Design of a log periodic strip grating microstrip antenna

The design of a log periodic strip grating antenna is described. The 12-element antenna is compact and has a measured power bandwidth of 22%. The antenna elements are mounted on the top of the top layer of a two-layer structure with its feed line located between the two dielectric layers providing electromagnetic coupling. The structure was analyzed using PMESHD, a moment method code for two-layer passive structures. The analysis and measurements are in good agreement. © 1993 John Wiley & Sons. Inc.     

On languages with a certain prefix property

A languageL has theprefix property if for allx, y L, eitherx is a prefix ofy ory is a prefix ofx. It is shown that for certain classes of languages, if a language in the class has the prefix property, then it is a regular set. The results provide new distinctions between classes as well as new profs of previously known distinctions.This research was supported in part by the National Science Foundation under Grant DCR-75-15945 and Grant MCS76-05744.     

Quantifier guided aggregation using OWA operators

We consider multicriteria aggregation problems where, rather than requiring all the criteria be satisfied, we need only satisfy some portion of the criteria. The proportion of the critera required is specified in terms of a linguistic quantifier such as most . We use a fuzzy set representation of these linguistic quantifiers to obtain decision functions in the form of OWA aggregations. A methodology is suggested for including importances associated with the individual criteria. A procedure for determining the measure of “orness” directly from the quantifier is suggested. We introduce an extension of the OWA operators which involves the use of triangular norms. © 1996 John Wiley & Sons, Inc.     

Communication in reactive multiagent robotic systems

Multiple cooperating robots are able to complete many tasks more quickly and reliably than one robot alone. Communication between the robots can multiply their capabilities and effectiveness, but to what extent? In this research, the importance of communication in robotic societies is investigated through experiments on both simulated and real robots. Performance was measured for three different types of communication for three different tasks. The levels of communication are progressively more complex and potentially more expensive to implement. For some tasks, communication can significantly improve performance, but for others inter-agent communication is apparently unnecessary. In cases where communication helps, the lowest level of communication is almost as effective as the more complex type. The bulk of these results are derived from thousands of simulations run with randomly generated initial conditions. The simulation results help determine appropriate parameters for the reactive control system which was ported for tests on Denning mobile robots.     

Seniors and Information Technology in China

Technology, particularly information technology (IT), is changing rapidly and offers many advantages for users. IT has the potential to improve one’s quality of life, but only if used. Research has shown that, in most developed and developing nations, senior use of IT lags behind that of other segments of society. This “gray divide” is a concern for government, business, and others. Concern about senior adoption and use of IT has been the motivation for numerous studies and is the motivation for this study of Chinese seniors. This exploratory study examines urban Chinese seniors’ IT use, computers and mobile phones in particular, but also their attitudes and behaviors as they relate to the use of those devices. More specifically it examines several potential factors that motivate or hinder senior’s use of information technology, including self-efficacy, satisfaction, comfort with technology, and both positive and negative attitudes. This study provides some insight into the quantity and diversity of Chinese senior technology use in urban China. Particularly noteworthy, the study found that technology ownership was quite high, and in general the Chinese seniors studied had positive attitudes and beliefs concerning information technology. This is generally good news for the Chinese government, which must efficiently provide services for the growing population of Chinese seniors, as well as for businesses that wish to capitalize on one of the largest senior populations in the world.     

Visualization of diversity in large multivariate data sets

Understanding the diversity of a set of multivariate objects is an important problem in many domains, including ecology, college admissions, investing, machine learning, and others. However, to date, very little work has been done to help users achieve this kind of understanding. Visual representation is especially appealing for this task because it offers the potential to allow users to efficiently observe the objects of interest in a direct and holistic way. Thus, in this paper, we attempt to formalize the problem of visualizing the diversity of a large (more than 1000 objects), multivariate (more than 5 attributes) data set as one worth deeper investigation by the information visualization community. In doing so, we contribute a precise definition of diversity, a set of requirements for diversity visualizations based on this definition, and a formal user study design intended to evaluate the capacity of a visual representation for communicating diversity information. Our primary contribution, however, is a visual representation, called the Diversity Map, for visualizing diversity. An evaluation of the Diversity Map using our study design shows that users can judge elements of diversity consistently and as or more accurately than when using the only other representation specifically designed to visualize diversity.     

The mechanical behavior of multiphase nanocrystalline materials

Most commercial structural materials are multiphase and it is expected that multiphase nanocrystalline materials will also eventually be the materials of choice for applications. There has been limited research so far on the influence of second-phase particles in a nanostructured matrix. More studies have been carried out on nanoscale second phases in an amorphous matrix. This paper will review the examples from the literature of mechanical properties in nanocrystalline materials as influenced by second-phase particles. Work from the authors’ laboratory on nanoscale particles in nanocrystalline aluminum and iron will be emphasized. These particles include both “hard” and “soft” phases and exhibit a wide range of hardness behavior. Mechanisms for the observed effects will be suggested.     

Zirconia Gels in Concentrated NaOH

The sol-gel process was used to produce zirconia powders that were pressed into compacts. The powders were synthesized from zirconium n-propoxide, diluted in propanol, and hydrolyzed with molar ratios of water either l-to-l or lo-to-l. Zirconia compacts produced in this manner were soaked in 1N NaOH to simulate a membrane cleaning process, and their weight loss was recorded. Zirconia samples with a higher weight fraction of tetragonal phase exhibited less weight loss than samples with more monoclinic phase. The weight fraction of the tetragonal phase was controlled by synthesis conditions and tiring temperature.