Bifurcation analysis of a microcantilever in AFM system

The atomic force microscope system (AFM) has become a popular and useful instrument to measure the intermolecular forces with atomic resolution that can be applied in electronics, biological analysis, materials, semiconductors, etc. This paper studies the bifurcation phenomenon and complex nonlinear dynamic behavior of the probe tip between the sample and microcantilever of an atomic force microscope using the differential transformation method. The dynamic behavior of the probe tip is characterized with reference to bifurcation diagrams, phase portraits, power spectra, Poincaré maps, and maximum Lyapunov exponent plots produced using the time-series data obtained from differential transformation method. The results indicate that the probe tip behavior is significantly dependent on the magnitude of the vibrational amplitude. Specifically, the probe tip motion changes from T-periodic to 3T-periodic, then from 6T-periodic to multi-periodic, and finally to chaotic motion with windows of periodic motion as the vibrational amplitude is increased from 0 to 5.0. Furthermore, it is demonstrated that the differential transformation method is in good agreement for the considered system.     

Dinosaurs of a Feather

<正>From the earliest days of paleontological research, the origin of birds was an area of special interest. Largely thanks to the work of Thomas Huxley and the     

Moral luck and computer ethics: Gauguin in cyberspace

I argue that the problem of ‘moral luck’ is an unjustly neglected topic within Computer Ethics. This is unfortunate given that the very nature of computer technology, its ‘logical malleability’, leads to ever greater levels of complexity, unreliability and uncertainty. The ever widening contexts of application in turn lead to greater scope for the operation of chance and the phenomenon of moral luck. Moral luck bears down most heavily on notions of professional responsibility, the identification and attribution of responsibility. It is immunity from luck that conventionally marks out moral value from other kinds of values such as instrumental, technical, and use value. The paper describes the nature of moral luck and its erosion of the scope of responsibility and agency. Moral luck poses a challenge to the kinds of theoretical approaches often deployed in Computer Ethics when analyzing moral questions arising from the design and implementation of information and communication technologies. The paper considers the impact on consequentialism; virtue ethics; and duty ethics. In addressing cases of moral luck within Computer Ethics, I argue that it is important to recognise the ways in which different types of moral systems are vulnerable, or resistant, to moral luck. Different resolutions are possible depending on the moral framework adopted. Equally, resolution of cases will depend on fundamental moral assumptions. The problem of moral luck in Computer Ethics should prompt us to new ways of looking at risk, accountability and responsibility.     

School psychologists' perceptions of priorities for dealing with the dropout problem

A sample of 444 (245 males and 199 females) Nationally Certified School Psychologists were surveyed to determine which causes of dropping out should be national priorities. A Principal Axis Factoring with oblimin rotation was conducted using the 42-item School Psychologist's Dropout Survey. The five factors which emerged were Criminal/Victimization, Different from Peer Group, School Conflict, Dysfunctional Family/Lack of Support, and Family Responsibilities. The factors comprised of items with loadings of .40 or higher were added together for each factor to obtain subscale total scores for each participant. Then, for each subscale all total scores were added together and divided by 444 to obtain an average subscale total score for the entire sample. This process was followed for all five subscales. Finally, the average subscale scores were ranked to identify which causes of dropping out were viewed by school psychologists as the most important national priority. School psychologists perceived school conflicts and dysfunctional families as the primary causes of dropping out that should be national priorities. © 1998 John Wiley & Sons, Inc.     

Students' application of the concept of interdependence to the issue of preservation of species: Observations on the ability to generalize

One of the aims of science education is that students should be able to apply scientific principles to contemporary issues. Individual interviews were used to investigate the way in which students (63 12-year-olds and 60 16-year-olds) applied the ecological concept of interdependence of species to the issue of preservation of species. Students were shown a list of items representing a range of living things and were asked to select those which they would want to save from extinction and explain their reasoning. Although most students used the concept of interdependence for some items, they did not apply it in a scientifically consistent way to all types of living things. Three probable reasons for this lack of consistency were anthropocentricism, mixed reasons (students appeared to spontaneously choose another type of reason depending on what image the item immediately provoked), and opposite reasons (students interpreted the idea of interdependence as applying to some types of living things but not to others). J Res Sci Teach 34: 837–850, 1997.     

Texas Cowboy Boots: America's Material Culture Melting Pot

Cowboy boots are some of the most recognizable dress icons in the United States and symbolize the American West. The mythology of these material culture objects has been built over hundreds of years in many types of oral and written narratives. The purpose of this study was to combine secondary sources focusing on specific dimensions of cowboy boots with interviews of bootmakers and firm owners, developing a clearer understanding of the multicultural evolution of this material culture icon. Results indicate that although most bootmakers are aware of the multicultural origins of cowboy boots, they do not possess a complete comprehension of the origins and development of this material culture icon.