Protective Oxide Film on Alloy X750 Formed in Air at 973 K

An effective pre-oxidation method for Alloy X750 was developed to reduce general corrosion in an oxygenated aqueous environment such as in BWR core water. The optimum condition of preoxidation in air at elevated temperatures was found to be 5–20 h at 973 K by considering the allowance condition of heat treatment for age-hardening.

Some characteristics of the corroded oxide film have been clarified by surface analyses with XMA, SIMS, AES, XPS etc. The film was composed of double oxide layers, namely a highly crystallized NiFe₂O₄ outer layer and a high Cr₂O₃ content inner layer. The passive property of the film has been recognized to be due to the nature of the oxides whereby NiFe₂O₄ restricts the dissolution of metals because of its low solubility and Cr₂O₃ restricts the diffusion of metal ions because of its high binding energy and low diffusion coefficient.     

轴封结构再造，减少轴封漏气

对汽轮机轴封结构进行科学合理的再造,减少轴封漏气,从根本上解决本车间锅炉蒸汽用量增加的问题。     

基于粒子群算法的汽车悬架弹簧的优化设计

粒子群算法容易理解、易于实现、编程简单。利用粒子群优化算法对汽车悬架弹簧进行优化设计,其速度要比用其它的方法要快得多,仅迭代很少的次数就能得出比较优的结果。有利于提高设计的速度,使设计易于实现,更大程度地提高设计的质量,为钢板弹簧系统、汽车悬架和整车的分析计算奠定坚实的基础。同时为少片弹簧和多片弹簧的优化设计提供了一种新的方法。     

光栅刻划中工作台过冲现象的改善

在分度运动控制系统中以 DMC2210控制卡为核心,采用光栅尺为分度运动反馈器件,实现了高精度的实时监测反馈。针对工作台“过冲”现象进行了两方面的分析优化：一方面,分析了步进电机减速方式对刻划效果的影响,通过分段减速初步改善了工作台“过冲”现象;另一方面,分析并模拟了弹簧(联接工作台和分度丝杠螺母)刚度对工作台“过冲”问题的影响,更换大刚度弹簧后,很大程度改善了工作台“过冲”现象。改进后对光栅刻线密度为79 g/mm的中阶梯光栅进行了多次刻划试验,计算的机器分度精度均在5 nm以内,选取其中一组较好的数据(机器分度精度为2.887 nm)与之前多次刻划试验中较好的一组数据(机器分度精度为7.759 nm)进行了比较,结果表明刻划机分度精度得到很大的提高。     

驾驶员座椅半主动空气悬架系统振动特性实验研究

构建了座椅半主动悬架振动特性测试实验系统,将带附加气室的空气弹簧、比例流量阀及磁流变减振器同时应用于座椅悬架,通过控制比例流量阀输入电压和磁流变减振器输入电流调节座椅悬架系统的刚度和阻尼,对不同参变量下座椅悬架系统的振动特性进行了实验研究。研究结果表明,在共振区,比例阀输入电压和磁流变输入电流的变化对系统位移传递率和加速度均方根值影响较大,而在低频振动区和隔振区影响较小;比例阀电压的增大可以降低系统的共振频率,磁流变电流的增大可以减小系统在共振区的位移传递率和加速度均方根值。     

Effect of Long-Term Forest Fertilization on Scots Pine Xylem Quality and Wood Borer Performance

We tested whether changes in long-term nutrient availability would affect the xylem quality and characteristics of Scots pine trees as a food source for the larvae of the xylophagous wood borer Hylotrupes bajulus L. (Cerambycidae). We looked for an effect of host plant growth and xylem structural traits on H. bajulus larval performance, and looked for delayed effects of long-term forest fertilization on xylem chemical quality. In general, larval performance was dependent on larval developmental stage. However, the growth of larvae also varied with host plant quality (increases in the concentration of nitrogen and carbon-based secondary compounds of xylem were correlated with a decrease in the larval growth rate). The greater annual growth of trees reduced tracheid length and correlated positively with second-instar H. bajulus growth rate. This is consistent with the hypothesis that intrinsic growth patterns of host plants influence the development of the xylophagous wood borer H. bajulus.     

