不同NPK配置对强筋小麦群体生物量与产量的效应研究

在关中川道灌区以强筋小麦陕253为材料,研究了不同NPK配置对其不同生育期生物产量、群体数量和产量的效应,结果表明提高施肥量可显著增加生物产量、群体数量及产量,处理平均值分别比常规处理增加11.9%~43.6%、4.1%~17.4%和8.3%,其最佳N、P、K配置依次为N135kg hm-2,P2O5和K2O各120kg hm-2、N135kg hm-2,P2O5225kghm-2,K2O120kg hm-2和N225kg hm-2,P2O5和K2O各120kg hm-2。在目前常规投肥水平下适度增加钾肥有利于生物产量的显著提高,增加磷肥和钾肥有利于群体数量的提高,增施氮钾肥有显著的增产效果。产量的最佳NPK配比较常规处理增产19.1%,其增加养分的平均产量4.44 kg kg-1,比各处理平均养分产量高1.6倍。     

皖南红黄壤地区连续施用磷钾肥对油菜产量、养分吸收及土壤肥力的影响

在皖南红黄壤地区利用大田试验研究了连续施用磷钾肥对油菜产量、养分吸收和土壤肥力的影响。结果表明:在施用氮肥的基础上合理配施磷钾肥,促进了油菜的生长发育,提高了油菜植株的养分含量和养分吸收量,从而显著增加了油菜的产量,并且磷肥的增产效应大于钾肥效应,三季油菜平均产量以处理P90K120最高,达到了1968.7 kg hm-2;同时连续施用磷钾肥能够改善土壤养分含量,显著提高了土壤速效钾、速效磷含量,与试验前土壤相比,速效磷增加了14.83~20.2 mg kg-1,速效钾增加了69.51~109.61 mg kg-1。     

长期施用无机NPK肥对保护地黄瓜光合特性及产量的影响

在长期单施无机氮肥(15年)条件下,黄瓜生长发育正常,而且随着施N量的增加(试验中的最高施N处理为每年600kghm-2),叶面积显著增大,叶片的叶绿素含量、光合速率显著提高,但处理间叶片胞间CO2浓度、气孔导度无显著差异,说明不同N水平对黄瓜叶片净光合速率的作用主要是由非气孔因素造成的,长期单施无机氮肥还显著地提高了黄瓜的产量、结瓜数、座瓜率,降低了畸形瓜率。N、P、K配施可进一步提高黄瓜叶片的叶绿素含量、光合速率、产量、结瓜数和座瓜率,降低畸形瓜率,但处理间叶片胞间CO2浓度、气孔导度仍无显著差异,说明不同N、P、K配施对黄瓜叶片净光合速率的作用主要也是由非气孔因素造成的。同时,在N、P、K配施试验中,以N对黄瓜光合作用及产量的影响最大,P次之,K较小。     

Damage-Coupled Progressive Failure and Yield Line Analyses of Metal Plates

Continuum damage mechanics based progressive failure analysis of an aluminum alloy AL2024-T3 plate has been carried out. Isotropic continuum damage mechanics model proposed by Chandrakanth and Pandey in 1995 has been implemented in a nonlinear finite element computational scheme based on damage-coupled and damage-uncoupled elastoplastic constitutive relationship. In order to model the progressive growth of damage and plasticity from extreme fibers toward the neutral axis, discrete layered approach has been adopted in the formulation using Ahmed’s degenerate isoparametric shell element, which accounts for shear deformation. A critical damage criteria is used for determining the onset and propagation of failure in the plate. Damage-coupled and damage-uncoupled analyses have been carried out on rectangular and triangular plates of aluminum alloy Al2024-T3. Yield line patterns have been generated using extensive nonlinear progressive failure analysis and comparison with conventional yield line analysis has been made. It is envisioned that employing the methodology presented herein, yield line pattern generation for structural components with complex shapes can be obtained, which would significantly assist engineers in analysis and design of structures.     

Experimental Study of Macro- and Microbehavior of Natural Diatomite

Diatomite is widely deposited in Oita prefecture of Japan. It has high natural water content but its consolidation yield stress is much higher than the overburden pressure. Oedometer and triaxial consolidated undrained shear tests were performed in this study to investigate its macrobehavior in terms of compressibility and strength. The test results indicate that the compressibility and undrained shear strength of diatomite in the preyield state (i.e., the consolidation stress lower than the yield stress) are independent of the consolidation stress level. When the consolidation stress is higher than the yield stress, however, like virtually all soils, the compressibility of the diatomite increases dramatically. Similarly, the undrained shear strength of the diatomite depends on the confining stress when the confining stress is higher than the transitional stress. Both mercury intrusion porosimetry analysis and scanning electron microscopy were performed to investigate the change of the microstructure of the natural diatomite with the consolidation stress. The test results indicate that the microstructure of the diatomite remains unchanged in the preyield state, but it changes significantly in the vicinity of the yield stress. This unchanged microstructure is attributed to the unchanged macrobehavior within the preyield state. The breakage of diatoms particles and the compression of interparticle pores between the diatom particles in the postyield state contribute to the high compressibility of the diatomite.     

