Observed Climatic Variations in the Growing Season of Field Crops in Northeast China from 1992 to 2012

To determine the potential effects of climate change on crop phenological development and productivity, an integrated analysis was conducted based on the observed climatic and phenological records of Northeast China from 1992 to 2012. A set of quality assurance procedures, including repeated record checks, agro-meteorological station selection, internal consistency checks, temporal outlier checks, spatial outlier checks, and interpolation of missing data, were designed and applied to the phenology datasets of spring maize and paddy rice. Our results indicated that almost all phenological dates of spring maize and paddy rice became increasingly delayed from 1992 to 2012, The duration of the growing season was prolonged, particularly for the grain-filling stage （GS3）. The prolonged growing season was beneficial to productivity. For spring maize, the average precipitation during GS3 decreased at a rate of 27.46 mm/decade, and the annual accumulated temperature over 10℃ increased at a rate of 31.07℃/ decade. Farmers initiatively adjusted crop cultivars and selected drought-resistant crops to cope with the challenges of drought.

SOME POSSIBLE ALTERNATIVE SOLUTIONS OF NEAR TIP FIELDS FOR STEADY CRACK GROWTH IN ELASTIC PERFECTLY-PLASTIC MEDIA

Some possible alternative solutions of near-tip fields are studied for plane-strain Mode-I qua- si-static steady crack growth in incompressible(v=1/2)elastic perfectly-plastic media.A group of four-sector so- lutions and a three-sector solution in which the elastic-unloading region vanishes are given.Stress functions,plas- tic flow factors and plastic strains in each region are also given.

The asymptotic field of a dynamically growing crack in a viscoelastic materia

A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, （σ-e）∝r^-1/（n-1）. The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n →∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund＇s elastic-ideally plastic material by analyzing basic equations.

STEADY GROWTH OF CRACKS IN COMPRESSIBLE ELASTIC-PLASTIC MEDIA

Based on the theoretical framework for crack growth analysis provided by Gao and Hwang, the 5-sector soiution of near-tip fields of mode-I cracks growing quasi-statically and steadily in compressible elastic perfectly plastic materials is obtained.As Poisson's ratio v tends to 1/2,the 5-sector solution degener- ates to the 4-sector solution of near-tip fields of crack growth in incompressible elastic perfectly plastic materials.

HIGHER ORDER ASYMPTOTIC SOLUTION OF MODE Ⅰ CRACK GROWTH IN ELASTIC-PERFECTLY PLASTIC MEDIA

A higher order asymptotic solution of near-tip field is studied for plane-atrain Mode-Ⅰ quasi-static steady crack growth in the incompressible (v=1/2) elastic perfectly-plastic media.The results show that the near-tip stress and strain are fully continuous,and the strain possesses In (A/r) singularity at the crack tip.The expressions of the stress,strain and velocity in each region are also given.

ALGORITHM DESIGN AND IMPLEMENTATION OF FINITE WAVELET GROW TREE

Based on grow tree composite model, Finite Field Wavelet Grow Tree (FW-GT) was proposed in this paper. FW-GT is a novel framework to be used in data encryption enhancing data security. It is implemented by replacement operator and wavelet operator. Forward integration and inverse decomposition of FW-GT are performed by replacement, inverse wavelets and its corresponding replacement, wavelet transforms. Replacement operator joined nonlinear factor, wavelet operator completed data transformation between lower dimensional space and higher dimensional space. FW-GT security relies on the difficulty of solving nonlinear equations over finite fields. By using FW-GT, high security of data could be obtained at the cost of low computational complexity. It proved FW-GT algorithm’s correctness in this paper. The experimental result and theory analysis shows the excellent performance of the algorithm.

Geometry independent C^(*)-T_(z) dominance of three-dimensional quasistatic growing crack-tip fields in creeping solids

In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo into three-dimensional solution(3D)for stationary cracks under the domination of C^(*)with the constraint factor Tz.However,how to characterize the 3D crack-tip fields under creep damage-induced quasistatic growing conditions remains challenging.In this study,we reveal that,for 3D quasistatic growing cracks,the leading singular solution can effectively characterize the crack-tip stress distributions with relative errors less than 10.8%for relative creep time up to 0.8 in various specimens with finite thickness.For a given relative time,Tz distributions can be unified by the equivalent thickness concept,Beq.The results show that C^(*)-T_(z) can effectively quantify both the load and constraint effects on the crack-tip fields.Such geometry independent dominance can considerably simplify the treatments of load and constraint effects,thereby promoting the application of fracture mechanics in high-temperature damage tolerance designs.

CORRECT FORMULATION AND SOLUTION OF NEAR-TIP FIELD PROBLEM FOR CRACK GROWING IN COMPRESSIBLE ELASTIC-PLASTIC MATERIALS

In the 5-sector solution by Drugan et al. for near-tip field of plane strain crack growing in compressible materials, the plastic flow rule is violated in the plastic zone (called the nonsingular zone by Rice) between the central fan sector and the elastic unloading sector. Based on the theoretical framework provided by Rice and supplemented by the "unloading boundary theorem", the correct formulation of the problem is given and the correct asymptotic solution for the near-tip field of the crack growth is obtained.

多年施用有机肥对植烟土壤酸化的缓解作用

【目的】探明多年有机肥还田对植烟土壤酸化的影响,为植烟土壤的酸度调控提供科学依据。【方法】以我国北方典型的植烟棕壤为研究对象,采用连续8年田间定位试验设置CK,不施肥;T_(1),单施化肥(N、P_(2)O_(5)、K_(2)O分别为82.20 kg/hm^(2)、83.25 kg/hm^(2)、249.75 kg/hm^(2));T_(2),在化肥基础上配施有机肥(N、P_(2)O_(5)、K_(2)O分别为82.20 kg/hm^(2)、83.25 kg/hm^(2)、249.75 kg/hm^(2),有机肥15.00 t/hm^(2));T_(3),单施有机肥(有机肥22.50 t/hm^(2))共4个处理,通过测定土壤的活性有机碳、pH、土壤交换性酸和土壤交换性盐基含量,分析其对土壤酸化的影响。【结果】与CK相比,单施化肥处理显著降低土壤pH;施有机肥处理增加土壤pH,其中,单施有机肥处理T_(3)效果最显著;施有机肥处理可显著降低交换性酸含量,其中,主要降低土壤交换性铝含量,对交换性氢含量的影响不显著,T_(3)降低效果最显著;施有机肥处理可显著增加交换性盐基总量,但分别对土壤交换性钾钠钙镁影响不显著;随着施肥和耕作年限的增加,施肥处理土壤的总有机碳和活性有机碳含量较CK均有所增加,其中,土壤活性有机碳含量显著增加,以无机肥配施有机肥处理T2效果最优,较CK显著增加143.14%。【结论】植烟土壤经多年有机肥还田后,土壤质量显著提升,有效防治土壤酸化。在实际生产中,合理配施有机肥,既能防治土壤酸化,又能全面提升土壤质量。

秸秆还田配施氮肥对小麦生长和产量的影响

为探明氮肥施用和秸秆还田对小麦生长和产量的影响,指导秸秆还田下小麦施氮用量,采用裂区设计,以秸秆还田为主区,设置秸秆不还田(W)和秸秆粉碎全量还田(S)试验,副区为氮肥处理,设置3个施氮量,分别为160 kg/hm^(2)(N1);200 kg/hm^(2)(N2);240 kg/hm^(2)(N3),研究小麦叶面积指数、干物质积累量、产量及产量构成因素的变化特征。结果表明,小麦叶面积指数、干物质积累量、穗粒数、千粒质量和产量在秸秆不还田处理下随着氮肥施用量的增加呈逐渐增加的趋势,在WN3处理时达到最大值,在秸秆全量粉碎还田处理下随着氮肥施用量的增加呈先升高后降低的趋势,在秸秆粉碎全量还田,施氮量200 kg/hm^(2)时产量最高,说明秸秆还田配施氮肥能够显著促进小麦生长,提高小麦产量,且能够在一定范围内减少氮肥施用量。

