C_4作物FACE(free-air CO_2 enrichment)研究进展

持续迅速上升的大气二氧化碳浓度([CO2])是全球变暖最大的驱动因子,但其作为光合作用底物直接增加了作物的生产力。相比C3作物,人们对未来高浓度CO2情形下C4作物的响应规律认识较少。与封闭或半封闭气室研究相比,FACE(free-airCO2 enrichment)试验在空气自由流动的大田条件下对作物表现进行研究,它提供了对未来作物生长环境的真实模拟,因此提供了评估CO2肥料效应以及揭示植物响应机制的最好机会。作为人类重要的粮食和饲料来源,高粱和玉米是最重要的C4作物。在简介美国玉米和高粱FACE系统的基础上,综述了FACE情形下高浓度CO2(模拟本世纪中叶大气CO2浓度,即550μmol/mol)对两大作物生理、生长和产量以及土壤特性等方面的影响,同时比较了与气室研究结果的异同点。(1)FACE使干旱条件下两作物光合作用显著增强,但湿润条件下没有影响;FACE条件下高粱出现光合适应现象,而玉米没有;(2)FACE使两作物气孔导度大幅下降,导致叶温升高、蒸腾速率下降、蒸发蒸腾总量减少或没有变化、叶片总水势和水分利用效率增加或没有变化;(3)FACE对两作物物候期和化学组分影响很少;(4)FACE使干旱条件下两作物生长和产量略有增加,但湿润条件下没有影响;(5)FACE使高粱田土壤丛枝状菌根真菌的长度和易提取胶状物质浓度显著增加,导致水稳性土壤团聚体增加;FACE对高粱田N2O或含氮气体(N2O+N2)的排放没有影响;(6)高浓度CO2对两作物气孔导度的影响FACE试验明显大于气室试验,而对生长和产量的影响呈相反趋势。阐明CO2与基因型、土壤湿度和大气温度间的互作效应及其机制是下一轮C4作物FACE研究优先考虑的方向,技术的不断进步已为利用大型FACE系统来研究这些互作效应提供了可能。

Four years of free-air CO_2 enrichment enhance soil C concentrations in a Chinese wheat field

Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems. The effects of free-air CO2 enrichment （FACE） and N fertilization on soil organic C （Corg）, dissolved organic C （DOC）, microbial biomass C （Cmic） and soil basal respiration （SBR） were investigated in a Chinese wheat field after expose to elevated CO2 for four full years. The results indicated that elevated CO2 has stimulative effects on soil C concentrations regardless of N fertilization. Following the elevated CO2, the concentrations of Corg and SBR were increased at wheat jointing stage, and those of DOC and Cmic were enhanced obviously across the wheat jointing stage and the fallow period after wheat harvest. On the other hand, N fertilization did not significantly affect the content of soil C. Significant correlations were found among DOC, Cmic, and SBR in this study.

Protecting the photosynthetic performance of snap bean under free air ozone exposure

Tropospheric ozone（O3） is a major air pollutant and causes serious injury to vegetation. To protect sensitive plants from O3 damage, several agrochemicals have been assessed,including cytokinin（e.g., kinetin, KIN） and ethylenediurea（EDU） with cytokinin-like activity.In higher plant, leaves are primarily injured by O3 and protective agrochemicals are often applied by leaf spraying. To our knowledge, the mitigating abilities of EDU and KIN have not been compared directly in a realistic setup. In the present research, impacts of elevated O3（2 × ambient O3, 24 hr per day, for 8 days） on an O3 sensitive line（S156） of snap bean（Phaseolus vulgaris）, which is often used for biomonitoring O3 pollution, were studied in a free air controlled exposure system. The day before starting the O3 exposure, plants were sprayed with a solution of EDU（300 ppm）, KIN（1 mmol/L） or distilled water, to compare their protective abilities. The results demonstrated that 2 × ambient O3 inhibited net photosynthetic rate and stomatal conductance, increased the minimal fluorescence yield of the dark-adapted state, decreased the maximal quantum yield of PSII photochemistry, and led to visible injury. KIN and EDU alleviated the reduction of the photosynthetic performance, and visible injury under O3 fumigation. The plants sprayed with EDU showed greater ability to mitigate the O3 damage than those sprayed with KIN. Chlorophyll fluorescence imaging may have detected more precisely the differences in O3 response across the leaf than the conventional fluorometer.