Nitrogen chemistry in coal pyrolysis: Catalytic roles of metal cations in secondary reactions of volatile nitrogen and char nitrogen

The present review focuses on elucidating the chemistry of nitrogen release during coal pyrolysis, in particular, on making clear catalytic roles of inherent Ca and Fe ions in not only the partitioning of volatile-N to tar-N, HCN, NH₃ and N₂ but also the conversion of char-N to N₂.     

Strong Size Effects in Supported Ionic Nanoparticles: Tailoring the Stability of NO x Storage Catalysts

Based on a well-defined model-catalyst approach, we study the particle size dependent properties of NO _x storage materials. The single-crystal based model systems are prepared on an ordered Al₂O₃ film, on which BaO nanoparticles are grown under ultrahigh-vacuum (UVH) conditions. Particle size and density are characterized by scanning tunneling microscopy (STM). The interaction with NO₂ is probed by molecular beam (MB) methods in combination with time-resolved IR reflection absorption spectroscopy (TR-IRAS). It is found that both, the stability and the formation kinetics of alumina supported barium nitrate nanoparticles show a strong dependence on particle size. Very small BaO particles are rapidly converted into nitrates, however, the resulting aggregates exhibit a strongly reduced thermal stability. Surface and bulk nitrate and nitrate features are identified by means of vibrational spectroscopy. It is concluded that the size dependencies are related to the formation and decomposition of surface-related BaNO _x species the decomposition temperature of which can be tuned over an exceptionally large temperature interval. It is suggested that the stability of these surface NO _x species is strongly modified by the underlying support.     

Soil nutrient evaluation from swine effluent application to five forage-system practices

Many contract swine producers are located in the southeastern U.S. In this region almost all of the swine effluent from swine production is applied to warm-season perennial species such as bermudagrass [Cynodon dactylon (L.) Pers.] which is widely grown for summer grazing and hay production. A 3-yr study was conducted to investigate the impact of forage double-cropping on nutrient accumulation and leaching in Mantachie fine loam soil fertilized with swine (Sus scrofa domesticus) lagoon effluent as the source of plant nutrients. Plots of previously established Tifton 44 bermudagrass were overseeded in the fall with one of four winter annuals: berseem clover (Trifolium alexandrinum L.); crimson clover (T. incarnatum L.); ryegrass (Lolium multiflorum L.); or wheat (Triticum aestivum L.). Four plots of bermudagrass were not overseeded and considered as control. Plots were harvested in spring for cool-season annual hay and in summer for bermudagrass hay. Swine effluent was applied during spring and summer on a need base. Suction lysimeters were installed in selected plots at two depths to monitor nutrient leaching. Surface soil samples were taken to determine baseline nutrient contents, followed by three other sampling dates during the study. Bermudagrass dry matter production (3-yr average = 9.8 Mg ha⁻¹) was not adversely affected by the overseeding treatments. Greatest dry matter production was achieved with bermudagrass overseeded with ryegrass (3-yr average  = 11.3 Mg ha⁻¹). Soil pH decreased by almost one unit by the end of the study. While total P (TP) did not change much, Mehlich-3 P (M3-P), K, Cu, and Zn increased significantly, Mg and Mn concentrations decreased by 2002 compared to the baseline levels. Soil P, Mg, K, Fe, Mn, and Zn accumulation were greater under bermudagrass/wheat combination. In general, the influence of double cropping on soil nutrient accumulation was not conclusive, however, this practice provides the year-round green forage for grazing and haying. Nutrient concentrations in soil and lysimeter leachate were directly related to the quantity of effluent applied. Results also demonstrated that effluent application must be coordinated with the nutrient requirements of the growing forages in order to minimize accumulation and leaching.     

Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Symbiotic N₂-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha⁻¹ under sole and 36 kg N ha⁻¹ under intercropping as estimated by the ¹⁵N isotope dilution method around peak biomass production. The amount of N₂-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha⁻¹ accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied ¹⁵N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha⁻¹. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha⁻¹. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.