在τ—ρ域用特征积分法反演层状介质的速度和密度

本文提出一种在τ-p 域内用特征积分法反演层状介质速度与密度的方法。该方法首先把有偏移距的地震资料变换到截取时间τ和水平慢度 P 域内,然后,对任取的二道平面波地震记录,分别用特征积分法反演波阻抗,再用这对波阻抗分离层状介质的速度和密度。文中讨论了误差对反演结果的影响,并对理论模型进行了试算,效果令人满意。     

Database considerations in manufacturing systems integration

This paper deals with ideas that could form a basis for manufacturing integration. In recent times more attention is being paid to the idea of applying artificial intelligence (AI) techniques to manufacturing. However, very little attention is being paid to the proper use of these techniques. This research work explores three basic ideas:

1. 1. Applications of the entity-relationship approach to knowledge representation.

2. 2. The basic philosophy of expert database systems and

3. 3. Integration of manufacturing systems from the above two concepts.

The approaches for 1 and 2 are explained with actual implementation experiences, while a framework for integration is proposed from a more philosophical perspective.     

Effect of nitrocarburizing on sulphide layer during nitrocarburizing-sulphurating treatment

Compared with the single sulphurating treatment, the duplex treatment of nitrocarburizing-sulphurating can more effectively improve the properties of steel such as friction-reducing, wear resistance and anti-scuffing. Under the same processing parameters, the sulphide layers were fabricated on the surface of CrMoCu alloy cast iron by single ion-sulphurating treatment and nitrocarburizing-sulphurating duplex treatment, respectively. Through the analysis of the sulphide, the effect of the nitrocarburizing on the fabrication of the sulphide layer was investigated. And the result shows that the fabrication of sulphide layer is promoted by the nitrocarburizing treatment.     

Ignition of nickel in environments containing oxygen and chlorine

The mixed oxidation of nickel in gases containing both oxygen and chlorine has been investigated using the techniques of thermogravimetric analysis and examination of the corrosion products by scanning electron microscopy. Two regimes of corrosion behavior have been detected: one in which a protective oxide film is present and the rate of corrosion is controlled by the transport of the volatile products of the reaction between the gas phase and the oxide, and one in which the protective film is penetrated and corrosion occurs rapidly enough to result in the ignition of the specimen. The oxide corrosion products on the specimens after corrosion have characteristic morphologies, with the products of volatilization type corrosion consisting of large grains and the products of ignition type attack consisting of fine spherical particles. Ignition is a serious hazard in environments containing 0.25 pct or more Cl₂ and 4 pct or more O₂ by volume at temperatures between 1000 K and 1100 K, but is not produced by exposures at higher temperatures. A model based on the stability of the protective film in steady state corrosion is presented which can be used to predict the transition from volatilization to ignition type attack.     

On the design of multiple key hashing files for concurrent orthogonal range retrieval between two disks

This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept.

A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system.     

Empirical efficiency and volume relationships for HPGe detectors

We have extended the empirical work of Vano et al.[1] relating the slope of the detector efficiency curve to the active volume for Ge detectors. The analysis was carried out using Monte Carlo techniques and covered a wide range of incident energies (200 keV-20 MeV) and active volumes (19.6 cm³–396 cm³). It is shown that the expression of Vano et al.[1] is only valid over the energy range 200 keV-3 MeV for active volumes <50 cm³. The upper bound decreases to 2 MeV for volumes of a few hundred cm³. The usable energy range can, however, be extended to 6 MeV by introducing higher order terms into the polynomial. Above this energy, the shape of the efficiency curve is better described by a non-linear function since linear forms fail simultaneously to fit large active volumes and high energies. We therefore propose a composite function which reduces to the form given in Vano et al. in the low energy/active volume limit. By comparison with the Monte Carlo results, it is estimated that relative efficiencies can be calculated to within 6% over the energy range 200 keV-20 MeV and active volumes 20 cm³–400 cm³. Since the largest errors occur for the smallest volumes, we recommend that for energies <3 MeV a two-fold approach be followed, i.e. using the expression of Vano et al.[1] for active volumes less than 50 cm³ and the proposed non-linear form for larger volumes. For high energy work (E > 3 MeV), we advocate the non-linear form. In this way, average errors can be kept 3%. Finally, we point out that the real power of the expression of Vano et al. lies not in predicting efficiencies, but active volumes.     

剂量率对聚四氟乙烯辐射裂解的影响

本文研究了在以电子加速器的电子射线为辐射源时,剂量率对PTFE辐射裂解的影响。在剂量相同的条件下,剂量率从1.44×10~4 rad/s增至5.75×10~4 rad/s,裂解效率提高3.3倍。剂量率和各断裂参数(单位剂量裂解度a_0,G(s)值等)均成线性关系。当裂解度一定时,剂量率与剂量成反变关系。     

利用软件无线电提高导弹引信的抗干扰能力

根据软件无线电的功能和特点,探讨了对于提高导弹无线电引信抗干扰能力的重要作用,阐述了软件无线电引信的概念及其优越性.在现有器件的水平上,研究了一种基于中频数字化的设计方案,讨论了正交调制中的基带信号产生算法,分析了实现软件无线电引信的关键技术.