Effects of free-air CO_2 enrichment on adventitious root development of rice under low and normal soil nitrogen levels

Free air CO2 enrichment(FACE) and nitrogen(N) have marked effects on rice root growth,and numerical simulation can explain these effects. To further define the effects of FACE on root growth of rice, an experiment was performed, using the hybrid indica cultivar Xianyou63. The effects of increasing atmospheric CO2 concentration [CO2], 200 μmol mol-1higher than ambient, on the growth of rice adventitious roots were evaluated, with two levels of N: low(LN, 125 kg ha-1) and normal(NN, 250 kg ha-1). The results showed a significant increase in both adventitious root number(ARN) and adventitious root length(ARL) under FACE treatment. The application of nitrogen also increased ARN and ARL, but these increases were smaller than that under FACE treatment. On the basis of the FACE experiment, numerical models for rice adventitious root number and length were constructed with time as the driving factor. The models illustrated the dynamic development of rice adventitious root number and length after transplanting, regulated either by atmospheric [CO2] or by N application.The simulation result was supported by statistical tests comparing experimental data from different years, and the model yields realistic predictions of root growth. These results suggest that the models have strong predictive potential under conditions of atmospheric [CO2] rises in the future.

Effect of free-air CO_2 enrichment on nematode communities in a Chinese farmland ecosystem

At a rice wheat rotational free air CO 2 enrichment(FACE) platform, the effect of elevated atmospheric CO 2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmospheric CO 2(ambient 370 μl/L + 200 μl/L). 32 families and 40 genera of nematode were observed in soil suspensions during the study period. Under FACE treatment, the numbers of total nematodes, bacterivores and fungivores exhibited an increasing trend. Because of the seasonal variation of soil temperature and moisture, the effect of elevated atmospheric CO 2 on soil nematodes was only observed under favorable conditions. The response of nematode communities to elevated atmospheric CO 2 may indicate the change of soil food web.

Effects of Free-air CO2 Enrichment on Root Characteristics and C:N Ratio of Rice at the Heading Stage

A hydroponics experiment was conducted to investigate the rice root growth in FACE （free-air carbon dioxide enrichment）. The root biomass, root volume, ratio of root/shoot, number of adventitious roots and root diameter significantly increased under FACE conditions, while the CO2 enrichment decreased the N concentration in rice roots without any change in the C content, leading to an increase in root C：N ratio. Moreover, the elevated CO2 resulted in a remarkable decrease of root activity, expressed as per unit root dry weight, which might be responsible for decreased N concentration in roots.

Modeling of the whole process of shock wave overpressure of freefield air explosion

The waveform of the explosion shock wave under free-field air explosion is an extremely complex problem.It is generally considered that the waveform consists of overpressure peak,positive pressure zone and negative pressure zone.Most of current practice usually considers only the positive pressure.Many empirical relations are available to predict overpressure peak,the positive pressure action time and pressure decay law.However,there are few models that can predict the whole waveform.The whole process of explosion shock wave overpressure,which was expressed as the product of the three factor functions of peak,attenuation and oscillation,was proposed in the present work.According to the principle of explosion similarity,the scaled parameters were introduced and the empirical formula was absorbed to form a mathematical model of shock wave overpressure.Parametric numerical simulations of free-field air explosions were conducted.By experimental verification of the AUTODYN numerical method and comparing the analytical and simulated curves,the model is proved to be accurate to calculate the shock wave overpressure under free-field air explosion.In addition,through the model the shock wave overpressure at different time and distance can be displayed in three dimensions.The model makes the time needed for theoretical calculation much less than that for numerical simulation.