水分管理影响稻田甲烷排放研究进展

水分管理是影响稻田甲烷(CH4)产生、氧化与排放的重要因素之一。根据国内外文献资料,综述了非水稻生长期和水稻生长期水分管理对稻田CH4产生排放的影响,以及非水稻生长期水分管理对水稻生长期CH4产生排放的影响,并提出有待研究的内容。综合多年的研究结果表明,冬季淹水不仅引起冬季(非水稻生长期)CH4的大量排放,还影响水稻生长期CH4排放量。非水稻生长期土壤水分含量越高,随后水稻生长期CH4排放量越大,产生和氧化能力越强。水稻生长期烤田相对于持续淹水能大量减少CH4排放。

稻鸭共育对稻田杂草和病虫害的生物防治效应

本文研究稻田全天放鸭对水稻病、虫、杂草的防治效果。试验结果表明,稻鸭共育后12和42d,共育田水稻基部飞虱、叶蝉的总量比不养鸭稻田平均减少63 8%和77 3%;稻鸭共育后10和40d,共育田杂草比不养鸭稻田平均减少50 6%和94 2%;分蘖高峰期和齐穗期的纹枯病病情指数,稻鸭共育田比不养鸭稻田分别低67 1%和52 5%。另外,稻鸭共育田的害虫天敌蜘蛛数量明显增加,比常规种稻田多1 66～2 61倍,这也显著改善了稻田的生态环境,抑制了水稻害虫的危害。

水分管理影响稻田氧化亚氮排放研究进展

稻田作为大气中N2O的重要来源而倍受关注。硝化反硝化是土壤中N2O生成的两个主要的微生物过程,水分管理是影响稻田土壤N2O产生排放的重要因素之一。本文综述了水稻生长期和非水稻生长期水分管理对N2O排放的季节变化、N2O产生和排放途径、N2O-N排放系数以及与N2O产生排放过程相关的土壤N素形态、浓度和土壤酶活性的影响,并提出了有待研究的问题。

作物茬口对棉花生长发育及产量的影响

2010年在连作8a的棉田分区种植小麦、甜菜和棉花,次年再全部种植棉花,研究不同作物茬口对棉花生长发育及其产量的影响。结果表明,麦茬地棉花的各项农艺性状优于连作棉花,其中麦茬地棉花的株高、主茎叶片数、果枝数与连作棉花间差异均达到极显著水平;麦茬地棉花单株干质量、叶绿素含量也均优于连作和甜菜茬棉花。倒茬地棉花比连作棉花平均增产15.2%,其中麦茬地棉花增产21.9%,甜菜茬棉花增产8.6%。麦茬地棉花产量的提高主要在于单株铃数和单铃质量的提高,分别比连作棉花提高23.5%和6.1%。

挠曲坡折带特征与油气勘探——以松辽盆地南部为例

根据中国东部伸展盆地的演化阶段、构造运动、断层发育及其对沉积体系的控制作用,结合沉积体系和砂体的分布特征,将坡折带划分为断裂坡折带和挠曲坡折带,并对两者的成因、差异、勘探领域和方向进行了对比。论证了松辽盆地南部挠曲坡折带的成因、分布规模以及隐蔽性油气藏的储集层类型、盖层条件,指出了有利勘探领域和重点勘探区块。

不同烟区和烟田烤烟挥发和半挥发性有机酸含量的差异分析

采用气相色谱法,对种植在云南大理相邻产烟县(宾川、弥渡)和相邻的水田、旱地,相同烤烟品种云烟85的不同部位烟叶中挥发和半挥发性有机酸含量进行分析。结果表明,弥渡烤烟中挥发和半挥发酸含量明显高于宾川烤烟,其中3-甲基戊酸和苯甲酸含量分别达到显著和极显著差异;而相邻地块的旱地烤烟中绝大多数挥发和半挥发性有机酸含量明显高于水田烤烟,其中3-甲基戊酸、十二酸和油酸含量差异分别达到极显著和显著水平;烤烟在部位间挥发和半挥发酸含量的差异表现为上、中部烟叶明显高于下部叶,而且烤烟部位间挥发和半挥发性有机酸含量的变化不受烟区和烟田类型的影响。

