two environments).Then we grew the 1^(st)-generation offspring ramets of each type under the high and the low nutrient level and obtained the so-called 2^(nd)-generation offspring ramets of four types.We repeated this procedure for another five times and analyzed clonal transgenerational effects on growth,morphology and biomass allocation of the 1^(st)-to the 6^(th)-generation offspring ramets.We found positive,negative or neutral(no)transgenerational effects of the ancestor nutrient condition on the offspring of S.polyrhiza,depending on the number of vegetative generations,the nutrient condition of the offspring environment and the traits considered.We observed significant clonal transgenerational effects on the 6^(th)-generation offspring;such effects occurred for all three types of traits(growth,morphology and allocation),but varied depending on the nutrient condition of the offspring environment and the traits considered.Our results suggest that clonal transgenerational effects can transmit for multiple vegetative generations and such impacts can vary depending on the environmental conditions of offspring.

勉县玉米-大豆带状复合种植玉米品种筛选试验

玉米-大豆带状复合种植技术目标是保证带状复合种植条件下玉米与单作相比不减产,增收一季豆。与玉米常规种植相比,种植的株行距变化较大,密度增加,玉米品种的株型、耐密性、抗逆性、丰产性等指标成为此项技术应用成功的前提。通过试验,“1.8m带型2+2模式”玉米-大豆带状复合种植玉米品种主推登海605、农科大8号和延科288,搭配种植五单2号、中金368。

2BP-2000型水稻育秧播种机分盘装置研制

针对现有育秧播种机分盘装置生产效率较低、高速作业时易出现卡盘和秧盘输送不连续等问题,该研究设计了一种生产效率不低于2000盘/h的机械气动式自动分盘装置,可快速、准确完成分盘和供盘,适配2BP-2000型水稻育秧播种机高速播种。阐述了分盘装置的基本结构和工作原理,开展分盘、接盘过程分析,确定装置稳定分盘、接盘作业的关键机构与工作参数。分盘稳定性试验结果表明,生产率为1600~2000盘/h时,分盘稳定性不低于98.67%。开展以层叠秧盘数、生产率和秧盘质量为试验因素,以接盘成功率为试验指标的三因素三水平正交旋转组合试验,得到影响接盘成功率的因素主次关系为生产率、层叠秧盘数、秧盘质量,其中生产率、层叠秧盘数对接盘成功率影响显著(P<0.05),秧盘质量对接盘成功率影响不显著(P≥0.05),表明分盘装置对不同质量的秧盘适应性较好,其最优参数组合为:生产率2000盘/h、层叠秧盘数6盘/层、秧盘质量750 g/盘,该条件下分盘装置的接盘成功率均值为98.43%,与预测值仅相差0.29个百分点。研究结果对提高水稻硬盘育秧播种机械化水平具有实用价值。

植物生理学综合设计性实验教学的改进与实践

植物生理学实验是高等院校生物类专业重要的专业基础课程之一,与理论课程相辅相成。在科学技术快速发展阶段,植物生理学实验教学也要与之相匹配,大量的生物学仪器设备在实验中得到广泛应用。针对植物生理学实验中的验证性、演示性实验多,综合设计性实验较少,实验方法新颖性有待提高等问题,对植物生理学实验教学进行了综合改革,设计了适合于当前植物生理学实验发展趋势和教学要求的综合性实验,实现培养学生科学探究、合作精神、自我发展和学习意识及能力的课程目标。

一型手推式玉米小区播种机研制与试验

由于我国育种单位众多且较分散,考虑投入产出比等经济效益指标影响,面临着小区试验面积小、分布不均等问题。针对玉米小区试验播种用工多、出苗差等问题,研制一种简单实用的手推式玉米小区试验播种机。对比国内外研发推广的小区播种机,该机械对操作人员技术要求不高,操作更简单;对播种地块、种子排列没有严格要求,实用性更强。非常切合我国玉米育种现状,具有很好的应用前景。

青菜高密度移栽机植苗机构的设计与试验

目前国内移栽机尚无成熟的适用于青菜等多行密植蔬菜移栽的植苗机构;针对小株距小行距、高效率的密植移栽要求,设计了一种非圆齿轮行星轮系八行同步植苗机构,并进行了运动学仿真和田间移栽试验。对非圆齿轮行星轮系进行了运动学建模与分析,开发了植苗机构辅助分析与优化设计软件;分析了不同机构参数对植苗轨迹姿态的影响,并通过人机交互的方式得到一组满足青菜小株距移栽要求的机构参数;建立了八行同步植苗机构的三维模型,利用虚拟样机仿真技术绘制出仿真轨迹,并与理论轨迹进行对比,以验证植苗机构三维设计的正确性;开展了田间移栽试验,以验证该机构的可行性和实用性。试验结果表明:在作业转速为15r/min、前进速度为55mm/s的情况下,八行植苗机构的作业株距和行距均为110mm,平均植苗成功率为93.9%,移栽密度超过70株/m2,试验移栽效率为240株/min,表明该机构在机械化密植移栽作业中有较高的应用价值。该研究为高密度移栽机植苗机构的研发提供了理论和试验依据,促进了密植型蔬菜钵苗机械化移栽的进程,为密植移栽机的进一步研究提供技术支持和参考。

基于Plant Simulation的白车身侧围焊装线仿真与优化

虚拟仿真技术是目前对焊装生产线进行工艺规划的主要手段。在分析某汽车白车身侧围焊装线的基础上,利用仿真软件Plant Simulation对侧围焊装线建立离散系统仿真模型,对设备工作情况和瓶颈工位进行分析,评估焊装线生产能力;通过设计Experiment Manager分析模块中的多因子试验,将焊装线产量作为指标,暂存区容量及添加位置作为影响因子,对暂存区的配置进行研究。结果表明合适的暂存区容量和添加位置能极大提高焊装线生产能力,为焊装线的优化提供理论依据和科学参考。

以检测为基础的高校转基因试验基地安全管理研究

转基因技术对选育高产、高品质的作物品种和全球粮食安全具有重要贡献。我国高度重视农业转基因技术的研究和发展,但转基因仍然存在一定的环境风险,需要被严格监管。高校转基因试验基地是开展转基因技术及其应用研究的重要平台。该文从转基因植物的种植现状及其潜在风险出发,以浙江大学为例详细介绍了以转基因检测为基础的全方位监管溯源流程,包括从种子—幼苗—果实—秸秆—土壤残留根系等不同阶段的取样检测,提出了以检测为基础的高校转基因试验基地安全监管方式。