Measurements of Air-kerma in Mammography X-Ray Standard Using Free-air Chamber

Mammography x-rays standard is required to improve the quality of mammary machine and reduce the dose for w omen and staff. The molybdenum target x-rays machine is used as the radiation source and free-air cylindrical chamber is designed for detecting photon. Four standard radiation qualities are established w ith international standard documents as references. The Correction factors including air attenuation,scattered radiation,fluorescence,w all transmission,electron loss are studied in the four radiation quality. The uncertainty in absolute measurement of air-kerma includes air volume measurement of ionization chambers,current measurement,measurement of temperature and pressure,measurement of correction factors,physical constants and orientation of the reference distance. The relative combined standard uncertainty is 0.24%.

Effect of surface free energy of acetylene black powder on air electrode performance

The effects of acetylene black powder surface free energy on air electrode electrochemical performance and lifetime were studied. The acetylene black was immersed in 30% H2O2 at room temperature and the changes of functional groups and surface free energy were investigated by X-ray Photoelectron Spectroscopy (XPS) and powder contact angle (CA). The air electrode performance was characterized by the potential polarization curves and the lifetime was measured by constant-current discharge. It shows that, its surface free energy is the lowest when the acetylene black is immersed in H2O2 for 240 h. The polarization potential of the air electrode prepared by the pretreated acetylene black is 0.25 V(vs. Hg/HgO), 0.21 V lower than the air electrode with untreated acetylene black when the working current density is 100 mA·cm-1. And its lifetime is over 800 h at 80 mA·cm-1. The pretreatment of acetylene black for proper time by H2O2 is favorable for the stability of the tri-phase reaction interface of air electrode and improvement of its performance.

Effects of Different Facilities on Laying Performance,Egg Quality and Air Quality for Layers Under Free Range System

[ Objective] This paper aimed to study the effects of different facilities on laying performance, egg quality and air quality for commercial layers under free range system. [Metbod] The single factorial arrangement was used in the tdal. 2 800 commercial Beijing You Chicken （BYC） at 23 weeks of age were chosen and randomly divided into four groups, three replicates each group, and 210 birds each replicate. The layers lived in loose housing condition with deep litter inside. Group 1 was the control, equipped with standard laying boxes, and flat-type perches; group 2 was e- quipped with common laying boxes, and flat-type perches; group 3 was equipped with common laying boxes, and erect-type perches, and group 4 was equipped with standard laying boxes, and erect-type perches. The laying performance, laying position and egg quality of birds during 24 to 32 weeks of age were recorded and measured, and average NH3, CO~ concentration of each group at 32 weeks of age were measured and detected. [Result] The results showed that laying performance of commercial BYC under loose housing condition were significantly different during 24 -32 weeks of age. The laying rate of the control group equipped with flat-type porches and standard laying boxes （33.25%） was significantly higher than in group equipped with flat-type perches and common laying boxes （21.83%） （P〈0.05）, and other two groups （26.04% and 27.48%） （P 〈0.05）. The ratio of floor eggs was significantly lower in groups with standard laying boxes than in the groups with common laying boxes （P 〈0. 05）, and the laying proportion in the first floor of layer boxes were much higher than those in the second floor （ P 〈 0.05）. There were no significant differences on egg quality among the groups （P〉0.05）. Average NH3, CO2 concentration of group 3 and 4 at 82 weeks of age were both signifi- cantly higher than of group 1 and 2 （P 〈0.05）. [ Conclusion] All of the above indicated that the utilization of facilities could improve layer＇s laying rate, especially with flat-type perches and standard laying boxes, and the indoor air quality was also affected to some extent.

Experimental Investigation of the Cooling Capacity of Gaseous Carbon Dioxide in Free Jet Expansion for Use in Portable Air-Cooling Systems

This paper investigates the possibility of using the free expansion of gaseous CO2 in portable air-cooling systems. The cooling capacity of the gaseous CO2 free jet expansion was calculated using three different approaches and the results showed that the simplified calculations would give approximated cooling values with an 11.6% maximum error. The mass flow rate, upstream pressure and cooling capacity of the gaseous CO2 decreased with time. A maximum 48.5 watts of cooling was recorded at minute 4 and a minimum value of 10.4 watts at the end of the test. The drop in cooling capacity is due to the evaporation of the liquid CO2 inside the small cylinder which cools the two-phase CO2 mixture and causes a pressure drop (from 6 MPa to 2.97 MPa), which also affects the mass flow rate of gaseous CO2 exiting the orifice (from 0.56 g/s to 0.24 g/s). If this cooling technique is to be considered in portable compact-cooling systems, the mass, pressure and cooling capacity drop with time must be solved. One of the solutions could be to cover the cylinder with a heating coat to compensate for the heat absorbed by the evaporation of the liquid CO2.

