摘要:

Changes in the structure, chemistry and bonding at internal interfaces often have a great influence on the properties of materials. High resolution imaging and Energy Dispersive X‐ray Spectroscopy in the Transmission Electron Microscope have been used extensively to study the structure and composition at interfaces. Spatially resolved Electron Energy Loss Spectroscopy (EELS) in the Scanning Transmission Electron Microscope (STEM) offers a new probe to explore the effect of structure and chemistry changes on the local bonding at interfaces. This paper reviews the relationship between EELS and electronic structure and illustrates the insights obtained from this technique with the help of examples which include: a) The effect of B segregation on grain boundaries in Ni3Al and Ni3Si. b) The effect of Bi segregation on grain boundaries in Cu. c) Bonding changes at two metal‐ceramic interfaces :Nb‐Al2O3and Cu‐ A12O3.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670425

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Infrared sensing techniques used in arc welding and resistance welding process monitoring and control are presented. A variety of IR sensors have been investigated for use in monitoring and controlling weld bead width, penetration depth, seam tracking and cooling rate during arc welding, and nugget size and cooling rate during resistance welding. In addition, factors that affect or interfere with infrared sensing are discussed.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670426

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Superplastic forming is a viable net‐shape forming technology. It is an attractive manufacturing technique because it bypasses machining, joining and riveting, and reduces material waste. This paper reviews the history and progress in the field of superplasticity. Fundamental understandings, such as microstructural prerequisites and deformation mechanisms, and technological applications for superplasticity are discussed. A wide range of structural materials, including metals, intermetallics, and ceramics are presented. Some of the most recent advances, for example, high strain rate superplasticity, low temperature superplasticity, and the development of ultrafine‐grained materials for superplasticity are also described.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670427

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

As a result of the prediction by Liu and Cohen that crystallineβ‐C3N4has mechanical properties similar to diamond, many research groups have attempted to synthesize carbon nitride using various deposition techniques. Most groups succeeded in producing amorphous carbon nitride coatings. These coatings, though softer than diamond, display excellent tribological properties and are now used as protective overcoats for computer hard drive systems. The lack of success to make crystalline coatings suggests thatβ‐C3N4is metastable. Using TiN(111) and ZrN(111) as seeding layers (which have similar lattice symmetry and commensurate unit cell dimensions asβ‐C3N4(001)), we were able to synthesize fully crystalline carbon nitride composite coatings with hardness in the 50 GPa range, which is in the low end of diamond films.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670428

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The pertinent issues of woven fiber fabric reinforced ceramic composites, such as processing, interface engineering, mechanical behavior, and theoretical modeling, have been discussed. The continuous plain‐weave Nicalon®fiber reinforced SiC composites have been successfully manufactured by a novel forced chemical vapor infiltration (FCVI) method. The FCVI technique can be modeled using a finite‐volume method to optimize the processing conditions, resulting in the savings of fabrication time and cost.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670429

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new approach is proposed in this paper for image matching an invariant to translation, rotation, anisotropic scaling, and skewing. A compact image is acquired by principal component analysis and rescaling the image on the principal axes. However, the direction of the principal axis is susceptible to the skewing effect, which will bring about the failure of the orientation normalization. In addition, overall scale normalization is not taken into consideration. Hence, the central idea of this paper is to find the normalized orientation and overall scale for the compact image by virtue of the moment normalization. In consequence, the resultant image becomes thoroughly normalized and can be directly employed for matching by simple similarity metrics. Alternatively, for the purpose of fast matching, two 1‐D projected results are evaluated for matching. These are undoubtly faster than the conventional pixel‐based correlation.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670430

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper we discuss detection problems for a high resolution radar. Fluctuation in the target radar cross section usually decreases the probability of detection. However, through integration of cells within range profiles of a high resolution radar, variation of the integrated magnitude with respect to the change of carrier frequency and target aspect becomes much smaller, and this is helpful for improving the probability of detection. Two detection algorithms, the cell integration method and the correlation method, for a high resolution radar are proposed, and their detection performances are compared with that obtained by a conventional low resolution radar. Some theoretical formulations are developed. Simulation results show the effectiveness of the proposed algorithms.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670431

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The quality of feeder load distribution estimations will affect the switching schedules and the effectiveness of shunt compensation in distribution system operations. Accurate load distribution estimations are required in order to achieve the best schedule for maximizing the loss reduction. In this paper, a new feeder load distribution estimation method that removes the assumption of coincident peak load made in previous methods is proposed. Considering the non‐conforming load effect, the new method uses data from load surveys and the customer information system to enhance the quality of the estimations. A dynamic programming algorithm is used to investigate the effects of time varying load distribution estimations on the switched capacitor schedules. Test results using actual measurement data have indicated that the proposed method could provide better estimations than the previous methods.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670432

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper, a combined grey relational analysis/differential dynamic programming approach for short‐term hydro generation scheduling is proposed. The purpose of short‐term hydro scheduling is to find the optimal amount of generated power for the hydro units in the system for the nextN(N=24in this study) hour. In the proposed method, the differential dynamic programming procedures are performed offline on historical load data. The results are compiled and valuable information is obtained by using grey relational analysis. Using the information obtained from the analysis, the differential dynamic programming algorithm is then performed online to give the hydro generation schedule for the forecast load. The effectiveness of the proposed approach is demonstrated by the short‐term hydro generation scheduling of the Taiwan power system, which consists of ten hydro plants. It is concluded from the results that the proposed approach can significantly reduce the execution time of the conventional differential dynamic programming algorithm when determining proper hydro generation schedules.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670433

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents the image technique and the moment method (MM) for analyzing electric field distributions inside a metallic house, located under 345 kV power transmission lines. The validity of the numerical method is checked by comparing it with the experimental results of the electric fields measured inside the metallic house. Results showed that the validity of the numerical method is extremely accurate. In the future, electric fields induced inside houses located under power transmission lines can be accurately calculated by using the MM technique in the place of time‐consuming measurements.

ISSN:0253-3839    

DOI:10.1080/02533839.1998.9670434

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor