关于立式绕线机拉力与单饼式线圈尺寸关系的分析

文章着重分析了立式绕线机的拉力设定与变压器单饼式线圈绕制后外型尺寸、导线线规变化情况以及线圈紧密度的关系。通过适当调整立式绕线机的拉力,从而调整线圈B端尺寸,解决现今线圈B端尺寸存在的问题。     

Biological control of invasive plant species: A stochastic analysis

Biological control agents are regarded as a relatively safe method to control weeds. However, their impact on weeds can be relatively low and unpredictable. The aims of this article were to: (i) assess whether or not a weevil (Apion onopordi) and a mycoherbicide (Sclerotinia sclerotiorum) are desirable as biological agents for the control of Californian thistle (Cirsium arvense) in New Zealand despite their uncertain effectiveness; (ii) identify the combination of control options that is optimal to control the thistle; (iii) analyze the economic consequences of excluding chemicals from the weed control strategy; and (iv) assess the feasibility of the eradication of this weed. Two optimization models were developed and compared: one deterministic model and one stochastic model. The results showed that taking into account the stochastic effectiveness of biological agents can change the optimal integrated strategy, particularly if the biological control agent is relatively expensive. However, for a cheaper biological agent, the stochastic efficacy is less likely to change the optimal control strategy. On the basis of the modeling results, the authors argue that, in the context of the agri‐environmental setting of this article's case study, chemicals can be replaced by more environmentally friendly control options at a relatively low cost. The authors also show that the eradication of the thistle is unlikely, at least given the efficacy of the existing control methods.     

Interactions between citrate and montmorillonite-A1 hydroxide polymer systems

Citrate forms strong complexes with A1 ions and may thus influence the stability and formation of Clay-A1 hydroxide polymer systems (CAIHO). We studied the adsorption of citrate to CAIHO and the influence of citrate on the stability and formation of CAIHO at different A1:clay and A1:citrate ratios and pH values and at a total salt concentration of 0·01 M monovalent anions. The amount of citrate sorbed to the aged CAIHO was independent of the A1 fixed to the clay as A1 hydroxide polymers (AIHO) at 5 < pH < 6·6. The added citrate seemed not to sorb to the AIHO but only to the edges of the clay. As the citrate: Al ratio increased from 15–1:l at pH 6, more of the AIHO of the aged CAMO systems dissolved. The change in the CEC of the clay indicated that the nature of the remaining AIHO is independent of the amount of A1 dissolved. Citrate influenced the formation of CAIHO systems as measured at pH 6·6, to an extent which depended on the citrate: Al ratio. At a small ratio (1:5), AIHO formed and all citrate was incorporated in the AIHO, probably leading to a coprecipitate. The amount of citrate incorporated depended linearly on the amount of AIHO present. Co-precipitation of AIHO and citrate probably led to the formation of a separate phase, which was only weakly bound to the clay particles. At a large citrate: Al ratio (1:1) soluble Al-citrate complexes became dominant, and only a small part of the added A1 was present as AIHO.     

Evaluation of the Burns model for nitrate movement in wet sandy soils

A simple model to predict nitrate leaching developed by Burns (1974) was tested. The measured and calculated nitrate concentrations in 100 cm wet sandy soil profiles were compared: the results showed reasonably good agreement between the two values. Adjusting the initial conditions and reducing the segment size from 10 to 5 cm did not improve the accuracy of the prediction. Better agreement was, however, obtained when only the samples above the groundwater table were considered.     

INFLUENCE OF SOIL PROPERTIES ON ADSORPTION OF PESTICIDE-DERIVED ANILINE AND p-CHLOROANILINE

Soil properties were significantly related to the adsorption of aniline and p-chloroaniline, greater adsorption always occurring with p-chloroaniline. Multiple regression analysis indicated that the organic matter plus available water (or clay) was better than the simple linear relationship, with organic matter alone. The resulting equations accounted for most of the variability in aniline or p-chloroaniline adsorbed (R²= 0·92 and 0·94, respectively). The contribution of organic matter to the adsorption was calculated as 79 and 77 per cent for aniline and p-chloroaniline. Experimental data on partially oxidized soils emphasized the major role played by soil organic matter. The variability in adsorption was mainly due to the organic matter left after oxidation (R²= 0·72 and 0·64 for aniline and p-chloroaniline). No other combinations of variables significantly improved these relationships.     

THERMODYNAMICS OF SINGLY CHARGED ION EXCHANGES IN THE TRACE REGIONS ON CAMP BERTEAU MONTMORILLONITE

Ion exchange equilibria for seven pairs of singly charged ions between aqueous chloride solutions and a montmorillonite clay have been studied at 25 °C for low values of the total normality of the equilibrium solution. Only the trace region for the preferred ion was investigated. Since the analogue of Henry's law was found to be valid, the exchanges being almost ideal, standard free energies were calculated from experimental data in the region where the analogue of Henry's law is obeyed by extrapolating to half-loading with one of the ions. The results satisfy the requirement of additivity and are in good agreement with known values.     

THE ALKALINITY OF ALKALI SOILS

The theoretically derived equation: log Alk–pH = log Pco₂–7.82 describes the relation between three easily estimated parameters, viz. the composition (alkalinity), CO, partial pressure and the pH of the soil solution. This equation is also important for understanding the formation of alkaline soils. The concept of residual alkalinity, i.e. the difference between the alkalinity and the total concentration of the divalent cations in the soil solution (on an equivalent basis) is introduced. In a closed basin with excess evaporation over precipitation highly alkaline soils, i.e. soils with a pH above 8 to 8.5, develop if the inflowing water has a positive residual alkalinity. A number of processes, such as weathering, oxidation and reduction, cation exchange, precipitation, addition of neutral salts, evaporation, which may influence the alkalinity and residual alkalinity of natural waters and soils are discussed briefly.     

A MATHEMATICAL MODEL FOR THE DIFFERENTIAL MOVEMENT OF TWO SOIL CONSTITUENTS INTO ILLUVIAL HORIZONS: APPLICATION TO CLAY RATIOS IN ARGILLIC HORIZONS

The effects of the migration of two soil constituents into illuvial horizons is described by a set of equations. Differential movement of clay fractions during illuviation causes changes in the fine to total clay ratios in A and B horizons. A mathematical model is used for the interpretation of clay fraction data in order to estimate the degree of profile development, the amounts of fine and total clay which have moved, and to determine the original composition of the parent material. No bulk density data of the soil horizons are necessary for the computation. The equations can be programmed on desk calculators. Comparison with measurements on Alfisols in temperate regions was found to be satisfactory.     

INFLUENCE OF ADSORBED SODIUM AND GYPSUM CONTENT ON PERMEABILITY OF GLACIAL TILL SOILS

The permeability of glacial till soils having mainly montmorillonite in the clay fraction was negligible when the exchangeable sodium percentage (ESP) exceeded 15 to 20. Relatively higher permeability values were obtained in soils containing gypsum, but water transmission through such soils was negligible above ESP of 30 to 35. The relative decrease in permeability with increase in exchangeable sodium depends not only on the ESP and electrolyte concentration in the soil solution but is affected by the types of clay minerals.