Sister chromatid exchange and DNA damage in human lymphocytes induced by air-dust in Lanzhou City: involvement in free radicals

The air-dust samples collected from petro-chemical industrial region in the suburb of Lanzhou and from a certain rural region 64 km away from the city were extracted, with a mixed solvent (benzene: hexane: isopropanol=7:2:1) for 8 hours. A strong free radical signal at g= 2.00 of air-dust itself and a hyperfine splitting EPR signal of extract from air-dust have been detected. The sister chromatid exchange frequency (SCE) was increased by extracts of both dusts from the industrial region and from the rural region. If a chemical is able to increase SCE up to twice as high as the control, this chemical is considered to be mutagenic and/or carcinogenic. The double SCE frequency concentration is 23 μg/ml for the dust extract obtained from the industrial region and 47μg/ml for that from the rural region. Extracts were able to damage to DNA template. Results indicated that the mutagenicity and/or carcinogenicity of the extracts obtained from the petro-chemical industrial region were stronger than that of the extracts from the rural region.

高流速、大流量无压洞掺气设施体形优化模型试验研究

高水头、大流量、高流速的泄水建筑物,往往需要设置掺气设施来降低空蚀破坏。结合新疆某水利枢纽工程实例,通过开展泄洪冲沙洞水工模型试验研究,对1号、2号掺气设施挑坎高度、通气孔面积、坡比及型式进行优化设计。结果表明:体形优化后,在各种工况下,掺气设施掺气效果良好,掺气空腔完整而稳定,坎下未出现较大回水等不利流态;通气孔通气顺畅,整体水流流态平顺,无水翅溅到洞顶等不利现象;沿程余幅均满足要求;过流能力和流量系数基本与原设计一致。研究结果可为类似工程的掺气设施体形研究提供指导与技术支撑。

无脉冲微流控片上蠕动微泵研制及其性能研究

为解决微流体连续输送过程中存在的流动脉冲、精度低等问题,研制一种基于微流控技术的片上蠕动微泵。该微泵由微流控芯片和电机驱动系统组成,利用驱动系统中的滚子轴承连续挤压微流控芯片中的微流道,以实现微流体的精确泵送。为研究微泵的流量特性,设计具有气腔稳流功能的微流道,采用光固化3D打印技术与模塑法制作微流控芯片样件;开发电机驱动系统,测试微泵在不同电机转速下的平均流量、总流量和瞬时流量,并将其流量特性与商业蠕动泵的流量特性进行对比。研究结果表明:随着电机转速增加,微泵的平均流量逐渐增大,瞬时流量误差逐渐减小;当电机转速大于60 r/min时,瞬时流量误差可控制在5%以内,其流量精度显著高于商业蠕动泵的流量精度;片上蠕动微泵可有效抑制微流体脉冲,提升微流体控制精度,在精密微流体输送中具有广阔的工程应用前景。

Numerical Simulation of Root Growth Dynamics of CO_2-Enriched Hybrid Rice Cultivar Shanyou 63 Under Fully Open-Air Field Conditions

