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41.
42.
R. Venkitaswamy S. Subramanian V. Veerabadran 《Nutrient Cycling in Agroecosystems》1991,28(3):315-321
The growth of weeds and their subsequent reduction of rice yield as affected by N source neem cake coated urea (NCU), dicyandiamide coated urea (DCU), rock phosphate coated urea (RPCU), urea supergranules (USG) and prilled urea (PU) was studied on a clay loam soil at Coimbatore, India. Experiments were conducted in northeast monsoon (NEM) 1981, summer 1982, and southwest monsoon (SWM) 1982 seasons.The crop was associated with eleven weed species, and the dominant weeds wereEchinochloa crus-galli, Cyperus difformis andMarsilea quadrifolia. The weed flora varied between seasons. Deep placement of USG reduced the dry weight of weeds in NEM and summer seasons at 60, 90 and 120 Kg N ha–1 whereas it increased the dry weight at 60 and 90 but not 120 Kg N ha–1 in SWM season. The dry weight of weeds decreased with increased N rates for all N sources during NEM and summer seasons. In SWM season, dry weight of weeds increased with increased N rates for all N sources except USG. The grain yield of rice was drastically reduced with the deep placement of USG at 60 but not 120 Kg N ha–1 in SWM season. The differential effect of the N sources between seasons was due to the change of the weed flora. Dominance ofE. crus-galli during SWM season had greater influence on weed dry weight and grain yield of rice.Nitrogen uptake by weeds was frequently greater in unfertilized plots, particularly in NEM and summer seasons. In SWM season, the apparent fertilizer N recovery by weeds was high for USG. It decreased from 53% for 60 Kg USG-N ha–1 to 4% for 120 Kg USG-N ha–1.Contribution from the part of Ph.D. work of the first author at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India. 相似文献
43.
When PS is tested in tension but immersed in water the yield stress is unchanged and the crazing stress is increased, as compared with tests conducted in air. The crazing pattern is otherwise unchanged. If the PS is first equilibrated with water and then tested under water, both crazing stress and yield stress are reduced. A very large number of small crazes are generated which result in a 23% increase in the fracture strain. 相似文献
44.
通过对广州石化乙烯厂裂解原料、收率、运行状况进行分析,揭示石脑油质量波动对乙烯收率的影响,研究了乙烯收率的偏低原因,并提出原料频繁变化条件下,原料优化运作和COT调整对策。 相似文献
45.
A new series of liquid crystalline polymers containing aromatic triad ester mesogen and 1,1′‐disubstituted ferrocene as a nonmesogenic unit along with polymethylene spacer was synthesized. The polymer was synthesized by a room temperature polycondensation reaction between bis(4‐chloroformyl phenyloxy alkyl ferrocene dicarboxylate) and quinol. The alkyl groups have been varied by an even number of methylene groups with a range from two to ten groups. All the polymers were found to possess liquid crystalline properties. The identification of the mesophase is more transparent with an increase in the spacer. The thermal characteristics were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the thermal stability of the polymers was decreased with increasing spacer length. The Tg, Tm, and Ti of the polymers decreased with increasing methylene groups. The incorporation of the ferrocene moiety also has a considerable effect on the glass transition temperature. The char yield of the polymer decreases with an increasing methylene chain length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3494–3501, 2002 相似文献
46.
David?Pérez-Martínez C.?Alvarez-Salas J.?A.?Morales-Rueda J.?F.?Toro-VazquezEmail author M.?Charó-Alonso E.?Dibildox-Alvarado 《Journal of the American Oil Chemists' Society》2005,82(7):471-479
The solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre-exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized
at temperatures (T
Cr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (T
M
o) and the supercooling (i.e., T
Cr
o−T
M
o) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [T
M
o=65.8°C (±3.0°C)] than in the CB/canola oil blend [T
M
o=33.7°C (±4.9°C)]. Therefore, under similar T
Cr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of T
Cr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from
DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with T
M
o explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′eq and σ* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′eq and σ* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of
small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′eq and σ* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we
could not find a particular relationship that described the overall behavior of G′eq and σ* as a function of D and independent of the system investigated. 相似文献
47.
Low temperature steam reforming of ethanol in the temperature range of 200–360°C was studied to maximize the production of H2. The optimum reaction conditions in presence of a suitable catalyst can produce mainly the desired products H2 and CO2. Cu/Al2O3 catalysts with six different concentrations ranging from 0 to 10 wt.% Mn, were prepared, characterized and studied for the ethanol-steam reforming reaction. Maximum ethanol conversion of 60.7% and hydrogen yield of 3.74 (mol H2 / mol ethanol converted) were observed at 360°C for catalyst with 2.5 wt.% Mn loading. 相似文献
48.
针对原富马酸重结晶过程中,漂浮物太多,产品粒度太小,导致重结晶收率低;改进重结晶工艺,使结晶收率达到95%以上,降低劳动强度,节能效果明显,质量明显改善。 相似文献
49.
何庆复 《武汉理工大学学报(材料科学英文版)》2009,24(3):428-431
Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling (ISC) and out-phase TMF was studied
on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the
total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 °C, but no hardening
and serrated yielding occurred under ISC at 800 °C. Stronger hardening with stress serration occurred at the thermal path
going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening
also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening
and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800 °C may due to
an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree
of the damage of the tested alloy under out-phase and ISC. 相似文献
50.
通过对25个结构钢缺口板进行的单向拉伸断裂试验,验证了提出的结构钢广义屈服模型和椭球面断裂准则.用ANSYS软件中的参数化设计语言APDL和用户编程功能UPFs,将提出的静水应力型广义屈服模型编制成子程序模块,对结构钢缺口板断裂试验进行了基于广义屈服模型和椭球面断裂准则的数值模拟分析.试验结果表明:裂纹起始于缺口边缘内侧,裂纹在厚度方向贯通后沿宽度发展,试件最终断裂于缺口薄弱断面.缺口板断裂应力场分析表明,提出的椭球面断裂准则对预测结构钢缺口板初始开裂具有广泛适用性和较高精度. 相似文献