Production of Carbopol 974P and Carbopol 971P pellets by extrusion-spheronization: optimization of the processing parameters and water content

Pellets obtained by extrusion-spheronization represent multiparticulate dosage forms whose interest in intestinal drug delivery can be potentiated and targeted through bioadhesive properties. However, adhesion itself makes the process difficult or even impossible. The problem of tackiness encountered with bioadhesive wet masses was previously eliminated by the use of electrolytes such as CaCl₂. This approach is known to reduce the viscosity of polyacrylic acids by disturbing the interactions between carboxylate groups on adjacent polymer molecules, thereby decreasing their bioadhesive properties. The present study aimed at producing pellets containing carbomers without addition of electrolytes in order to maintain their bioadhesive potentiality at its maximum. Carbopol® 974P (10%, 15% and 20%) and Carbopol® 971P (10%) were used in combination with Avicel® PH101. The extrusion speed (30, 45, 60, 90, and 150 rpm), spheronizer speed (350, 700, 960, 1000, and 1300 rpm), spheronization time (5, 10, 15, and 20 minutes) and amount of water (45%, 50%, 54%, and 58%) were optimized in order to obtain the highest yield of spherical pellets ranging 710-1000 µm in diameter. For pellets containing 10%, 15% Carbopol® 974P or 10% Carbopol® 971P and 45% water content, 30 rpm extrusion speed, 960 rpm, and 10 minutes spheronization speed and time led to the highest yields and sphericities, respectively, 72% and 0.91, 67% and 0.78, and 76% and 0.80. Production of pellets with 20% Carbopol® 974P could be achieved through the increase of the water content up to 58% and implementation of 30 rpm extrusion speed, 1300 rpm, and 10 minutes spheronization speed and time. The yield and sphericity were 42% and 0.78 respectively.     

Collapse Behavior of Compacted Silty Clay in Suction-Monitored Oedometer Apparatus

This paper presents a methodology to investigate the collapse behavior of unsaturated soils using suction-monitored oedometer tests. By incorporating independent suction measurement, the oedometer apparatus is capable of following the same stress paths as in double oedometer tests, while continuously monitoring the suction. The proposed method has been used to investigate the collapse behavior of a compacted silty clay and to confirm the uniqueness of the loading-collapse surface as identified from loading and wetting paths. A new mathematical form of the yield surface within an elastoplastic framework is proposed on the basis of test results over a wide range of suctions (0 to 30,000?kPa) and net stresses (up to 7,000?kPa). The fundamental assumptions of the newer type of elastoplastic framework, which incorporate the degree of saturation within their stress variables, are evaluated, and the limitations of such models are identified. The collapse behavior of samples with different fabrics induced by differing compaction characteristics is also investigated within an elastoplastic framework. The difference in fabric, which is observed through a petrological microscope, can be presented in a quantitative way with different model parameters.     

Dendritic Microstructure Affecting Mechanical Properties and Corrosion Resistance of an Al-9 wt% Si Alloy

It has been reported that the mechanical properties and corrosion resistance of metallic alloys depend strongly on the solidification microstructural arrangement. The correlation of corrosion behavior and mechanical properties with microstructure parameters can be very useful for planning solidification conditions in order to achieve desired final properties. The aim of the present work is to investigate the influence of dendritic microstructural parameters of an Al-9 wt.% Si alloy on mechanical properties and corrosion resistance. The experimental results establish correlations between secondary dendrite arm spacings (λ₂) and ultimate tensile strength (σ_u), yield strength (σ_y), corrosion potential (E_Corr), and corrosion rate (i_Corr).     

Variety Comparative Test of Direct - seeding Rape in Wenzhou City

通过田间试验对直播条件下8个油菜品种的产量、生育期和农艺性状进行考察，结果表明：浙油19、浙大619、浙油50和浙油18产量水平高，机收适应性好，建议进一步加大在温州市的示范推广规模。     

异型铸件立式离心铸造的工艺技术和应用

叙述了异型铸件立式离心铸造的工艺，其中包括设计原则和工艺参数。该技术在不同铸钢件上得到验征和应用它和重力铸造相比，提高铸钢工艺出口率１５％～３０％，极大地改善材料性能和降低生产成本，能获得无缺陷高质量的铸件。