Discrete time sliding mode controllers with relative degree one and two switching variables

In this paper, a new reaching law based sliding mode control strategy for discrete time systems is introduced. Contrary to most existing approaches, the new strategy uses a sliding variable with relative degree two. It is demonstrated that the new reaching law drives the sliding variable to a narrower quasi-sliding mode band than its relative degree one equivalent, while simultaneously ensuring the desired dynamic properties of the system. Furthermore, it is shown that the smaller quasi-sliding mode band width is reflected in reduced magnitude of all state variables in the sliding mode.     

On the continuous time-varying JLQG

In this paper, the optimal control law for the continuous infinite time-varying stochastic control system with jumps and quadratic cost is found under the assumption that the coefficient have limits as time tends to infinity and the boundary system is absolutely observable and stabilizable. In addition, the asymptotic properties of the solution of the differential Riccati equations for continuous time Markovian jump linear quadratic control problem with time-varying coefficient are established.     

On direct controllability of discrete time jump linear system

In this paper we consider a problem of controllability of discrete time linear system with randomly jumping parameters which can be described by finite state Markov chain. Necessary and sufficient conditions for existence of control which governs the system from any initial conditions to zero, from zero initial condition to any final value and from any initial condition to any final value in given time and with probability one are given. The relations between such kinds of controllability and stochastic stabilizability are discussed.     

Desirability of personal characteristics associated with creativity: Through the eyes of Polish and Chinese university students

The social desirability of characteristics associated with creativity and cultural stereotypes was examined across Polish and Chinese cultures. Polish responses were compared with those from an earlier Chinese study (n = 451). First, we carried out an initial study among 116 Polish students to determine what traits are parts of the national stereotype. Then we sought answers from another set of Poles (n = 610) as to what traits were, first, creative and, secondly, desirable. To analyze the responses we first ranked the traits that both Polish and Chinese students found desirable and then compared the desirable traits across cultures with traits known to be trademarks of creativity. As expected, we found differences between the two samples arising from underlying social origins in that: (a) Poles desired more creative traits and more western traits, whereas Chinese desired more Confucianism based traits and less creative traits; and (b) both Poles and Chinese found creativity traits are desirable albeit Poles found them more desirable than Chinese. An interesting side note is that Poles, unlike Chinese, do not take a positive view of their cultural traits.     

On the Road to Brussels: Enhancing the Quality of Communication for and Through Better Co-operation

Co-operation among the Central and South Eastern European countries has lost its dynamics. It can develop in the future within the framework of the European Union. For the time being, the countries of both regions are engaged in efforts to score points with the European Union and to reach Brussels as soon as possible. As yet, communication has not contributed sufficiently to the countries of Central and South Eastern Europe. However, at present, the potential for such co-operation is almost exhausted. Of the countries of both regions, Poland deserves special attention owing to its being particularly in advance with regard to the safeguarding of the free media, to the transformation of the national economy, and to the implementation of human rights.     

Encoding and retaining information in the visuals and verbals of an educational movie

This study shows that when viewers watching an educational movie are presented simultaneously with information in two media-visual and verbal /auditory, there is no competition fa resources. When encoding information in one medium, one is not hindered from encoding information in the other; even when visual and linguistic information are presented sequentially, doubling study time, the extraction of information is not increased. College students appear to be good dual media processors. This work was supported by the Office of Naval Research, Contract #N00014-78-C0433, and National Institute of Mental Health postdoctoral fellowship #5 F32 MH07588-02, to the first author. Some of the results were presented at the 1980 annual meeting of the Psychonomics Society in St. Louis. We thank Agda Bearden for helping with data collection and scoring and R. Michael Perry for implementing the computer package for data analysis. Requests for reprints should be sent to Patricia Baggett, Psychology Department, University of Colorado, Campus Box 345, Boulder, Colorado, 80309. This report is #108 of the Institute of Cognitive Science’s Technical Report Series.     

The weighted walking test as an alternative method of assessing aerobic power

The aim of the present study was to determine maximal oxygen uptake (VO2max) directly during uphill walking exercise and to compare these values with those achieved during running and cycling exercise. Forty untrained students (20 males and 20 females) took part in three exercise tests. The running test was performed on a horizontal treadmill and the speed was gradually increased by 0.3 m . s(-1) every 3 min. The walking test was conducted on a treadmill inclined at 12% (speed of 1.8 m . s(-1)). The load was further increased every 3 min by the addition of a mass of one-twentieth of the body mass of the participant (plastic containers filled with water and added to a backpack carried by the participant). During the bicycle ergometry test, the workload was increased by 20 W every 2 min. All tests were performed until volitional exhaustion. During all tests, oxygen uptake, minute ventilation, tidal volume, respiratory frequency, heart rate, hydrogen ion concentration, base excess, and blood lactate concentration were analysed. The Pearson correlation coefficients between the weighted walking test and the commonly applied running and bicycle ergometry tests indicate a strong association with the new test in evaluating maximal oxygen uptake. The negligible differences in VO2max between the three tests for the male participants (running: 61.0 ml . kg(-1) . min(-1); walking: 60.4 ml . kg(-1) . min(-1); cycling: 60.2 ml . kg(-1) . min(-1)), and the fact that the females achieved better results on the walking test than the cycle ergometer test (running: 45.0 ml . kg(-1) . min(-1); walking: 42.6 ml . kg(-1) . min(-1); cycling: 40.1 ml . kg(-1) . min(-1)), confirm the suitability of the new method for evaluating aerobic power. The weighted walking test could be useful in the assessment of aerobic power in individuals for whom running is not advised or is difficult. In addition, the new test allows for determination of VO2max on small treadmills with a limited speed regulator, such as those found in specialist physiotherapy and fitness centres.     

On the use of ASTM closed vessel tests in accelerated ageing research

The ASTM D6819-02e3 standard for testing the accelerated ageing of paper, published in 2002, recommends using closed glass vials in order to keep the degradation products in contact with the paper and thus permitting a better simulation of the natural ageing conditions inside closed books. In the present study, the actual conditions and their stability inside closed vessels have been evaluated. The necessity of assuring a very high sealing performance (tightness) of the systems in order to avoid leakage of water vapour is the main drawback of this ageing method. Systematic studies presented in this publication tried to monitor this tightness and have provided data that helped to answer the question of what circumstances could lead to achieving its improvement. Both gravimetric monitoring of water content in vials and “in situ” IR measurements of the aged paper humidity have been applied for this purpose. As a result, better sealing materials (gaskets and caps) than those recommended by the ASTM standard, have been found. Additionally, application of a dynamometric spanner for closing the vials is recommended, as this is a guarantee of reasonably high and recurring tightness of the systems used in tests. Nevertheless, the systematic, linear with time, loss of moisture for all used vials was observed. A 9% loss of the initial moisture content in samples of the aged paper was observed for the tested conditions (14 days at 90 °C). Therefore, it seems that including some kind of gravimetric control for ageing tests performed in closed vessels is of essential importance.Kinetic studies of accelerated ageing in both closed and open systems, as monitored by DP and breaking length measurements, unexpectedly show that no statistically meaningful difference of degradation rates can be observed. On the other hand, the pH and whiteness index values reveal a meaningful difference between the rates of ageing in these systems, thus confirming the basic assumption of the ASTM test concerning the interaction of paper degradation products with the paper itself.