Hybrid indica rice （Oryza sativa L.） cultivars play an important role in rice production system due to its heterosis, resistance to environmental stress, large panicle, and high yield potential. However, no attention has been given to its root growth dynamic responses to rising atmospheric CO2 concentration （[CO2]） in conjunction with nitrogen （N） availability. Free air COz enrichment （FACE） and N have significant effects on rice root growth. In this experiment, a hybrid cultivar Shanyou 63 （Oryza sativa L.） was used to study the effects of FACE and N levels on roots growth of rice. The results showed a significant increase in both adventitious root volume （ARV） and adventitious root dry weight （ARD） under the FACE treatment. The application of nitrogen also increased ARV and ARD, but the increase was smaller than that under FACE treatment. On the basis of the FACE experiment, numerical models for rice adventitious root volume and dry weight were built with the time as the driving factor. The models illustrated the dynamic development of rice adventitious root volume and dry weight after transplanting, regulated either by the influence factor of atmospheric [CO2] or by N application. The models were successfully used to predict ARV and ARD under FACE treatment in a different year with the predicted data being closely related to the actual experimental data. The model had guiding significance to growth regulation of rice root under the condition of atmospheric [CO2] rising in the future.

基于热固耦合的无油空压机连杆轴承装配参数优化研究

连杆大头轴承是无油空压机往复运动关键的传动部件,由于没有润滑油的润滑及冷却作用,连杆大头轴承承受复杂的交变载荷和温度载荷,因此连杆大头轴承合理的装配设计对无油空压机的可靠传动具有重要意义。采用热固耦合的有限元分析方法对于无油空压机分体式连杆装配工艺参数对轴承外圈与连杆大头端配合的影响规律进行了理论研究。结果表明:无油空压机工作时轴承的温度越高,配合面所需的过盈量越大才能保证轴承外圈与连杆大头的有效接触;当高温下过盈量能保证轴承外圈的有效接触时,连杆螺栓的预紧力越大越能保证轴承外圈的有效配合,但过盈量越大也会造成连杆螺栓预紧力的衰减越严重。最终选用的连杆螺栓的预紧力为30 kN,轴承外圈与连杆大头间的过盈量为0.05 mm。

20℃的静止空气中直径5 mm的雨滴的自由下落运动研究

文章采用球形雨滴模型,利用空气阻力系数C_(D)的较严格的表达式即Wallis公式,计算出直径5 mm的雨滴在20℃的静止空气中自静止开始自由下落时的v~t图像.文章又在C_(D)统一取作0.44的近似下,解出解析的、普适的v(t)函数,并作出相应的v~t图像.结果显示这两条v~t曲线几乎完全重合,这就意味着近似处理是完全合适的.文章解释了其中的原因,并指出实测极限速率比球形雨滴模型下的理论值小2.00 m/s的原因在于实际雨滴的形状呈现汉堡状,其实际的空气阻力系数经计算约为0.52.文章认为球形雨滴模型从总体上看是比较实用的.

无氟防水剂X-702M在化纤面料上的洗后晾干应用

研究了一款无氟聚氨酯防水剂X-702M在化纤面料上的洗后晾干防水性能。织物经过X-702M处理后的手抓痕较浅,且具有较柔软的手感。探讨了不同交联剂对化纤面料洗后晾干防水性能的影响。结果发现,交联剂AX-101Z洗后晾干的防水性能较好。当X-702M用量为50 g/L、AX-101Z用量为10 g/L时,织物具有较好的防水性能、洗后晾干防水性能、手抓痕、手感,在化纤面料上可以做到初期防水性能为5级(100分),洗涤5次后室温晾干防水性能达到3~4级(80~90分)。

无油螺杆空压机典型故障分析与研究

针对英格索兰SM110无油螺杆空压机日常运行出现的机头锈蚀、冷却器进口管线连接处断裂、主电机过载等典型故障,根据无油螺杆空压机的工作原理,深入分析空压机频繁出现故障原因,对空压机运行方式进行深入探讨,通过平衡压缩空气供耗气量的方式实现单台空压机连续加载运行,避免空压机频繁加载卸载,为无油螺杆空压机的典型故障处理和预防提供了新思路。

乳制品行业压缩空气系统无油化改造案例浅析

阐述催化式除油系统在内蒙古蒙牛圣牧高科奶业有限公司喷油螺杆压缩机系统改造项目中的应用,结合催化燃烧式除油原理,以及改造后实际应用效果,针对乳制品及相关食品行业对无油空气等级的严格要求,提出一种将含油压缩空气系统无油化改造思路和方法,并针对无油螺杆压缩机实际运行环境提出优化建议。