Consensus of second-order multi-agent systems with nonuniform time delays

In this study, the consensus problem for a class of second-order multi-agent systems with nonuniform time delays is investigated. A linear consensus protocol is used to make all agents reach consensus and move with a constant velocity. By a frequency-domain analysis, a simplified sufficient condition is given to guarantee the consensus stability of the dynamic system. Finally, the effectiveness of the obtained theoretical results is illustrated through numerical simulations.

Obstacle avoidance technology of bionic quadruped robot based on multi-sensor information fusion

In order to improve the ability of a bionic quadruped robot to percept the location of obstacles in a complex and dynamic environment, the information fusion between an ultrasonic sensor and a binocular sensor was studied under the condition that the robot moves in the Walk gait on a structured road. Firstly, the distance information of obstacles from these two sensors was separately processed by the Kalman filter algorithm, which largely reduced the noise interference. After that, we obtained two groups of estimated distance values from the robot to the obstacle and a variance of the estimation value. Additionally, a fusion of the estimation values and the variances was achieved based on the STF fusion algorithm. Finally, a simulation was performed to show that the curve of a real value was tracked well by that of the estimation value, which attributes to the effectiveness of the Kalman filter algorithm. In contrast to statistics before fusion, the fusion variance of the estimation value was sharply decreased. The precision of the position information is 4. 6 cm, which meets the application requirements of the robot.

Time, Length, and Mass Are Derived Quantities

Fundamental units of measurements are kilograms, meters, and seconds—in regards to mass length, and time. All other measurements in mechanical quantities including kinetic quantities and dynamic quantities are called derived units. These derived units can be expressed in terms of fundamental units, such as acceleration, area, energy, force, power, velocity and volume. Derived quantities will be referred to as time, length, and mass. In order to explain that fundamental units are not equivalent with fundamental quantities, we need to understand the contraction of time and length in Special Relativity. If we choose the velocity of light as fundamental quantity and length and time as derived quantities, then we are able to construct three-dimensional space-time frames. Three-dimensional space-time frames representing time with polar coordination, time contraction and length contraction can be shown graphically.

Degradation characteristics of two Bacillus strains on the Microcystis aeruginosa

The degradation kinetics of strains P05 and P07 and the degradation effects of mixed strain on Microcystis aeruginosa were studied. The results showed that: (1) The degradation processes of strains P05 and P07 on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chl-a concentration was from 0 to 1500 μg/L. (2) The initial bacterium densities had a strong influence on the degradation velocity. The greater the initial bacterium density was, the faster the degradation was. The degradation velocity constants of P05 were 0.1913, 0.2175 and 0.3092 respectively, when bacterium densities were 4.8×10 5, 4.8×10 6, 2.4×10 7 cells/ml. For strain P07, they were 0.1509, 0.1647 and 0.2708. The degradation velocity constant of strain P05 was higher than that of P07 when the bacterium density was under 4.8×10 5 cells/ml, but the constant increasing of P07 was quicker than that of P05. (3) The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chl-a was high, the degradation effects of mixed strain excelled that of any single strains. But with the decrease of the Chl-a concentration, this advantage was not clear. When the concentration was less than 180 μg/L, the degradation effects of mixed were consistent with that of strain P07.

Analysis of sand particles’ lift-off and incident velocities in wind-blown sand flux

In the research of windblown sand movement,the lift-off and incident velocities of saltating sand particles play a significant role in bridging the spatial and temporal scales from single sand particle＇s motion to windblown sand flux.In this paper,we achieved wind tunnel measurements of the movement of sand particles near sand bed through improving the wind tunnel experimental scheme of paticle image velocimetry（PIV） and data processing method.And then the influence of observation height on the probability distributions of lift-off and incident velocities of sand particles was analyzed.The results demonstrate that the observation height has no obvious influence on the distribution pattern of the lift-off and incident velocities of sand particles,i.e.,the probability distribution of horizontal and vertical velocities of lift-off and incident sand particles follow a Gaussian distribution and a negative exponential distribution,respectively.However,it influences the center of the Gaussian distribution,the decay constant and the amplitude of the negative exponential distribution.