钢在饱和CO2的NaCl盐水中腐蚀特征

钢材在无氧的CO_2水溶液中形成一种FeCO_3腐蚀产物层,对钢材的进一步腐蚀有一定的保护作用。其保护性依赖于环境因素和钢材的本质。本文介绍了FeCO_3的结构特征,并讨论了其组织对腐蚀机理的影响。对FeCO_3腐蚀层的检验表明,腐蚀层有两种结构,且其厚度的变化依赖于钢材的显微组织。     

设有蓄水池的船闸充水系统的水力计算

对配有节水池和错船渠的两种类型的船闸，在几个节水池同时工作时，推荐采用船闸闸室充水和泄水过程数学模型的计算方法，此法无需做物理模型便可选定船闸供水系统部件的结构及其尺寸，这对现有同类型船闸顺利转入新的运用方式至关重要。     

Progress towards using the speed of ultrasound for beef leanness classification

Following the observation of a high correlation between the reciprocal of the speed of ultrasound and lean proportion in beef carcasses, commercial equipment (VOSI) was developed and its performance alongside a smaller assembly (Mini G) is reported. The speed of ultrasound was measured through six sites on beef carcasses within 1 h of stunning: three sites with VOSI and three sites with Mini G. Sides were also scored for fatness and conformation using the EAAP system, and subcutaneous fat depth was measured at 25,50 and 75% of the width of M. longissimus thoracis from the midline at the last rib. All sides were dissected into subcutaneous fat, intermuscular fat, muscle and bone. The reciprocal speed averaged over the three VOSI sites (RV346) was the best single predictor of the proportion of lean in the side. Multiple regression analyses, in predicting per cent lean, showed that addition of conformation score improved the precision of fat score and fat depth for a group of 26 sides. It did not provide a significant improvement over RV346. However, in another group of 50 sides showing more variation in side mass and conformation, conformation score did significantly improve RV346. The best prediction of per cent lean, involving RV346 and tissue thicknesses, gave a residual standard deviation of 1·35%, and conformation score did not significantly improve this regression.     

Three-dimensional display in nuclear medicine

Several surface and volume rendering techniques are compared using nuclear medicine data including several new methods developed by the authors specifically for scintigraphic data. The techniques examined are summed projection, thresholded projection, threshold-based surface illumination, volumetric compositing, maximum-activity projection, sun-weighted maximum-activity projection, and variable attenuation. The advantages and disadvantages of each method are discussed in relation to the goals of three-dimensional display, which are defined herein. Selected images are shown to illustrate the usefulness of the methods.     

A method for using a time interval counter to measure frequency stability

An interval timer is used in a single-mixer frequency-stability measurement system in place of an event timer. The dead-time problem is avoided with the aid of a reference pulse train and an algorithm for ambiguity resolution. The noise floor test and the unfolding algorithm are described. Advantages of the technique are high precision, convenient interfacing, and low cost. A disadvantage is the vulnerability of the technique to missing data.     

A model for the analysis of neighbor finding in pointer-based quadtrees

A natural byproduct of the tree-like nature of the quadtree is that many basic image processing operations can be implemented as tree traversals which differ in the nature of the computation that is performed at each node. Some of these computations involve the inspection of a node's adjacent neighbors (termed neighbor finding). A new model is developed for images represented by quadtrees, and it is used to analyze various neighbor-finding techniques. The model's predicted costs for neighbor finding correlate very closely with empirical results and it is superior to the model that was used previously.     

Responses of the Aphids Phorodon humuli and Rhopalosiphum padi to Sex Pheromone Stereochemistry in the Field

Gynoparous female and male damson-hop aphids, Phorodon humuli (Schrank), were caught in the field by water traps that were releasing the sex pheromone of this species, (1RS,4aR,7S,7aS)-nepetalactol. No behavioral activity was elicited by (4aS,7S,7aR)-nepetalactone, the major sex pheromone component of other aphid species such as Megoura viciae Buckton, even though olfactory cells were found in the secondary rhinaria on the third antennal segment of P. humuli that responded strongly to this compound. Gynoparous female P. humuli in the field responded less strongly to (1R,4aS,7S,7aR)-nepetalactol, the sex pheromone of the bird cherry-oat aphid, Rhopalosiphum padi (L.), than they did to the (4aR,7S,7aS)-nepetalactols, but males responded only to the latter. The (4aR,7S,7aS)-nepetalactone showed no electrophysiological activity so was not used in field trials. Releasing either the (4aS,7S,7aR)-nepetalactone or the (1R,4aS,7S,7aR)-nepetalactol with the (4aR,7S,7aS)-nepetalactols did not inhibit the response of P. humuli gynoparous females and males to the latter. Males of R. padi responded as strongly to the (4aR,7S,7aS)-nepetalactols as they did to (1R,4aS,7S,7aR)-nepetalactol. Males of P. humuli and R. padi responded positively to an increased concentration of the (4aR,7S,7aS)-nepetalactols released from two vials compared with that from a single vial, as did P. humuli (in one of two experiments) and R. padi to the (1RS,4aR,7S,7aS)- and (1R,4aS,7S,7aR)-nepetalactols when released together.