This paper focuses on the delay induced Hopf bifurcation in a dual model of Internet congestion control algorithms which can be modeled as a time-delay system described by a one-order delay ...differential equation (DDE). By choosing communication delay as the bifurcation parameter, we demonstrate that the system loses its stability and a Hopf bifurcation occurs when communication delay passes through a critical value. Moreover, the bifurcating periodic solution of system is calculated by means of perturbation methods. Discussion of stability of the periodic solutions involves the computation of Floquet exponents by considering the corresponding Poincare -Lindstedt series expansion. Finally, numerical simulations for verify the theoretical analysis are provided.
This paper focuses on Hopf bifurcation control in a dual model of Internet congestion control algorithms which is modeled as a delay differential equation (DDE). By choosing communication delay as a ...bifurcation parameter, it has been demonstrated that the system loses stability and a Hopf bifurcation occurs when communication delay passes through a critical value. Therefore, a time-delayed feedback control method is applied to the system for delaying the onset of undesirable Hopf bifurcation. Theoretical analysis and numerical simulations confirm that the delayed feedback controller is efficient in controlling Hopf bifurcation in Internet congestion control system. Moreover, the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are determinated by applying the center manifold theorem and the normal form theory.
Cognitive Styles and Distance Education Liu, Yuliang; Ginther, Dean
Online Journal of Distance Learning Administration,
1999, Letnik:
2, Številka:
3
Journal Article
Considers how to adapt the design of distance education to students' cognitive styles. Discusses cognitive styles, including field dependence versus independence, holistic-analytic, sensory ...preference, hemispheric preferences, and Kolb's Learning Style Model; and the characteristics of distance education, including technology. (Contains 92 references.) (Author/LRW)
Study on spatial distribution pattern of thrip(Odentot hrips lati) on alfalfa(Medicago sativa) Zhao Lili, Guizhou University, Guiyang (China)，College of Animal Science; Wang Puchang, Guizhou Practaculture Research Institute, Guiyang (China); Liu Yuliang, Inner Mongolia Agricultural University, Hohhot (China)
Hunan agricultural science & technology newsletter : HASTN,
Jul. 2011, Letnik:
12, Številka:
7
Journal Article
Objective The aim of this study was to reveal and analyze the spatial distribution pattern of thrip (Odentot hrips lati) on alfalfa (Medicago sativa). Method Within alfalfa plantation areas, ...experimental plots with the sizes of 10×10, 10×20, 10×30, 20×30, 20×40, 20×80, 30×30, 30×40, 30×50, 40×40, 40×50, 40×80 and 50×50 m2 respectively were set up in the randomly selected sampling sites of 1 m ×2 m in size. During bud-emerging period and florescence period of alfalfa in the experimental plots, the number of thrips was counted and their distribution pattern was measured using XU Ru-mei’s method. Result During bud-emerging period of alfalfa, the spatial distribution of thrips assumed an elliptic shape sized of 40 ×30 ― 40×40 cm2 at horizontal level and that presented an ascending―falling trend of tress density down from the top at vertical level. During the florescence period of alfalfa, it showed a homogeneous distribution or randomly distributed pattern at horizontal level and a falling trend of tress density from the top to the apex to the root at vertical level. Conclusion Our results provide theoretical basis for field selection of insect-resistant alfalfa varieties.
A novel ambient intelligence interactive technique are introduced here. First, the mechanism of our AmI system and several idiographic technique issue is expounded stepwise. For providing ...personalized service an algorithm of face recognition based on HMM is researched and the experimental results show efficient. In this way the user can be identified by the method of face recognition, and the system with a LCS can provide personalized services. Otherwise, we adopt the wavelet analysis and template matching technique to estimate the user's basic face orientation, thus the video projector is driven to rotate toward the same direction. In sum, the study described here is likely to be used in intelligent meeting or medical treatment environment.
Study on physiological activity of the resistance of Medicago sativa to thrips Liu YuLiang, Inner Mongolia Agricultural University, Hohhot (China); Mi FuGui, Inner Mongolia Agricultural University, Hohhot (China); Te Muerbuhe, Inner Mongolia Agricultural University, Hohhot (China)
Hunan agricultural science & technology newsletter : HASTN,
Jun. 2009, Letnik:
10, Številka:
3
Journal Article
Objective The experiment explored of resistance of different Medicago Sativa through synthetic variations of all physiological indexes and the correlation analysis between physiological activity and ...damage degree after thrips damage. Method According to studying physiological activity (POD activity, SOD activity, PPO activity, PAL activity, MDA content and free proline content) of alfalfa in alfalfa resistance to different number of thrips, the correlation between physiological activity and resistance was investigated. Result It was shown that there were negative correlations among POD, SOD, PPO, PAL, MDA, free praline and the number of thrips, and there were negative correlations among POD,SOD,PPO,PAL,MDA ,free praline and CAT. The content changes of POD,SOD,PPO,CAT,MDA and free proline in high resistant alfalfa were slow and PAL was quick and the activities of PPO,PAL,CAT were high, and the activities of POD、SOD were low. Conclusion The research provided theoretical basis and materials for identifying resistance varieties of alfalfa to thrip.
Two-dimensional photonic crystals working in near infrared region are fabricated into silicon-on-insulator wafer by 248-nm deep UV lithography. We present an efficient way to measure the photonic ...crystal waveguide's light transmission spectra at given polarization states
Dianshan Lake is one of the important water supply sources for Shanghai City. The contents of heavy metals in the sediments are obviously higher than those in the overlying water body. The contents ...of Pb in the sediments vary seasonally; with increasing depth, the contents of Cd, Pb, Cu, Cr and Fe show no variation generally, but Mn varies in the peak pattern. Cd, Pb, Cu, Cr and Fe in the sediments are present predominantly in sludge phase, but iron and manganese oxide form of Pb and organic matter-sulfide form of Cu are their respective preferential combining forms. Manganese is present largely in exchangeable form, iron-manganese oxide combined form and sludge form. The contents of the various forms of Cd, Pb, Cu, Cr and Fe tend to vary with changing season and depth. The contents of exchangeable forms of Fe and Mn vary with depth in the peak-like pattern.
This study investigated how the online instruction in a graduate instructional technology course affects learners psychological factors, such as locus of control and achievement motivation. It was ...expected that learners would be more internal at the completion of the course than at the beginning, and that learners would have higher achievement motivation scores at the completion than at the beginning of an online course. Twelve graduate students participated in this project, which used a single group pretest-posttest design. The first hypothesis was supported in that participants internal locus of control scale scores increased by the completion of the online course, although scale scores had indicated externality at the beginning on both scales used. The second hypothesis was not supported, since no significant differences were found in any of the three achievement motivation subscales, work mastery, and competitiveness, over the pretests, midterm tests, and posttests. (Contains 10 references.) (SLD)
A practical packaging technique for a temperature independent Fiber Bragg grating sensor is proposed. A uniform strength cantilever with two FBG attached on the upper and lower surfaces is utilized ...as the key element. By detecting the differential output of two wavelengths, the applied force can be obtained and temperature effects can be eliminated. Experimental results show that the sensor has a linear response and the output signal fluctuates less than 12 pm as the temperature changes from -10/spl deg/C to 50/spl deg/C. The maximum thermal error is less than 0.3% of the full measurement range.