过冷熔体定向凝固过程枝晶生长的相场法模拟

利用二元合金相场模型与溶质场进行耦合计算,以Al-4.5%Cu合金为例模拟了二元合金定向凝固的枝晶生长过程。研究了不同过冷度下二元合金过冷熔体定向凝固时枝晶的演化过程及其溶质场的分布情况。结果表明:利用相场模型可以逼真地模拟枝晶的生长过程,以及界面形貌从平界面向柱状晶生长的转变,可再现枝晶演变过程中相互之间的竞争生长和熔合现象。

静电场作用下H_2O偶极极化对冰晶形成过程的影响

采用去离子水为实验样品,在-30℃低温环境中冷冻,冷冻过程中施加不同强度的静电场干扰,研究静电场对去离子水冰核形成及冰晶生长过程的影响.研究发现,在冷冻过程初期静电场的引入可以诱发冰核形成,导致过冷点升高,但在随后液相到固相的相变过程中,静电场对冰晶生长具有抑制作用.分析认为,在静电场作用下电偶极矩沿电场方向分布的H2O具有最稳定的状态,能量的分布函数具有最大值,这些结果是诱发冰核形成、抑制冰晶生长的原因.

田间生长条件甘蔗光合特性的研究

在田间正常生长条件下 ,测定了 4个甘蔗品种ROC16、ROC2 0、GT11和F172的气体交换日变化和不同叶位的气体交换、叶片叶绿素和氮素含量、GT11和F172光合速率及其对光合有效辐射 (PAR)的响应及ROC2 0和GT11叶片 ψW (脉势 )的日变化。结果表明 ,不同叶序的气体交换率存在明显的差异 ,上位叶高于下位叶 ,其强弱趋势为 :1～ 3>0 >4 >5>6～ 8。在相同的环境条件下 ,叶序间的气体交换率不同的主要原因是它们在量子转化效率 (a)、最高净光合速率 (Pm)和呼吸速率 (Rd)等光合能力和生理活性上存在差异。在田间条件下 ,甘蔗叶片的光合速率 (Pn)随PAR增强而提高 ,没有明显的光饱和现象。叶片的Pn、气孔导度 ( gs)和蒸腾速率 (E)的日变化趋势相似 ,气体交换率随PAR的变化而变化。在高PAR下 ,Pn 主要受到胞间CO2 浓度 (Ci)的限制 ;而在低PAR下 ,Pn 受到气孔和非气孔因素的限制。叶片的Pn、gs 和E对PAR反应的敏感性表现为Pn>E >gs。甘蔗叶片 ψw的日变化在清晨达最高值 ,午后最低。 4个甘蔗品种中GT11具有较高的同化效率和气体交换率 ,这与其叶片较高的 ψw有关 ,而叶片叶绿素和氮素含量对Pn 影响并不明显。

超旱生小灌木——红砂大田育苗技术研发

采用对比试验，研究了红砂（Reamuria songarica（Pall．））大田容器育苗的容器选择、种子处理、覆土厚度、覆盖保护和灌水方式等措施对出苗率、成苗率和容器苗质量的影响。结果表明：红砂适宜的育苗容器为底部多孔的大规格容器，适宜的覆土厚度为0．3～0．6cm，覆盖材料的适宜遮光率应控制在60％以下；以遮光率60％的遮荫网为例，适宜的覆盖时间为20～30d左右；细质地的河沙表面覆盖是较好的覆盖方式。育苗容器和覆盖方式对幼苗质量有显著影响。覆土厚度和覆盖时间对出苗率和成苗率均有显著影响；覆盖方式仅对出苗率有显著影响；种子处理和灌水方式对出苗率、成苗率均无显著影响，但从生产的经济实用性及容器苗质量方面综合评价，种子机械处理和漫灌＋喷灌灌水方式更符合生产推广要求。